UNITED STATES DEPARTMENT OF THE INTERIOR
MAP SERIES NO. 75
FLORIDA DEPARTMENT OF NATURAL RESOURCES
published by BUREAU OF GEOLOGY
89a 88 87 86 8 84V 83 82 81 80*
NITROGEN LOADS AND
Larry J. Slack and Donald A. Goolsby
Prepared in cooperation with the
BUREAU OF WATER RESOURCES MANAGEMENT
FLORIDA DEPARTMENT OF ENVIRONMENTAL REGULATION
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES
Nitrogen is a fundamental component of all biological systems and, like phosphorus,
carbon, and numerous other elements, is a nutrient that is essential for the growth of both
terrestrial and aquatic plants. Inorganic nitrogen compounds in high concentration in
water can stimulate undesirable plant growth, including algal blooms, increase the rate of
eutrophication of lakes, and result in a general deterioration in water quality. Knowledge
of the occurrence and distribution of nitrogen compounds is essential so that water
management and regulatory agencies can understand the water-quality aspects of Florida
streams. This report pictorially presents information on the generalized distribution,
nature, and significance of nitrogen concentrations and the loads of nitrogen discharged
annually by major Florida streams.
SOURCES AND SIGNIFICANCE OF NITROGEN FORMS
The nitrogen cycle (fig. 1) is a complex biochemical phenomenon in a constant state of
interaction. Almost 34,500 tons of atmospheric nitrogen exist over each acre of land
surface throughout the world (Task Group Report, 1967). The upper 0.5 foot of most soils
inm the United States contains an average of about 1.5 tons of total nitrogen per acre (Task
Group Report, 1967) Atmospheric nitrogen (primarily Na) and terrestrial nitrogen
(primarily stable organic nitrogen or completed compounds) are major natural sources of
the nitrogen n surface water.
Nitrate (NO.-) is usually the form of inorganic nitrogen most prevalent in uncon-
taminated water because it is the end product of the aerobic decomposition of organic
nitrogen. Concentrations of nitrate are seldom high in natural surface waters because it is
constantly being converted to organic nitrogen by photosynthesis. Nitrate may occur in
high concentrations in contaminated water that has undergone self-purification or aerobic
treatment processes High concentrations of nitrate may also result from excessive
Largely because of serious and occasionally fatal poisonings in infants after ingesting
water containing high concentrations of nitrate nitrogen, the Environmental Protection
Agency (National Academy of Sciences and National Academy of Engineering, 1973)
recommends that the nitrate (expressed as nitrogen) concentration in public water supply
sources not exceed 10 mg/1 (milligrams per liter).
Ammonia nitrogen refers to the total of NH,, NHI, and NH.+. Most ammonia occurs as
the ion NH. Ammonia is produced by the decomposition of organic nitrogen compounds
and by nitrogen fixation.
Ammonia (in the form of ammonium salts) is a major component of nitrogen. fertilizer,
but owing to the rapid conversion of ammonia to nitrate, little of the applied ammonia
remains in its original form. The presence of more than 0.1 mg/1 of ammonia in water
sometimes is an indication of organic pollution (Rudolph, 1931). Although an ammonia
concentration of 0.3 mg/1 causes a noticeable drop in the oxygen content of the blood of
fish, a concentration of 1.5 mg/1 is not harmful to most varieties offish (McKee and Wolf,
1963) According to Brezonik (1972), algae derive most of their nitrogen from ammonia,
often in spite of higher nitrate concentrations in the water.
Domestic wastes usually contain about 8 to 12 pounds of total nitrogen per capital per
year (Task Group Report, 1967). In general, about 20-50 percent of the total nitrogen in
domestic waste is removed by treatment and about half of the organic nitrogen in domestic
wastes can be enzymatically hydrolyzed to ammonia by the time the wastes leave the
treatment plant. Based on a removal of about 30 percent of the total nitrogen and an
average waste flow of 100 gallons per day per capital, treatment-plant effluent would
contain 18-28 mg/1 total nitrogen.
The Environmental Protection Agency (National Academy of Sciences and National
Academy of Engineering, 1973) recommended that ammonia nitrogen in public water
supply sources not exceed 0.5 mg/1 "because ammonia may be indicative of pollution and
because of its significant effect on chlorinationa..."
Nitrite (NOa ) is an unstable intermediate product generally formed by the action of
bacteria upon ammonia and organic nitrogen and is readily oxidized to nitrate. Nitrite is
also an intermediate form in the ammonification of nitrate. Nitrite in water sometimes
indicates organic contamination. The Environmental Protection Agency recommended
limit for nitrite nitrogen for public supply sources is 1 0 mg/1 (National Academy of
Sciences and National Academy of Engineering, 1973).
Organic nitrogen includes all nitrogenous organic compounds, chiefly amino acids,
polypeptides, and proteins Because of the natural inflow of nitrogenous products by
overland flow and normal biological activity, organic nitrogen is present in all surface
waters Concentrations of organic nitrogen often are high in municipal and industrial
effluents. Organic nitrogen generally is not pathologically significant, but is important in
aquatic biological activity because of its potential as a source of nitrogen for both plant
and animal life. Organic nitrogen is sometimes an indicator of pollution also.
Total nitrogen is the sum of the four individual nitrogen species. Ifts value is important
because of the cycling and interrelations among the various species of nitrogen. A
knowledge of total nitrogen concentrations is necessary for making mass balance studies,
for determining nitrogen loads discharged by streams, and in understanding the sources of
nitrogen. According to McKee and Wolf (1963), the enormous growth of plants in streams
and lakes, so common where the water bodies have become contaminated, does not occur
where the total nitrogen concentration is below 0.6 mg/1
METHODS OF ANALYSIS
Approximately 4,000 nitrogen analyses from 204 stations were used in the preparation
of this report. These data were collected by the U.S. Geological Survey in cooperation with
numerous state, local, and federal agencies. Most data used in this report were collected
between October 1.971 and May 1975. For a few sites the data-collection period extended
back to October 1968. Total nitrogen loads were computed for 86 stations where
streamflow data were available. Loads were computed from the following relationship:
Total Average x Average x 0.0027 x 365
Nitrogen Total Nitrogen Annual a conversion No. of
Load Concentration Flow constant days/yr
(ton/yr) (mg/1) (ftR/s)
As a check on the validity of this approach, annual loads for a few selected stations were
also computed from a linear regression analysis for streamflow versus total nitrogen loads.
Results from the two approaches compared favorably (table 1). Basin loads were prorated
on the basis of drainage area size.
The distribution and concentration of total nitrogen in Florida surface waters is shown
on the large map. The interpretations in this atlas are based on data for the 204 stations
mentioned in the previous section and the interpretative reports listed in the Selected
References. As data are limited over much of the state, regional concentration patterns are
of necessity generalized and local variations may be expected.
The concentrations of total nitrogen are generally lowest in northwest Florida streams
and highest in central and southern Florida. This is due, at least in part, to
differences in total nitrogen concentrations in bulk precipitation m the two areas. Average
concentrations of total nitrogen in rainwater and bulk precipitation at various locations
are compared in table 2. The average concentration of total nitrogen in rainfall in south
Florida is 0.90 mg/1 (Joyner, 1974). This exceeds the average concentration of total
nitrogen in most of the surface waters of northwest Florida. Brezonik (1972) points out
that total nitrogen concentrations in rainfall exhibit such large temporal and real
variability as to render mean values meaningless for simple predictive models. Waller
(1975), reports that for the conservation areas of south Florida, bulk precipitation was the
single largest source of total nitrogen. It contributed 78 percent of the total nitrogen that
entered those areas.
TOTAL NITROGEN LOAD
(tons per year)
Less than 200 1,000 5,000
200- 500 5,000 -10,000
500 -1,000 Greater than 10,000
S24-. ,r 49 Long-term nitrogen-data stations. Numbers are
A those referred to in text, Figure 3 or Table 1.
AiTn. oa JA21 Mouth of river basin. Numbers are those referred
to on Table 3.
Streams with the highest total nitrogen concentrations are those that rec -
waste [such as Elevenmile, Swift, and Hunter Creeks and the Fenh, -. -
(numbers 30, 31, 32, and 33, respectively, on the map)], those that receive i -
heavily fertilized areas [such as Magnolia Creek (34)], or those that rec -
sewage effluent [such as the Econlockhatchee River (35) and Plantation Road Canal (36)].
Organic nitrogen is the dominant species at practically all the surface-water stations
throughout the state. The major exceptions to this are found at the stations described in
the previous paragraph. In Magnolia Creek the dominant nitrogen species is nitrate and
in the Econlockhatchee River, Plantation Road Canal, Swift and Hunter Creeks the
dominant species is ammonia.
The average nitrate nitrogen concentration is less than 1 0 mg/ at 196 of the 204
stations for which data are utilized for this report. The maximum average nitrate-nitrogen
concentration is 4.1 rmg/l, on Magnolia Creek (34), which drains an area in which
fertilizers are heavily used.
The average nitrite-nitrogen concentration is highest, 0 67 mg/1, at Elevenmile Creek
(30), which receives industrial waste. At only 6 of the stations is the average
nitrite-nitrogen concentration greater than 0.10 mg/i
The average ammonma-nitrogen concentration is less than 0.50 mg/1 at 190 of the
stations. Except for 2 stations within the Everglades, all the stations with ammonia-
nitrogen concentrations greater than 0.50 mg/1 receive industrial, municipal, or
The average organic-nitrogen concentration is less than 1 0 mg/1 at 106 of the stations.
It is highest, (5.0 mg/1), at Lake Apopka (37)
Concentration of total nitrogen is generally independent of discharge, unlike many
chemical constituents which show an inverse relation between concentration and
discharge. Moreover, the concentration of total nitrogen does not appear to vary seasonally
for all sites, that is, concentrations at some sites may be low in a given season one year,
and high for the same season the next year.
Total nitrogen load depends more on the volume of water than on the concentration of
nitrogen in the water inasmuch as the flow volume fluctuates over a much greater range
than does the concentration of nitrogen (table 3, fig. 2) Consequently, the load is greatest
for the largest streams in the State.
Total nitrogen loads generally vary directly with drainage area. A plot of nitrogen loads
versus drainage area (fig. 3) indicates that 1 ton of nitrogen per square mile per year is a
reasonable order of magnitude estimate for nitrogen yields. Stream waters with nitrogen
yields greatly exceeding 1 ton per square mile per year usually receive industrial,
municipal, or agricultural effluents. The following are notable examples:
(35) Econlockhatehee River near Chuluota (4 6 tons)
(38) St. Johns River near Deland (1.8 tons)
(39) Apopka-Beauclair Canal near Astatula (2.3 tons)
(40 Peace River at Arcadia (2 0 tons)
(41) Hillsborough River near Zephyrhills (2 1 tons)
(33) FenhoIloway River at Foley (5 0 tons)
Stream waters with nitrogen yields much less than 1 ton per square mile per year
generally have a low mean discharge to drainage area ratio. These included.
(44) Aucilla River at Lamont (0.5 ton)
(52) Withlacoochee River near Holder (0.42 ton)
(43) Oklawaha River at Rodmanm, near Oran Dam, near Orange Springs (0 45 ton)
Approximately 73,000 tons of nitrogen ae discharged annually through Florida
streams, springs, and canals. Of this amount about 21,000 tons are discharged to the
Atlantic Ocean and 52,000 tons to the Gulf of Mexico.
Brezonik, P. L.
1972 Nitrogen: Sources and transformations n natural waters, m Allen, H. E., and
Kramer, J R., Nutrients in natural waters: New York, John Wiley and Sons,
Brezonik, P. L, Morgan, W. H., Shannon, E E., and Putnam, H. D.
1969 Eutrophication factors in north central Florida lakes: Florida Univ Eng. and
Indus. Expt. Sta
Brown, Eugene, Skougstad, M W, and Fishman, M. J.
1970 Methods for collection and analysis of water samples for dissolved minerals
and gases: U.S. Geol. Survey Techniques Water-Resources Inv., book 5, chap.
Al, 160 p.
Freiberger, H. J.
1972 Nutrient survey of surface waters in southern Florida during a wet and a dry
season: September 1970 and March 1971' U.S. Geol. Survey open-file rept.
72008, 28 p.
Gamboll, A W., and Fisher, D. W.
1966 Chemical composition of rainfall, eastern North Carolina and southeastern
Virginia: U.S. Geol. Survey Water-Supply Paper 1535-K.
Harriss, R. C., and Turner, R. R.
1974 Job completion report-Lake Jackson investigations: Florida Game and Fish
Comm rept. F-12-15,231 p.
Joyner, B. F.
1973 Nitrogen, phosphorus, and trace elements in Florida surface waters, 1970-71:
U.S. Geol. Survey open-file rept. 73028, 30 p.
1974 Chemical and biological conditions of Lake Okeechobee, Florida, 1969-72:
Florida Bur. Geology, Rept. Inv. 71, 94 p
McKee, J. E., and Wolf, H. W.
1963 Water quality criteria, State Water Quality Control Board, pub. 3A,
Sacramento, Calif., 548 p.
National Academy of Sciences and National Academy of Engineering
1973 Water quality criteria 1972: (U.S.) Environmental Protection Agency rept.
EPA Re 73 033, 594 p.
Rainwater, F. H., and Thatcher, L. L.
1960 Methods for collection and analysis of water samples: U S. Geol. Survey
Water-Supply Paper 1454, 301 p.
1931 Principles of the determination of the physical and chemical standards of water
for drinking, industrial, and domestic purposes: Water Pollution Abs. 4
Schneider, R. F., and Little, J. A.
1969 Characterization of bottom sediments and selected nitrogen and phosphorus
sources in Lake Apopka, Florida: Athens, Georgia, Federal Water Pollution
Task Group Report
1967 Sources of nitrogen and phosphorus in water supplies: Am. Water Works
Assoc. Jour., v. 59, p. 344-366.
U.S. Geological Survey
1975 Water resources data for Florida, Part 1, Surface water records, 1974.
Waller, B. G.
1975 Distribution of nitrogen and phosphorus in the conservation areas in south
Florida from July 1972 to June 1973: U.S. Geol. Survey Water-Resources Inv.
5-75, 33 p.
.-- "N (-L .... 7----
Table 1.-Comparison of annual omtrogen loads c
(Stations cited are shown on map by numb
40 Peace Rive at Arcada 112
43 Oklawaha River at Rodan Dam, 1,910
45 St Mays River near Macclenny 689
46 St. Johns Rvernear Cocoa 1,094
47 OklawhaRiverat Moss Bluff 351
48 Fisheatmg Creek at Palmdale 265
49 Kiss Rer at S5E, 2.188
50 Snake C k Canal at S-29, 391
at North Miamn Beach
51 AlaiaRiver at Lthum 377
52 Wthlacooiet River nea Holder 763
53 Suwo Rver at Brford 6,920
54 Sopchoppy Rver near Sopchoppy 187
55 Apalachicola Rver 22,100
56 Chipola River nr Aha 1,474
57 EmbRiver n Century 6,033
a Stations 307, 41, 42a and 58 di sd text or hw
becac sufficient data exist to allow uie of the region metho
b Cmputed from Average ennation Average dcharge 0
c Computed from regmreson equation Total N (tons/yr) cQ X 3
c d d e ff a meant d e nent devby the mpu
wluchmexist a mean dicharge
S. ..... I ,.
AVERAGE TOTAL NITROGEN CONCENTRATIONS
(milligrams per litre)
Less than 0.60
II ST. JOHNS
] 1.20- 2.40
Greater than 2.40
DIXIE i .
computed by two methods i
bered solid circles.) LEV ; --- -
mtgen Ntgen load _. __
mececo etoseo c---
23 2,70 2,300 --- .,
64 1,200 970 T i l
556 52o Table 2.-Nitrogen concentrations m rainfall and bulk precipita- 17- --
i 1-0 1w stion at various locations, in milligrams per lter '- ---
17 6o0 540 [A, Joyner .(1974); B, Brezonik and others (1969); I
s15 400 43 C, Schneider (1969); D, Gambell and Fisher (1966); 1.'
12 a. 2,6a E, Waller (oral commun., 1975); F, Harriss and Turner --'
16 t.0 620t 974/] -
Surce A B c D* E*_ E u SE
16 580 73so Ntrate(N -N) 010 020 9 013 0.49 031 .
68 510 40 Nitn.(NG.-N) 0M 0 02 0K4 )_0-R% ID.:
89 6,100 5,900 Amona(NH. N) 38 21 18 .07 31 12 I
70 130 150 Organs en N) 42 32 59 -
65 14,200 3,800 Total nitrogen (N) 90 74 43 14 -
*Bukpreipition (oMWt falot) ---- --- -
0 1,1i 1,10- \
-52 3,100 2,900 __.. ..-
od ion raph but ng list in thi table .. I .
1 s 4- tput Im
a 27 t a i ii\ 365 -,'
65, where Q s e amnual discharge, i a
ar for syafic MMAmbary mlations
Table 3.-Nitrogen loads and concentrations for major rver basins in Florida.
(Stations cited are shown on map by numbered solid triangles.
No RcerIbasr disarge* Ntorgn ia
S St Marys 1,460 1,100
2 Okilawaha 1,910 1200
3 St. Johns 10,500 12,0o0
4 Kiaimmee(ati5E) 2,188 2,500
5 St Lucieanal 1,105 9mo
West Palm Beach Canal 435 2,100
Hills. r Canal 339 510
8 North NewRiverCanal 451 770
9 Miami Canal 312 510
* Tamam Cana 300 1,800
11 Ca]osahatch C al 1722i 2,00
12 PaceRiver 2,100 4,800
13 Myakka 610 940
14 Manatee as350 320
15 Alaia 470 730
6 Hillrborugh 860 1,40
17 Withlacoohee 2,100 1,000
8 Suwann 1,000 8,000
19 Fenholloway 32 550
20 Auclla 450 470
21 St Marks 1,100 500
22 Oclkon 2,000 2200
23 Chlipola 2,300 1,800
24 Apalachcola 25,20 17,000
25 Choctawhata 7,100 4,100
6so Yellow 3000 1,300
7 Blackwater 1,300 590
28 Esamia 6,700 3,400
9 Per.dio 1,700 87c
NO,-N NH S-N Org0-N TotNal
003 04 0 68 076
04 03 1 12
10 o6 0 12
O08 06 72 8
16 10 17 21
13 18 12 1.5
o4 28 12 1
,14 10 15 1
15 04 99 12
S 07 86 22 s
096 9 52 17
31 03 40 75
00 1,00 31 42
o1 .03 10 O
,42 09 62 12
21 -05 37 65
17 .04 37 59
07 03 41 41
10 04 37 52
08 02 41 51
AND SOIL NITROGEN-,.AM
(FROM PLANTS, FERTILIZERS,
Figure i.-A simplified diagram of
a E --' -
I..So ..--- LI
.. ... MOo .
i "- ul! t.I 1 -
',.I 'i a, r' LEE sE .
ST. c --. A
S-7---. - 27'
From Water resurc data for Florda, Part 1, Surface water rerds, 1974
**Refer to aggregate quantity of sheet flow perpendula to Tamam Canal as aured at four staton
CGL LIE P
100,000 r-v-1 n -,---,- r -- ...-.. .. ... .
-- 38. _
S44 NOTE: Numbers are those
for stations on large map
100 1000 10,000
DRAINAGE AREA, IN SQUARE MILES
Figure 3.-Relation between yearly total nitrogen load and drainage area for selected stations.
TOTAL NITROGEN LOAD, IN TONS PER DAY
Figure 2.-Relation between total nitrogen load and discharge at selected stations.
0 to10 20 30 '- SO MILES
Graphics by D. F. Tucker and J, Tomberlin I
FL..ORIDA (GE(O1..TIC SURVEY M'AP SERIE
>< i ^^i::
No 7 57
I I I I I I I
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