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 Copyright
 Introduction
 SO2 chemical characteristics and...
 SO2 effects on plants
 Acid rain
 Genetic adaptations to airborne...
 Research at Arec-Bradenton
 Reference






Group Title: Research report - Bradenton Agricultural Research & Education Center - GC1979-17
Title: Effects of airborne sulfur dioxide on Florida vegetation
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00067730/00001
 Material Information
Title: Effects of airborne sulfur dioxide on Florida vegetation
Series Title: Bradenton AREC research report
Physical Description: 6 leaves : ; 28 cm.
Language: English
Creator: Woltz, S. S
Howe, T. K ( Teresa K )
Agricultural Research & Education Center (Bradenton, Fla.)
Publisher: Agricultural Research & Education Center, IFAS, University of Florida
Place of Publication: Bradenton Fla
Publication Date: 1979
 Subjects
Subject: Plants -- Effect of air pollution on -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 6).
Statement of Responsibility: S.S. Woltz and Teresa K. Howe.
General Note: Caption title.
General Note: "November 1979."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067730
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 73146033

Table of Contents
    Copyright
        Copyright
    Introduction
        Page 1
    SO2 chemical characteristics and plant entry
        Page 2
    SO2 effects on plants
        Page 3
    Acid rain
        Page 4
    Genetic adaptations to airborne SO2
        Page 5
    Research at Arec-Bradenton
        Page 5
    Reference
        Page 6
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida






f"^ #) AGRICULTURAL RESEARCH & EDUCATION CENTER
IFAS, University of Florida
66C Bradenton, Florida

Bradenton AREC Research Report GC1979-17 November 1979

7 '/ EFFECTS OF AIRBORNE SULFUR DIOXIDE ON FLORIDA VEGETATION*
S. S. WoltzdanTr- esa-K,-tHowe.

I. INTRODUCTION I OLi 1980

Prospects for SO2 air pollution problems are increase ng in Florida as fossil
fuel use patterns are adjusted toj perhii$.ui.f ipjhq g sulfur-containing fuels.
Controls are being weakened in th" fare-f-the-4 petroleum shortage. We, in
Florida agriculture, need to initiate the establishment of trade-off effects to com-
bat the steadily increasing SO2 air pollution on yield and quality of both agricul-
tural produce and on native and landscape vegetation. Once these effects have been
evaluated to some practical degree, decisions can be made as to what SO2 levels agri-
culture can tolerate and how it can adjust to the problem.

The approach to SO2 air pollution problems from the agricultural viewpoint will
most likely result in benefits in general environmental preservation since effects of
S02 on plants are more easily demonstrable than on humans. If SO2 levels for plants
are controlled by industrial and governmental efforts, then society in general will
benefit. Preliminary indications are that S02 is not a serious problem at this time
in Florida. However, detailed information is needed in regard to the specific condi-
tions of the state presently and, with the passage of time and probable increase in
SO2 air pollution.
The economic damage to plants is usually estimated directly from the percentage
leaf area injured or destroyed. Less apparent injury such as a mild chlorosis or
growth retardation can not be evaluated by this procedure. Thus, a need is created
for controlled-atmosphere evaluations of the effects of specific levels, durations,
and intensities of SO2 exposure on plant growth, quality, and quantity of yield. The
"tolerable" standard for average annual SO, in the United States as a whole is 80
micrograms of the chemical compound per cubic meter of air. Conformity to this
standard does not assure freedom from plant injury since some plants are damaged by
half this level. Information is needed as to maximum short-term and continuous expo-
sure levels that are tolerable for locally occurring plant species and agricultural
patterns of operation.

SO2 effects have been studied mainly as those of a single pollutant. Ozone,
when found as a pollutant in combination with SO2, causes variable effects. Ozone
may alleviate or enhance damage attributable to S02, or damage may result from the
combined effect of SO2 and ozone, but not from either gas alone. Nitrogen dioxide,
on the other hand, causes a synergistic effect when combined with SO2, causing sig-
nificant damage that does not result from the individual pollutants at their same
respective concentrations,
The continued efforts of this research program at AREC-Bradenton are to evaluate
the prospective disruptions and minimize damage to agriculture in Florida from SO2
air pollution. This report summarizes recent studies of the effects of airborne
sulfur dioxide on vegetation.


*Supported in part by a grant from the University of Florida Gatorade Fund to the
Interdisciplinary Center for Aeronomy and (other) Atmospheric Sciences and by fund-
ing from the IFAS Center for Environmental and Natural Resources Program.





-2-


II. SO2 CHEMICAL CHARACTERISTICS AND PLANT ENTRY
For agriculture and ecology, the principal deterrent to steadily increasing
fossil fuel-burning activities is the sulfur present in the fuels. Biologically,
sulfur is indispensable, being a major constituent of amino acids, and thus pro-
tein, and performs a variety of roles in metabolic intermediaries. Sulfur is re-
quired by plants at about one-tenth the level of nitrogen, principally as a compo-
nent of the amino acids methionine, cysteine, and cystine. The sulfur requirement
is acquired principally as sulfate from the soil, but also as other organic and
inorganic sulfur compounds.

Sulfur dioxide is somewhat similar to carbon dioxide in physico-chemical qual-
ities. It is a heavy gas, readily absorbed by porous materials, and easily lique-
fied. It dissolves readily in water, producing a relatively weak acid, somewhat
stronger than carbonic and hydrofluoric acids. The acid produced, sulfurous acid
H2SO3, is poorly characterized in terms of physical structure. SO2 acts with water,
both as an oxidizing and as a reducing agent. Biochemically, SO2 may be either
oxidized or reduced to a variety of sulfur-containing compounds. SO2 is extremely
soluble in fat solvents such as acetone, which indicates a lipophilic quality which
aids in penetration of plant cuticle. An affinity for water as well as lipids makes
the molecule readily mobile in plant tissue, having relatively easy access to most
cell types. Plant material effectively scrubs SO2 from the air up to certain con-
centrations. The geometry of the plant and successive plant contacts of a moving
mass of air determines the scrubbing efficiency. Thus, successive rows of trees or
other plants receive decreasing SO2 dosages from a traveling air mass. Plant uptake
of airborne SO2 is primarily into the leaves via the stomates or "breathing pores."
Uptake via the inter-stomatal epidermal cells via the cuticle is also significant,
but not as damaging. SO2 absorbed by the epidermal cells contributes significantly
to increased foliar sulfur content with less damage than uptake via the stomates.

The degree of stomatal aperture is of such importance in SO damage to leaves
during episodes of high level fumigation (>2600 pg/m3) that in short exposures of
1 to 4 hours on susceptible plants, the pattern of acute injury coincides approxi-
mately with the pattern of leaf areas possessing functioning open stomates. The
youngest and oldest leaves frequently escape damage because stomates are immature
and not yet functional in young leaves and closed because of senescence in old
leaves. Individual plants that are suffering from water deficiency and have closed
stomates and/or a higher diffusive resistance to gases, generally escape acute dam-
age from high level, short duration exposure to SO2. Environmental factors that
favor increased stomatal aperture also enhance susceptibility to fumigation damage
from SO2 through the stomatal opening mechanism. Higher relative humidities (above
70-80%) increase susceptibility to acute SO2 damage, whereas low relative humidity
(below 30-40%) clearly aids in the protection of plant life exposed to atmospheric
SO2. Stomatal opening on many plant species corresponds to diurnal periods of
enhanced photosynthetic activity. This happens for most plants during the morning
hours on sunny days when temperatures are optimal for the plant species involved.
Heavy SO2 exposure at this time is generally much more damaging than at other times
of the day. Species with high gas exchange capacity are usually more susceptible
to damage from SO2. Species with slow growth rates, low rates of photosynthesis
and low gas exchange characteristics are much less susceptible to S02 damage.
Shade plants (those which grow best at low sunlight intensities and very poorly at
high light intensities) are adapted to low gas exchange, low rates of photosynthesis
and are generally less subject to SO2 injury.

Plant nutritional status also clearly alters both SO2 sensitivity and stomatal
opening patterns. Increased levels of nitrogen lower the SO2 susceptibility appar-
ently by increasing sulfur nutritional needs for protein synthesis. High levels of
fertilization with sulfates increase the damage from SO2 air pollution, especially
from long-term, low-level fumigation.




-3-


III. SO2 EFFECTS ON PLANTS

The effects of SO2 on plants have been under investigation for over a century.
S02 is the oldest recognized air pollutant and has been long associated with coal-
burning and industry. The responses of plants to atmospheric SO include 1) bene-
ficial effects due to a supply of an indispensable nutrient, sulfur, 2) hidden or
invisible injury reflecting a reduced growth rate and impaired plant metabolism,
3) chronic injury visible as foliar chlorosis, stunting, and possibly impaired
produce quality, and 4) acute injury causing the death of plant tissues, espec-
ially foliage, resulting in a characteristic interveinal "scorch" of leaf laminae
(necrotic tissue between leaf veins).

The interpretation of SO2 effects on plants is usually linked to the degree
of visible leaf damage, i.e. percentage of leaf area destroyed. Although this is
a tangible and usually accepted criterion for economic damage estimation, it does
not take into account certain types of hidden, chronic injury. While most emphasis
should be on acute injury, some allowances need to be made for chronic injury. Many
changes have been found in metabolic and physiologic processes due to SO2 but have
not been directly applicable to plant damage estimates. Effects on plants and micro-
organisms are of ecological significance due to changes in vigor, structure and
composition of the flora. SO2 and SO3 cause changes in soil pH, nutrient providing
capacity, and microorganism population which in turn affect higher plant population
stability and resistance to stress.

There is an extremely wide range in susceptibility-tolerance categorization
for plant species in response to airborne SO2 effects. Information on the relative
tolerance of native and cultivated species can be used to advantage in land use
planning for locating fossil fuel-burning facilities and in selecting species for
planting within the range of influence of SO2 emissions. Tolerant species that
effectively scrub SO2 from the air may be used to minimize air pollution problems.
Large acreages surrounding a facility could be planted to something like Eucalyptus
trees that grow very rapidly in the southeastern United States and can be harvested
for pulp operations. The value of preventive planting would be determined by an
evaluation of distribution patterns of SO2 emissions into the atmosphere. If a
source emitted SO2 at 300 ft elevation, the planting effects would not be effective
locally, but would be if the SO2 were moving at ground level.

Indicator plants are used in diagnosing plant damage caused by SO2 air pollu-
tion. If symptoms on susceptible species are representative of SO2 damage and the
range of effects on a number of other species correlates well with their tolerances
to S02, this correlation should lead to a further study into the cause of apparent
SO2 damage. Included should be air sample and meterology monitoring relative to
potential emission sources of SO2. Also, within the limitations of plant analysis
and with due attention to other sources such as fertilizers and sprays, sulfur
analysis of plant material may give supplemental indications of the cause. Plant
analysis alone is not reliable in SO2 damage evaluation.

IV. SO2 FUMIGATION + SO2 DOSE RESPONSE RELATIONSHIP FOR PLANTS

Controlled fumigation of plants with SO2 provides information on the qualitative
and quantitative effects on various species. Cultivated and native plants may be
categorized for their response to airborne SO2. Such information is useful in:
(a) diagnostic technique for plant damage of unknown etiology; (b) land use planning,
to suit the plant species to the ambient SO2 problems as well as the reverse, to
suit the SO2 air pollution to the susceptibility of the surrounding plant populations;
(c) for tracing the path of SO0 plumes or assistance in establishing isopleths of
S02 effects around an isolated emission source; and (d) establishment of bioindicator
techniques in SO2 biological air quality evaluation.






The effects of a given concentration of S02 for a specific time period are the
dose-response relationships. Atmospheres may be controlled with standardized fumi-
gation or, when warranted, ambient atmospheric SO2 levels may be closely monitored
and the effects under each individual condition documented. It is clearly evident
that short duration but high concentration exposure is much more damaging than low
concentrations of SO2 over extended exposure periods. A basic principle encountered
in the peculiar effects of SO? is that detoxification of SO2 may prevent acute dam-
age if the atmospheric level is below a critical level wherein SO2 is metabolized
into less toxic compounds before acute damage occurs. If atmospheric SO2 is above
the critical level for the environmental conditions, acute damage will result.

Dose-response levels for plants are not first class criteria for prediction of
damage. Alfalfa, for example, is reported as receiving injury at concentrations
lower than some cases where injury did not occur. This is attributable to differ-
ences in environmental conditions and the physiological status of the plants. Since
plant response from exposure to SO2 is not accurately predictable, plant dose-response
predictions are more relative than absolute. Relative comparisons have special
meaning as, for example, in comparing an assortment of plant species for SO2 suscep-
tibility in the same experiment under the same environment. Dose-response data for
one plant species for reliable predictions would have to be relative, namely com-
paring the combinations of concentration and duration of exposure under the same
environmental conditions. For each new environment, there may be a different response
to a given dose. This does not represent an insurmountable obstacle but reinforces
the concept of relativity and the need for comparative observations among species
and among environments. The variability in response relative to environment may be
partially attributed to changes in the physiological basis of response.

V. ACID RAIN

Acid rain and acid mist (H2S04 + HNO3) have several types of effects on vege-
tation, soil, bodies of water, and ecological balance. These effects have not yet
become as pronounced in the southeast as they have in the northeastern United States,
Canada, and Northern Europe. The problems of acid rain are associated with the long
range transport of sulfur dioxide and acid sulfates and are attributable to the prac-
tice of exporting SO2 from tall stacks instead of trapping the gas locally. Rain-
water in equilibrium with atmospheric CO2 has a pH of 5.6 due to CO2 acidification.
SOx + NOx may lower the pH to 4.0 or occasionally less, which is potentially quite
harmful biologically. In 1972-73, the principal rainwater pH range for the south-
east was 5,0 to 4.4, whereas in 1955-56, the range was 5.6 to 4.7. The effects of
acid rain on vegetation including spotting of upper leaf surfaces by deposited fine
droplets of acid mist, especially on beet, Swiss chard, and alfalfa; decreased pro-
ductivity of forests affected by acidified rain; reduction in the incidence of cer-
tain plant diseases; inhibition of nitrogen fixation; erosion of leaf cuticle;
increased disease susceptibility after acid rain damage to leaves; and leaching of
nutrient cations from leaves. Soil acidification by acid rain results in impairment
in soil microbiology, nitrogen fixation, and leaching losses of soil nutrient cations.
Toxicity and enhanced uptake of undesirable elements also may occur, as for example,
enrichment of plant produce with cadmium. It was suggested that acid rain altered
cellwall and membrane structures making plants more susceptible to other pollutants
and to plant parasites. If standards for sulfates are not prescribed and enforced,
forests in affected areas will be degraded. The combined effects of acid rain will
threaten the profitability of agriculture and disrupt the native ecosystems; The
effects of acid rain require some length of time for manifestation; once at hand,
a long period of time is required for correction following abatement in acid rain.

The acidification of lakes and streams by acid rain and SO2 effects may cause
severe stress on aquatic ecosystems. The specific effects of acidification of
natural waters are many: acidified reservoirs will have an increase in metal






concentrations that can exceed public health limits for drinking water; acid lakes
will not support fish populations and will become visually unattractive due to dense
growth of filamentous algae and sphagnum mosses; and unique communities of aquatic
populations as well as individual species may be in danger of extinction.

VI. GENETIC ADAPTATIONS TO AIRBORNE SO2

Atmospheric S02 has an effect on the genetic makeup of native populations of
perennial ryegrass and on Geranium carolinianum. The selection pressure of SO2 air
pollution results in the evident changes of native populations in affected geographic
areas to the extent that the populations from polluted areas are statistically super-
ior in SO2 resistance over populations from nearby unpolluted geographic areas.
There is a precedent for this in the genetic response of native populations whereby
increased tolerance occurs to pollution with heavy metal residues. The demonstrated
evolution of increased native resistance to an environment-degrading factor has wide
implications for ecosystems in that it holds hope that "nature" will adapt to man's
changes in the environmental influences impinging on native ecosystems and biota.

VII. RESEARCH AT AREC-BRADENTON

The physiological, metabolic, and anatomical bases for SO2 susceptibility have
not been well explored. Additionally, there is a need to assess SO2 pollution as it
impacts Florida's unique native plant and agricultural species.

At AREC-Bradenton, seven fumigation greenhouses, each 9'x12' in size with an air
volume of about 800 cubic feet, were designed and constructed to provide steady state
levels of airborne SO2. Container-grown ornamental, vegetable, and tree species are
fumigated under conditions of 75% natural light. Stable atmosphere of SO2 is obtained
by metering the flow of source gas above a fan which draws air through evaporative
cooling pads into the fumigation chambers. The concentration of S02 in the fumiga-
tion chambers has been monitored by drawing chamber air into an impinger containing
a solution of hydrogen peroxide. Future studies will be monitored by a pulsed
fluorescent SO2 analyzer. Dose-exposure treatments are chosen to determine thresholds
for chronic injury, as well as to simulate expected levels of atmospheric pollution.

Preliminary findings at AREC-Bradenton on the tolerance-susceptibility charac-
teristics of selected forest, vegetable, ornamental, and pasture plant species demon-
strate the variable response to SO2 (Table 2). Susceptibility is assessed in terms
of visible or chronic injury, such as chlorosis, necrosis, altered growth habit and
inferior produce quality. It is interesting to note that response to SO2 can be
quite different, even within the same genus. Eucalyptus, for example, falls into
all three susceptibility categories. Current research also includes the development
of analytical techniques for the determination of total and water soluble sulfur
content of plant material. Evidence suggests that the water soluble fraction may
be an indicator of SO2 exposure.

Present and projected research goals include: further quantification of the
effects of accumulated SO2 on sulfur content and metabolism; assessment of the
effects of nutrition on susceptibility and sulfur accumulation and metabolism;
quantification of relationships of stomatal aperture and diffusive resistance on
the absorption of SO2; examination of the effects of water limiting situations on
SO2 absorption and stomatal response; and accumulation of additional data on sympto-
mology and tolerance responses.
These goals, when met, will provide useful information on plant physiological
responses and susceptibilitytolerance levels of many Florida species. This will
facilitate accurate diagnosis of S02 injuries; landscape design practices to avoid
potential damaging situations as well as to effectively scrub S02-polluted air near
emission sources; and development of breeding programs to consider plant suscepti-
bility to airborne SO2'






concentrations that can exceed public health limits for drinking water; acid lakes
will not support fish populations and will become visually unattractive due to dense
growth of filamentous algae and sphagnum mosses; and unique communities of aquatic
populations as well as individual species may be in danger of extinction.

VI. GENETIC ADAPTATIONS TO AIRBORNE SO2

Atmospheric S02 has an effect on the genetic makeup of native populations of
perennial ryegrass and on Geranium carolinianum. The selection pressure of SO2 air
pollution results in the evident changes of native populations in affected geographic
areas to the extent that the populations from polluted areas are statistically super-
ior in SO2 resistance over populations from nearby unpolluted geographic areas.
There is a precedent for this in the genetic response of native populations whereby
increased tolerance occurs to pollution with heavy metal residues. The demonstrated
evolution of increased native resistance to an environment-degrading factor has wide
implications for ecosystems in that it holds hope that "nature" will adapt to man's
changes in the environmental influences impinging on native ecosystems and biota.

VII. RESEARCH AT AREC-BRADENTON

The physiological, metabolic, and anatomical bases for SO2 susceptibility have
not been well explored. Additionally, there is a need to assess SO2 pollution as it
impacts Florida's unique native plant and agricultural species.

At AREC-Bradenton, seven fumigation greenhouses, each 9'x12' in size with an air
volume of about 800 cubic feet, were designed and constructed to provide steady state
levels of airborne SO2. Container-grown ornamental, vegetable, and tree species are
fumigated under conditions of 75% natural light. Stable atmosphere of SO2 is obtained
by metering the flow of source gas above a fan which draws air through evaporative
cooling pads into the fumigation chambers. The concentration of S02 in the fumiga-
tion chambers has been monitored by drawing chamber air into an impinger containing
a solution of hydrogen peroxide. Future studies will be monitored by a pulsed
fluorescent SO2 analyzer. Dose-exposure treatments are chosen to determine thresholds
for chronic injury, as well as to simulate expected levels of atmospheric pollution.

Preliminary findings at AREC-Bradenton on the tolerance-susceptibility charac-
teristics of selected forest, vegetable, ornamental, and pasture plant species demon-
strate the variable response to SO2 (Table 2). Susceptibility is assessed in terms
of visible or chronic injury, such as chlorosis, necrosis, altered growth habit and
inferior produce quality. It is interesting to note that response to SO2 can be
quite different, even within the same genus. Eucalyptus, for example, falls into
all three susceptibility categories. Current research also includes the development
of analytical techniques for the determination of total and water soluble sulfur
content of plant material. Evidence suggests that the water soluble fraction may
be an indicator of SO2 exposure.

Present and projected research goals include: further quantification of the
effects of accumulated SO2 on sulfur content and metabolism; assessment of the
effects of nutrition on susceptibility and sulfur accumulation and metabolism;
quantification of relationships of stomatal aperture and diffusive resistance on
the absorption of SO2; examination of the effects of water limiting situations on
SO2 absorption and stomatal response; and accumulation of additional data on sympto-
mology and tolerance responses.
These goals, when met, will provide useful information on plant physiological
responses and susceptibilitytolerance levels of many Florida species. This will
facilitate accurate diagnosis of S02 injuries; landscape design practices to avoid
potential damaging situations as well as to effectively scrub S02-polluted air near
emission sources; and development of breeding programs to consider plant suscepti-
bility to airborne SO2'







REFERENCES


1. Woltz, S. S., and Jimmy J. Street. 1980. Agriculture. In Coal
A.E.S. Green, ed. University Pressses of Florida, Gainesville,
(In press).
2. Zimmerman, P. W., and A. E. Hitchcock. 1956. Susceptibility of
fluoric acid and sulfur dioxide gases. Contrib. Boyce Thompson


Burning Issues,
Fla. pp 249-276.

plants to hydro-
Inst., 18:263-279.


Table 1. Comparative susceptibility of plant species to SO2 fumigation.

Susceptible Intermediate Resistant

Chicory Azalea Jerusalem cherry
Spanish needles Honeysuckle Gladiolus
Nightshade Plantain Tulip
Celery Grape, wild Sorghum
Tomato Rose Ixora
Pumpkin Lamb's-quarter Corn, field and sweet
Cucumber Galinsoga Stevia
Pigweed Taxus Deutzia
Alfalfa Bean Lily
Clover, sweet Iris
Coleus Apple
Geranium Cotton
Eggplant
Blueberry
Hibiscus

Source Zimmerman and Hitchcock, 1956 (2).


Table 2. Comparative susceptibility of plant species to SO2 fumigation.


Susceptible Intermediate Resistant

Eucalyptus cineria Baldcypress Sweetcorn
Eucalyptus amplifolia Eucalyptus viminalis Turkey oak
Eucalyptus camaldulensis Soybean Eucalyptus robusta
Bushbean Gloxinia Box elder
Aster Petunia Live oak
Zinnia Rosewood Tobacco
Begonia Squash Red mangrove
Tomato Bahiagrass
Pepper Sorghum
Cat's claw Kalanchoe
Buttonwood
Slash pine
Blackeyed pea
Geranium


Source Woltz and Street, 1980 (1).




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