TABLE 2 (continued)

Injury Index (%)

b/

Plants by Name Dose= 2.5 4 6 10 «14 15 20 20 35
(Common, Cultivar, Conc. 5 4 3 20 2 15 10 5 5
Scientific) Time 0.5 1 2 0.4 7 ] 2 4 7
Tobacco, Bell Ws 0 0 6 15 0 2 0) 0 0
Tobacco, Burley 21 0 0 0 8 0 0 0 0 0
Corn, Pioneer 509-W 1 0.60 1 0 ] 0 0 0
(Zea mays, L.)
Corn, Golden Cross 0 0 0 0 0 0 0 0 2
Azalea, Alaska e/ 0 0 0 0 0 ] 0 0 0
(Rhododendron, sp. )=
Sorghum, Martin 0 0 0a 0 0 0 0 0 0
(Sorghum, sp.)
Cucumber, Long Marketer 0 0 0 0 0 0 0 0 0

(Cucumis sativus, L.)

=" Plants were exposed in Cincinnati, Ohio. Each value is the average of 4
replicate plants except as noted. Plants are listed in general order of
sensitivity. Scientific names are included except when already given in
Table 1. Equations are shown in Table 3. Plants were exposed from July
22 through September 20, 1968 except for wheat, oats (Pendek and 329-80)
broccoli and cucumber which were exposed in early November

b/ Dose = ppm/hrs, conc. = ppm, time = hr.
e/ Three replications per treatment.

a Two replications per treatment.

e/

=’ Ornamental plants obtained from nursery, injury indices are determined as
whole plant values.


SECTION 4
DISCUSSION

The interrelations of time and concentration (dose) as they affect injury
to vegetation are essential for an understanding of air pollution effects.
Time-concentration effects have been inadequately studied and are therefore
poorly understood. A discussion of time-concentration relations should con-
sider acute, chronic, and physiological responses. At this time, there is
insufficient literature relating the effects of time and concentration to the
production of chronic injury, or to the reduction of growth, yield, or quality
of plant material. The acute effects of nitrogen dioxide, as related to a
series of times and concentrations, have not been widely studied, but the
reports discussed in the introduction along with the results presented in this
paper have permitted the development of estimates of concentrations that will
produce injury to plants.

Researchers in the area of air pollution effects on vegetation have
generally been content to view a plant's response to a pollutant or group of
pollutants in a subjective way. They have preferred to look at effects and
make their own interpretations. In the biological as well as the physical
sciences, response should be quantified whenever possible to remove the sub-
jective interpretations of the investigator. The response of plants to spe-
cific times and concentrations of pollutants is subject to quantification
through mathematical modeling. The first such model was developed by O'Gara
(1922) for the relations of dose (time x concentration) to acute plant injuy
from sulfur dioxide.

The O'Gara equation is a mathematical form that fits experimental data
obtained from exposures of relatively short duration (less than 1 day).
Guderian et al. (1960) did not believe the O'Gara equation would fit their
observations (derived from continuous exposures over several hundred hours)
and suggested an exponential relationship to best describe their data. In the
short time span (1 to 12 hr), both equations give a reasonable fit to avail-
able data. The exponential form fits over a wider range of time for the
sulfur dioxide work reported. Both of these equations relate time and concen-
tration to a specific percentage injury and thus are capable of developing
only a two-dimensional model; both also require a good estimate of a threshold
injury concentration before they can be solved.

Heck et al (1966) developed a response surface showing the variation in
injury to pinto bean and tobacco from ozone exposures as time and concentra-
tion varied. Surfaces of this type make apparent the steep slope that is
frequently observed in the injury versus concentration or injury versus time
planes. The steep portions of the slopes indicate that relatively slight
changes in many factors (environmental, nitrogen dioxide concentration, time,
and others) can cause large variations in the amount of injury produced.

6


TECHNICAL REPORT DATA .
(Please read Instructions on the reverse before completing)

7 REPORT NO, 2 SB. RECIPIENT'S ACCESSION NO.
EPA-600/3-79-057
ja. TITLE AND SUBTITLE 5. REPORT DATE

. Svidas Timac - . ", 79 issuing date
Nitrogen Dioxide: rryueyconcentration Model to Predict tay 1973 GAGANIZATION CODE

7 ATT eas 8. PERFORMING ORGANIZATION REPORT NO.

ter W.Heck
David T. Tingey

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.

TAA602

Environmental Research Laboratory--Corvallis
Office of Research and Development

U.S. Environmental Protection Agency
Corvallis. OR_97330

11. CONTRACT/GRANT NO,

12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
inhouse-final
Same 14. SPONSORING AGENCY CODE
EPA/600/02

75. SUPPLEMENTARY NOTES.

16. ABSTRACT

An experimental design was developed utilizing five time periods from 0.5 to 7
hours with two nitrogen dioxide concentrations at each time period. Concentrations
were chosen that would produce threshold and severe injury at these time periods.
From these data for each plant species, an equation was developed utilizing
concentration as the dependent variable, and both foliar injury and time as in-
dependent variables. The model allows for the development of a three-dimensional
response surface within the limits of the times and concentrations used. The
model should be of practical importance in predicting the concentration of nitrogen
dioxide that will produce a given amount of injury to a specific crop during a
single 12+4our day. Research to date suggests the model may be used for other
pollutants and for other plant species that show injury following exposure to high
ambient nitrogen dioxide concentrations.

17, KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS Je. COSAT! Iietd/Group
Air Pollution Dose-response equations

Nitrogen Dioxide Vegetation 06/F

Plants (botany)

78. DISTRIBUTION STATEMENT 19 SECURITY CLASS (Thus Report) 21.NO OF PAGES
unclassified
Release to Publish 20. SECURITY CLASS (This page) 22. PRICE

unclassified

orm 2220-1 (Rev. 4~77
EPA Form 2220-1 (Rev. 4—77) 7 ty US Government Printing Ollice 1979 - 698-858 169



FOREWORD

Effective regulatory and enforcement actions by the Environmental Protec-
tion Agency would be virtually impossible without sound scientific data on
pollutants and their impact on environmental stability and human health.
Responsibility for building this data base has been assigned to EPA's Office
of Research and Development and its 15 major field installations, one of which
is the Corvallis Environmental Research Laboratory (CERL).

The primary mission of the Coravllis Laboratory is research on the ef-
fects of environmental pollutants on terrestrial, freshwater, and marine
ecosystems; the behavior, effects and control of pollutants in lake and stream
systems; and the developmnt of predictive models on the movement of pollutants
in the biosphere.

This report contains previously unpublished research results that were
originally planned for publication in BioScience in 1971. This reference was
used in the 1971 Air Quality Criteria document for Nitrogen Oxides (Chapter 8,
ref. 8). Data from Taylor was deleted from the present manuscript. The au-
thors are publishing these results because they still represent the best and
most extensive dose-response information for nitrogen dioxide on vegetation.
The research was completed in 1968. The authors believe this information
should be available to the scientific community.

James C. McCarty
Acting Director, CERL

ii


vl

TABLE 3.

TIME-CONCENTRATION RESPONSE EQUATIONS FOR A SELECTED GROUP OF PLANTS TO NITROGEN DIOXIDE~

a/

Concentrations (ppm) to produce the

Plants by Name®/ Equation d/ I Cin %) in T Chr)
(common, Cultivars) (C = Ay +A, 1+ A, /T)S!/ R2- T-5, T=1 [=5, T=8 1=50, T=] I=50, T=8
Susceptible
Oats (Clintland 64) c 1.45 + 0.13 I 2.39/T 0.76 4.5 2.3 10.3 8.3
Radish (Cherry Belle) C = 2.43 + 0.14 1 + 1.02/T 0.83 4.) 3.2 10.5 9.6
Oats (329-80) c 1.75 + 0.15 IT 3..24/T 0.56 5.7 2.9 12.5 9.7
Bromegrass (Sac C = 2.49 + 0.16 I + 1.90/T 0.71 5.2 3.5 12.4 10.7
Smooth)
Begonia (Thousand C= 2.45 + 0.15 I 2.99/T 0.63 6.2 3.5 12.9 10.3
Wonders White)
Chrysanthemum (Oregon) C = 3.16 + 0.16 I + 2.14/T 0.72 6.1 3.7 13.3 11.4
Oats (Pendek) C= 2.79 + 0.14 1 2.88/T 0.50 6.4 3.8 12.7 10.2
Wheat (Wells) C= 2.80 + 0.13 I 2.94/T 0.52 6.4 3.8 10.2 7.7
Sultana (White Imp) C = 3.93 + 0.13 I 1.73/T 0.67 6.3 4.8 12.2 10.7
Broccoli (Calabreese) C = 3.07 + 0.20 1 + 2.94/T 0.53 7.0 4.5 16.0 13.4
Periwinkle (Bright C= 2.92 + 0.23 I 3.02/T 0.55 7.1 4.5 17.4 14.8
Eyes)
Intermediate
Cotton (Paymaster) C = 2.97 + 0.23 I + 1.94/T 0.58 7.1 5.3 17.4 15.7
Cotton (Acala 4-42) C = 3.68 + 0.22 I + 3.15/T 0.50 7.9 5.2 17.8 15.1
Tobacco (Bel B) C = 3.62 + 0.21 I + 3.98/T 0. 38 8.7 5.2 18.1 14.6
Tobacco (Bel W3) C = 3.65 + 0.18 I + 4.40/T 0.31 9.0 5.2 17.1 13.2
Tobacco (White Gold) C = 4.03 + 0.30 I + 3.56/T 0.40 9.1 6.0 22.6 19.5

continued ...


TABLE 4. PROJECTED NITROGEN DIOXIDE CONCENTRATION RANGES WHICH WILL
PRODUCE, FOR SHORT-TERM EXPOSURES, FIVE PERCENT INJURY TO

VEGETATION GROWN UNDER SENSITIVE conDITIoNs!/

Concentrations (ppm) Necessary to Produce Injury in Three

Time Susceptibility Groupings of Plants

Chr) Susceptible Intermediate Tolerant
0.5 6- 10 9-17 > 16
1.0 4- 8 7-14 > 13
2.0 3- 7 6 12 211
4.0 2- 6 5 10 > 9
8.0 2- 5 4 9 > 8

V/

-" The values in this table were developed from a subjective evaluation of
the earlier tables and references included in the introduction.


TABLE 1. ACUTE INJURY TO SELECTED CROPS AFTER A

1-HOUR EXPOSURE TO NITROGEN prox10e2/

Plants by Name b/ Injury Index (%)
(Common, Cultivar, Scientific)= 8 ppm 16 ppm 32 ppm

Tomato, Romac/
(Lycopersicon esculentum, Mill.)

Wheat, Wel1s@/ 0 47 90

(Triticum durum, Desm. )

Soybean, Scotto’
(Glycine max, (L.) Merr. )

Tobacco, Bel Wa°/ 0 23 97

(Nicotiana tabacum, L.)

Bromegrass, Sac Smooth/ 2 7 97

(Bromus inermis, L.)

1 48 100

0 26 100

Swiss Chard, Fordhook Giant’ 0 VW 62
(Beta vulgaris L.)

Tobacco, White Goldo/ 0 1 70

(Nicotiana tabacum, L.)

Cotton, Acala 4-420/ 0 0 54
(Gossypium hirsutum, L.)

Beet, Perfected petroitd/ 0 0 36

(Beta vulgaris, L.)

Orchard Grass, Potomacd/ 0 1 18
(Dactylis glomerata, L.)

Tobacco, Bel wad! 0 0 5

a/ Plants were exposed in Cincinnati, Ohio.

=’ Scientific name is given when plant is first listed.

c/ Plants were exposed in August with light intensity at 2200 ft-c, tempera-
ture 28°C, humidity 75 percent.

=’ Plants were exposed in January with light intensity at 1400 ft-c, tempera-
ture 21°C, humidity 70 percent.


Investigators have reported plant responses to several time-concentration
combinations of nitrogen dioxide, but not for the express purpose of general-
izing their data to develop predictive equations. Several reports in the
literature are of value, however, and will be summarized. The threshold
concentration for visible injury to pinto bean was 3 to 4 ppm in an 8-hr
exposure; a 2-hr exposure at 30 ppm killed the leaves (Middleton et al.,
1858). A group of agricultural and horticultural crops exposed to 30 ppm
nitrogen dioxide for 1 hr developed little or no injury (Czech and Nothdurft,
1952). Exposure of 10 weed species to 20 or 50 ppm nitrogen dioxide for 4 hr
during midday caused from zero to medium injury on leaves of well-watered
plants; only mustard showed well defined injury (Benedict and Breen, 1955).
Sixty plant species were exposed to 2.5 to 10 ppm nitrogen dioxide for 4 to 8
hr and compared with plants exposed to similar levels of sulfur dioxide; the
plants were approximately 2.5 times less sensitive to the nitrogen dioxide
(van Haut and Stratmann, 1967). Cotton, pinto bean and endive were slightly
injured at 1 ppm nitrogen dioxide for 48 hr, were uninjured at 0.5 or 2.0 ppm
for 21 hr or at 1.0 ppm for 12 hr, while 3.5 ppm for 21 hr produced slight
injury to cotton and pinto bean and death of endive leaves (Heck, 1964).
Tobacco was uninjured at 2.3 ppm for 8.7 hr; pinto bean was not injured until
exposed for 4 hr to 10 ppm (Taylor and Eaton, 1966). Navel orange trees
continuously exposed to 0.06, 0.12, 0.25, 0.5 and 1.0 ppm nitrogen dioxide
showed extensive chronic injury after 35 days at the two highest concentra-
tions. Increased leaf drop and reduced yields occurred with the 0.25 ppm
treatment after 8 months (Thompson et al., 1970). Fourteen ornamental species
and six citrus varieties were exposed to from 10 to 250 ppm for periods of 0.2
to 8 hr with extensive injury reported in all plants; young shoot necrosis
occurred at exposures of 200 ppm for 4 to 8 hr or 250 ppm for 1 hr (MacLean et
al., 1968).

The degree of injury to vegetation by nitrogen dioxide is influenced by
factors such as plant species, stage of plant development, plant environment
(temperature, light, humidity, soil moisture, mineral nutrition), variable
susceptibility within species (cultivar or clone), and the interaction of more
than one phytotoxic gas in the plant atmosphere (Heck, 1968). Depending upon
the kind of plant and its environment, one factor may be more important than
another, but all factors must eventually be understood before adequate effects
modeling can be completed.

Taylor and MacLean (1970) recognized the increased sensitivity of plants
to nitrogen dioxide caused by low light intensity. They reported that 2-hr
exposures of sensitive plants to 3 ppm nitogen dioxide under low light condi-
tions caused as much injury as 6 ppm in light equivalent to full sunlight.
Several reports have shown that night exposures to nitrogen dioxide may cause
more injury than day exposures (Czech and Nothdurft, 1952; Tingey, 1969; van
Haut and Stratmann, 1967). van Haut and Stratmann (1967) reported that rye
plants were most sensitive to nitrogen dioxide from noon to 4 pm. Oats had a
bimodal sensitivity to nitrogen dioxide with more injury occurring from mid-
night to 2 am than at noon to 2 pm.

The report by Tingey et al. (1971) is of special interest. They exposed

six species to various mixtures of nitrogen dioxide and sulfur dioxide for 4
hr They found that over 2.0 ppm of nitrogen dioxide or 0.5 ppm of sulfur


CONTENTS

Foreword .
Abstract
Acknowledgments
1. Introduction
2. Experimental Methods and Procedures
3. Experimental Designs and Results
4. Discussion
References

Page

iii


ABSTRACT

An understanding of the response of plant species to specific doses of an
air pollutant or a group of pollutants is essential before air quality stan-
dards can be established in areas under crop production. Selected plant
species were exposed to two nitrogen dioxide concentrations chosen to produce
threshold and severe injury at five time periods ranging from 0.5 to 7 hr.
From these data for each species, an equation was developed using concentra-
tion as the dependent variable, and foliar injury and time as independent
variables. The model allows for the development of a three~dimensional re-
sponse surface within the limits of the exposure times and concentrations
used. The model is useful in predicting the concentration of nitrogen dioxide
that will produce a given amount of injury to a specific crop during a single
12-hr day. Research to date suggests the model may be used for other pollut-
ants and for other plant species that show injury following exposure to high
ambient nitrogen dioxide concentrations.

iv


TABLE 2. ACUTE INJURY TO SELECTED PLANTS USED IN DEVELOPING CONCENTRATION-

TIME RESPONSE EQUATIONS FOR NITROGEN pIox1pE3/

Injury Index _(%)

b/

Plants by Name Dose- 2.5 4 6 10 «#14 15 20 20 35
(Common, Cultivar, Conc. 5 4 3 20 2 15 10 5 5
Scientific) Time 0.5 ] 2 0.4 7 1 2 4 7
Oats, Clintland 64 o/ 0 o 8 2 a 39 0 21
(Avena sativa, L.)
Radish, Cherry Belle co 9 0 9 0 90% 31 1 2
(Raphanus sativus, L.)
Bromegrass, Sac Smooth oc/ 0 60 69 0 50¢/ 26 1 0
Begonia, Thougand Won- 0 1 0 26 0 35 49 4 5
ders, White’ ,
(Begonia Rex, Putz. )
Chrysanthemum, oregon®/ ] 1 1 34 0 4) 25 4 1
(Chrysanthemum, sp.)
Sultana, White Imp2/ 0 0 0 5) 0 22% 24 +O 0
(Impatiens sultani,
Hook)
Oats, 329-80°/ 2 2 ] 32 1 18 14 9 14
Cotton, Paymaster 0 0 66 50 0 27 2 2 ]
Wheat, Wells 3 2 1 3] 3 34 2 3 1
Cotton, Acala 4-42 0 0 0 28 0 28 i) 0 }
Periwinkle, Bright 0 o 0 13 0 20 23 1 1
Eyes—" (Vinca minor, L.)
Oats, Pendek’/ 1 2 0 39 0 2 2 1 2
Broccoli, Calabreese 0 0 60 19 0 21 0 0 0
(Brassica oleracea
botrytis, L.)
Tobacco, Bel B 0 0 3 18 0 7 0 0 0
Tobacco, White Gold 0 0 1 18 0 6 0 0 0

continued
12


SECTION 1
INTRODUCTION

The introduction of nitrogen dioxide as an air pollutant was first infer~
red in California when photochemical oxidants were shown to adversely affect
vegetation. Through the photochemical production of atmospheric oxidants,
including peroxyacety] nitrate (PAN) and ozone, nitrogen dioxide exerts a
secondary, though significant effect on vegetation. At ambient concentra-
tions, the direct effects of nitrogen dioxide on vegetation are more difficult
to assess except around localized sources.

Glater (1970) stated that increasing ambient levels of nitrogen dioxide
may have been responsible for some of the chronic injury to vegetation which
was prevalent in the Los Angles Basin. The increase of nitrogen oxides was
attributed to the increase in emissions from motor vehicles whose contro]
devices reduced hydrocarbons and carbon monoxide but failed to reduce nitrogen
oxides. Glater suggested that injury from nitrogen dioxide was replacing the
PAN-type of injury. The symptoms discussed by Glater, however, were not found
by Taylor and Eaton (1966) after exposing plants for several days to low
concentrations of nitrogen dioxide. The nitrogen dioxide injury (reported by
Glater) is similar to that reported from low-level, controlled ozone exposures
and/or high ambient oxidant concentrations in eastern urban areas by the
authors of this paper and others. The responses reported by Glater probably
are more related to ozone or to pollutant interactions than to the nitrogen
oxides alone.

Direct plant responses to phytotoxic levels of nitrogen dioxide can be
divided into three broad categories: physiological, chronic and acute injury.
Physiological injury includes growth alterations, reduced yields (Taylor and
Eaton, 1966) and reduced photosynthesis (Hill and Bennett, 1970). Chronic
injury results from intermittent low level exposure over long time periods.
Chronic injury produces chlorotic and/or other pigmented patterns in leaf
tissues and may be accompanied by an increase in leaf drop (Glater, 1970;
Thompson et al , 1970). Acute foliar injury often resembles the intercostal
bifacial necrosis associated with the response of plants to sulfur dioxide.
High nitrogen dioxide concentrations produce foliar markings that first appear
as water-soaked areas and may develop into white, tan, brown, or bronze necro-
tic lesions. Lesions, although normally intercostal, are often marginal and
more toward the leaf apex. A discoloration of leaves with a waxy appearance
has been reported for several weed species (Benedict and Breen, 1955) Short
exposures (measured in hours) to high levels of nitrogen dioxide may produce
acute symptoms within 2 to 48 hr after exposure. Two publications give good
descriptions of nitrogen dioxide injury and include colored plates showing
acute injury (Taylor and MacLean, 1970; van Haut and Stratmann, 1967).


United States Environmental Research EPA-600/3-79-057
Environmental Protection Laborator May 1979

y
Agency Corvallis OR 97330

Research and Development

SEPA Nitrogen Dioxide

Time-Concentration
Model to Predict
Acute Foliar Injury

> Hy»


SECTION 2
EXPERIMENTAL METHODS AND PROCEDURES

Plants used in this study (Tables 1 and 2) were grown in 10 cm diameter
pots, in a 1:1 peat-perlite mix, in charcoal-filtered greenhouses at about 27
C day and 21 C night temperatures. Supplemental fluorescent lighting insured
a minimum 12-hr photoperiod of 10 klux throughout the year. Relative humidity
varied from 30 to 80% depending on outside conditions. Plants were watered
daily with a half strength Hoagland's nutrient solution. Rapid growing plants
were seeded directly into the peat-perlite potting mix; slow developing seed-
lings were seeded in vermiculite and transplanted into the regular potting
mix. The five ornamentals (Table 2) were purchased as young plants from a
local nursery and established in the potting mix before exposure. Plants
started directly from seed in the potting mix were overseeded and thinned to
one plant per pot 7 days after seeding.

Plants were exposed to nitrogen dioxide in greenhouse exposure chambers
(Heck et al., 1968) at a young stage of growth (three to six fully expanded
leaves) for the crop species and when the ornamentals were still actively
growing. One percent nitrogen dioxide was injected into the chamber using a
two-stage dilution system and was continuously monitored with a Mast oxidant
meter to insure a uniform concentration in the chamber Chamber concentra-
tions were determined after Saltzman (1954) using one to three 5-min bubbler
samples. The number of samples varied with the length of exposure. Values
are reported as parts of nitrogen dioxide per million parts of air (ppm)? on a
v/v basis.

Plant injury was assessed 2 to 3 days after exposure when all leaves were
examined to determine the percent area of each leaf, showing chlorosis and/or
necrosis. Injury on each leaf was visually estimated in 5% increments (0 to
100% scale), and an injury index was computed on the basis of the average
injury to the three most severely injured leaves per plant. The injury index
included a three leaf average even if any or all of the leaves showed no
injury. The injury indices for the five ornamental plants (Table 2) were
based on a visual estimation of the whole plant rather than individual leaves.

2 One ppm of nitrogen dioxide is equivalent to 1.9 mg/m? of nitrogen diox-
ide at 760 mmHg and 25 C.


dioxide were required to produce injury when the gases were administered
separately, but all species were injured by various combinations of the two
gases in the concentration ranges of 0.05 to 0.25 ppm. The relative sensitiv~
ity of the six species from highest to least sensitive was soybean, radish,
pinto bean, oats, tobacco, and tomato. Injury developed as a chlorotic or
necrotic flecking on the upper leaf surface and was similar to injury produced
by ozone.

This paper reports experiments designed to more accurately predict acute
injury to a selected group of plants from nitrogen dioxide exposures that are
limited in time. The factors discussed above, which influence injury re-
sponse, have not been controlled in the design used. The predictive mode)
reported here allows for the prediction of concentrations of nitrogen dioxide
that will produce acute foliar injury when the environmental conditions are
not known. The model can be used to suggest combinations of time and concen-
trations of nitrogen dioxide that should not be exceeded in the atmosphere
without injuring specific types of vegetation.


ACKNOWLEDGMENTS

The authors acknowledge the assistance of Mr. Hans Hamann, North Carolina
State University, in the statistical analysis of the data. Appreciation is
also extended to Mr. Frank Fox, formerly with the National Center for Air
Pollution Control, for technical assistance in the early experimental designs.

vi


SL

TABLE 3 (continued)

Concentrations (ppm) to produce the

Plants by Name®/ Equation c/ d/ I (in %) in T (hr)
(common, Cultivars) (Cc = Ay + A, 1 + Ag/T)= R2 1-5, T=] 1=5, T=8 I=50, T=] 1=50, [=8

Tolerant

Tobacco (Burley 21) None 1 of 36 plants injured; 0.5 hr., 26 ppm, 33
percent

Corn (Pioneer 509-W) None 4 of 36 plants injured; all injuries were
1.6 percent

Corn (Golden Cross) None 1 of 36 plants injured; 7.0 hr, 6 ppm, 7
percent

Azalea (Alaska) None 1 of 36 plants injured; 1.0 hr, 17 ppm, 5
percent

Sorghum (Martin) None 0 of 36 plants injured

Cucumber (Long Marketer) None 0 of 36 plants injured

a/

Equations were developed from exposures limited in time (0.5 - 7.0 hr) and denote acute injury symp-
toms to the plants. Concentrations used ranged from 1 to 20 ppm of nitrogen dioxide. Plants are
grouped in 3 susceptibility categories. Specific injury averages are given in Table 2.

Scientific names are given in Tables 17 and 2.

C is nitrogen dioxide concentration in ppm; I is percent injury; T is time in hr; and Ao, A, and A?
are constants (partial regression coefficients) specific for pollutant, plant species, and environ-
mental conditions used

R2, multiple correlation coefficient squared which represents the percent variation explained by the
model.


DISCLAIMER

This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica~
tion. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.


The models discussed above give an insight into what may happen under a
given set of circumstances. These relationships are probably universal and
could be derived for any toxicant producing a definite acute-type of injury.
Relationships of this type permit the prediction, with reasonable assurance
that no acute injury will occur as long as a certain threshold concentration
is not exceeded for a given period of time.

The predictive equation reported in this paper for nitrogen dioxide was
first developed for ozone (Heck and Tingey, 1971). The equation handles time
and concentration separately and permits the development of a three-dimen-
sional injury response surface similar to that reported by Heck et al. (1966).
The equation treats concentration as the dependent variable and both injury
and time as independent variables and is represented as:

CHAS +A, I+ Ay/T

where C is nitrogen dioxide concentration in ppm, I is percent foliar injury,
T is exposure time in hours, and A., A,, and Ay are constants (partial regres~
sion ccefficients) which are specific for the pollutant, plant species, and
the environmental conditions used. The equation permits the development of
either a two-dimensional curve or a three-dimensional response surface and
eliminates the necessity of determining a threshold concentration before the
equation can be solved. The predictive equations reported in Table 3 elimi-
nate the necessity for each researcher or control official to give a subjec-
tive interpretation of the data shown in Table 2 and permit a uniform interp-
retation of results by all who review them. The equation can also be used by
a researcher or control official to predict the nitrogen dioxide concentration
that could be in the atmosphere over a limited time period that would produce
zero or slight injury to a given variety or species of plant. The medel
indicates that a given dose (concentration x time) of nitrogen dioxide over a
range of times does not give constant injury.

The experimental data presented in Table 3 were developed from greenhouse
exposures over several days in time and thus include an averaging effect of
many environmental variables. They do not represent any specific combination
of environmental conditions tnat would tend to make any given plant particu~
larly responsive to nitrogen dioxide. Thus, in some cases, plants exposed
under field conditions could be more sensitive to nitrogen dioxide than would
be predicted from a given equation. The equations do not consider fluctua-
tions in concentration over a given time interval or the effect of repeated
fumigations over either several days or even several hours in one day The
data are from short exposures and thus should not be extrapolated to long time
periods.


Middleton, J. T., E. F. Darley, and R. F. Brewer. 1958. Damage to Vegetation
from Polluted Atmosphere. J. Air Poll. Cont. Assoc. 8:9-15.

O'Gara, P. J. 1922. Sulfur Dioxide and Fume Problems and Their Solutions.
Abst. J. Ind. Eng. Chem. 14:744.

Saltzmann, B. E£. 1954. Colorimetric Microdetermination of Nitrogen Dioxide
in the Atmosphere. Anal. Chem. 26:1949-1955.

Taylor, 0. C. and F. M. Eaton. 1966. Suppression of Plant Growth by Nitrogen
Dioxide. Plant Physiol. 41:132-135.

Taylor, 0. C. and D. C. MacLean. 1970. Nitrogen Oxides and the Peroxyacy]
Nitrates. In: Recognition of Air Pollution Injury to Vegetation: A
Pictorial Atlas, J. S$. Jacobson and A. C. Hill, eds. Air Pollution
Control Assoc. , Pittsburgh, Pennsylvania, p. E1-E14.

Thompson, C. R., E. G. Hensel, G. Kats and 0. C. Taylor. 1970. Effects of
Continuous Exposure of Navel Oranges to Nitrogen Dioxide. Atmos. Envi-
ron. 4:349-355.

Tingey, D. T. 1969. Foliar Absorption of Nitrogen Dioxide, Masters Thesis,
Univ. of Utah, Salt Lake City, Utah, 46 p.

Tingey, D. T., R. A. Reinert, J. A. Dunning and W. W. Heck. 1971. Vegetation
Injury from the Interaction of Nitrogen Dioxide and Sulfur Dioxide.
Phytopathology 61: 1506-1511

van Haut, H. and H. Stratmann. 1967. Experimental Investigations of the
Effect of Nitrogen Dioxide on Plant (Experimentelle Untersuchungen tiber
die Wirkung von Stickstoffdioxid auf Pflanzen). Schriftenreihe der
Landensanstalt fiir Immissions-und Bodennutzungsschutz des Landes Nord-
rhein-Westfalen, (Essen), No. 7:50-70.


EPA-600/3-79-057
May 1979

NITROGEN DIOXIDE: TIME-CONCENTRATION MODEL
TO PREDICT ACUTE FOLIAR INJURY

by

Walter W. Heck
Agricultural Research
Science and Education Administration
United States Department of Agriculture and
Botany Department, North Carolina State University
Raleigh, N.C. 27650

and

David T. Tingey
Corvallis Environmental Research Laboratory
United States Environmental Protection Agency
200 S.W. 35th Street, Corvallis, OR 97330

CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

Environmental Health Effects Research

Environmental Protection Technology

Ecological Research

Environmental Monitoring

Socioeconomic Environmental Studies

Scientific and Technical Assessment Reports (STAR)
Interagency Energy-Environment Research and Development
“Special Reports

9. Miscellaneous Reports

MBNA wWNH=

This reporthas been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments

This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161


SECTION 3
EXPERIMENTAL DESIGNS AND RESULTS

. Two experimental designs were used to study time-concentration effects of
nitrogen dioxide on a group of plants. The first design was used to help
select times and concentrations for the second, which was designed to develop
time-concentration response equations for the plants studied.

The first design was for a I-hr time period using three nitrogen dioxide
concentrations (8, 16 and 32 ppm). Treatments were replicated four times.
The results are shown as the average of four replicates per concentration
(Table 1). The plants, listed in order of decreasing sensitivity, show the
variability in sensitivity of different plant species to nitrogen dioxide.
The results also show the effects of environment. The design was purposefully
developed to include Bel Wz tobacco in the summer and winter exposures. The
plants exposed in winter were much more resistant.

The second experimental design was used in developing time-concentration
response equations for a group of plants exposed to nitrogen dioxide using a
time scale of 0.5 to 7 hr. These equations were developed by exposing se-
lected species to nine different combinations of time and concentration (Table
2). Each time-concentration combination was replicated on 4 successive days
using 36 observations (plants) of each species to develop each equation.
Plant injury indices were assessed as previously described except for begonia,
sultana, chrysanthemum, periwinkle and azalea. For these species a single
percent injury rating was determined for the whole plant. Mean plant injury
values for each time-concentration combination of the design are shown in
Table 2. A multiple regression model was applied to the plant injury indices
to develop the time-concentration response equations shown in Table 3.

The amount of variation explained by the model, tne coefficient of varia-
tion (R%), is shown for each equation in Table 3. Plants in this table are
listed in order of their sensitivity to nitrogen dioxide, using three suscep-
tibility groupings (susceptible, intermediate, tolerant). Examples of calcu-
jated concentrations for four combinations of percent foliar injury and time
are also shown in Table 3. These equations and the survey of literature
presented in the introduction of the response of plants to acute doses of
nitrogen dioxide, aided in the development of the susceptibility groupings
shown in Table 4. Values in this table are not absolute and should be treated
as suggested limits for the given susceptibility grouping.


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