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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY




FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director




REPORT OF INVESTIGATIONS NO. 46




FLUORIDE IN WATER IN THE ALAFIA AND

PEACE RIVER BASINS, FLORIDA




By
L. G. Toler








Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
and the
FLORIDA GEOLOGICAL SURVEY


TALLAHASSEE, FLORIDA
1967








Zli (

AGRI-
CULTURAL
UBRARY

FLORIDA STATE BOARD


OF


CONSERVATION







CLAUDE R. KIRK, JR.
Governor


TOM ADAMS
Secretary of State




BROWARD WILLIAMS
Treasurer




FLOYD T. CHRISTIAN
Superintendent of Public Instruction


EARL FAIRCLOTH
Attorney General




FRED O. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director








LETTER OF TRANSMITTAL


A


I-"
C


Tftorida geoloOicd S4rvey

TALLAHASSEE
April 27, 1967

Honorable Claude R. Kirk, Jr., Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Kirk:
The Division of Geology of the Florida Board of Conservation is
publishing, as Report of Investigations No. 46, a study of the quality
of water as found in the Alafia and Peace River Basins, Florida. The
report, entitled "Fluoride in Water in the Alafia and Peace River Basins,
Florida," was prepared by L. G. Toler, of the U.S. Geological Survey,
in cooperation with the Southwest Florida Water Management District
and the Division of Geology.
You will recognize that waste water from phosphate chemical plants
in the tributary headquarters of these two basins contribute waste
products, including fluorides, to the river water. Fluoride concentrations
range from 3.2 to 30 parts per million in the Alafia River, and .6 to 2.2
parts per million in the Peace River. While the concentration in the
Peace River is probably beneficial, that contained in the Alafia River
is excessive for human consumption.
It is hoped that a detailed investigation of some of the plant opera-
tions and settling lagoons will establish the geologic and hydrologic con-
ditions necessary to control these wastes more effectively.
Respectfully yours,
Robert 0. Vernon
Director and State Geologist




















































Completed manuscript received
April 27, 1967
Published for the Florida Geological Survey
By St. Petersburg Printing Company
St. Petersburg, Florida


iv








CONTENTS


Page
Abstract ........... ............... ............ ...... 1
Introduction ..................-....... ...-....-........- ....... -. 2.....-- 2
Purpose and scope ........-..............-------------- -.........--...--.. .-.....-- ...-.. 2
Description of the area.. ..............................------- -------------- 2
Previous work ....------................ ---....... --.... ..........---.........- ......................- 6
Phosphate mining and processing ... -------- ..-----------------------......-- 8
Significance of fluoride and associated waste products in water ........................................ 10
Fluoride ...... --------................ ...---------------------------......-.......------ 10
Phosphate ..............--------------------------------.......---------... ..... 11
pH ...-..........-...--------------.....................- 12
Turbidity ..... ----...... ----------........ ....----.---------------------. 13
Geochemistry of fluorine .-....--.... -- ............-------------------- 13
Surface water ...---...........-..-----..----------- -.----......-- 14
Ground water ...--..--.......--------..-------------------------- 26
General geohydrology -.......----....-.....---.--------- --------------.....-.-- 26
Fluoride distribution ---....----.............-------- ........-----............. 29
Pollution potential and physical chemistry of fluoride ........--------.................. .......... 35
Monitoring of fluoride in ground water....------..... ............ ..... .....---------------- 42
Summary .......------..--..--..............--. ..-.---- ---- .--- ...------ 43
References .....--..-------...... ....----------------.......------ 445











ILLUSTRATIONS
Figure Page
1 Location of the Alafia and Peace River basins ........................................... ...... 3
2 Location of sampling sites on streams and area of phosphate mining
and processing ........ ............................. ...................................................... ............. 4
3 Frequency curves of specific conductance and concentration of fluoride
for the Alafia River at Lithia .................................................................................. 16
4 Frequency curves of pH and concentration of phosphate for the Alafia
River at Lithia ................................. ........................................... ................................ 17
5 Discharge and concentrations of fluoride and phosphate for the Alafia
River at Lithia from October 1964 to September 1965....................................... 18
6 Discharge and concentrations of fluoride and phosphate for the Peace
River at Arcadia from October 1964 to September 1965...........------ .....-........---... 19
7 Fluoride load in streams in Alafia and Peace River basins during
periods of low and high flow 1965........----..........----.....................------------.. 24
8 Dissolved fluoride load of the Alafia River at Lithia and the Peace
River at Arcadia from October 1964 to September 1965..........-............... ..... 25
9 Piezometric surface of the Floridan aquifer in southwest Florida
in January 1964 ...................................---.....- -....... -------.......................---- 27
10 Dissolved solids concentration in the Floridan aquifer in southwest
Florida .............................-.......--- ..........--..... .......................--- ------------- 29
11 Concentration of fluoride in ground water in southwest Florida .......................... 30
12 Location of cross sections A-A' and B-B' .-.................-- .... ........------....-- 32
13 Cross section A-A' showing geologic formations and fluoride con-
centrations in ground water .... ...... ................................. ...-.. 33
14 Cross section B-B' showing geologic formations and fluoride con-
centration in ground water ..... --- ----.............. .............-. .-..-- 34
15 Fluoride concentrations in shallow wells in the phosphate mining area .--............ 35
16 Relation of the activity coefficient of calcium and fluoride to ionic
strength of a solution ...-......-------------.------....... 38
17 Relation of ionic strength to the specific conductance of some ground
waters ......----.-------------------- 39
18 Scatter diagram of calcium versus fluoride for analyses of ground
water in southwest and northwest Florida and graphs showing the
relation of calcium to fluoride on solutions of different ionic strength
saturated with respect to fluorite .........................-------.-------.------------- 41



TABLES
Page
Table 1. Sampling sites, drainage areas, and discharge data for streams .-...--..........-- 5
2. Chemical analyses of surface waters in the Alafia and Peace River
basins during periods of relatively low and high discharge .......--..-....- ....... 21
3. Chemical analysis of water from a phosphate chemical plant
settling lagoon, Polk County, Florida ..................---------.- ....--- -- 23
vii










FLUORIDE IN WATER IN THE ALAFIA AND
PEACE RIVER BASINS, FLORIDA

By
L. G. Toler

ABSTRACT
Waste water from phosphate chemical plants in the tributary head-
water areas contributes fluoride and other waste products to the Alafia
and Peace rivers.
The fluoride concentration of the Alafia River at Lithia, Florida,
ranged from 3.2 to 30 ppm (parts per million) and the Peace River at
Arcadia, Florida, ranged from 0.6 to 2.2 ppm in samples of water collected
daily from October 1964 to September 1965.. The natural fluoride con-
centration in streams in the Alafia and Peace River basins generally
ranged from 0.2 to 0.4 ppm as determined from analysis of water from
streams away from the active areas of mining and processing of fluoride-
bearing phosphatic minerals.
Most of the waste water from the phosphate chemical plants is routed
to lagoons (gypsum ponds) where the solids settle out and the water
circulates for reuse. High concentrations of fluoride and phosphate in
samples of surface water at sites downstream from the phosphate chemical
plants indicate that some waste water enters the streams continuously.
Analysis of the relation between concentration of fluoride, dissolved
fluoride load, and discharge of the streams suggests that much more
waste water is released to the streams during periods of high discharge
than during periods of low discharge. Overflow of the settling lagoons,
flushing of naturally ponded water from flat headwater areas or con-
trolled release of water of high fluoride content during periods of high
discharge could account for the observed relations.
Fluoride in waste water has apparently not entered the ground in
sufficient quantity to cause widespread increases in the concentration
of fluoride in ground water. Fluoride does occur naturally in ground
water and ranges from 0.0 to about 4.0 ppm. The concentration of
fluoride in ground water is highest in water from the Hawthorn Formation
and Tampa Formation of Miocene age. The fluoride apparently dissolves
from the fluoride-bearing phosphatic minerals in the rocks.
The areal approach used in this investigation did not resolve whether
contamination of ground water by fluoride occurs locally. The greatest
potential hazard to ground water appears to be the chemical plant
settling lagoons.






REPORT OF INVESTIGATIONS No. 46


Predictions of the zonal pattern of a fluoride -contaminant in the
ground requires a knowledge of the ground-water flow patterns and
the effects of any chemical reactions between the fluoride and the water
and rocks in the ground. A detailed investigation of one or more of the
chemical plant settling lagoons is desirable to establish the geologic-
hydrologic conditions and ground-water flow patterns in the vicinity
of the lagoons. The chemical reactions between water of high fluoride
content and water in a limestone aquifer need investigation.

INTRODUCTION
PURPOSE AND SCOPE
The use of the Peace and Alafia rivers to dispose of phosphate and
other wastes has caused local and statewide concern about contamination
of the river water. Recently, this concern has been expanded to include
the possible effects on ground-water supplies, should the contaminants
enter the ground and mix with the fresh water. This report is a product
of an investigation with the general objectives of appraising the problem
of contamination and evaluating the need for additional investigations.
The specific objectives of this report are to determine to what degree,
if any, ground-water contamination has occurred; evaluate the effects
of fluoride from phosphate mining and processing on ground water;
determine the quantity of selected constituents being wasted to the
streams; examine the effect of these constituents on the quality of water
in the streams; and determine some system of monitoring wastes in
streams and ground-water supplies.

DESCRIPTION OF THE AREA
The Alafia and Peace rivers both have their headwaters in Polk
County, Florida. They have a combined drainage area of 2,820 square
miles and discharge an average total of about 1,500 million gallons
of water per day to the Gulf of Mexico. The locations of the basins
within the state are shown in figure 1. Figure 2 shows the drainage
patterns of the streams and the political boundaries of the Peace and
Alafia River Basins Boards. The political boundary of the Alafia Basin
Board (fig. 2) encompasses the drainage area of the Alafia River and
part of the Little Manatee River. Drainage areas and a summary of
flow statistics are included in table 1. For the Peace River the political
boundary closely approximates the natural drainage divide. In the
headwater area, the drainage divide is not always well defined but
may be in flat swampy areas where the direction of flow is governed







FLUORIDE IN WATER IN THE ALAA AND PEACE -RVER BASINS


/7


EXPLANATION


River basin
River basin
Boundary


0 10 20 30 40 50miles
oa -.


Figure 1.-Location of the Alafia and Peace River basins.


Im1 Alofio
Peace
Basin








REPORT OF INVESTIGATIONS No. 46


by the amount of rainfall on different parts of the area. South of
Bartow, the main stem of the Peace River has a well-defined channel.

Drainage is dendritic except where altered by strip mining for phos-
phate. The river flows southward from Polk County through Hardee
and DeSoto counties and into Charlotte Harbor in Charlotte County.


-6. a-Inem-V-3 _mec*nsci
Sa \ 'sota


EXPLANATION nk
| Phosphate mMne
c PhasphOle chemical pant
a* ai dnlischarge or stage.
daily samples
3 Daiy discharge or stage,
periodic samples
S Periodic discharge measurements
anid samples
S Periodic samples, no
discharge data
Approximate boundary of calcium
Sphosahate zone (after Cathcart
/ and Lawrence .959, p223)
S Cawage dride
Z3 'a er of site as listed in table 1.
-LBoundary. Peace and Alafri Basin Boards

Wd


6 5o s Ia s 1Oni


45' 81'3


Figure 2.--Location of sampling sites on streams and area of phosphate mining and
processing.

The U.S. Geological Survey has maintained gaging stations on the
main stem of the Peace River at Bartow for 26 years, at Zolfo Springs
for 32 years, and at Arcadia for 34 years prior to September 1965.


Beo00








FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 5

TABLE 1.--Sampling sites, drainage areas, and discharge data for streams.
I discharge measurements made at time sample collected.
P periodic, about 8 times per year.
D --daily.
Dates refer to water year ending September 30
Frequency
Discharge Average of
Drainage area record Discharge sampling
Number Station name square miles began cfs 1961-1966
ALAFIA RIVER BASIN
1. North Prong Alafia River
at Mulberry 1964 I P
2. North Prong Alafia River
at Keysville 135 1950 185 P
3. English Creek near Mulberry 1964 I
4. South Prong Alafia River P
near Lithia 107 1962 109 P
5. Turkey Creek near Durant 15 1964 P
6. Alafia River at Lithia 335 1933 385 D
7. Alafia River at Riverview None P
PEACE RIVER BASIN
8. Saddle Creek at Structure P-11 135 1964 P
9. Saddle Creek near Bartow None P
10. McKinney Branch near Bartow 1964 I P
P 1965
11. Peace River at Bartow 390 1939 313 D 1966
12. Sixmile Creek near Bartow 1964 I P
P 1965
13. Peace River at Fort Meade 465 1964 Stage only D 1966
14. Bowlegs Creek near Fort Meade 47 1964 P
15. Mill Branch tributary 1964 I P
16. Mill Branch near Fort Meade 1964 I P
17. Whidden Creek near Fort Meade 1964 I P
18. Paynes Creek near Bowling Green 121 1964 111 P
19. Peace River at Zolfo Springs 826 1933 772 D
20. Charlie Creek near Gardner 330 1950 335 P
21. Peace River at Arcadia 1,367 1931 1,280 D
22. Joshua Creek at Nocatee 132 1950 121 P
23. Peace River at Fort Ogden 1,790 1964 Stage only P

Table 1 summarizes the streamflow data for the basin. Total drainage


area of the basin is about 2,400 square miles.
The Alafia River has the headwaters of its


major tributaries, the


North and South Prongs, in the phosphate mining area of western Polk
County. These tributaries merge in eastern Hillsborough County to
form the Alafia River which flows westward into Hillsborough Bay.
Phosphate mining began in southwest Florida with the dredging
of river pebble deposits along the Peace River in the late 1800's.
Several periods of prosperity and depression have governed the rate
of development of the phosphate deposits. In the years following World
War II, the demand for phosphate and phosphate products has con-
tinually been on the upswing and the industry has flourished accord-
ingly. The Alafia and Peace rivers are the only streams that drain
the area of phosphate mining and they have received waste from the
industry.
Most of the waste products from the mining and processing of
phosphate rock do not reach the streams. The solid waste is retained
in settling lagoons and the clear water circulated for reuse. Never-
theless, a significant amount of waste water enters the streams, either






REPORT OF INVESTIGATIONS No. 46


directly or from overflow of the settling lagoons. The character of
the water in the settling lagoons depends on the source of the waste
water. Water from the mining operations is essentially sediment-laden
waste water and is not of bad chemical quality. Water from the
phosphate processing plants, however, may be of poor chemical quality.
These waste waters, which contain high concentrations of inorganic
chemicals acquired during the processing, have entered the streams
in sufficient quantities to cause water in some of the streams to be
unfit for some uses. In recent years, the increase in mining activity
and the increase in the number of chemical plants have increased the
volume of waste products dissipated to the streams.
The investigation was conducted by the U.S. Geological Survey
in cooperation with the Alafia and Peace River Basin Boards of the
Southwest Florida Water Management District as a part of the co-
operative program to evaluate the water resources of Florida with the
Florida Geological Survey, Division of Geology, Florida Board of
Conservation. The investigation was performed under the general
direction of C. S. Conover, District Chief, Water Resources Division,
US. Geological Survey.

PREVIOUS WORK
The Florida State Board of Health (1955a) reported the first com-
plaint about turbidity in the Alafia River from a resident at Riverview
in 1946. Subsequent investigations by various organizations, generally
sponsored by the phosphate companies, have resulted in a number of
reports on pollution of the rivers and recommendations for minimizing
pollution of the water.
Specht (1950) concluded the clear effluent from phosphate process-
ing was not deleterious to fish life. His work included experiments
with electrolytes to flocculate the colloidal phosphate slimes and reduce
the turbidity of effluent to the streams.
The Florida State Board of Health (1955a, 1955b) reported on the
results of investigations of the Peace and Alafia rivers during the
period 1950 to 1953. They recognize three major sources of pollution
in the Peace River; municipal and domestic sewage, the citrus process-
ing industry, and the phosphate mining and processing industry. They
divide the Peace River into two segments based on type and intensity
of pollution. The segment north of Homeland (about 5 miles south
of Bartow) was considered excessively polluted by organic and chem-
ical pollutants and the segment south of Homeland suffered only from
intermittent excessive inorganic turbidity and slime.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 7

Two major sources of pollution considered by the Florida State
Board of Health (1955b) for the Alafia River were domestic sewage
from cities and towns and the waste products from the phosphate
operations.
From 1953 to 1955 the major concern of the State Board of Health
about waste products from the phosphate industry was the turbidity
and slime from mining and washing operations of the phosphate ore.
The waste products from the phosphate processing plants were only
beginning to be a major source of pollution, especially in the Alafia
River basin. They recommended waste disposal be controlled so that
the pH of the rivers not be reduced below 5.0 and the concentration
of fluoride not exceed 5.0 ppm.
Lanquist (1955), as a part of the investigation by the State Board
of Health, made a biological survey of the Peace River. His conclu-
sion number 4 (p. 67) states that, "at times the effects of acid water
from the phosphatic fertilizer plant at Bartow produced near-sterile
conditions in Bear Branch, adversely affected the water-hyacinths and
fauna in the Peace River at Bartow and possibly affected the Crustacea
at P-11."
Specht (1960) described the mining of phosphate ore and process-
ing of the phosphate minerals to superphosphate, triple superphosphate
and elemental phosphorous. He also describes the methods employed
by the industry to reduce the turbidity, acidity, and fluoride content
of waste water discharged to the streams.
In preparing a basic plan for development of the water resources
of the Peace and Alafia rivers, Johnson (1960, 1963) recognized the
need for control of pollution of the rivers. He (1963. p.ii.) noted an
increase in the number of major phosphate chemical plants since the
survey by the State Board of Health in 1953 and presented data col-
lected by the State Board of Health (1963, p. 1-16, 1-18) to show an
increase in acidity and fluoride content of the Alafia River during the
ten-year interval.
Menke, Meredith, and Wetterhall, (1961) conducted an investiga-
tion of the water resources of Hillsborough County from 1956 to 1958.
Graphical presentations of fluoride and pH of the Alafia River at Lithia
for the period October 1957 to September 1958 show the fluoride con-
centration as high as 17 ppm but below the 5.0 ppm maximum set by
the State Board of Health about 65 percent of the time. The pH
during this period ranged from 5.5 to 6.7. They did not report on
fluoride in ground water but warned that: "Extensive use of Alafia Ri.er






REPORT OF INVESTIGATIONS No. 46


waters for irrigation could result in contamination of ground-water
supplies hydraulically connected downgradient from the irrigated land."
Woodard (1964) in a preliminary report on the geology and ground-
water resources of Hardee and DeSoto counties reported on the occur-
rence of fluoride in ground water in south peninsular Florida and
suggests that the geographic spread is controlled by the hydrology of
the area. The possibility is presented that the source of fluoride is the
phosphatic sediments of Miocene age and that the high fluorides are
confined to the upper part of the Floridan aquifer. In referring to the
piezometric surface of the Floridan aquifer, Woodard stated: "The
high pressure areas north and east of the phosphate deposits would
cause the fluorides entering the aquifer to move to the south and
west." He found no evidence which pointed to contamination of ground
water by the phosphate processing industry.
Shattles (1965) mapped with distribution of dissolved solids and
selected constituents in the Floridan aquifer in Hillsborough County.
He shows an increase in all constituents from the interior toward the
coast. Fluoride was not mapped though the fluoride content of water
from 25 of 28 wells sampled was below 0.8 ppm.

PHOSPHATE MINING AND PROCESSING
In the early days of phosphate mining on the Peace River only the
coarse phosphate pebbles were recovered by screening and the fine
material was wasted back to the stream. Later the discovery of "land
pebble" phosphate deposits that could be removed by strip-mining
methods moved the mining operations away from the river.
The "land pebble" phosphate deposits are located in a shield-shaped
area that covers large parts of Polk, Hillsborough, Hardee, and Manatee
counties and extends into Sarasota and DeSoto counties as shown in
figure 2. Most of the large mining operations are currently in Polk
and Hillsborough counties.
Advances in technology, which made it possible to remove thick
over-burdened deposits and to mine the phosphate ore below the water
table, and greater demand for phosphate opened large areas as economic
phosphate deposits. Improved methods of recovery, especially the intro-
duction of the flotation process to recover fine-grained phosphate, greatly
aided the growth of the phosphate industry.
The phosphate is mined by first removing the overburden, which
is as much as 60 feet thick, with large capacity draglines. The un-
derlying phosphate ore may be from 5 to 50 feet thick and consists
of a mixture of phosphate pebbles and granules, cobbles and boulders
of phosphatized limestone, quartz sand and silt, and clay.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 9

The phosphate ore is then deposited, by the dragline, into a shallow
pit from where it is sluiced to a pump through a four-inch grizzly.
The slurry formed by the sluicing operation is then pumped to the
washer which may be several miles from the mine. This pumping
operation requires large quantities of water which help to disaggregate
the ore but which must be separated during the washer operation and
disposed of or recycled.
The slurry from the mine goes through two processes to separate
the phosphate from the matrix. A combination of washing, scrubbing,
and screening separates the pebble phosphate larger than about one
millimeter from the fine grained matrix. The pebble phosphate is then
ready for shipment or chemical processing. The smaller material is
then separated by flotation. In the flotation cells the fine material is
treated to cause the phosphate particles to float off in an oily froth.
Reagents used are caustic soda, fuel oil, and a mixture of fatty and
resin acids. Some quartz sand is floated in this process and in a
second flotation cell the phosphate is selectively depressed by use of
an amine.
From the washing and flotation plants the water which still carries
the waste material from each stage of the process is pumped to large
settling areas. After the solids have settled the water may be reused
in the mining operation. Some of this water may be wasted to streams,
especially during the rainy season (Specht 1960). Because most of
the reagents used in the flotation process adhere to the minerals (State
Board of Health, 1955a, 1955b), the reagents probably are not a serious
source of stream pollutants.
From the screening and flotation plants, the phosphate minerals
may be marketed directly or transported to the chemical plants for
further processing. The details of chemical processing of phosphate
rock and the products obtained vary according to the plant and the
nature of the product obtained. Some generalization about the process
may be made which is pertinent to water pollution by chemical plant
effluent.
The processes of converting the phosphate minerals into a form
more readily available as plant nutrients require acidification of the
phosphate mineral. Subsequently, some of the fluorides are released.
For making superphosphate, phosphate rock is treated with sulfuric
acid to form a monocalcium phosphate fertilizer. Silicon tetrafluoride,
carbon dioxide, and fluorosilisic acid are other products of the reaction.
Triple superphosphate is produced by allowing the above reaction






REPORT OF INVESTIGATIONS No. 46


to go to completion to form phosphoric acid which is used to treat
more phosphate rock to form the triple superphosphate.
The two part reaction may be generalized as follows:
(1) Ca5(P04)3F + 5H2SO4 = 3HaPO4 + 5CaSO4 + HF
Phosphate Sulfuric Phosphoric Gypsum Acid
rock acid acid fluoride
(2) Cas(P04)3F + 7H3P04 = 5Ca(H2P04)2 + HF
Phosphate Phosphoric Monocalcium Acid
rock acid phosphate fluoride

The gypsum, precipitated in the first reaction, is separated from
the phosphoric acid by vacuum filtration, washed and wasted to a
settling lagoon where it may settle. The water is returned to the
plant for reuse. Owing to silica and carbonate impurities, carbon
dioxide and silicon tetrafluoride are evolved as gases. A complex system
of multiple scrubbing, washing and evaporating removes and concen-
trates the fluorides as fluorosilisic acid which is recovered.
Water waste from the scrubbing process may go to the settling
lagoons or to the streams. During rainy seasons some water may
overflow from the settling lagoons and thus enter the streams. Con-
siderable water containing high fluoride and phosphate enters the
streams as evidenced by analyses of water from many locations down-
stream from the processing plants.

SIGNIFICANCE OF FLUORIDE AND ASSOCIATED
WASTE PRODUCTS IN WATER

FLUORIDE
The effect of fluoride in drinking water has been the subject of
intense investigations since 1931 when endemic mottled enamel in
teeth was recognized as being associated with drinking water con-
taining fluoride. Later investigations showed that small amounts of
fluoride could prevent dental caries without the mottled enamel effect.
The U.S. Public Health Service (1962a) compiled 142 papers writ-
ten by Public Health personnel prior to 1962 into one volume which
describe dental fluorosis and dental caries and the physiological effects,
analysis, and chemistry of fluoride. The results of many investigations
by the Public Health Service have resulted in the adoption of standards
of optimum concentrations of fluoride in drinking water on interstate
carriers and which serve as a guide for others interested in maintaining






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 11

good, safe water supplies. According to the U.S. Public Health Service
(1962b) the optimum fluoride level in drinking water in a given com-
munity depends on climatic conditions because the amount of water
consumed by an individual is primarily influenced by air temperatures.
The following table is taken from the U.S. Public Health Service
(1962b, p. 8).

Annual average of maximum Recommended control limits-
daily air temperatures F Fluoride concentrations in mg/1
Lower Optimum Upper
50.0 53.7 0.9 1.2 1.7
53.8 58.3 0.8 1.1 1.5
58.4 63.8 0.8 1.0 1.3
63.9 70.6 0.7 0.9 1.2
70.7 79.2 0.7 0.8 1.0
79.3 90.5 0.6 0.7 0.8

Water supplies subject to Federal quarantine regulations are sub-
ject to rejection when the fluoride concentration is greater than two
times the optimum concentration.
These optimum concentrations of fluoride in drinking water are
considered effective in preventing mottled enamel and caries in the
teeth of children during the period of tooth development. McKee and
Wolf (1963) report that concentrations of fluoride of 3 or 4 ppm are
not likely to cause endemic cumulative fluorosis and skeletal effects in
adults. Concentrations of 8 to 20 ppm, when consumed over a long
period of time may cause some skeletal effects in adults.
McKee and Wolf (1963) have also summarized the reported effects
of fluoride in water on stock and wildlife, fish and other aquatic life,
and industrial uses. They report (p. 191) that the effects of fluoride
in drinking water for animals are analogous to those for humans, but
that fluoride ions appear to have direct toxic properties towards aquatic
life. They summarize the available information with the following table
of concentrations of fluoride that will not interfere with specified ben-
eficial uses:
a. Domestic water supply 0.7 to 1.2 ppm
b. Industrial water supply 1.0 ppm
c. Irrigation water 10.0 ppm
d. Stock watering 1.0 ppm
e. Aquatic life 1.5 ppm

PHOSPHATE
Phosphates may occur in water from leaching of phosphatic min-
erals, agricultural drainage, decomposition of organic matter, sewage,






REPORT OF INVESTIGATIONS No. 46


industrial wastes or cooling waters that have undergone phosphate
treatment (McKee and Wolf, 1963, p. 240).
Usually, these sources contribute only minor amounts of phosphate
to natural waters and probably have little physiological significance;
however, they serve as a nutrient for growth of algae which is unde-
sirable.
McKee and Wolf (1963, p. 240-241) summarize the work of other
investigators on the effects of phosphate in water. Their summary in-
cludes effects on:
a. Domestic water supplies. Polyphosphates are used to prevent
scale formation and corrosion. In raw water sources, polyphosphates
interfere with coagulation, flocculation, and the lime soda treatment of
water.
b. Irrigation. Phosphate in irrigation water may help increase the
fertility of soil moisture; however, experiments with blueberry plants
showed that 60 ppm may reduce the availability of inorganic iron and
be detrimental.
c. Fish and aquatic life. Phosphates in streams and lakes may
result in overabundant growth of algae with concomitant odors and
detriment to fish. Phosphates are usually not toxic and may be ben-
eficial to fish by increasing algae and zooplankton.
d. Industrial water. Phosphates may be beneficial by preventing
scale formation and corrosion; however, they may encourage biological
growth and be detrimental.
Phosphate in ground water is relatively rare. Small amounts may
be present from the above sources; however, most phosphate is prob-
ably redeposited from ground water in the form of calcium, iron, and
aluminum phosphate.

pH
The pH of water is a measure of the acidity of water. A pH of 7
is considered neutral, below 7 is acid and above 7 is basic. Waters
that have a low pH tend to be corrosive to metal and concrete and
are usually undesirable for domestic supplies. Water with a pH of
about 4.0 may taste sour.
McKee and Wolf (1963, p. 236) summarize numerous investigations
on the effect of pH on fish. Ranges of several pH units can be tolerated
by most species; however, the range may depend on other factors, such
as temperature, dissolved oxygen, prior acclimatization, and the content
of other dissolved material.






FLuoRIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 13

TURBIDITY
Turbidity is an optical property of water that contains suspended
and colloidal matter. This suspended material reduces light penetra-
tion into the water as a function of both the concentration and particle
size of the material. Turbidity is reported as parts per million and is
equivalent to the turbidity of standard solutions of silica.
Turbidity in streams may be caused by micro-organisms, organic
detritus, silica, clay, or silt or any suspended material and may result
from natural processes or domestic and industrial effluent.
The U.S. Public Health Service (1962b, p. 6) recommends that
turbidity in drinking water should not exceed 5 ppm. McKee and
Wolf (1963, p. 290) state that turbidity is generally undesirable for
most industrial uses of water. They give recommended limiting values
of turbidity for many industrial uses ranging from 1.0 to 100 ppm.
Turbidity in water may affect fish by reducing photosynthetic action
and decreasing the productivity of fish-food organisms or by modifying
the temperature structure of bodies of water. Turbid water is con-
sidered less productive for fish than is clear water; however, several
hundred ppm turbidity have not been found lethal to fish (McKee
and Wolf, 1963, p. 291).

GEOCHEMISTRY OF FLUORINE
Fluorine is a minor constituent in the rocks forming the earth's
crust. Many minerals contain fluorine in minor amounts in complex
mineral systems. The most important of these relative to the Alafia
and Peace River Basin areas are the apatite group of minerals that
are primarily calcium phosphate and vary according to the amount of
fluoride, chloride, hydroxyl, and carbonate they contain. Fluorapatite
has the general formula Car,(P04)3F and contains 3.8 percent fluoride.
Chloride or the hydroxyl ion commonly substitutes for fluoride.
In Florida, the only rocks on or near the surface are sedimentary
rocks. Barraclough (1962, p. 24) reported glauconite, phosphate, and
muscovite (mica) in the sedimentary rocks in west Florida. Mica was
reported to be especially abundant. The author has found minor
amounts of fluoride in insoluble residues of limestone well cuttings
from Sumter County in peninsular Florida.
The apatite group of minerals (phosphate rock) occur in the rocks
in many areas in Florida. Where found, the amount varies from a few
scattered grains to large minable deposits. The phosphate rock mined
in the Alafia and Peace River basins is primarily fluorapatite.
Fluoride is usually one of the minor constituents of dissolved mate-






REPORT OF INVESTIGATIONS No. 46


rial in natural water. Hem (1959) reported concentrations of fluoride
in natural water may be 50 parts per million or more, but that con-
centrations of over 10 ppm are rare and surface waters rarely contain
more than 1.0 ppm.

SURFACE WATER
The Peace and Alafia rivers have been described with respect to
inorganic chemical contaminants by previous investigators. The con-
ditions causing excessive inorganic pollution have been established
(Florida State Board of Health, 1955a, 1955b) and recommendations
made which give limits in terms of concentrations that certain constit-
uents in river water should not exceed.
The Florida State Board of Health (1955b, p. 9) recommended
that the waters of the Peace River basin should be maintained so that
the following limits are not exceeded:
Dissolved Oxygen-not less than 3.5 ppm at all points.
Turbidity-not more than 100-200 ppm provided the duration
is short. For continuing waste discharge, the resultant
turbidity should not exceed 50 ppm.
Settleable solids-not more than .05 milliliters per liter.
pH-over 5.0 and under 8.5
Fluoride-not more than 5.0 ppm
Their recommendations for the Alafia River are the same (Florida State
Board of Health, 1955a, p. 8) except for turbidity for which a recom-
mended limit of 100 ppm is given.
A program of sampling and analysis of stream water was established
as a part of the present investigation to define the ranges in concen-
tration of chemical constituents, to define the sources and character
of the chemical constituents, and to evaluate changes in concentrations
from those conditions described by previous investigators. Particular
attention was given to the fluoride and phosphate content of the streams.
Three sites were selected at the start of the investigation for sam-
pling on a daily basis. Daily samples from each of the sites were
analyzed for specific conductance, pH, turbidity, phosphate and fluoride.
A reconnaissance of the basin was made early in the investigation
during which water samples were collected at 48 stream sites and
analyses made for specific conductance, phosphate and fluoride. From
these analyses, 23 sites were selected for periodic sampling and analysis.
Of this number 14 were at gaging stations and 7 were at sites where
discharge measurements were made at the time of sampling. Samples
were collected at approximately six-week intervals. Figure 2 shows






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 15

the location of all stream sampling sites and the sites are identified
in table 1.
Seven sites were selected on the Alafia River and its tributaries
for periodic sampling for chemical analysis. Four of the sites are at
gaging stations. The chemical analyses from all these sites are pub-
lished in annual reports by the U.S. Geological Survey.
The stream-gaging site on the Alafia River at Lithia was selected
for daily sampling because it is downstream from most of the phos-
phate mining operations, records of discharge for the river are avail-
able at this site, and earlier records of chemical analyses are available
(Menke, Meredith, and Wetterhall, 1961).
Menke, Meredith and Wetterhall (1961) reported on a 2-year sam-
pling program of the Alafia River at Lithia from October 1956 to
September 1958. Their frequency curves for chemical constituents for
one year, October 1957 to September 1958, are replotted with frequency
curves for October 1964 to September 1965 in figures 3 and 4. The
frequency curves for specific conductance (fig. 3) for both periods
were prepared from measurements of daily samples and equally in-
dicate conditions during each of these periods. The frequency curves
for pH and concentrations of fluoride and phosphate were prepared
from measurements made on daily samples for the 1965-66 period but
for the 1957-58 period, they were prepared from measurements made
on composite samples from 10 daily samples. The measurements rep-
resented an average for the 10-day period.
Frequency curves constructed by each of the two methods should
give similar values at the 50 percent frequency; however, the greater
number of measurements when daily samples are analyzed individually
will give a wider range of values than will the measurements of the
average composite sample by ten-day periods. The two curves should
cross at about the 50 percent frequency and the curve prepared from
the measurements of composite samples should be flatter than the one
constructed from the daily measurements. Comparing the two curves
for each constituent gives an indication of the changes in water quality
since 1957-58.
The specific conductance of a water is a measure of the capacity
of the water to conduct electricity. Pure water is a poor conductor
of electricity; however, if water contains materials that ionize in solu-
tion, the capacity of the water to conduct electricity increases propor-
tional to the ionization of material in solution. The proportionality
factor will vary according to the type of material that is dissolved in
the water. Menke, Meredith and Wetterhall (1961, p. 53) reported







REPORT OF INVESTIGATIONS No. 46


700 28
E ~Oct. 1964 to Sept. 1965
600 \ 24


S500 -20 g
C -Oct. 1957 to Sept. 1958
400 16
*---Specific Conductance
3 12

re .-Freec c rves of specific conducance and concenraion of fluoride for
200- 8
Oct. 1957 to Sept. 1958
Oct. 1964 to Sept. 1965- -
1 00- 4

0 1 11 1 1 1 1 1 I I 1 1 1 11 1
0.1 05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 99.9
Percent of time specific conductance was equal to or greater than a given value

Figure 3.-Frequency curves of specific conductance and concentration of fluoride for
the Alafia River at Lithia.

that, for the Alafia River at Lithia, the mineral content of the water,
in parts per million, was about 77 percent of the specific conductance
in micromhos.
The two frequency curves for specific conductance in figure 3 show
that the specific conductance, and hence the mineral content, of water
in the Alafia River at Lithia during 1964-65 was generally higher than
during 1957-58. The median value (50 percent frequency) was about
340 micromhos in 1957-58 compared to 580 micromhos in 1964-65. These
values correspond to about 262 and 447 ppm mineral content, respectively.
The frequency curves for concentrations of fluoride and phosphate
(figs. 3 and 4) show that both these constituents also were generally
higher in 1964-65 than in 1957-58. The concentration of fluoride in
water in the Alafia River at Lithia (fig. 3) exceeded the 5.0 ppm
recommended by the Florida State Board of Health about 98 percent
of the time during 1964-65 compared to about 30 percent of the time
during 1957-58.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


C
140 -

120- H
s. 7 -
S100 O\ ct. 1957 to Sept. 1958 -6.0

8 /Oct. 1964 to Sept. 1965

0 -

p. Phosphote wee 5.0

Oct. 1957 to Sept. 1958Z X
20-

0 1 11 I I 1 1 1 1 I I 1 1 1 111 4.0
0.1 05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 99.
Percent of time concentre ion was equal to or greater thon o given value

Figure 4.-Frequency curves of pH and concentration of phosphate for the Alafia River
at Lithia.

Figure 5 shows hydrographs of discharge and concentrations of
fluoride and phosphate for the Alafia River at Lithia from October
1964 to September 1965. The maximum concentrations of fluoride and
phosphate during the year were 30 and 192 ppm, respectively. The
concentration of phosphate was generally 5 to 7 times greater than that
for fluoride.
Frequency curves for pH of water in the Alafia River at Lithia
(fig. 4) show a wider range in pH during 1964-65 than during 1957-
58. The differences between the two curves is probably, in large part,
caused by the different sampling and analytical techniques. The pH
was below the 5.0 lower limit recommended by the Florida State Board
of Health for two percent of the time during 1964-65.
Turbidity was generally low in the Alafia Biver at Lithia but ex-
ceeded the 100 ppm, recommended as maximum, during a six-day
period in February 1965 when a retaining dam for phosphate slime
failed on one of the headwater tributaries.







REPORT OF INVESTIGATIONS NO. 46


3000

1000
500


Oct Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep.
Figure 5.-Discharge and concentrations of fluoride and phosphate for the Alafia River
at Lithia from October 1964 to September 1965.

The program of stream sampling in the Peace River basin was
similar to that in the Alafia River basin. Of 15 sites selected for
periodic sampling, 9 were at gaging stations.
The concentrations of fluoride and phosphate in the Peace River at
Arcadia are shown in figure 6 and are not as high as those in the Alafia
River at Lithia. From October 1964 to September 1965, the pH and
fluoride concentrations of the Peace River at the daily sampling stations
at Zolfo Springs and Arcadia remained within the limits set by the
Florida State Board of Health. The turbidity of the Peace River at
Zolfo Springs and Arcadia was above the 50 ppm limit (continuing
waste turbidity) for 22 percent of the time at both stations from
October 1964 to September 1965.
Several factors affect the amount of dissolved material carried by
a stream. Some material dissolves from the atmosphere when water
falls as rain. Additional material dissolves from the material on the
land surface and from the soil zone as water flows to the streams.
Some of the water that falls on the land surface enters the ground,
moves downward to the water table and may eventually reach the
streams. This water has a. longer period of contact with the earth







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Nov.
1964


Apr. May.
1965


Jun. Jul. Aug. Sep.


Figure 6.-Discharge and concentrations of fluoride and phosphate for the Peace River
at Arcadia from October 1964 to September 1965.


materials and, consequently, contains higher concentrations of dissolved
materials than water.that flows on the surface to the streams.

The above are natural factors which affect the amount and kind
of dissolved materials in water in a stream. During periods of little
rainfall, most of the water in a stream, under natural conditions, is
that which has moved through the ground to the stream. Generally,
under natural conditions, there will be an inverse relation between the
concentrations of dissolved solids of water in a stream and the dis-
charge of the stream owing to most water flowing to the stream on






REPORT OF INVESTIGATIONS No. 46


the surface during high discharge and most flowing through the ground-
during low discharge. However, the dissolved load (weight per unit
time) is higher at high discharge than at low discharge because of
the large volume of water that contains material dissolved from the
surface.
If a stream receives waste products from municipal, industrial, or
other sources, the above relations between the mineral content of water
in a stream and discharge of the stream will be altered. For example,
if a stream receives soluble waste at a constant rate, the mineral con-
tent of water in the stream will be higher at both low and high dis-
charge than if no waste were being received. The inverse relation
between mineral content and discharge will still occur owing to dilu-
tion at high discharge. If the waste material furnishes the larger part
of any constituent in the stream, the dissolved load of that constituent
should be nearly constant at all values of discharge. If the release of
waste materials is controlled, so that more enters the stream at high
discharge, there may be no relation between concentration and dis-
charge and the dissolved load will be much higher at high discharge
than at low discharge. If there is no consistent pattern of release of
waste, there may be no consistent relation between discharge and con-
centration or load.
Chemical analyses of surface water in the Alafia and Peace River
basins for periods of relatively low and high discharge are given in
table 2. The drainage areas for stations 14, 20, and 22 (see fig. 2 for
location) include no phosphate mining or processing operations and
the concentrations of fluoride and phosphate in water at these sites are
low. The concentration of fluoride in streams not affected by phosphate
mining and processing was determined to generally be from 0.2 to 0.4
ppm from analyses of samples collected periodically at these sites and
from samples collected at other sites during the early reconnaissance
of the basins.
The mining and processing of phosphate rock have apparently affected
the quality of water in the streams at all other stations shown on figure
2 and for which the analyses are given in table 2. The concentrations
of all constituents are generally higher than for streams not affected.
The analysis in table 3 shows the constituents in water from a phosphate
chemical plant settling lagoon. The water from which this sample was
taken was not observed entering the streams, but the analysis probably
indicates the type and relative concentrations of constituents typical of
the phosphate chemical plant effluents.













TABLE 2.-Chemical analyses of surface waters in the Alafia and Peace River basins during periods of relatively low and high discharge
(Analyses in parts per million. See table 1 for station name and figure 2 for location)
Analyses by the U. S. Geological Survey


Hardness
as CaCOo


I N Fi


ALAFIA RIVER BASIN
1 6.02.65 I 85 80 .14 56 102 52 8.0 0 472 85 17 18 224 1,050 560 560 1,150 4.4 20 81
9.18.65 I 77 98 .20 2.6 ll 15 66 8.0 0 840 22 24 8.6 112 810 888 888 1,000 4.6 40 82
2 6.02.65 M 79 64 .17 .9 126 20 53 2.8 0 800 42 16 .9 158 802 397 897 980 6.5 20 80
9.14.65 M 128 70 .21 94 13 62 4.1 1 282 48 19 9.9 108 661 288 287 788 4.7 40 80
8 6.02.65 I 0.2 14 .00 27 19 12 2.5 184 29 21 8.1 .0 5.8 199 144 84 310 7.8 10 79
9.13865 I 10 19 .05 .6 22 7.6 26 8.4 54 19 48 5.2 .8 18 196 86 42 850 7.0 40 79
4 6.02.65 M 20 15 .23 .0 46 12 80 1.2 0 100 82 7.8 .2 86 869 164 164 465 6.6 40 80
9.14.65 M 117 80 .14 2.8 40 8.8 26 2.9 1 88 26 11 .0 88 826 186 185 370 5.9 100 81
5 6.02.65 8.3 .03 25 4.4 15 .2 79 82 10 .5 .0 .7 180 76 11 280 7.6 20 80
9.14-65 M 6 8.4 .19 12 4.5 8.9 1.0 37 20 12 .7 .4 1.8 88 48 18 150 7.0 90 -
6 6.02-65 M 187 54 .10 106 18 44 1.9 0 250 85 18 .0 148 665 838 888 810 6.5 20 80
9.14.65 M 841 45 .16 2.5 63 9.9 40 8.4 3 152 86 14 7.9 86 461 198 195 688 5.4 85 80
7 9.14-65 -- 21 .05 199 18 8280 507 63 772 5470 7.4 5.6 8.7 10,800 570 519 16,000 6.7 40 80


0 14
188 14
9.4 18
19 19
23 12
248 17
8.5 18
82 5.5
18
14
6.4 6.3


27
20
28
258
84
21
54
80
15
19
6.4


PEACE RIVER BASIN
1.4 100 116 7.0 8.1
2.7 68 37 21 1.1
.6 94 122 34 2.9
5.0 b227 280 32 11
1.0 91 119 82 2.6
2.6 50 64 28 2.1
.4 154 144 15 8.2
.8 92 105 11 2.6
1.0 138 70 10 1.1
2.4 63 51 18 1.4
.8 6 4.0 12 .2


470
242
525
1,400
515
820
685
480
405
280
79


5
80
10
20
10
80
5
20
10
80
160


6.01.65
9.14.65
6.01.65
9.18.65
6.01.65
9.14.65
6.01-65
9.14.65
6.01.65
9.14.65
9.14.65
















TABLi 2,-Continued
Hardnes.
as CaCOa





15 6.02.65 I 8 1 i .00 42 15 5.8 .5 120 64 5.5 8.8 .1 1.7 212 168 70 840 7.9 5 108
9.14.65 I .7 20 .00 62 16 6.8 .8 140 83 8.0 8.1 .1 13 282 220 106 455 7.5 5 87
16 6.02.65 I 8.2 33 .08 80 81 44 .8 0 892 15 7.8 1.1 156 760 408 408 885 6.8 15 82
9.14.65 I 5.2 88 .18 8.1 64 18 34 1.0 0 210 12 7.0 .2 181 511 234 284 620 4.6 70 87
17 6.02-65 I 24 18 .01 50 80 24 .4 81 184 16 2.6 .4 883 98 248 182 576 7.7 15 76
9.14.65 I 69 18 .05 .6 40 13 16 1.2 28 106 18 4.2 .1 86 811 154 154 890 7.0 40 -
18 6.01.65 M 5.2 2.5 .19 16 7.5 11 .1 42 84 12 .8 5.2 2.0 112 71 86 210 7.4 20 78
9.14.65 M 52 7.8 .32 18 4.9 8.0 .8 25 24 14 .9 1.4 8.7 91 52 82 152 6.7 110 78
19 6.01-65 M 59 12 .05 49 17 26 1.2 101 119 16 2.0 1.0 9.7 802 192 109 515 7.6 10 84
9.14.65 M 581 14 .09 80 9,0 16 2.4 47 64 16 1.7 2.9 8.5 264 112 74 280 6.8 95 81
20 6.02.65 M 4.0 8.9 .12 16 6.2 8.8 .6 62 14 14 .7 .0 2.2 98 66 14 185 7.4 40 80
9.14.65 M 87 8,8 .27 7.0 4.5 7.5 1.0 21 4.8 18 .8 .2 1.6 64 86 19 98 6.5 240 83
21 6.02.65 M 74 11 .03 48 17 25 1.8 105 126 18 1.7 .9 6.8 308 190 104 495 7.6 10 81
9.14.65 M 837 12 .12 25 8,6 18 1.8 55 46 16 1.7 1.4 8.8 161 98 53 245 6.8 110 83
22 9.14.65 M 28 8.8 .46 33 6.7 16 2.1 91 29 29 .4 .6 1.2 172 110 86 288 7.0 100 88
23 9.14-65 11 .17 23 7,2 12 1.9 56 87 14 1.5 1.0 5.8 148 87 41 232 6.9 100 83
M Average daily discharge
I Discharge measurement
a Chemical analyses for Station 9 discharge data for Station 8
b Includes 80 ppm as Carbonate (COa)







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


TABLE 3.-Chemical analysis of water from a phosphate
plant settling lagoon, Polk County, Florida
(Analysis by the U. S. Geological Survey)


Silica (SiO,)
Iron (Fe)
Aluminum (Al)
Manganese (Mn)
Calcium (Ca)
Magnesium (Mg)
Sodium (Na)
Potassium (K)
Total Acidity as H+
Bicarbonate (HCO,)
Sulfate (SO,)
Chloride (Cl)
Fluoride (F)
Nitrate (NO,)
Phosphate (PO,)
Dissolved Solids
Total Hardness as CaCO,
Non-Carbonate hardness as CaCO,
Specific electrical conductance in micromhos
pH
Color


chemical

parts per million
(except specific conductance,
pH, and color)
1,180
87
64
2.7
1,110
50
155
12
123
0
2,710
37
1,410
0.5
7,540
14,400
2,980
2,980
10,100
2.0
140


Most of the phosphate chemical plants are located in the headwater
areas of the Alafia River basin (fig. 2), and the water from streams in
the basin contains higher concentrations of fluoride and phosphate than
the streams in the Peace River basin. Drainage to the tributaries in
the flat headwater areas is controlled, in large part, by the mining op-
erations. No attempt was made to determine the amount of waste water
contributed to the streams by an individual plant.
Table 2 shows that the concentrations of fluoride and phosphate in
surface water may be as high or higher at high discharge as at low
discharge. The hydrographs for stations 6 and 21 (figs. 5 and 6) also
show that the concentration of fluoride or phosphate may be the same
with wide ranges in discharge. This indicates that the streams do not
receive fluoride and phosphate at a constant rate.
The load the stream carries shows the amount of waste and indicates
the period during which most of the waste is received by the stream.
The dissolved fluoride loads of streams in the Alafia and Peace River
basins at relatively low and high discharge are shown in figure 7. The
figure illustrates that a relatively high dissolved fluoride load is carried
by the Alafia River as compared to the Peace River. It also indicates
there is no major loss of fluoride from the streams.






REPORT OF INVESTIGATIONS No. 46


Figure 7.-Fluoride load in streams in Alafia and Peace River basins during periods of
low and high flow 1965.

The fluoride load of each stream at the daily sampling sites was
calculated using the fluoride concentrations of the daily sample and
the mean daily discharge for the station. Hydrographs of fluoride load
are shown in figure 8 for the Peace River at Arcadia and the Alafia
River at Lithia. The calculations of daily samples also show that the
Alafia River carries much more fluoride than the Peace River. The
fluoride load hydrographs closely parallel the shape of the discharge
hydrograph (figs. 5 and 6) showing that much more fluoride is carried
by the streams at high discharge than at low discharge. The fluoride
load hydrographs have the peak loads in August coincident with the
discharge peaks. Of the approximately 4,000 tons of fluoride carried
by the Alafia River at Lithia from October 1964 to September 1965,
slightly more than one-fourth was during the month of August. During
this year, 781 tons of fluoride was measured on the Peace River at
Zolfo Springs and 900 tons at Arcadia. The larger amount at Arcadia






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


C0 1



W.0 -Peace River at Arcadia






S Oct Nov. Dec. Jan. Feb. Mar Apr. May Jun. July Aug. Sept.
1964 1965

Figure 8.-Dissolved fluoride load of the Alafia River at Lithia and the Peace River at
Arcadia from October 1964 to September 1965.


is of the magnitude to be expected as contribution from the uncontam-
inated tributaries between the two stations. Apparently, fluoride is not
lost from the stream to the ground water between the two stations.

Much of the difference in fluoride load carried by the Alafia and
Peace rivers may be accounted for by the greater number of chemical
processing plants in the Alafia basin. Other differences undoubtedly
are due to differences in the size and type of plant and to methods of
waste disposal.

The high fluoride load of the streams at high discharge is probably
caused, in large part, by either controlled or accidental release of
larger amounts of waste water from the settling lagoons during these
periods. Some of the load during high discharge periods may be due
to natural ponding of waste water in flat, swampy upland areas during
periods of low rainfall and subsequent flushing of these areas during
periods of high rainfall.






REPORT OF INVESTIGATIONS No. 46


GROUND WATER
GENERAL GEOHYDROLOGY1
The geologic formations which form the aquifer systems in the
Alafia and Peace River Basins range in age from Eocene to Recent.
The Floridan aquifer is the principal water producer. It includes the
lower part of the Hawthorn Formation and the Tampa Formation of
Miocene age, the Suwannee Limestone of Oligocene age and the lime-
stones of the Ocala Group, the Avon Park Limestone, and the Lake
City Limestone, of Eocene age. Generally, the upper sandy and clayey
part of the Hawthorn Formation serves to confine water in the un-
derlying formations under artesian pressure.
Overlying the Hawthorn Formation are the sands, clays, and marls
of Pliocene to Recent age that may contain water under water-table
conditions and which serve to supply many small domestic wells.
The Floridan aquifer is at or near the surface in the northeastern
part of the area and dips to the southwest. In the southwestern part
of the area, the Floridan aquifer is at depths of several hundred feet.
Menke, Meredith, and Wetterhall (1961, p. 75) reported the depth
of the confining beds of the Floridan aquifer in Hillsborough County
to range from a few feet in the north-central part of the county to about
300 feet in the southeastern part. Woodard (1964, p. 20) stated, "The
bottom of the [Hawthorn] Formation, which in most cases marks the
top of the Floridan aquifer, ranges from about 200 feet below sea level
in north Hardee County to about 450 feet below sea level in south
DeSoto County." Surface elevations in southern DeSoto County range
from about 25 to 125 feet above sea level and the depth to the Floridan
aquifer is as much as 575 feet.
Regionally, the Floridan aquifer in peninsular Florida functions as
an aquifer system. Water enters the aquifer in the central peninsular
area where the aquifer is at or near the surface, and in areas where it
may leak through the confining beds, and moves radially away from
the central part of the peninsula toward the coast. Figure 9 shows the
piezometric surface of the Floridan aquifer in the study area. The
general direction of ground-water movement is considered to be from
the areas of high to low pressures or south and west from north-central
Polk County.
Locally, the Floridan aquifer may sometimes function as two or
more hydraulic units. In Hillsborough County (Menke, Meredith, and
Wetterhall, 1961, p. 72) the limestones of the Ocala Group tend to
lThe stratigraphic nomenclature in this report conforms to the usage of the Florida
Geological Survey and not necessarily to that of the U. S. Geological Survey.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 27

restrict the vertical flow of water and the aquifer functions as two units,
one above and one below the Ocala Group. Woodard (1964) found
similar conditions in Hardee and DeSoto counties. In Hardee County,
most of the water pumped is from the zone below the Ocala Group.
South of Hardee County, in DeSoto County, where the Tampa Forma-
tion and Suwannee Limestone above the Ocala Group are deeper and
thicker, they form the most used zone. Sutcliffe and Joyner (1966)
used packers in wells in Sarasota County to show three producing zones.
Generally, the upper, permeable zones have a better quality of water


Figure 9.-Piezometric surface of the Floridan aquifer in southwest Florida in January
1964.






REPORT OF INVESTIGATIONS No. 46


than the lower zones where circulation of water is inhibited. Figure 10
shows the general distribution of dissolved solids in the Floridan aquifer.
The map is prepared from maps and data presented by Shattles (1965),
Peek (1958), N. P. Dion and M. Kaufman (personal communication,
1966), B. F. Joyner (personal communication, 1965), and supplementary
data collected during this investigation. The maps were prepared from
chemical analyses that generally represent water from wells open to a
large section of the aquifer and do not show differences in the dissolved
solids in the different zones of the aquifer. Evidence in the literature
shows that differences in the chemical quality of water occur with depth
of penetration into the aquifer. Peek (1958, p. 66-67) shows large dif-
ferences in his dissolved solids maps in water from the Tampa Forma-
tion and water from the Suwannee and older formations.
Differences in artesian pressure in the different zones of the aquifer
in some locations affect the general flow pattern of the water. In order
for water to move downward into an aquifer, the water level in the
aquifer must be lower than the water level in the sediments overlying
the aquifer. For the water to move downward through the aquifer,
the water level from a well deep into the aquifer must be lower than
in a well which only penetrates the upper part of the aquifer. Woodard
(1964, p. 28) reported that the water table stands as much as 45 feet
above the piezometric surface in northwest Hardee County, and that
the artesian water level becomes lower with depth. The Floridan
aquifer is being recharged in the ridge section of Hardee County
southward to the Hardee-DeSoto county line where the water table
and piezometric surface are at about the same elevation.
Along the Peace and Alafia rivers, an opposite relation of water
level with depth prevails. Water is released from the aquifer through
springs along the river valleys. This release of water lowers the pres-
sure of the upper part of the aquifer to a level below that of the lower
part of the aquifer. This reversal allows water to move from the lower
part to the upper part of the aquifer. Dion and Kaufman (personal
communication, 1966) have shown this condition to exist for the Peace
River, and Menke, Meredith, and Wetterhall (1961) have discussed it
for some springs in Hillsborough County. The manner in which these
areas of recharge and discharge affect the chemical quality of water
by altering the general flow pattern can be observed on figure 10 by
the upstream indentation of the high dissolved solids patterns along the
river valleys in Hardee and Hillsborough counties.
The natural zonation and local alteration of the general flow pattern
in the Floridan aquifer are significant in explaining the variations in
natural chemical quality of water. They also illustrate the need for a






THE ALAFA AND PEACE RIVER BASINS


Figure 10.-Dissolved solids concentration in the Floridan aquifer in southwest Florida.
very detailed knowledge of local hydrologic conditions to locate and to
predict the effects of introducing a contaminant into the aquifer at any
point.

FLUORIDE DISTRIBUTION
The distribution of fluoride in ground water in the Alafia and Peace
river basins and adjacent coastal areas was mapped to determine the
natural concentrations of fluoride, to determine if contamination of ground
water by fluoride effluent from phosphate processing plants has occurred,


FLUORIDE IN WATER IN






30 REPORT OF INVESTIGATIONS No. 46
and to provide a base from which any future changes in fluoride con-
centration can be detected.
Figure 11 is a map of fluoride concentrations in ground water. The
wells shown range widely in depth and in the section of the aquifer
system they penetrate. All wells except those that penetrate only the
surficial sands are included.
Some general trends in the distribution of fluoride can be noted. In
the northern part of the area, the concentration of fluoride in ground
water generally ranges from 0.0 to 1.0 ppm. The concentration of


Figure 11.-Concentration of fluoride in ground water in southwest Florida.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 31

fluoride generally increases from the northern boundary of the Peace
River -basin district, both westward into Hillsborough County and
southward into Hardee County.
In Hardee County the concentration of fluoride is slightly higher
than in Polk and Hillsborough -and generally ranges from 0.5 to 1.5
ppm. The fluoride concentration in the western part of the county is
slightly higher than in the eastern part. Further south in DeSoto County,
the concentration of fluoride may be more than 2.0 ppm. The concen-
tration of fluoride in many wells in Charlotte, Sarasota, and Manatee
counties ranges from about 1.0 to 3.0 ppm.
There are many exceptions to these generalities on areal distribu-
tion of fluoride in ground water. Most of the variations can probably
be attributed to vertical hydrologic zonation of the aquifer system and
the amount of water produced from each zone in a particular well,
to local deviations from the generalized areal ground water flow pat-
terns, and to variations in the amount of fluoride source minerals avail-
able in the rocks.
North-south cross sections, located along the lines shown in figure
12, are shown in figures 13 and 14 to illustrate the vertical zoning of
concentrations of fluoride in ground water. These sections also sub-
stantiate the general southward increase in concentrations of fluoride
shown on the map in figure 11. The higher concentrations of fluoride
generally occur at shallower depths.
Because the sections were constructed by projecting well locations
as much as 5 miles and because only a few geologic control points
were used, the wells are not all finished in the geologic formations
exactly as shown. It is evident, however, that the higher fluoride con-
centrations are in water from the Hawthorn Formation and Tampa
Formation and possibly from the upper part of the Suwannee Lime-
stone. This is best shown by wells with only a small producing interval
or where samples were collected at different depths while the well was
being drilled.
This zonation of high fluoride concentrations in the more shallow
formations strengthens the conclusions of Woodard (1964) that the most
probable source of the fluorides are the fluoride-bearing phosphate min-
erals in the Hawthorn Formation and Tampa Formation. No attempt
was made to relate the fluoride concentration in ground water to the
percent of phosphate minerals in the rock at different locations; how-
ever, such a relation appears likely.
It is also evident from figures 13 and 14 that the fluoride concentra-
tion in any location may'depend on the vertical movement of ground






REPORT OF INVESTIGATIONS No. 46


Figure 12.-Location of cross sections A-A' and B-B'.


water as well as the lateral. movement. If there is vertical hydraulic
connection between all formations and water movement is downward
(recharging conditions), fluoride in water would tend to move down-
ward to the underlying formations. If the vertical movement is upward
(discharge conditions), however, the fluoride concentration should rep-
resent, in part, that from water which has moved upward from the
lower formations. Geohydrologic environments favorable to both con-
ditions occur in the area. Discharge occurs through springs and prob-







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 33



A -i Ai '


B S [ .-e f i t .. ..i.-- f i--
-200 I i ,A 1 I--' o A -
-I, -,




l -600-- .-'i oi- NI2 r- o -1 -
,' I-Ig ud at-- e I I --- : It
,I 4 .-0 '- I _
1'I A "'I









and Peace riv I/. a e omcu legcollecled fum flowing ...... difge ect
,I l 0\0 -- "I Ih : dephs di "" drillng
a y fr th e. T B Somple ctllecled from seoop er oi different
oiw .ha b od fine represents producing int of well
I i Ii- I ,--00 .
sI II






-1400 f ior I I iter t


t G Well use d c for geologic control


io o t Number is fluoride conccntroionin p
Sdretl to the streak a the wer reahes dof both the ifi
iand Peae e re 1 ours along much of the ridgo te s rectio






away from the river. The general effect of these opposing conditions
on water quality has been noted in figure 10 by the indentatio n of the
contours of high dissolved solids along the lower reaches of the rivers.
As conentrations of fluoride in ground water are relatively low and
variable, it is difficult to evaluate these various: factrs on the oncen- .
traction of f13.-Cruoride at a particular geoloic formations and fluoride concentrationsn.
Thably directly to the streams along the lower reachells of both the Alsurficia
and Peace rivdeters.mined at 30 loccurations yearlong the active phosphate sectminingon
away from the river. The distribution of wells sampled and these opposing conditions
fluorideon water quality has been noted in figure 15. Fluoride by thin watiner from the surf thcial




macontours of high dissolved from 0.0 to 1.0 ppm. The numblower reaches of shallow wells
available for stamping is limiicult to evaluated, because mvarious factorwells are fin tished in then-
tration of f-luoride at a particular location.
The ~fluoride content of water from shallow wells in the surficiak
sands 1as determined at 30 locations near the active phosphate mining





underlying limestone; however, it can be concluded from figure 15 that
there is no widespread occurrence of high fluoride concentration in water
in the surficial sands. However, the data shown in figure 15 do not pre-






REPORT OF INVESTIGATIONS No. 46


-- l o i




I .. I tole, ---od. ioi --
I --- ,, '-; ..7- -. 1,----








in. .epth ia pror
.. 0 0 4 --- 'oui ,C
N e To It t I boA 1l 0 I



r GIQ ^ "--1 0 .2 1" B ... dr











elude any contamination of the shallow ground water on a local scale.
Generally, there are no wells available for sampling near the phosphate
mines, chemical plants, and settling lagoons, the places where local
contamination of shallow ground water would be expected.
From the maps (figs. 11 and 15) and sections (figs. 13 and 14),
the following general conclusions can be made about the occurrence
of fluoride in ground water in southwest Florida. Fluoride concentra-
tions of 2 ppm or more are confined to waters in the Hawthorn For-
mation and Tampa Formation and possibly in the upper part of the
nnee Limestone; uoride concentrations in the social materials









and in the underlying limestone in the areas of active phosphate mining
are low (generally less than 1.0 ppm); widespread pollution of the
,EXPLANATION
. 1400 --- os section B-B shooG f a t'sa d fuori gelogc control
















r d water by uoride is not evident; and the formations that have








high fluoride concentrations in interstitial water are the formations that
contain phosphatic minerals, and these are the probable source of the
luoride in the water. If contamination of the shallow ground water by fluoride
contamination of shallow ground water would be expected.
From the maps (figs. 11 and 15) and sections (figs. 13 and 14),
the following general conclusions can be made about the occurrence
of fluoride in ground water in southwest Florida. Fluoride concentra-
tions of 2 ppm or more are confined to waters in the Hawthorn For-
mation and Tampa Formation and possibly in the upper part of the
Suwannee Limestone; fluoride concentrations in the surficial materials
and in the underlying limestone in the areas of active phosphate mining
are low (generally less than 1.0 ppm); widespread pollution of the
ground water by fluoride is not evident; and the formations that have
high fluoride concentrations in interstitial water are -the formations that
contain phosphatic minerals, and these are the probable source of the
fluoride in the water. If contamination of ground water by fluoride






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Figure 15.-Fluoride concentrations in shallow wells in the phosphate mining area in
southwest Florida.

occurs from the mining and processing of phosphate rock, such con-
taminations apparently are local and not evident from the areal ap-
proach used for this investigation.

POLLUTION POTENTIAL AND PHYSICAL
CHEMISTRY OF FLUORIDE
The general mining and processing of the phosphate ore do not
appear to be causing widespread contamination of the ground water
supplies. The greatest potential hazard to ground water would appear
to be the settling lagoons at the chemical plants which receive water
containing several hundred ppm fluoride (see analysis table 3). The






REPORT OF INVESTIGATIONS No. 46


lagoons become lined with the fine waste material from the operation
which inhibits leakage to the aquifer. Even if leakage does not occur,
waste waters might enter the aquifer by collapse of the surficial mate-
rials into solution chambers in the underlying limestone as happens in
the formation of many sinkholes in Florida and has happened in Polk
County.
Prediction of what would happen to the fluoride, should it enter
the aquifer from the lagoons, involves (1) a detailed knowledge of the
hydrology and geology of the aquifer near and down gradient from the
lagoons and (2) knowledge of the chemical changes exacted upon the
wastes by the laws of chemical equilibrium when they reach the aquifer
environment.
The flow patterns in the aquifer near the waste disposal lagoons
probably could be delineated satisfactorily by detailed hydrologic in-
vestigations. This would involve extensive drilling and testing to deter-
mine the direction a contaminant would move away from a point where
it was injected into the aquifer and the general geometric shape the
moving mass would assume.
Little experimental work has been done, however, on the role of
chemical reactions of contaminants with the minerals and water which
they encounter, particularly on what may happen to a fluoride contam-
inant in a limestone aquifer.
Aumeras (1927), reported in Hem (1959), states that fluoride is
soluble in pure water at 250 C. to the extent of 8.7 ppm fluoride. For
such a sparingly soluble compound as calcium fluoride, this information
is sufficient to calculate a "solubility product" for the compound. The
principle of a solubility product is useful in investigating the geochem-
istry of ground water and recently has been applied to saturation studies
of calcium carbonate in ground water (Back, 1961, 1963; Hem, 1961).
The significance.of the solubility product is that "when a solution
is at equilibrium with a given salt, the product of the activities (or
concentrations) of its constituent ions, raised to the appropriate powers,
must be constant" (Glasstone, 1946, p. 490). Because calcium fluoride
(CaF2) requires two fluoride ions to balance each calcium ion the ap-
propriate power for the fluoride concentration is 2 and the equation
for the solubility product (K) is
K C = Ca++ X(F-)2

where Ca++ and F- represent the molal concentrations of calcium and
fluoride.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 37

Both temperature and the concentration of all constituents in solu-
tion affect the solubility constant (K). For the range of temperature
of most ground water the effect is small and the standard temperature
of 770 F. may be used for this area. The effect of concentrations of
other ions in solution requires the use of activities of Ca++ and F-
instead of concentrations as given in the above equation.
The effect of other constituents in solution is to suppress the effec-
tive activity of an ion below that expressed by the concentration of
the ion. This effect is related to the ionic strength of the solution which
can be calculated from the concentration and the valence of the ion
in the solution by:
M = MiZI + M Z2 + 3MZ .
where A = ionic strength
M = molal concentration of each constituent
Z = valence of the ion in solution
From the ionic strength a number can be calculated which, when
multiplied by the concentration of an ion, will give its effective activity.
This number will be less than 1.0 and is called the activity coefficient.
Hem (1961) gives in detail the calculations to obtain ionic strengths
and resulting activity coefficients along with nomographs to eliminate
many of the calculations.
Figure 16 shows the relation of the activity coefficient of calcium
and fluoride to the ionic strength of a solution. The ionic strength may
be obtained from the above quotation or from nomographs given in
Hem (1961, plate I), either of which requires a chemical analysis and
considerable calculations. As the ionic strength depends only on the
type and amount of dissolved material and as most natural water con-
tains only a relatively few major constituents, a fair approximation of
the ionic strength can usually be obtained from a measure of the dis-
solved solids.
Pure water is a poor conductor of electricity. The dissolved material
in the water that conducts electricity and the specific electrical conduc-
tance is a good indicator of the amount of dissolved solids. Figure 17
shows the relation of ionic strength to specific electrical conductance of
several ground water analyses. Most of the points on the graph rep-
resent samples of ground water from Florida except those above 2,000
micromhos which are analyses from the literature and which had rel-
atively high fluoride concentrations. The specific electrical conductance
multiple by a factor of 0.60 gives a good approximation of the dissolved
solids content of ground water in southwest Florida.








OJ














0.01





C3
c
c
o

C
0


LLi


1Ilif11fi


ilifIIIIIfI I


REPORT OF INVESTIGATIONS No. 46
ItI I Ir TTTFFt F FII III I l T I l IT II I lII 1T1 111111











F-/

Co++







/t


u.uu


09 0.8 0.7 0.6 0.5 0.4
Activity coefficient (a)
Figure 16-Relation of the activity coefficient of calcium and fluoride to ionic strength
of a solution.


,t 11111t


u~uur


r I I I III I It I I l


1000E
.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 39

Utilizing the activities of the ions in solution, the solubility product
for calcium fluoride becomes
K c= aCa++ X (aF-)2

where K caF = equilibrium constant for calcium fluoride

a = activity coefficient for the ions
Ca++ and F- = molal concentrations of the ions


Specific electrical


0.10












0.
















0.001
10


1000
conductance, micromhos


Figure 17.-Relation of ionic strength to the specific conductance of some ground waters.


The Handbook of Chemistry and Physics (1954, p. 1634) gives the
solubility product of calcium fluoride at 260 C. (78.80 F.) as 3.95 x
10-11. Using this value and assuming that ground water system is at


______ ____ __ __ ___ _______ ___ _____ __ __- z p ::z z~
SI I_________ ___________










AS
J0
_






/
_____-
= = = = : == = = = =
==^^::=====:=

-^: rill
!^---


10,000


0






REPORT OF INVESTIGATIONS No. 46


chemical equilibrium, the maximum fluoride concentration for any given
calcium concentration in a saturated solution may be calculated by:
V 3.95X10--n

aCa++
F- =
1 ^----- ----
aF-
Figure 18 shows a set of curves for a saturated solution of calcium
fluoride with respect to fluorite at several ionic strengths. An ionic
strength of 0.10 is considered about the maximum at which the above
calculations hold (Hem, 1961). From figure 17 this is seen to be at
a specific conductance of about 8,000 micromhos (4,800 ppm dissolved
solids). The lowest curve is a theoretical curve for ionic strength (/L)
equal zero and activity coefficients (a) equal one. For potable ground
water in southwest Florida, the practical curves to consider are from
about ionic strength of 0.002 to 0.02 or about 70 to 900 ppm dissolved
solids.
Figure 18 shows analyses of fluoride versus calcium from ground
water in Florida. The dots represent samples from the Peace and Alafia
River basins that contain more than 0.5 ppm fluoride. The triangular
points represent samples from northwest Florida (Toler, 1966) and are
included to show that the solubility product principle apparently holds
for higher fluoride concentrations.
Most of the points in figure 18 plot to the left of the family of equi-
librium curves showing the water to be undersaturated in fluoride with
respect to fluorite. Those points falling within the family of curves are
from analyses of ground water of relatively high ionic strength. They
also plot to the left of the saturation position for the ionic strength of
that sample and are undersaturated. Figure 18 shows graphically that
the product of the activities of calcium and fluoride in ground water
in Florida approaches, but does not exceed, the theoretical values based
on the concept of chemical equilibrium.
From the concept of the solubility product principle and the analysis
of the graph in figure 18, it is apparent that large concentrations of
fluoride in ground water at equilibrium are limited by the amount of
calcium present. This is significant in southwest Florida where ground
water is obtained from limestone rocks and generally has high calcium
concentrations. For a calcium concentration of 40 ppm and an ionic
strength of 0.01 (dissolved solids about 420 ppm), the maximum fluoride
concentration at equilibrium would be 5 ppm. The role that solubility
would play in event of contamination by water of extremely high fluoride
concentrations makes the reaction important. If contaminating water,
high in fluorides entered the aquifer, the water would quickly become






FLUOIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Fluoride, ports per million
Figure 18.-Scatter diagram of calcium versus fluoride for analyses of ground water in
southwest and northwest Florida and graphs showing the relation of calcium
to fluoride in solutions of different ionic strength saturated with respect
to fluoride.


supersaturated with respect to fluorite. The tendency for the water to
reach equilibrium and satisfy the solubility product should cause chem-
ical precipitation of calcium fluoride in the aquifer and thereby remove






REPORT OF INVESTIGATIONS No. 46


fluoride from solution. Both chemical precipitation and dilution should
act to reduce the concentration of fluoride.
If the assumption is made that, because of its slow movement, ground
water has sufficient time to come to equilibrium with the solid phases
it contacts, and that an unlimited supply of calcium is available from
the limestone aquifer, then the concept of chemical equilibrium can
aid in making a first approximation about the fate of a fluoride contam-
inant that might be introduced into the aquifer.
Many other factors must be considered to predict what might hap-
pen to a contaminant after it enters ground water. LeGrand (1965)
discussed the difficulties involved in making such predictions, and sum-
marizes the present knowledge about the patterns of contaminated zones
of water in the ground. His interpretations of various types of contam-
inated zones are generally some modification of a rectangular prism or
a wedge which forms in the upper part of the zone of saturation.
LeGrand states (p. 83): "Two opposing tendencies need be in focus
before an evaluation of contaminated zones is undertaken: (1) the
tendency of contaminants to be entrained in ground water flow and
(2) the tendency for contaminants to be attenuated to varying degrees
by dilution in water, decay with time, or some other 'die-away' mech-
anism, and sorption on earth materials." The mechanisms of attenuation
of a fluoride contaminant in a limestone aquifer would be largely dilu-
tion and chemical precipitation of fluoride as calcium fluoride.

MONITORING OF FLUORIDE IN GROUND WATER
The areal (fig. 11) and vertical (figs. 13 and 14) distribution of
fluoride in ground water gives no indication of any significant contam-
ination of the ground-water supplies. Because there is presently (1966)
no indication of widespread contamination, any feasible system of mon-
itoring fluoride in ground water that was designed to include all the
phosphate mining area would probably be ineffective and fail to quickly
detect a contaminating mass of fluoride should it enter the aquifer.
If any system of monitoring any contaminant in ground water is to
be effective, it must be capable of quickly detecting the contaminant
near its point of entry into the ground. Therefore, any system of mon-
itoring fluoride in ground water that will quickly and effectively detect
any contamination of the ground-water supplies should be designed in-
dividually around the greatest potential hazards, the chemical plant
settling lagoons.
The lagoons may cover several hundred acres. A detailed investiga-
tion of one or more lagoons would be desirable to (1) firmly establish






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RPER BASINS 43

whether there is leakage to the aquifer or through the banks to the
surrounding area, (2) determine effects of leakage, if any, on the gra-
dient of the water table and piezometric surface, and (3) acquire data
to prepare hydrogeologic maps adequate for making accurate predic-
tions of local ground-water flow patterns. After sufficient detail of the
hydrology in the vicinity of a lagoon is established, monitoring wells
could be located so they would be most effective. They should be along
the down gradient side of the lagoons with respect to the piezometric
surface and the water table and be constructed to enable collection of
water samples from the surficial materials, the top of the artesian aqui-
fer and from a deeper zone in the aquifer.

SUMMARY
Fluoride concentrations of several parts per million occur in the
surface waters of the Alafia and Peace River basins as a result of waste
water disposal from the mining and processing of phosphate deposits.
The Alafia River carries more fluoride waste than the Peace River and
usually has a fluoride concentration several times as high as the Peace
River.
The Alafia River discharged about 4,000 tons of fluoride from October
1964 to September 1965 compared to about 900 tons for the Peace River.
During this same period, the fluoride concentration of the Alafia River
at Lithia ranged from 3.2 to 30 ppm and the Peace River at Arcadia
ranged from 0.6 to 2.2 ppm. There was no apparent loss of fluoride from
the river to the ground water.
Fluoride occurs naturally in ground water in southwest Florida in
concentrations from 0.0 to about 4.0 ppm. The concentration of fluoride
in ground water is generally lowest in northern and central Polk County
and is generally highest in the southern part of the area. There is both
areal and vertical variability in fluoride concentrations. The highest con-
centrations are usually found in water from the Hawthorn Formation
and Tampa Formation of Miocene age. The source of the fluoride is
apparently the phosphate minerals within the formations.
The waste water in the settling lagoons at the phosphate chemical
processing plants contains fluoride concentrations of several hundred
ppm. Fine waste material deposited in these lagoons appears to retard
leakage of the waste water to the aquifer. The lagoons are a potential
pollution hazard if the fine waste material is not effective in preventing
leakage, or if solution of the underlying limestone should allow collapse
of the surface materials into solution chambers to breach the fine de-
posits. If such should occur, the fluoride could contaminate the ground-






44 REPORT OF INVESTIGATIONS No. 46

water supplies for several miles from the point of entry into the aquifer.
Any system of monitoring fluoride in ground-water should be de-
signed about the chemical plant settling lagoons to best detect a possible
fluoride contaminant. A detailed investigation is desirable to firmly es-
tablish the geologic-hydrologic conditions in the vicinity of one or more
of the lagoons. Such an investigation would establish the best proce-
dures to be followed in designing an effective monitoring system for
ground water. Experimental investigation of the fate of solutions con-
taining high concentrations of fluoride when they enter a limestone
environment is essential to predict the effects on ground water should
water from the lagoons enter the ground.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Aumeras, M.
1927

Back, Willian
1961

1963

Barraclough,
1962

Cathcart T. I


REFERENCES

Equilibrium of calcium fluoride and dilute hydrochloric acid: Jour.
Chem. Phys., v. 24, p. 548-571.

Calcium carbonate saturation in ground water from routine analyses:
U.S. Geol. Survey Water-Supply Paper 1535-D.
Preliminary results of calcium carbonate saturation of ground water
in central Florida: Internat. Assoc. Sci. Hydrology, v. VIII, No. 3.
J. T.
(and Marsh, O. T.) Aquifers and quality of ground water along the
Gulf Coast of western Florida: Fla. Geol. Survey Rept. Inv. 29.
B.


1959 (and Lawrence, J. M.) Results of geologic exploration by core drilling,
1953, land pebble phosphate district, Florida: U.S. Geol. Survey
Bull. 1046-K.
Florida State Board of Health
1955a Peace and Alafia Rivers, stream sanitation studies 1950-1953: Volume
I, The Alafia River, Fla. State Bd. of Health, Jacksonville, Florida.
1955b Peace and Alafia Rivers, stream sanitation studies 1950-1953: Volume
II, The Peace River, Fla. State Bd. of Health, Jacksonville, Florida.
Glasstone, Samuel
1946 The elements of physical chemistry: D. Van Nostrand Co., Inc.,
Princeton, New Jersey.
Handbook of Chemistry and Physics
1954 The 36th edition: Chemical Rubber Pub. Co., Cleveland, Ohio.
Hem, J. D.
1959 Study and interpretation of the chemical characteristics of natural


water: U. S. Geol. Survey Water-Supply Paper 1473.
1961 Calculation and use of ion activity: U.S. Geol. Survey Water-Supply
Paper 1535-C.
Johnson, Lamar
1960 A report on a plan of improvement for the Peace River Valley:
Peace River Valley Water Conserv. and Drainage Dist., Consult. Eng.
Rept.
1963 A basic plan for the Alafia River basin: Alafia River Basin Bd.,
Consult. Eng. Rept.
Joyner, B.F. (See Sutcliffe, H.)


Lanquist, Ellis
1955


Lawrence, J. M.
LeGrand, H. E.
1965

McKee, J. E.
1963

Menke, C. G.
1961

Meredith, E. W.
Peek, H. M.
1958

Shattles, D. E.
1965


A biological survey of the Peace River, Florida, Peace and Alafia
Rivers, stream sanitation studies, supplement II to volume II: Fla.
State Bd. of Health, Jacksonville, Fla.
(See Cathcart, J. B.)

Patterns of contaminated zones of water in the ground: Water Re-
sources Research, v. 1, no. 1, p. 83-95.

(and Wolf, H. W.) Water quality criteria, second edition: The Re-
sources Agency of Calif., State Water Quality Control Bd., Pub. No. 3-A.

(Meredith, E. W., and Wetterhall, W. S.) Water resources of Hills-
borough County, Florida: Fla. Geol. Survey Rept. Inv. 25.
(See Menke, C. G.)

Ground water resources of Manatee County, Florida: Fla. Geol. Survey
Rept. Inv. 18.

Quality of water from the Floridan aquifer in Hillsborough County,
Florida, 1963: Fla. Geol. Survey Map Series No. 9.






REPOTr OF INVESTIGATIONS No. 46


Specht, R. C
1950 Phosphate waste studies: Fla. Eng. and Ind. Exper. Sta. Bull. No. 32.
1960 Disposal of wastes from the phosphate industry: Jour. Water Poll.
Control Feder., v. 32, No. 9, p. 964-974.
Satcliffe, .L
1966 (and Joyner, B. F.) Packer testing in water wells near Sarasota,
Florida: Ground Water, Jour. Tech. Div. Nat. Water Well Assoc.,
v. 4, No. 2, p. 23-27.
Toler, L. G.
1966 Fluoride content of water from the Floridan aquifer in northwestern
Florida: Fla. Geol. Survey Map Series No. 23.
United States Public-Health Service
1962a Fluoride drinking waters: U.S. Public Health Serv. Pub. 825.
1962b Drinking water standards: U.S. Public Health Serv. Pub. 956.
Wetterhall,W. S. (See Menke, C. G.)
Wolf, L W. (See McKee, J. E.)
Woodard, H. J.
1964 Preliminary report on the geology and ground water resources of
Hardee and DeSoto counties: Fla. Div. Water Resour. and Cons. Pub.




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Title: Fluoride in water in the Alafia and Peace River basins, Florida ( FGS: Report of investigations 46 )
Series Title: ( FGS: Report of investigations 46 )
Physical Description: 46 p. : ;
Language: English
Creator: Toler, L. G
Publisher: n.p.
Place of Publication: Tallahassee
Publication Date: 1967
 Subjects
Subjects / Keywords: Water -- Fluoridation -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by L. G. Toler. Prep. by the U. S. Geological Survey in cooperation with the Southwest Florida Water Management District and the Florida Geological Survey.
Bibliography: Bibliography.
 Record Information
Source Institution: University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000957328
oclc - 01722521
notis - AES0064
System ID: UF00001233:00001

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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY




FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director




REPORT OF INVESTIGATIONS NO. 46




FLUORIDE IN WATER IN THE ALAFIA AND

PEACE RIVER BASINS, FLORIDA




By
L. G. Toler








Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
and the
FLORIDA GEOLOGICAL SURVEY


TALLAHASSEE, FLORIDA
1967








Zli (

AGRI-
CULTURAL
UBRARY

FLORIDA STATE BOARD


OF


CONSERVATION







CLAUDE R. KIRK, JR.
Governor


TOM ADAMS
Secretary of State




BROWARD WILLIAMS
Treasurer




FLOYD T. CHRISTIAN
Superintendent of Public Instruction


EARL FAIRCLOTH
Attorney General




FRED O. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director








LETTER OF TRANSMITTAL


A


I-"
C


Tftorida geoloOicd S4rvey

TALLAHASSEE
April 27, 1967

Honorable Claude R. Kirk, Jr., Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Kirk:
The Division of Geology of the Florida Board of Conservation is
publishing, as Report of Investigations No. 46, a study of the quality
of water as found in the Alafia and Peace River Basins, Florida. The
report, entitled "Fluoride in Water in the Alafia and Peace River Basins,
Florida," was prepared by L. G. Toler, of the U.S. Geological Survey,
in cooperation with the Southwest Florida Water Management District
and the Division of Geology.
You will recognize that waste water from phosphate chemical plants
in the tributary headquarters of these two basins contribute waste
products, including fluorides, to the river water. Fluoride concentrations
range from 3.2 to 30 parts per million in the Alafia River, and .6 to 2.2
parts per million in the Peace River. While the concentration in the
Peace River is probably beneficial, that contained in the Alafia River
is excessive for human consumption.
It is hoped that a detailed investigation of some of the plant opera-
tions and settling lagoons will establish the geologic and hydrologic con-
ditions necessary to control these wastes more effectively.
Respectfully yours,
Robert 0. Vernon
Director and State Geologist




















































Completed manuscript received
April 27, 1967
Published for the Florida Geological Survey
By St. Petersburg Printing Company
St. Petersburg, Florida


iv








CONTENTS


Page
Abstract ........... ............... ............ ...... 1
Introduction .......................---.......... ..............------------------- 2
Purpose and scope ........-..............-------------- -......... --... -.. -.....--...-.. 2
Description of the area...............................-- ------ -------------- 2
Previous work .... -----............... -----........ .... --------------..........-....................... 6
Phosphate mining and processing ..---..-........-.. ----..---.....- ..--- ..--- 8
Significance of fluoride and associated waste products in water ........................................ 10
Fluoride ...-........-..............------------------ ---------- ....----................. 10
Phosphate .-------..........---------------------------------------- ...---- --------. 11
pH ...-..........--......-----------------.-.....................- 12
Turbidity .....----......... -------------- -------- ------------- 13
Geochemistry of fluorine .....--.....--. ...... .....--- -------------------- 13
Surface water ......---.............-------------------.....-- ..-- 14
Ground water ..-- ........--------------------------------- 26
General geohydrology -.......----....-......--.--------- --------------.....-.-- 26
SFluoride distribution --.............----.. ----....... .................----.--- 29
Pollution potential and physical chemistry of fluoride ........--------.................. .......... 35
Monitoring of fluoride in ground water ..------......- ... ...................---------------- 42
Summary ......-....---............--- ..-...--.------- .. --.---...---.--- 43
References .........-----------.-------...----------....-..-.------ 45






















V











ILLUSTRATIONS
Figure Page
1 Location of the Alafia and Peace River basins ........................................... ...... 3
2 Location of sampling sites on streams and area of phosphate mining
and processing ........ ............................. ...................................................... ............. 4
3 Frequency curves of specific conductance and concentration of fluoride
for the Alafia River at Lithia .................................................................................. 16
4 Frequency curves of pH and concentration of phosphate for the Alafia
River at Lithia ................................. ........................................... ................................ 17
5 Discharge and concentrations of fluoride and phosphate for the Alafia
River at Lithia from October 1964 to September 1965....................................... 18
6 Discharge and concentrations of fluoride and phosphate for the Peace
River at Arcadia from October 1964 to September 1965...........------ .....-........---... 19
7 Fluoride load in streams in Alafia and Peace River basins during
periods of low and high flow 1965........----..........----.....................------------.. 24
8 Dissolved fluoride load of the Alafia River at Lithia and the Peace
River at Arcadia from October 1964 to September 1965..........-............... ..... 25
9 Piezometric surface of the Floridan aquifer in southwest Florida
in January 1964 ...................................---.....- -....... -------.......................---- 27
10 Dissolved solids concentration in the Floridan aquifer in southwest
Florida .............................-.......--- ..........--..... .......................--- ------------- 29
11 Concentration of fluoride in ground water in southwest Florida .......................... 30
12 Location of cross sections A-A' and B-B' .-.................-- .... ........------....-- 32
13 Cross section A-A' showing geologic formations and fluoride con-
centrations in ground water .... ...... ................................. ...-.. 33
14 Cross section B-B' showing geologic formations and fluoride con-
centration in ground water ..... --- ----.............. .............-. .-..-- 34
15 Fluoride concentrations in shallow wells in the phosphate mining area .--............ 35
16 Relation of the activity coefficient of calcium and fluoride to ionic
strength of a solution ...-......-------------.------....... 38
17 Relation of ionic strength to the specific conductance of some ground
waters ......----.-------------------- 39
18 Scatter diagram of calcium versus fluoride for analyses of ground
water in southwest and northwest Florida and graphs showing the
relation of calcium to fluoride on solutions of different ionic strength
saturated with respect to fluorite .........................-------.-------.------------- 41



TABLES
Page
Table 1. Sampling sites, drainage areas, and discharge data for streams .-...--..........-- 5
2. Chemical analyses of surface waters in the Alafia and Peace River
basins during periods of relatively low and high discharge .......--..-....- ....... 21
3. Chemical analysis of water from a phosphate chemical plant
settling lagoon, Polk County, Florida ..................---------.- ....--- -- 23
vii










FLUORIDE IN WATER IN THE ALAFIA AND
PEACE RIVER BASINS, FLORIDA

By
L. G. Toler

ABSTRACT
Waste water from phosphate chemical plants in the tributary head-
water areas contributes fluoride and other waste products to the Alafia
and Peace rivers.
The fluoride concentration of the Alafia River at Lithia, Florida,
ranged from 3.2 to 30 ppm (parts per million) and the Peace River at
Arcadia, Florida, ranged from 0.6 to 2.2 ppm in samples of water collected
daily from October 1964 to September 1965.. The natural fluoride con-
centration in streams in the Alafia and Peace River basins generally
ranged from 0.2 to 0.4 ppm as determined from analysis of water from
streams away from the active areas of mining and processing of fluoride-
bearing phosphatic minerals.
Most of the waste water from the phosphate chemical plants is routed
to lagoons (gypsum ponds) where the solids settle out and the water
circulates for reuse. High concentrations of fluoride and phosphate in
samples of surface water at sites downstream from the phosphate chemical
plants indicate that some waste water enters the streams continuously.
Analysis of the relation between concentration of fluoride, dissolved
fluoride load, and discharge of the streams suggests that much more
waste water is released to the streams during periods of high discharge
than during periods of low discharge. Overflow of the settling lagoons,
flushing of naturally ponded water from flat headwater areas or con-
trolled release of water of high fluoride content during periods of high
discharge could account for the observed relations.
Fluoride in waste water has apparently not entered the ground in
sufficient quantity to cause widespread increases in the concentration
of fluoride in ground water. Fluoride does occur naturally in ground
water and ranges from 0.0 to about 4.0 ppm. The concentration of
fluoride in ground water is highest in water from the Hawthorn Formation
and Tampa Formation of Miocene age. The fluoride apparently dissolves
from the fluoride-bearing phosphatic minerals in the rocks.
The areal approach used in this investigation did not resolve whether
contamination of ground water by fluoride occurs locally. The greatest
potential hazard to ground water appears to be the chemical plant
settling lagoons.






REPORT OF INVESTIGATIONS No. 46


Predictions of the zonal pattern of a fluoride -contaminant in the
ground requires a knowledge of the ground-water flow patterns and
the effects of any chemical reactions between the fluoride and the water
and rocks in the ground. A detailed investigation of one or more of the
chemical plant settling lagoons is desirable to establish the geologic-
hydrologic conditions and ground-water flow patterns in the vicinity
of the lagoons. The chemical reactions between water of high fluoride
content and water in a limestone aquifer need investigation.

INTRODUCTION
PURPOSE AND SCOPE
The use of the Peace and Alafia rivers to dispose of phosphate and
other wastes has caused local and statewide concern about contamination
of the river water. Recently, this concern has been expanded to include
the possible effects on ground-water supplies, should the contaminants
enter the ground and mix with the fresh water. This report is a product
of an investigation with the general objectives of appraising the problem
of contamination and evaluating the need for additional investigations.
The specific objectives of this report are to determine to what degree,
if any, ground-water contamination has occurred; evaluate the effects
of fluoride from phosphate mining and processing on ground water;
determine the quantity of selected constituents being wasted to the
streams; examine the effect of these constituents on the quality of water
in the streams; and determine some system of monitoring wastes in
streams and ground-water supplies.

DESCRIPTION OF THE AREA
The Alafia and Peace rivers both have their headwaters in Polk
County, Florida. They have a combined drainage area of 2,820 square
miles and discharge an average total of about 1,500 million gallons
of water per day to the Gulf of Mexico. The locations of the basins
within the state are shown in figure 1. Figure 2 shows the drainage
patterns of the streams and the political boundaries of the Peace and
Alafia River Basins Boards. The political boundary of the Alafia Basin
Board (fig. 2) encompasses the drainage area of the Alafia River and
part of the Little Manatee River. Drainage areas and a summary of
flow statistics are included in table 1. For the Peace River the political
boundary closely approximates the natural drainage divide. In the
headwater area, the drainage divide is not always well defined but
may be in flat swampy areas where the direction of flow is governed







FLUORIDE IN WATER IN THE ALAA AND PEACE -RVER BASINS


/7


EXPLANATION


River basin
River basin
Boundary


0 10 20 30 40 50miles
oa -.


Figure 1.-Location of the Alafia and Peace River basins.


Im1 Alofio
Peace
Basin








REPORT OF INVESTIGATIONS No. 46


by the amount of rainfall on different parts of the area. South of
Bartow, the main stem of the Peace River has a well-defined channel.

Drainage is dendritic except where altered by strip mining for phos-
phate. The river flows southward from Polk County through Hardee
and DeSoto counties and into Charlotte Harbor in Charlotte County.


-6. a-Inem-V-3 _mec*nsci
Sa \ 'sota


EXPLANATION nk
| Phosphate mMne
c PhasphOle chemical pant
a* ai dnlischarge or stage.
daily samples
3 Daiy discharge or stage,
periodic samples
S Periodic discharge measurements
anid samples
S Periodic samples, no
discharge data
Approximate boundary of calcium
Sphosahate zone (after Cathcart
/ and Lawrence .959, p223)
S Cawage dride
Z3 'a er of site as listed in table 1.
-LBoundary. Peace and Alafri Basin Boards

Wd


6 5o s Ia s 1Oni


45' 81'3


Figure 2.--Location of sampling sites on streams and area of phosphate mining and
processing.

The U.S. Geological Survey has maintained gaging stations on the
main stem of the Peace River at Bartow for 26 years, at Zolfo Springs
for 32 years, and at Arcadia for 34 years prior to September 1965.


Beo00








FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 5

TABLE 1.--Sampling sites, drainage areas, and discharge data for streams.
I discharge measurements made at time sample collected.
P periodic, about 8 times per year.
D --daily.
Dates refer to water year ending September 30
Frequency
Discharge Average of
Drainage area record Discharge sampling
Number Station name square miles began cfs 1961-1966
ALAFIA RIVER BASIN
1. North Prong Alafia River
at Mulberry 1964 I P
2. North Prong Alafia River
at Keysville 135 1950 185 P
3. English Creek near Mulberry 1964 I
4. South Prong Alafia River P
near Lithia 107 1962 109 P
5. Turkey Creek near Durant 15 1964 P
6. Alafia River at Lithia 335 1933 385 D
7. Alafia River at Riverview None P
PEACE RIVER BASIN
8. Saddle Creek at Structure P-11 135 1964 P
9. Saddle Creek near Bartow None P
10. McKinney Branch near Bartow 1964 I P
P 1965
11. Peace River at Bartow 390 1939 313 D 1966
12. Sixmile Creek near Bartow 1964 I P
P 1965
13. Peace River at Fort Meade 465 1964 Stage only D 1966
14. Bowlegs Creek near Fort Meade 47 1964 P
15. Mill Branch tributary 1964 I P
16. Mill Branch near Fort Meade 1964 I P
17. Whidden Creek near Fort Meade 1964 I P
18. Paynes Creek near Bowling Green 121 1964 111 P
19. Peace River at Zolfo Springs 826 1933 772 D
20. Charlie Creek near Gardner 330 1950 335 P
21. Peace River at Arcadia 1,367 1931 1,280 D
22. Joshua Creek at Nocatee 132 1950 121 P
23. Peace River at Fort Ogden 1,790 1964 Stage only P

Table 1 summarizes the streamflow data for the basin. Total drainage


area of the basin is about 2,400 square miles.
The Alafia River has the headwaters of its


major tributaries, the


North and South Prongs, in the phosphate mining area of western Polk
County. These tributaries merge in eastern Hillsborough County to
form the Alafia River which flows westward into Hillsborough Bay.
Phosphate mining began in southwest Florida with the dredging
of river pebble deposits along the Peace River in the late 1800's.
Several periods of prosperity and depression have governed the rate
of development of the phosphate deposits. In the years following World
War II, the demand for phosphate and phosphate products has con-
tinually been on the upswing and the industry has flourished accord-
ingly. The Alafia and Peace rivers are the only streams that drain
the area of phosphate mining and they have received waste from the
industry.
Most of the waste products from the mining and processing of
phosphate rock do not reach the streams. The solid waste is retained
in settling lagoons and the clear water circulated for reuse. Never-
theless, a significant amount of waste water enters the streams, either






REPORT OF INVESTIGATIONS No. 46


directly or from overflow of the settling lagoons. The character of
the water in the settling lagoons depends on the source of the waste
water. Water from the mining operations is essentially sediment-laden
waste water and is not of bad chemical quality. Water from the
phosphate processing plants, however, may be of poor chemical quality.
These waste waters, which contain high concentrations of inorganic
chemicals acquired during the processing, have entered the streams
in sufficient quantities to cause water in some of the streams to be
unfit for some uses. In recent years, the increase in mining activity
and the increase in the number of chemical plants have increased the
volume of waste products dissipated to the streams.
The investigation was conducted by the U.S. Geological Survey
in cooperation with the Alafia and Peace River Basin Boards of the
Southwest Florida Water Management District as a part of the co-
operative program to evaluate the water resources of Florida with the
Florida Geological Survey, Division of Geology, Florida Board of
Conservation. The investigation was performed under the general
direction of C. S. Conover, District Chief, Water Resources Division,
US. Geological Survey.

PREVIOUS WORK
The Florida State Board of Health (1955a) reported the first com-
plaint about turbidity in the Alafia River from a resident at Riverview
in 1946. Subsequent investigations by various organizations, generally
sponsored by the phosphate companies, have resulted in a number of
reports on pollution of the rivers and recommendations for minimizing
pollution of the water.
Specht (1950) concluded the clear effluent from phosphate process-
ing was not deleterious to fish life. His work included experiments
with electrolytes to flocculate the colloidal phosphate slimes and reduce
the turbidity of effluent to the streams.
The Florida State Board of Health (1955a, 1955b) reported on the
results of investigations of the Peace and Alafia rivers during the
period 1950 to 1953. They recognize three major sources of pollution
in the Peace River; municipal and domestic sewage, the citrus process-
ing industry, and the phosphate mining and processing industry. They
divide the Peace River into two segments based on type and intensity
of pollution. The segment north of Homeland (about 5 miles south
of Bartow) was considered excessively polluted by organic and chem-
ical pollutants and the segment south of Homeland suffered only from
intermittent excessive inorganic turbidity and slime.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 7

Two major sources of pollution considered by the Florida State
Board of Health (1955b) for the Alafia River were domestic sewage
from cities and towns and the waste products from the phosphate
operations.
From 1953 to 1955 the major concern of the State Board of Health
about waste products from the phosphate industry was the turbidity
and slime from mining and washing operations of the phosphate ore.
The waste products from the phosphate processing plants were only
beginning to be a major source of pollution, especially in the Alafia
River basin. They recommended waste disposal be controlled so that
the pH of the rivers not be reduced below 5.0 and the concentration
of fluoride not exceed 5.0 ppm.
Lanquist (1955), as a part of the investigation by the State Board
of Health, made a biological survey of the Peace River. His conclu-
sion number 4 (p. 67) states that, "at times the effects of acid water
from the phosphatic fertilizer plant at Bartow produced near-sterile
conditions in Bear Branch, adversely affected the water-hyacinths and
fauna in the Peace River at Bartow and possibly affected the Crustacea
at P-11."
Specht (1960) described the mining of phosphate ore and process-
ing of the phosphate minerals to superphosphate, triple superphosphate
and elemental phosphorous. He also describes the methods employed
by the industry to reduce the turbidity, acidity, and fluoride content
of waste water discharged to the streams.
In preparing a basic plan for development of the water resources
of the Peace and Alafia rivers, Johnson (1960, 1963) recognized the
need for control of pollution of the rivers. He (1963. p.ii.) noted an
increase in the number of major phosphate chemical plants since the
survey by the State Board of Health in 1953 and presented data col-
lected by the State Board of Health (1963, p. 1-16, 1-18) to show an
increase in acidity and fluoride content of the Alafia River during the
ten-year interval.
Menke, Meredith, and Wetterhall, (1961) conducted an investiga-
tion of the water resources of Hillsborough County from 1956 to 1958.
Graphical presentations of fluoride and pH of the Alafia River at Lithia
for the period October 1957 to September 1958 show the fluoride con-
centration as high as 17 ppm but below the 5.0 ppm maximum set by
the State Board of Health about 65 percent of the time. The pH
during this period ranged from 5.5 to 6.7. They did not report on
fluoride in ground water but warned that: "Extensive use of Alafia Ri.er






REPORT OF INVESTIGATIONS No. 46


waters for irrigation could result in contamination of ground-water
supplies hydraulically connected downgradient from the irrigated land."
Woodard (1964) in a preliminary report on the geology and ground-
water resources of Hardee and DeSoto counties reported on the occur-
rence of fluoride in ground water in south peninsular Florida and
suggests that the geographic spread is controlled by the hydrology of
the area. The possibility is presented that the source of fluoride is the
phosphatic sediments of Miocene age and that the high fluorides are
confined to the upper part of the Floridan aquifer. In referring to the
piezometric surface of the Floridan aquifer, Woodard stated: "The
high pressure areas north and east of the phosphate deposits would
cause the fluorides entering the aquifer to move to the south and
west." He found no evidence which pointed to contamination of ground
water by the phosphate processing industry.
Shattles (1965) mapped with distribution of dissolved solids and
selected constituents in the Floridan aquifer in Hillsborough County.
He shows an increase in all constituents from the interior toward the
coast. Fluoride was not mapped though the fluoride content of water
from 25 of 28 wells sampled was below 0.8 ppm.

PHOSPHATE MINING AND PROCESSING
In the early days of phosphate mining on the Peace River only the
coarse phosphate pebbles were recovered by screening and the fine
material was wasted back to the stream. Later the discovery of "land
pebble" phosphate deposits that could be removed by strip-mining
methods moved the mining operations away from the river.
The "land pebble" phosphate deposits are located in a shield-shaped
area that covers large parts of Polk, Hillsborough, Hardee, and Manatee
counties and extends into Sarasota and DeSoto counties as shown in
figure 2. Most of the large mining operations are currently in Polk
and Hillsborough counties.
Advances in technology, which made it possible to remove thick
over-burdened deposits and to mine the phosphate ore below the water
table, and greater demand for phosphate opened large areas as economic
phosphate deposits. Improved methods of recovery, especially the intro-
duction of the flotation process to recover fine-grained phosphate, greatly
aided the growth of the phosphate industry.
The phosphate is mined by first removing the overburden, which
is as much as 60 feet thick, with large capacity draglines. The un-
derlying phosphate ore may be from 5 to 50 feet thick and consists
of a mixture of phosphate pebbles and granules, cobbles and boulders
of phosphatized limestone, quartz sand and silt, and clay.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 9

The phosphate ore is then deposited, by the dragline, into a shallow
pit from where it is sluiced to a pump through a four-inch grizzly.
The slurry formed by the sluicing operation is then pumped to the
washer which may be several miles from the mine. This pumping
operation requires large quantities of water which help to disaggregate
the ore but which must be separated during the washer operation and
disposed of or recycled.
The slurry from the mine goes through two processes to separate
the phosphate from the matrix. A combination of washing, scrubbing,
and screening separates the pebble phosphate larger than about one
millimeter from the fine grained matrix. The pebble phosphate is then
ready for shipment or chemical processing. The smaller material is
then separated by flotation. In the flotation cells the fine material is
treated to cause the phosphate particles to float off in an oily froth.
Reagents used are caustic soda, fuel oil, and a mixture of fatty and
resin acids. Some quartz sand is floated in this process and in a
second flotation cell the phosphate is selectively depressed by use of
an amine.
From the washing and flotation plants the water which still carries
the waste material from each stage of the process is pumped to large
settling areas. After the solids have settled the water may be reused
in the mining operation. Some of this water may be wasted to streams,
especially during the rainy season (Specht 1960). Because most of
the reagents used in the flotation process adhere to the minerals (State
Board of Health, 1955a, 1955b), the reagents probably are not a serious
source of stream pollutants.
From the screening and flotation plants, the phosphate minerals
may be marketed directly or transported to the chemical plants for
further processing. The details of chemical processing of phosphate
rock and the products obtained vary according to the plant and the
nature of the product obtained. Some generalization about the process
may be made which is pertinent to water pollution by chemical plant
effluent.
The processes of converting the phosphate minerals into a form
more readily available as plant nutrients require acidification of the
phosphate mineral. Subsequently, some of the fluorides are released.
For making superphosphate, phosphate rock is treated with sulfuric
acid to form a monocalcium phosphate fertilizer. Silicon tetrafluoride,
carbon dioxide, and fluorosilisic acid are other products of the reaction.
Triple superphosphate is produced by allowing the above reaction






REPORT OF INVESTIGATIONS No. 46


to go to completion to form phosphoric acid which is used to treat
more phosphate rock to form the triple superphosphate.
The two part reaction may be generalized as follows:
(1) Ca5(P04)3F + 5H2SO4 = 3HaPO4 + 5CaSO4 + HF
Phosphate Sulfuric Phosphoric Gypsum Acid
rock acid acid fluoride
(2) Cas(P04)3F + 7H3P04 = 5Ca(H2P04)2 + HF
Phosphate Phosphoric Monocalcium Acid
rock acid phosphate fluoride

The gypsum, precipitated in the first reaction, is separated from
the phosphoric acid by vacuum filtration, washed and wasted to a
settling lagoon where it may settle. The water is returned to the
plant for reuse. Owing to silica and carbonate impurities, carbon
dioxide and silicon tetrafluoride are evolved as gases. A complex system
of multiple scrubbing, washing and evaporating removes and concen-
trates the fluorides as fluorosilisic acid which is recovered.
Water waste from the scrubbing process may go to the settling
lagoons or to the streams. During rainy seasons some water may
overflow from the settling lagoons and thus enter the streams. Con-
siderable water containing high fluoride and phosphate enters the
streams as evidenced by analyses of water from many locations down-
stream from the processing plants.

SIGNIFICANCE OF FLUORIDE AND ASSOCIATED
WASTE PRODUCTS IN WATER

FLUORIDE
The effect of fluoride in drinking water has been the subject of
intense investigations since 1931 when endemic mottled enamel in
teeth was recognized as being associated with drinking water con-
taining fluoride. Later investigations showed that small amounts of
fluoride could prevent dental caries without the mottled enamel effect.
The U.S. Public Health Service (1962a) compiled 142 papers writ-
ten by Public Health personnel prior to 1962 into one volume which
describe dental fluorosis and dental caries and the physiological effects,
analysis, and chemistry of fluoride. The results of many investigations
by the Public Health Service have resulted in the adoption of standards
of optimum concentrations of fluoride in drinking water on interstate
carriers and which serve as a guide for others interested in maintaining






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 11

good, safe water supplies. According to the U.S. Public Health Service
(1962b) the optimum fluoride level in drinking water in a given com-
munity depends on climatic conditions because the amount of water
consumed by an individual is primarily influenced by air temperatures.
The following table is taken from the U.S. Public Health Service
(1962b, p. 8).

Annual average of maximum Recommended control limits-
daily air temperatures F Fluoride concentrations in mg/1
Lower Optimum Upper
50.0 53.7 0.9 1.2 1.7
53.8 58.3 0.8 1.1 1.5
58.4 63.8 0.8 1.0 1.3
63.9 70.6 0.7 0.9 1.2
70.7 79.2 0.7 0.8 1.0
79.3 90.5 0.6 0.7 0.8

Water supplies subject to Federal quarantine regulations are sub-
ject to rejection when the fluoride concentration is greater than two
times the optimum concentration.
These optimum concentrations of fluoride in drinking water are
considered effective in preventing mottled enamel and caries in the
teeth of children during the period of tooth development. McKee and
Wolf (1963) report that concentrations of fluoride of 3 or 4 ppm are
not likely to cause endemic cumulative fluorosis and skeletal effects in
adults. Concentrations of 8 to 20 ppm, when consumed over a long
period of time may cause some skeletal effects in adults.
McKee and Wolf (1963) have also summarized the reported effects
of fluoride in water on stock and wildlife, fish and other aquatic life,
and industrial uses. They report (p. 191) that the effects of fluoride
in drinking water for animals are analogous to those for humans, but
that fluoride ions appear to have direct toxic properties towards aquatic
life. They summarize the available information with the following table
of concentrations of fluoride that will not interfere with specified ben-
eficial uses:
a. Domestic water supply 0.7 to 1.2 ppm
b. Industrial water supply 1.0 ppm
c. Irrigation water 10.0 ppm
d. Stock watering 1.0 ppm
e. Aquatic life 1.5 ppm

PHOSPHATE
Phosphates may occur in water from leaching of phosphatic min-
erals, agricultural drainage, decomposition of organic matter, sewage,






REPORT OF INVESTIGATIONS No. 46


industrial wastes or cooling waters that have undergone phosphate
treatment (McKee and Wolf, 1963, p. 240).
Usually, these sources contribute only minor amounts of phosphate
to natural waters and probably have little physiological significance;
however, they serve as a nutrient for growth of algae which is unde-
sirable.
McKee and Wolf (1963, p. 240-241) summarize the work of other
investigators on the effects of phosphate in water. Their summary in-
cludes effects on:
a. Domestic water supplies. Polyphosphates are used to prevent
scale formation and corrosion. In raw water sources, polyphosphates
interfere with coagulation, flocculation, and the lime soda treatment of
water.
b. Irrigation. Phosphate in irrigation water may help increase the
fertility of soil moisture; however, experiments with blueberry plants
showed that 60 ppm may reduce the availability of inorganic iron and
be detrimental.
c. Fish and aquatic life. Phosphates in streams and lakes may
result in overabundant growth of algae with concomitant odors and
detriment to fish. Phosphates are usually not toxic and may be ben-
eficial to fish by increasing algae and zooplankton.
d. Industrial water. Phosphates may be beneficial by preventing
scale formation and corrosion; however, they may encourage biological
growth and be detrimental.
Phosphate in ground water is relatively rare. Small amounts may
be present from the above sources; however, most phosphate is prob-
ably redeposited from ground water in the form of calcium, iron, and
aluminum phosphate.

pH
The pH of water is a measure of the acidity of water. A pH of 7
is considered neutral, below 7 is acid and above 7 is basic. Waters
that have a low pH tend to be corrosive to metal and concrete and
are usually undesirable for domestic supplies. Water with a pH of
about 4.0 may taste sour.
McKee and Wolf (1963, p. 236) summarize numerous investigations
on the effect of pH on fish. Ranges of several pH units can be tolerated
by most species; however, the range may depend on other factors, such
as temperature, dissolved oxygen, prior acclimatization, and the content
of other dissolved material.






FLuoRIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 13

TURBIDITY
Turbidity is an optical property of water that contains suspended
and colloidal matter. This suspended material reduces light penetra-
tion into the water as a function of both the concentration and particle
size of the material. Turbidity is reported as parts per million and is
equivalent to the turbidity of standard solutions of silica.
Turbidity in streams may be caused by micro-organisms, organic
detritus, silica, clay, or silt or any suspended material and may result
from natural processes or domestic and industrial effluent.
The U.S. Public Health Service (1962b, p. 6) recommends that
turbidity in drinking water should not exceed 5 ppm. McKee and
Wolf (1963, p. 290) state that turbidity is generally undesirable for
most industrial uses of water. They give recommended limiting values
of turbidity for many industrial uses ranging from 1.0 to 100 ppm.
Turbidity in water may affect fish by reducing photosynthetic action
and decreasing the productivity of fish-food organisms or by modifying
the temperature structure of bodies of water. Turbid water is con-
sidered less productive for fish than is clear water; however, several
hundred ppm turbidity have not been found lethal to fish (McKee
and Wolf, 1963, p. 291).

GEOCHEMISTRY OF FLUORINE
Fluorine is a minor constituent in the rocks forming the earth's
crust. Many minerals contain fluorine in minor amounts in complex
mineral systems. The most important of these relative to the Alafia
and Peace River Basin areas are the apatite group of minerals that
are primarily calcium phosphate and vary according to the amount of
fluoride, chloride, hydroxyl, and carbonate they contain. Fluorapatite
has the general formula Car,(P04)3F and contains 3.8 percent fluoride.
Chloride or the hydroxyl ion commonly substitutes for fluoride.
In Florida, the only rocks on or near the surface are sedimentary
rocks. Barraclough (1962, p. 24) reported glauconite, phosphate, and
muscovite (mica) in the sedimentary rocks in west Florida. Mica was
reported to be especially abundant. The author has found minor
amounts of fluoride in insoluble residues of limestone well cuttings
from Sumter County in peninsular Florida.
The apatite group of minerals (phosphate rock) occur in the rocks
in many areas in Florida. Where found, the amount varies from a few
scattered grains to large minable deposits. The phosphate rock mined
in the Alafia and Peace River basins is primarily fluorapatite.
Fluoride is usually one of the minor constituents of dissolved mate-






REPORT OF INVESTIGATIONS No. 46


rial in natural water. Hem (1959) reported concentrations of fluoride
in natural water may be 50 parts per million or more, but that con-
centrations of over 10 ppm are rare and surface waters rarely contain
more than 1.0 ppm.

SURFACE WATER
The Peace and Alafia rivers have been described with respect to
inorganic chemical contaminants by previous investigators. The con-
ditions causing excessive inorganic pollution have been established
(Florida State Board of Health, 1955a, 1955b) and recommendations
made which give limits in terms of concentrations that certain constit-
uents in river water should not exceed.
The Florida State Board of Health (1955b, p. 9) recommended
that the waters of the Peace River basin should be maintained so that
the following limits are not exceeded:
Dissolved Oxygen-not less than 3.5 ppm at all points.
Turbidity-not more than 100-200 ppm provided the duration
is short. For continuing waste discharge, the resultant
turbidity should not exceed 50 ppm.
Settleable solids-not more than .05 milliliters per liter.
pH-over 5.0 and under 8.5
Fluoride-not more than 5.0 ppm
Their recommendations for the Alafia River are the same (Florida State
Board of Health, 1955a, p. 8) except for turbidity for which a recom-
mended limit of 100 ppm is given.
A program of sampling and analysis of stream water was established
as a part of the present investigation to define the ranges in concen-
tration of chemical constituents, to define the sources and character
of the chemical constituents, and to evaluate changes in concentrations
from those conditions described by previous investigators. Particular
attention was given to the fluoride and phosphate content of the streams.
Three sites were selected at the start of the investigation for sam-
pling on a daily basis. Daily samples from each of the sites were
analyzed for specific conductance, pH, turbidity, phosphate and fluoride.
A reconnaissance of the basin was made early in the investigation
during which water samples were collected at 48 stream sites and
analyses made for specific conductance, phosphate and fluoride. From
these analyses, 23 sites were selected for periodic sampling and analysis.
Of this number 14 were at gaging stations and 7 were at sites where
discharge measurements were made at the time of sampling. Samples
were collected at approximately six-week intervals. Figure 2 shows






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 15

the location of all stream sampling sites and the sites are identified
in table 1.
Seven sites were selected on the Alafia River and its tributaries
for periodic sampling for chemical analysis. Four of the sites are at
gaging stations. The chemical analyses from all these sites are pub-
lished in annual reports by the U.S. Geological Survey.
The stream-gaging site on the Alafia River at Lithia was selected
for daily sampling because it is downstream from most of the phos-
phate mining operations, records of discharge for the river are avail-
able at this site, and earlier records of chemical analyses are available
(Menke, Meredith, and Wetterhall, 1961).
Menke, Meredith and Wetterhall (1961) reported on a 2-year sam-
pling program of the Alafia River at Lithia from October 1956 to
September 1958. Their frequency curves for chemical constituents for
one year, October 1957 to September 1958, are replotted with frequency
curves for October 1964 to September 1965 in figures 3 and 4. The
frequency curves for specific conductance (fig. 3) for both periods
were prepared from measurements of daily samples and equally in-
dicate conditions during each of these periods. The frequency curves
for pH and concentrations of fluoride and phosphate were prepared
from measurements made on daily samples for the 1965-66 period but
for the 1957-58 period, they were prepared from measurements made
on composite samples from 10 daily samples. The measurements rep-
resented an average for the 10-day period.
Frequency curves constructed by each of the two methods should
give similar values at the 50 percent frequency; however, the greater
number of measurements when daily samples are analyzed individually
will give a wider range of values than will the measurements of the
average composite sample by ten-day periods. The two curves should
cross at about the 50 percent frequency and the curve prepared from
the measurements of composite samples should be flatter than the one
constructed from the daily measurements. Comparing the two curves
for each constituent gives an indication of the changes in water quality
since 1957-58.
The specific conductance of a water is a measure of the capacity
of the water to conduct electricity. Pure water is a poor conductor
of electricity; however, if water contains materials that ionize in solu-
tion, the capacity of the water to conduct electricity increases propor-
tional to the ionization of material in solution. The proportionality
factor will vary according to the type of material that is dissolved in
the water. Menke, Meredith and Wetterhall (1961, p. 53) reported







REPORT OF INVESTIGATIONS No. 46


700 28
E ~Oct. 1964 to Sept. 1965
600 \ 24


S500 -20 g
C -Oct. 1957 to Sept. 1958
400 16
*---Specific Conductance
3 12

re .-Freec c rves of specific conducance and concenraion of fluoride for
200- 8
Oct. 1957 to Sept. 1958
Oct. 1964 to Sept. 1965- -
1 00- 4

0 1 11 1 1 1 1 1 I I 1 1 1 11 1
0.1 05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 99.9
Percent of time specific conductance was equal to or greater than a given value

Figure 3.-Frequency curves of specific conductance and concentration of fluoride for
the Alafia River at Lithia.

that, for the Alafia River at Lithia, the mineral content of the water,
in parts per million, was about 77 percent of the specific conductance
in micromhos.
The two frequency curves for specific conductance in figure 3 show
that the specific conductance, and hence the mineral content, of water
in the Alafia River at Lithia during 1964-65 was generally higher than
during 1957-58. The median value (50 percent frequency) was about
340 micromhos in 1957-58 compared to 580 micromhos in 1964-65. These
values correspond to about 262 and 447 ppm mineral content, respectively.
The frequency curves for concentrations of fluoride and phosphate
(figs. 3 and 4) show that both these constituents also were generally
higher in 1964-65 than in 1957-58. The concentration of fluoride in
water in the Alafia River at Lithia (fig. 3) exceeded the 5.0 ppm
recommended by the Florida State Board of Health about 98 percent
of the time during 1964-65 compared to about 30 percent of the time
during 1957-58.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


C
140 -

120- H
s. 7 -
S100 O\ ct. 1957 to Sept. 1958 -6.0

8 /Oct. 1964 to Sept. 1965

0 -

p. Phosphote wee 5.0

Oct. 1957 to Sept. 1958Z X
20-

0 1 11 I I 1 1 1 1 I I 1 1 1 111 4.0
0.1 05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 99.
Percent of time concentre ion was equal to or greater thon o given value

Figure 4.-Frequency curves of pH and concentration of phosphate for the Alafia River
at Lithia.

Figure 5 shows hydrographs of discharge and concentrations of
fluoride and phosphate for the Alafia River at Lithia from October
1964 to September 1965. The maximum concentrations of fluoride and
phosphate during the year were 30 and 192 ppm, respectively. The
concentration of phosphate was generally 5 to 7 times greater than that
for fluoride.
Frequency curves for pH of water in the Alafia River at Lithia
(fig. 4) show a wider range in pH during 1964-65 than during 1957-
58. The differences between the two curves is probably, in large part,
caused by the different sampling and analytical techniques. The pH
was below the 5.0 lower limit recommended by the Florida State Board
of Health for two percent of the time during 1964-65.
Turbidity was generally low in the Alafia Biver at Lithia but ex-
ceeded the 100 ppm, recommended as maximum, during a six-day
period in February 1965 when a retaining dam for phosphate slime
failed on one of the headwater tributaries.







REPORT OF INVESTIGATIONS NO. 46


3000

1000
500


Oct Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep.
Figure 5.-Discharge and concentrations of fluoride and phosphate for the Alafia River
at Lithia from October 1964 to September 1965.

The program of stream sampling in the Peace River basin was
similar to that in the Alafia River basin. Of 15 sites selected for
periodic sampling, 9 were at gaging stations.
The concentrations of fluoride and phosphate in the Peace River at
Arcadia are shown in figure 6 and are not as high as those in the Alafia
River at Lithia. From October 1964 to September 1965, the pH and
fluoride concentrations of the Peace River at the daily sampling stations
at Zolfo Springs and Arcadia remained within the limits set by the
Florida State Board of Health. The turbidity of the Peace River at
Zolfo Springs and Arcadia was above the 50 ppm limit (continuing
waste turbidity) for 22 percent of the time at both stations from
October 1964 to September 1965.
Several factors affect the amount of dissolved material carried by
a stream. Some material dissolves from the atmosphere when water
falls as rain. Additional material dissolves from the material on the
land surface and from the soil zone as water flows to the streams.
Some of the water that falls on the land surface enters the ground,
moves downward to the water table and may eventually reach the
streams. This water has a. longer period of contact with the earth







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Nov.
1964


Apr. May.
1965


Jun. Jul. Aug. Sep.


Figure 6.-Discharge and concentrations of fluoride and phosphate for the Peace River
at Arcadia from October 1964 to September 1965.


materials and, consequently, contains higher concentrations of dissolved
materials than water.that flows on the surface to the streams.

The above are natural factors which affect the amount and kind
of dissolved materials in water in a stream. During periods of little
rainfall, most of the water in a stream, under natural conditions, is
that which has moved through the ground to the stream. Generally,
under natural conditions, there will be an inverse relation between the
concentrations of dissolved solids of water in a stream and the dis-
charge of the stream owing to most water flowing to the stream on






REPORT OF INVESTIGATIONS No. 46


the surface during high discharge and most flowing through the ground-
during low discharge. However, the dissolved load (weight per unit
time) is higher at high discharge than at low discharge because of
the large volume of water that contains material dissolved from the
surface.
If a stream receives waste products from municipal, industrial, or
other sources, the above relations between the mineral content of water
in a stream and discharge of the stream will be altered. For example,
if a stream receives soluble waste at a constant rate, the mineral con-
tent of water in the stream will be higher at both low and high dis-
charge than if no waste were being received. The inverse relation
between mineral content and discharge will still occur owing to dilu-
tion at high discharge. If the waste material furnishes the larger part
of any constituent in the stream, the dissolved load of that constituent
should be nearly constant at all values of discharge. If the release of
waste materials is controlled, so that more enters the stream at high
discharge, there may be no relation between concentration and dis-
charge and the dissolved load will be much higher at high discharge
than at low discharge. If there is no consistent pattern of release of
waste, there may be no consistent relation between discharge and con-
centration or load.
Chemical analyses of surface water in the Alafia and Peace River
basins for periods of relatively low and high discharge are given in
table 2. The drainage areas for stations 14, 20, and 22 (see fig. 2 for
location) include no phosphate mining or processing operations and
the concentrations of fluoride and phosphate in water at these sites are
low. The concentration of fluoride in streams not affected by phosphate
mining and processing was determined to generally be from 0.2 to 0.4
ppm from analyses of samples collected periodically at these sites and
from samples collected at other sites during the early reconnaissance
of the basins.
The mining and processing of phosphate rock have apparently affected
the quality of water in the streams at all other stations shown on figure
2 and for which the analyses are given in table 2. The concentrations
of all constituents are generally higher than for streams not affected.
The analysis in table 3 shows the constituents in water from a phosphate
chemical plant settling lagoon. The water from which this sample was
taken was not observed entering the streams, but the analysis probably
indicates the type and relative concentrations of constituents typical of
the phosphate chemical plant effluents.













TABLE 2.-Chemical analyses of surface waters in the Alafia and Peace River basins during periods of relatively low and high discharge
(Analyses in parts per million. See table 1 for station name and figure 2 for location)
Analyses by the U. S. Geological Survey


Hardness
as CaCOo


I N Fi


ALAFIA RIVER BASIN
1 6.02.65 I 85 80 .14 56 102 52 8.0 0 472 85 17 18 224 1,050 560 560 1,150 4.4 20 81
9.18.65 I 77 98 .20 2.6 ll 15 66 8.0 0 840 22 24 8.6 112 810 888 888 1,000 4.6 40 82
2 6.02.65 M 79 64 .17 .9 126 20 53 2.8 0 800 42 16 .9 158 802 397 897 980 6.5 20 80
9.14.65 M 128 70 .21 94 13 62 4.1 1 282 48 19 9.9 108 661 288 287 788 4.7 40 80
8 6.02.65 I 0.2 14 .00 27 19 12 2.5 184 29 21 8.1 .0 5.8 199 144 84 310 7.8 10 79
9.13865 I 10 19 .05 .6 22 7.6 26 8.4 54 19 48 5.2 .8 18 196 86 42 850 7.0 40 79
4 6.02.65 M 20 15 .23 .0 46 12 80 1.2 0 100 82 7.8 .2 86 869 164 164 465 6.6 40 80
9.14.65 M 117 80 .14 2.8 40 8.8 26 2.9 1 88 26 11 .0 88 826 186 185 370 5.9 100 81
5 6.02.65 8.3 .03 25 4.4 15 .2 79 82 10 .5 .0 .7 180 76 11 280 7.6 20 80
9.14-65 M 6 8.4 .19 12 4.5 8.9 1.0 37 20 12 .7 .4 1.8 88 48 18 150 7.0 90 -
6 6.02-65 M 187 54 .10 106 18 44 1.9 0 250 85 18 .0 148 665 838 888 810 6.5 20 80
9.14.65 M 841 45 .16 2.5 63 9.9 40 8.4 3 152 86 14 7.9 86 461 198 195 688 5.4 85 80
7 9.14-65 -- 21 .05 199 18 8280 507 63 772 5470 7.4 5.6 8.7 10,800 570 519 16,000 6.7 40 80


0 14
188 14
9.4 18
19 19
23 12
248 17
8.5 18
82 5.5
18
14
6.4 6.3


27
20
28
258
84
21
54
80
15
19
6.4


PEACE RIVER BASIN
1.4 100 116 7.0 8.1
2.7 68 37 21 1.1
.6 94 122 34 2.9
5.0 b227 280 32 11
1.0 91 119 82 2.6
2.6 50 64 28 2.1
.4 154 144 15 8.2
.8 92 105 11 2.6
1.0 138 70 10 1.1
2.4 63 51 18 1.4
.8 6 4.0 12 .2


470
242
525
1,400
515
820
685
480
405
280
79


5
80
10
20
10
80
5
20
10
80
160


6.01.65
9.14.65
6.01.65
9.18.65
6.01.65
9.14.65
6.01-65
9.14.65
6.01.65
9.14.65
9.14.65
















TABLi 2,-Continued
Hardnes.
as CaCOa





15 6.02.65 I 8 1 i .00 42 15 5.8 .5 120 64 5.5 8.8 .1 1.7 212 168 70 840 7.9 5 108
9.14.65 I .7 20 .00 62 16 6.8 .8 140 83 8.0 8.1 .1 13 282 220 106 455 7.5 5 87
16 6.02.65 I 8.2 33 .08 80 81 44 .8 0 892 15 7.8 1.1 156 760 408 408 885 6.8 15 82
9.14.65 I 5.2 88 .18 8.1 64 18 34 1.0 0 210 12 7.0 .2 181 511 234 284 620 4.6 70 87
17 6.02-65 I 24 18 .01 50 80 24 .4 81 184 16 2.6 .4 883 98 248 182 576 7.7 15 76
9.14.65 I 69 18 .05 .6 40 13 16 1.2 28 106 18 4.2 .1 86 811 154 154 890 7.0 40 -
18 6.01.65 M 5.2 2.5 .19 16 7.5 11 .1 42 84 12 .8 5.2 2.0 112 71 86 210 7.4 20 78
9.14.65 M 52 7.8 .32 18 4.9 8.0 .8 25 24 14 .9 1.4 8.7 91 52 82 152 6.7 110 78
19 6.01-65 M 59 12 .05 49 17 26 1.2 101 119 16 2.0 1.0 9.7 802 192 109 515 7.6 10 84
9.14.65 M 581 14 .09 80 9,0 16 2.4 47 64 16 1.7 2.9 8.5 264 112 74 280 6.8 95 81
20 6.02.65 M 4.0 8.9 .12 16 6.2 8.8 .6 62 14 14 .7 .0 2.2 98 66 14 185 7.4 40 80
9.14.65 M 87 8,8 .27 7.0 4.5 7.5 1.0 21 4.8 18 .8 .2 1.6 64 86 19 98 6.5 240 83
21 6.02.65 M 74 11 .03 48 17 25 1.8 105 126 18 1.7 .9 6.8 308 190 104 495 7.6 10 81
9.14.65 M 837 12 .12 25 8,6 18 1.8 55 46 16 1.7 1.4 8.8 161 98 53 245 6.8 110 83
22 9.14.65 M 28 8.8 .46 33 6.7 16 2.1 91 29 29 .4 .6 1.2 172 110 86 288 7.0 100 88
23 9.14-65 11 .17 23 7,2 12 1.9 56 87 14 1.5 1.0 5.8 148 87 41 232 6.9 100 83
M Average daily discharge
I Discharge measurement
a Chemical analyses for Station 9 discharge data for Station 8
b Includes 80 ppm as Carbonate (COa)







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


TABLE 3.-Chemical analysis of water from a phosphate
plant settling lagoon, Polk County, Florida
(Analysis by the U. S. Geological Survey)


Silica (SiO,)
Iron (Fe)
Aluminum (Al)
Manganese (Mn)
Calcium (Ca)
Magnesium (Mg)
Sodium (Na)
Potassium (K)
Total Acidity as H+
Bicarbonate (HCO,)
Sulfate (SO,)
Chloride (Cl)
Fluoride (F)
Nitrate (NO,)
Phosphate (PO,)
Dissolved Solids
Total Hardness as CaCO,
Non-Carbonate hardness as CaCO,
Specific electrical conductance in micromhos
pH
Color


chemical

parts per million
(except specific conductance,
pH, and color)
1,180
87
64
2.7
1,110
50
155
12
123
0
2,710
37
1,410
0.5
7,540
14,400
2,980
2,980
10,100
2.0
140


Most of the phosphate chemical plants are located in the headwater
areas of the Alafia River basin (fig. 2), and the water from streams in
the basin contains higher concentrations of fluoride and phosphate than
the streams in the Peace River basin. Drainage to the tributaries in
the flat headwater areas is controlled, in large part, by the mining op-
erations. No attempt was made to determine the amount of waste water
contributed to the streams by an individual plant.
Table 2 shows that the concentrations of fluoride and phosphate in
surface water may be as high or higher at high discharge as at low
discharge. The hydrographs for stations 6 and 21 (figs. 5 and 6) also
show that the concentration of fluoride or phosphate may be the same
with wide ranges in discharge. This indicates that the streams do not
receive fluoride and phosphate at a constant rate.
The load the stream carries shows the amount of waste and indicates
the period during which most of the waste is received by the stream.
The dissolved fluoride loads of streams in the Alafia and Peace River
basins at relatively low and high discharge are shown in figure 7. The
figure illustrates that a relatively high dissolved fluoride load is carried
by the Alafia River as compared to the Peace River. It also indicates
there is no major loss of fluoride from the streams.






REPORT OF INVESTIGATIONS No. 46


Figure 7.-Fluoride load in streams in Alafia and Peace River basins during periods of
low and high flow 1965.

The fluoride load of each stream at the daily sampling sites was
calculated using the fluoride concentrations of the daily sample and
the mean daily discharge for the station. Hydrographs of fluoride load
are shown in figure 8 for the Peace River at Arcadia and the Alafia
River at Lithia. The calculations of daily samples also show that the
Alafia River carries much more fluoride than the Peace River. The
fluoride load hydrographs closely parallel the shape of the discharge
hydrograph (figs. 5 and 6) showing that much more fluoride is carried
by the streams at high discharge than at low discharge. The fluoride
load hydrographs have the peak loads in August coincident with the
discharge peaks. Of the approximately 4,000 tons of fluoride carried
by the Alafia River at Lithia from October 1964 to September 1965,
slightly more than one-fourth was during the month of August. During
this year, 781 tons of fluoride was measured on the Peace River at
Zolfo Springs and 900 tons at Arcadia. The larger amount at Arcadia






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


C0 1



W.0 -Peace River at Arcadia






S Oct Nov. Dec. Jan. Feb. Mar Apr. May Jun. July Aug. Sept.
1964 1965

Figure 8.-Dissolved fluoride load of the Alafia River at Lithia and the Peace River at
Arcadia from October 1964 to September 1965.


is of the magnitude to be expected as contribution from the uncontam-
inated tributaries between the two stations. Apparently, fluoride is not
lost from the stream to the ground water between the two stations.

Much of the difference in fluoride load carried by the Alafia and
Peace rivers may be accounted for by the greater number of chemical
processing plants in the Alafia basin. Other differences undoubtedly
are due to differences in the size and type of plant and to methods of
waste disposal.

The high fluoride load of the streams at high discharge is probably
caused, in large part, by either controlled or accidental release of
larger amounts of waste water from the settling lagoons during these
periods. Some of the load during high discharge periods may be due
to natural ponding of waste water in flat, swampy upland areas during
periods of low rainfall and subsequent flushing of these areas during
periods of high rainfall.






REPORT OF INVESTIGATIONS No. 46


GROUND WATER
GENERAL GEOHYDROLOGY1
The geologic formations which form the aquifer systems in the
Alafia and Peace River Basins range in age from Eocene to Recent.
The Floridan aquifer is the principal water producer. It includes the
lower part of the Hawthorn Formation and the Tampa Formation of
Miocene age, the Suwannee Limestone of Oligocene age and the lime-
stones of the Ocala Group, the Avon Park Limestone, and the Lake
City Limestone, of Eocene age. Generally, the upper sandy and clayey
part of the Hawthorn Formation serves to confine water in the un-
derlying formations under artesian pressure.
Overlying the Hawthorn Formation are the sands, clays, and marls
of Pliocene to Recent age that may contain water under water-table
conditions and which serve to supply many small domestic wells.
The Floridan aquifer is at or near the surface in the northeastern
part of the area and dips to the southwest. In the southwestern part
of the area, the Floridan aquifer is at depths of several hundred feet.
Menke, Meredith, and Wetterhall (1961, p. 75) reported the depth
of the confining beds of the Floridan aquifer in Hillsborough County
to range from a few feet in the north-central part of the county to about
300 feet in the southeastern part. Woodard (1964, p. 20) stated, "The
bottom of the [Hawthorn] Formation, which in most cases marks the
top of the Floridan aquifer, ranges from about 200 feet below sea level
in north Hardee County to about 450 feet below sea level in south
DeSoto County." Surface elevations in southern DeSoto County range
from about 25 to 125 feet above sea level and the depth to the Floridan
aquifer is as much as 575 feet.
Regionally, the Floridan aquifer in peninsular Florida functions as
an aquifer system. Water enters the aquifer in the central peninsular
area where the aquifer is at or near the surface, and in areas where it
may leak through the confining beds, and moves radially away from
the central part of the peninsula toward the coast. Figure 9 shows the
piezometric surface of the Floridan aquifer in the study area. The
general direction of ground-water movement is considered to be from
the areas of high to low pressures or south and west from north-central
Polk County.
Locally, the Floridan aquifer may sometimes function as two or
more hydraulic units. In Hillsborough County (Menke, Meredith, and
Wetterhall, 1961, p. 72) the limestones of the Ocala Group tend to
lThe stratigraphic nomenclature in this report conforms to the usage of the Florida
Geological Survey and not necessarily to that of the U. S. Geological Survey.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 27

restrict the vertical flow of water and the aquifer functions as two units,
one above and one below the Ocala Group. Woodard (1964) found
similar conditions in Hardee and DeSoto counties. In Hardee County,
most of the water pumped is from the zone below the Ocala Group.
South of Hardee County, in DeSoto County, where the Tampa Forma-
tion and Suwannee Limestone above the Ocala Group are deeper and
thicker, they form the most used zone. Sutcliffe and Joyner (1966)
used packers in wells in Sarasota County to show three producing zones.
Generally, the upper, permeable zones have a better quality of water


Figure 9.-Piezometric surface of the Floridan aquifer in southwest Florida in January
1964.






REPORT OF INVESTIGATIONS No. 46


than the lower zones where circulation of water is inhibited. Figure 10
shows the general distribution of dissolved solids in the Floridan aquifer.
The map is prepared from maps and data presented by Shattles (1965),
Peek (1958), N. P. Dion and M. Kaufman (personal communication,
1966), B. F. Joyner (personal communication, 1965), and supplementary
data collected during this investigation. The maps were prepared from
chemical analyses that generally represent water from wells open to a
large section of the aquifer and do not show differences in the dissolved
solids in the different zones of the aquifer. Evidence in the literature
shows that differences in the chemical quality of water occur with depth
of penetration into the aquifer. Peek (1958, p. 66-67) shows large dif-
ferences in his dissolved solids maps in water from the Tampa Forma-
tion and water from the Suwannee and older formations.
Differences in artesian pressure in the different zones of the aquifer
in some locations affect the general flow pattern of the water. In order
for water to move downward into an aquifer, the water level in the
aquifer must be lower than the water level in the sediments overlying
the aquifer. For the water to move downward through the aquifer,
the water level from a well deep into the aquifer must be lower than
in a well which only penetrates the upper part of the aquifer. Woodard
(1964, p. 28) reported that the water table stands as much as 45 feet
above the piezometric surface in northwest Hardee County, and that
the artesian water level becomes lower with depth. The Floridan
aquifer is being recharged in the ridge section of Hardee County
southward to the Hardee-DeSoto county line where the water table
and piezometric surface are at about the same elevation.
Along the Peace and Alafia rivers, an opposite relation of water
level with depth prevails. Water is released from the aquifer through
springs along the river valleys. This release of water lowers the pres-
sure of the upper part of the aquifer to a level below that of the lower
part of the aquifer. This reversal allows water to move from the lower
part to the upper part of the aquifer. Dion and Kaufman (personal
communication, 1966) have shown this condition to exist for the Peace
River, and Menke, Meredith, and Wetterhall (1961) have discussed it
for some springs in Hillsborough County. The manner in which these
areas of recharge and discharge affect the chemical quality of water
by altering the general flow pattern can be observed on figure 10 by
the upstream indentation of the high dissolved solids patterns along the
river valleys in Hardee and Hillsborough counties.
The natural zonation and local alteration of the general flow pattern
in the Floridan aquifer are significant in explaining the variations in
natural chemical quality of water. They also illustrate the need for a






THE ALAFA AND PEACE RIVER BASINS


Figure 10.-Dissolved solids concentration in the Floridan aquifer in southwest Florida.
very detailed knowledge of local hydrologic conditions to locate and to
predict the effects of introducing a contaminant into the aquifer at any
point.

FLUORIDE DISTRIBUTION
The distribution of fluoride in ground water in the Alafia and Peace
river basins and adjacent coastal areas was mapped to determine the
natural concentrations of fluoride, to determine if contamination of ground
water by fluoride effluent from phosphate processing plants has occurred,


FLUORIDE IN WATER IN






30 REPORT OF INVESTIGATIONS No. 46
and to provide a base from which any future changes in fluoride con-
centration can be detected.
Figure 11 is a map of fluoride concentrations in ground water. The
wells shown range widely in depth and in the section of the aquifer
system they penetrate. All wells except those that penetrate only the
surficial sands are included.
Some general trends in the distribution of fluoride can be noted. In
the northern part of the area, the concentration of fluoride in ground
water generally ranges from 0.0 to 1.0 ppm. The concentration of


Figure 11.-Concentration of fluoride in ground water in southwest Florida.






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 31

fluoride generally increases from the northern boundary of the Peace
River -basin district, both westward into Hillsborough County and
southward into Hardee County.
In Hardee County the concentration of fluoride is slightly higher
than in Polk and Hillsborough -and generally ranges from 0.5 to 1.5
ppm. The fluoride concentration in the western part of the county is
slightly higher than in the eastern part. Further south in DeSoto County,
the concentration of fluoride may be more than 2.0 ppm. The concen-
tration of fluoride in many wells in Charlotte, Sarasota, and Manatee
counties ranges from about 1.0 to 3.0 ppm.
There are many exceptions to these generalities on areal distribu-
tion of fluoride in ground water. Most of the variations can probably
be attributed to vertical hydrologic zonation of the aquifer system and
the amount of water produced from each zone in a particular well,
to local deviations from the generalized areal ground water flow pat-
terns, and to variations in the amount of fluoride source minerals avail-
able in the rocks.
North-south cross sections, located along the lines shown in figure
12, are shown in figures 13 and 14 to illustrate the vertical zoning of
concentrations of fluoride in ground water. These sections also sub-
stantiate the general southward increase in concentrations of fluoride
shown on the map in figure 11. The higher concentrations of fluoride
generally occur at shallower depths.
Because the sections were constructed by projecting well locations
as much as 5 miles and because only a few geologic control points
were used, the wells are not all finished in the geologic formations
exactly as shown. It is evident, however, that the higher fluoride con-
centrations are in water from the Hawthorn Formation and Tampa
Formation and possibly from the upper part of the Suwannee Lime-
stone. This is best shown by wells with only a small producing interval
or where samples were collected at different depths while the well was
being drilled.
This zonation of high fluoride concentrations in the more shallow
formations strengthens the conclusions of Woodard (1964) that the most
probable source of the fluorides are the fluoride-bearing phosphate min-
erals in the Hawthorn Formation and Tampa Formation. No attempt
was made to relate the fluoride concentration in ground water to the
percent of phosphate minerals in the rock at different locations; how-
ever, such a relation appears likely.
It is also evident from figures 13 and 14 that the fluoride concentra-
tion in any location may'depend on the vertical movement of ground






REPORT OF INVESTIGATIONS No. 46


Figure 12.-Location of cross sections A-A' and B-B'.


water as well as the lateral. movement. If there is vertical hydraulic
connection between all formations and water movement is downward
(recharging conditions), fluoride in water would tend to move down-
ward to the underlying formations. If the vertical movement is upward
(discharge conditions), however, the fluoride concentration should rep-
resent, in part, that from water which has moved upward from the
lower formations. Geohydrologic environments favorable to both con-
ditions occur in the area. Discharge occurs through springs and prob-







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 33



A -i Ai '


B S [ .-e f i t .. ..i.-- f i--
-200 I i ,A 1 I--' o A -
-I, -,




l -600-- .-'i oi- NI2 r- o -1 -
,' I-Ig ud at-- e I I --- : It
,I 4 .-0 '- I _
1'I A "'I









and Peace riv I/. a e omcu legcollecled fum flowing ...... difge ect
,I l 0\0 -- "I Ih : dephs di "" drillng
a y fr th e. T B Somple ctllecled from seoop er oi different
oiw .ha b od fine represents producing int of well
I i Ii- I ,--00 .
sI II






-1400 f ior I I iter t


t G Well use d c for geologic control


io o t Number is fluoride conccntroionin p
Sdretl to the streak a the wer reahes dof both the ifi
iand Peae e re 1 ours along much of the ridgo te s rectio






away from the river. The general effect of these opposing conditions
on water quality has been noted in figure 10 by the indentatio n of the
contours of high dissolved solids along the lower reaches of the rivers.
As conentrations of fluoride in ground water are relatively low and
variable, it is difficult to evaluate these various: factrs on the oncen- .
traction of f13.-Cruoride at a particular geoloic formations and fluoride concentrationsn.
Thably directly to the streams along the lower reachells of both the Alsurficia
and Peace rivdeters.mined at 30 loccurations yearlong the active phosphate sectminingon
away from the river. The distribution of wells sampled and these opposing conditions
fluorideon water quality has been noted in figure 15. Fluoride by thin watiner from the surf thcial




macontours of high dissolved from 0.0 to 1.0 ppm. The numblower reaches of shallow wells
available for stamping is limiicult to evaluated, because mvarious factorwells are fin tished in then-
tration of f-luoride at a particular location.
The ~fluoride content of water from shallow wells in the surficiak
sands 1as determined at 30 locations near the active phosphate mining





underlying limestone; however, it can be concluded from figure 15 that
there is no widespread occurrence of high fluoride concentration in water
in the surficial sands. However, the data shown in figure 15 do not pre-






REPORT OF INVESTIGATIONS No. 46


-- l o i




I .. I tole, ---od. ioi --
I --- ,, '-; ..7- -. 1,----








in. .epth ia pror
.. 0 0 4 --- 'oui ,C
N e To It t I boA 1l 0 I



r GIQ ^ "--1 0 .2 1" B ... dr











elude any contamination of the shallow ground water on a local scale.
Generally, there are no wells available for sampling near the phosphate
mines, chemical plants, and settling lagoons, the places where local
contamination of shallow ground water would be expected.
From the maps (figs. 11 and 15) and sections (figs. 13 and 14),
the following general conclusions can be made about the occurrence
of fluoride in ground water in southwest Florida. Fluoride concentra-
tions of 2 ppm or more are confined to waters in the Hawthorn For-
mation and Tampa Formation and possibly in the upper part of the
nnee Limestone; uoride concentrations in the social materials









and in the underlying limestone in the areas of active phosphate mining
are low (generally less than 1.0 ppm); widespread pollution of the
,EXPLANATION
. 1400 --- os section B-B shooG f a t'sa d fuori gelogc control
















r d water by uoride is not evident; and the formations that have








high fluoride concentrations in interstitial water are the formations that
contain phosphatic minerals, and these are the probable source of the
luoride in the water. If contamination of the shallow ground water by fluoride
contamination of shallow ground water would be expected.
From the maps (figs. 11 and 15) and sections (figs. 13 and 14),
the following general conclusions can be made about the occurrence
of fluoride in ground water in southwest Florida. Fluoride concentra-
tions of 2 ppm or more are confined to waters in the Hawthorn For-
mation and Tampa Formation and possibly in the upper part of the
Suwannee Limestone; fluoride concentrations in the surficial materials
and in the underlying limestone in the areas of active phosphate mining
are low (generally less than 1.0 ppm); widespread pollution of the
ground water by fluoride is not evident; and the formations that have
high fluoride concentrations in interstitial water are -the formations that
contain phosphatic minerals, and these are the probable source of the
fluoride in the water. If contamination of ground water by fluoride






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Figure 15.-Fluoride concentrations in shallow wells in the phosphate mining area in
southwest Florida.

occurs from the mining and processing of phosphate rock, such con-
taminations apparently are local and not evident from the areal ap-
proach used for this investigation.

POLLUTION POTENTIAL AND PHYSICAL
CHEMISTRY OF FLUORIDE
The general mining and processing of the phosphate ore do not
appear to be causing widespread contamination of the ground water
supplies. The greatest potential hazard to ground water would appear
to be the settling lagoons at the chemical plants which receive water
containing several hundred ppm fluoride (see analysis table 3). The






REPORT OF INVESTIGATIONS No. 46


lagoons become lined with the fine waste material from the operation
which inhibits leakage to the aquifer. Even if leakage does not occur,
waste waters might enter the aquifer by collapse of the surficial mate-
rials into solution chambers in the underlying limestone as happens in
the formation of many sinkholes in Florida and has happened in Polk
County.
Prediction of what would happen to the fluoride, should it enter
the aquifer from the lagoons, involves (1) a detailed knowledge of the
hydrology and geology of the aquifer near and down gradient from the
lagoons and (2) knowledge of the chemical changes exacted upon the
wastes by the laws of chemical equilibrium when they reach the aquifer
environment.
The flow patterns in the aquifer near the waste disposal lagoons
probably could be delineated satisfactorily by detailed hydrologic in-
vestigations. This would involve extensive drilling and testing to deter-
mine the direction a contaminant would move away from a point where
it was injected into the aquifer and the general geometric shape the
moving mass would assume.
Little experimental work has been done, however, on the role of
chemical reactions of contaminants with the minerals and water which
they encounter, particularly on what may happen to a fluoride contam-
inant in a limestone aquifer.
Aumeras (1927), reported in Hem (1959), states that fluoride is
soluble in pure water at 250 C. to the extent of 8.7 ppm fluoride. For
such a sparingly soluble compound as calcium fluoride, this information
is sufficient to calculate a "solubility product" for the compound. The
principle of a solubility product is useful in investigating the geochem-
istry of ground water and recently has been applied to saturation studies
of calcium carbonate in ground water (Back, 1961, 1963; Hem, 1961).
The significance.of the solubility product is that "when a solution
is at equilibrium with a given salt, the product of the activities (or
concentrations) of its constituent ions, raised to the appropriate powers,
must be constant" (Glasstone, 1946, p. 490). Because calcium fluoride
(CaF2) requires two fluoride ions to balance each calcium ion the ap-
propriate power for the fluoride concentration is 2 and the equation
for the solubility product (K) is
K C = Ca++ X(F-)2

where Ca++ and F- represent the molal concentrations of calcium and
fluoride.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 37

Both temperature and the concentration of all constituents in solu-
tion affect the solubility constant (K). For the range of temperature
of most ground water the effect is small and the standard temperature
of 770 F. may be used for this area. The effect of concentrations of
other ions in solution requires the use of activities of Ca++ and F-
instead of concentrations as given in the above equation.
The effect of other constituents in solution is to suppress the effec-
tive activity of an ion below that expressed by the concentration of
the ion. This effect is related to the ionic strength of the solution which
can be calculated from the concentration and the valence of the ion
in the solution by:
M = MiZI + M Z2 + 3MZ .
where A = ionic strength
M = molal concentration of each constituent
Z = valence of the ion in solution
From the ionic strength a number can be calculated which, when
multiplied by the concentration of an ion, will give its effective activity.
This number will be less than 1.0 and is called the activity coefficient.
Hem (1961) gives in detail the calculations to obtain ionic strengths
and resulting activity coefficients along with nomographs to eliminate
many of the calculations.
Figure 16 shows the relation of the activity coefficient of calcium
and fluoride to the ionic strength of a solution. The ionic strength may
be obtained from the above quotation or from nomographs given in
Hem (1961, plate I), either of which requires a chemical analysis and
considerable calculations. As the ionic strength depends only on the
type and amount of dissolved material and as most natural water con-
tains only a relatively few major constituents, a fair approximation of
the ionic strength can usually be obtained from a measure of the dis-
solved solids.
Pure water is a poor conductor of electricity. The dissolved material
in the water that conducts electricity and the specific electrical conduc-
tance is a good indicator of the amount of dissolved solids. Figure 17
shows the relation of ionic strength to specific electrical conductance of
several ground water analyses. Most of the points on the graph rep-
resent samples of ground water from Florida except those above 2,000
micromhos which are analyses from the literature and which had rel-
atively high fluoride concentrations. The specific electrical conductance
multiple by a factor of 0.60 gives a good approximation of the dissolved
solids content of ground water in southwest Florida.








OJ














0.01





C3
c
c
o

C
0


LLi


1Ilif11fi


ilifIIIIIfI I


REPORT OF INVESTIGATIONS No. 46
ItI I Ir TTTFFt F FII III I l T I l IT II I lII 1T1 111111











F-/

Co++







/t


u.uu


09 0.8 0.7 0.6 0.5 0.4
Activity coefficient (a)
Figure 16-Relation of the activity coefficient of calcium and fluoride to ionic strength
of a solution.


,t 11111t


u~uur


r I I I III I It I I l


1000E
.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS 39

Utilizing the activities of the ions in solution, the solubility product
for calcium fluoride becomes
K c= aCa++ X (aF-)2

where K caF = equilibrium constant for calcium fluoride

a = activity coefficient for the ions
Ca++ and F- = molal concentrations of the ions


Specific electrical


0.10












0.
















0.001
10


1000
conductance, micromhos


Figure 17.-Relation of ionic strength to the specific conductance of some ground waters.


The Handbook of Chemistry and Physics (1954, p. 1634) gives the
solubility product of calcium fluoride at 260 C. (78.80 F.) as 3.95 x
10-11. Using this value and assuming that ground water system is at


______ ____ __ __ ___ _______ ___ _____ __ __- z p ::z z~
SI I_________ ___________










AS
J0
_






/
_____-
= = = = : == = = = =
==^^::=====:=

-^: rill
!^---


10,000


0






REPORT OF INVESTIGATIONS No. 46


chemical equilibrium, the maximum fluoride concentration for any given
calcium concentration in a saturated solution may be calculated by:
V 3.95X10--n

aCa++
F- =
1 ^----- ----
aF-
Figure 18 shows a set of curves for a saturated solution of calcium
fluoride with respect to fluorite at several ionic strengths. An ionic
strength of 0.10 is considered about the maximum at which the above
calculations hold (Hem, 1961). From figure 17 this is seen to be at
a specific conductance of about 8,000 micromhos (4,800 ppm dissolved
solids). The lowest curve is a theoretical curve for ionic strength (/L)
equal zero and activity coefficients (a) equal one. For potable ground
water in southwest Florida, the practical curves to consider are from
about ionic strength of 0.002 to 0.02 or about 70 to 900 ppm dissolved
solids.
Figure 18 shows analyses of fluoride versus calcium from ground
water in Florida. The dots represent samples from the Peace and Alafia
River basins that contain more than 0.5 ppm fluoride. The triangular
points represent samples from northwest Florida (Toler, 1966) and are
included to show that the solubility product principle apparently holds
for higher fluoride concentrations.
Most of the points in figure 18 plot to the left of the family of equi-
librium curves showing the water to be undersaturated in fluoride with
respect to fluorite. Those points falling within the family of curves are
from analyses of ground water of relatively high ionic strength. They
also plot to the left of the saturation position for the ionic strength of
that sample and are undersaturated. Figure 18 shows graphically that
the product of the activities of calcium and fluoride in ground water
in Florida approaches, but does not exceed, the theoretical values based
on the concept of chemical equilibrium.
From the concept of the solubility product principle and the analysis
of the graph in figure 18, it is apparent that large concentrations of
fluoride in ground water at equilibrium are limited by the amount of
calcium present. This is significant in southwest Florida where ground
water is obtained from limestone rocks and generally has high calcium
concentrations. For a calcium concentration of 40 ppm and an ionic
strength of 0.01 (dissolved solids about 420 ppm), the maximum fluoride
concentration at equilibrium would be 5 ppm. The role that solubility
would play in event of contamination by water of extremely high fluoride
concentrations makes the reaction important. If contaminating water,
high in fluorides entered the aquifer, the water would quickly become






FLUOIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Fluoride, ports per million
Figure 18.-Scatter diagram of calcium versus fluoride for analyses of ground water in
southwest and northwest Florida and graphs showing the relation of calcium
to fluoride in solutions of different ionic strength saturated with respect
to fluoride.


supersaturated with respect to fluorite. The tendency for the water to
reach equilibrium and satisfy the solubility product should cause chem-
ical precipitation of calcium fluoride in the aquifer and thereby remove






REPORT OF INVESTIGATIONS No. 46


fluoride from solution. Both chemical precipitation and dilution should
act to reduce the concentration of fluoride.
If the assumption is made that, because of its slow movement, ground
water has sufficient time to come to equilibrium with the solid phases
it contacts, and that an unlimited supply of calcium is available from
the limestone aquifer, then the concept of chemical equilibrium can
aid in making a first approximation about the fate of a fluoride contam-
inant that might be introduced into the aquifer.
Many other factors must be considered to predict what might hap-
pen to a contaminant after it enters ground water. LeGrand (1965)
discussed the difficulties involved in making such predictions, and sum-
marizes the present knowledge about the patterns of contaminated zones
of water in the ground. His interpretations of various types of contam-
inated zones are generally some modification of a rectangular prism or
a wedge which forms in the upper part of the zone of saturation.
LeGrand states (p. 83): "Two opposing tendencies need be in focus
before an evaluation of contaminated zones is undertaken: (1) the
tendency of contaminants to be entrained in ground water flow and
(2) the tendency for contaminants to be attenuated to varying degrees
by dilution in water, decay with time, or some other 'die-away' mech-
anism, and sorption on earth materials." The mechanisms of attenuation
of a fluoride contaminant in a limestone aquifer would be largely dilu-
tion and chemical precipitation of fluoride as calcium fluoride.

MONITORING OF FLUORIDE IN GROUND WATER
The areal (fig. 11) and vertical (figs. 13 and 14) distribution of
fluoride in ground water gives no indication of any significant contam-
ination of the ground-water supplies. Because there is presently (1966)
no indication of widespread contamination, any feasible system of mon-
itoring fluoride in ground water that was designed to include all the
phosphate mining area would probably be ineffective and fail to quickly
detect a contaminating mass of fluoride should it enter the aquifer.
If any system of monitoring any contaminant in ground water is to
be effective, it must be capable of quickly detecting the contaminant
near its point of entry into the ground. Therefore, any system of mon-
itoring fluoride in ground water that will quickly and effectively detect
any contamination of the ground-water supplies should be designed in-
dividually around the greatest potential hazards, the chemical plant
settling lagoons.
The lagoons may cover several hundred acres. A detailed investiga-
tion of one or more lagoons would be desirable to (1) firmly establish






FLUORIDE IN WATER IN THE ALAFIA AND PEACE RPER BASINS 43

whether there is leakage to the aquifer or through the banks to the
surrounding area, (2) determine effects of leakage, if any, on the gra-
dient of the water table and piezometric surface, and (3) acquire data
to prepare hydrogeologic maps adequate for making accurate predic-
tions of local ground-water flow patterns. After sufficient detail of the
hydrology in the vicinity of a lagoon is established, monitoring wells
could be located so they would be most effective. They should be along
the down gradient side of the lagoons with respect to the piezometric
surface and the water table and be constructed to enable collection of
water samples from the surficial materials, the top of the artesian aqui-
fer and from a deeper zone in the aquifer.

SUMMARY
Fluoride concentrations of several parts per million occur in the
surface waters of the Alafia and Peace River basins as a result of waste
water disposal from the mining and processing of phosphate deposits.
The Alafia River carries more fluoride waste than the Peace River and
usually has a fluoride concentration several times as high as the Peace
River.
The Alafia River discharged about 4,000 tons of fluoride from October
1964 to September 1965 compared to about 900 tons for the Peace River.
During this same period, the fluoride concentration of the Alafia River
at Lithia ranged from 3.2 to 30 ppm and the Peace River at Arcadia
ranged from 0.6 to 2.2 ppm. There was no apparent loss of fluoride from
the river to the ground water.
Fluoride occurs naturally in ground water in southwest Florida in
concentrations from 0.0 to about 4.0 ppm. The concentration of fluoride
in ground water is generally lowest in northern and central Polk County
and is generally highest in the southern part of the area. There is both
areal and vertical variability in fluoride concentrations. The highest con-
centrations are usually found in water from the Hawthorn Formation
and Tampa Formation of Miocene age. The source of the fluoride is
apparently the phosphate minerals within the formations.
The waste water in the settling lagoons at the phosphate chemical
processing plants contains fluoride concentrations of several hundred
ppm. Fine waste material deposited in these lagoons appears to retard
leakage of the waste water to the aquifer. The lagoons are a potential
pollution hazard if the fine waste material is not effective in preventing
leakage, or if solution of the underlying limestone should allow collapse
of the surface materials into solution chambers to breach the fine de-
posits. If such should occur, the fluoride could contaminate the ground-






44 REPORT OF INVESTIGATIONS No. 46

water supplies for several miles from the point of entry into the aquifer.
Any system of monitoring fluoride in ground-water should be de-
signed about the chemical plant settling lagoons to best detect a possible
fluoride contaminant. A detailed investigation is desirable to firmly es-
tablish the geologic-hydrologic conditions in the vicinity of one or more
of the lagoons. Such an investigation would establish the best proce-
dures to be followed in designing an effective monitoring system for
ground water. Experimental investigation of the fate of solutions con-
taining high concentrations of fluoride when they enter a limestone
environment is essential to predict the effects on ground water should
water from the lagoons enter the ground.







FLUORIDE IN WATER IN THE ALAFIA AND PEACE RIVER BASINS


Aumeras, M.
1927

Back, Willian
1961

1963

Barraclough,
1962

Cathcart T. I


REFERENCES

Equilibrium of calcium fluoride and dilute hydrochloric acid: Jour.
Chem. Phys., v. 24, p. 548-571.

Calcium carbonate saturation in ground water from routine analyses:
U.S. Geol. Survey Water-Supply Paper 1535-D.
Preliminary results of calcium carbonate saturation of ground water
in central Florida: Internat. Assoc. Sci. Hydrology, v. VIII, No. 3.
J. T.
(and Marsh, O. T.) Aquifers and quality of ground water along the
Gulf Coast of western Florida: Fla. Geol. Survey Rept. Inv. 29.
B.


1959 (and Lawrence, J. M.) Results of geologic exploration by core drilling,
1953, land pebble phosphate district, Florida: U.S. Geol. Survey
Bull. 1046-K.
Florida State Board of Health
1955a Peace and Alafia Rivers, stream sanitation studies 1950-1953: Volume
I, The Alafia River, Fla. State Bd. of Health, Jacksonville, Florida.
1955b Peace and Alafia Rivers, stream sanitation studies 1950-1953: Volume
II, The Peace River, Fla. State Bd. of Health, Jacksonville, Florida.
Glasstone, Samuel
1946 The elements of physical chemistry: D. Van Nostrand Co., Inc.,
Princeton, New Jersey.
Handbook of Chemistry and Physics
1954 The 36th edition: Chemical Rubber Pub. Co., Cleveland, Ohio.
Hem, J. D.
1959 Study and interpretation of the chemical characteristics of natural


water: U. S. Geol. Survey Water-Supply Paper 1473.
1961 Calculation and use of ion activity: U.S. Geol. Survey Water-Supply
Paper 1535-C.
Johnson, Lamar
1960 A report on a plan of improvement for the Peace River Valley:
Peace River Valley Water Conserv. and Drainage Dist., Consult. Eng.
Rept.
1963 A basic plan for the Alafia River basin: Alafia River Basin Bd.,
Consult. Eng. Rept.
Joyner, B.F. (See Sutcliffe, H.)


Lanquist, Ellis
1955


Lawrence, J. M.
LeGrand, H. E.
1965

McKee, J. E.
1963

Menke, C. G.
1961

Meredith, E. W.
Peek, H. M.
1958

Shattles, D. E.
1965


A biological survey of the Peace River, Florida, Peace and Alafia
Rivers, stream sanitation studies, supplement II to volume II: Fla.
State Bd. of Health, Jacksonville, Fla.
(See Cathcart, J. B.)

Patterns of contaminated zones of water in the ground: Water Re-
sources Research, v. 1, no. 1, p. 83-95.

(and Wolf, H. W.) Water quality criteria, second edition: The Re-
sources Agency of Calif., State Water Quality Control Bd., Pub. No. 3-A.

(Meredith, E. W., and Wetterhall, W. S.) Water resources of Hills-
borough County, Florida: Fla. Geol. Survey Rept. Inv. 25.
(See Menke, C. G.)

Ground water resources of Manatee County, Florida: Fla. Geol. Survey
Rept. Inv. 18.

Quality of water from the Floridan aquifer in Hillsborough County,
Florida, 1963: Fla. Geol. Survey Map Series No. 9.






REPOTr OF INVESTIGATIONS No. 46


Specht, R. C
1950 Phosphate waste studies: Fla. Eng. and Ind. Exper. Sta. Bull. No. 32.
1960 Disposal of wastes from the phosphate industry: Jour. Water Poll.
Control Feder., v. 32, No. 9, p. 964-974.
Satcliffe, .L
1966 (and Joyner, B. F.) Packer testing in water wells near Sarasota,
Florida: Ground Water, Jour. Tech. Div. Nat. Water Well Assoc.,
v. 4, No. 2, p. 23-27.
Toler, L. G.
1966 Fluoride content of water from the Floridan aquifer in northwestern
Florida: Fla. Geol. Survey Map Series No. 23.
United States Public-Health Service
1962a Fluoride drinking waters: U.S. Public Health Serv. Pub. 825.
1962b Drinking water standards: U.S. Public Health Serv. Pub. 956.
Wetterhall,W. S. (See Menke, C. G.)
Wolf, L W. (See McKee, J. E.)
Woodard, H. J.
1964 Preliminary report on the geology and ground water resources of
Hardee and DeSoto counties: Fla. Div. Water Resour. and Cons. Pub.