Natural Influences of Forests on Local
and Regional Air Quality
Emissions and Air Resource
Management Within Forests
'
Michael A. Fosberg and H o l l i s Record
2
Abstract:
S u b s t a n t i a l p o r t i o n s of t h e emissions i n v e n t o r y
w i t h i n f o r e s t e d l a n d s a r e from d i s p e r s e d i n t e r m i t t e n t
sources.
Chief s o u r c e s a r e smoke from w i l d f i r e and pres c r i b e d f i r e , emissions a s s o c i a t e d with c o n c e n t r a t e d recr e a t i o n and second-home developments , and f u g i t i v e d u s t
from unpaved r o a d s and e o l i a n s o i l s .
E f f e c t s of smoke o n
f l o r a range from reduced p h o t o s y n t h e t i c e f f i c i e n c y a t low
dosages t o t i s s u e n e c r o s i s a t high dosages.
E f f e c t s on
fauna a r e n o t c l e a r l y d e f i n e d .
E f f e c t of smoke on s o c i a l
v a l u e s , p r i m a r i l y v i s i b i l i t y , is recognized but not unders t o o d . D i s p e r s i o n p r o c e s s i n complex t e r r a i n , t h e physiog r a p h i c s e t t i n g f o r most f o r e s t e d l a n d s , i s complicated by
topography and s p a t i a l l y varying wind f i e l d s , a h i g h e r
degree of a n i s o t r o p y of t u r b u l e n c e , and a wider range of
t u r b u l e n c e i n t e n s i t i e s t h a n found over l e v e l ground.
Management of a i r r e s o u r c e s w i t h i n f o r e s t e d a r e a s is
l i m i t e d t o land management planning a c t i v i t i e s because of
t h e complexi t y of emission c h a r a c t e r i s t i c s , d i s p e r s i o n
p r o c e s s e s , and e f f e c t s of p o l l u t a n t s from w i t h i n f o r e s t
sources.
Much of t h i s symposium t r e a t s e f f e c t s of poll u t a n t s from major s t a t i o n a r y s o u r c e s on ecosystems.
Significant pollutants treated i n other
papers a r e n i t r o u s o x i d e s , o x i d e s of s u l f u r , react i v e hydrocarbons, and t h e photochemical d e r i v e d
p o l l u t a n t , ozone.
E f f e c t s of NOn, SO2, and O n a r e
w e l l documented i n t h e companion papers i n t h i s
volume.
s i o n s from f i r e a r e Con, CO, p a r t i c u l a t e s , and
hydrocarbons.
R e c r e a t i o n a l and second-home developments emit C O , CO, p a r t i c u l a t e s , and hydrocarbons from f i r e p l a c e s and campfires; SO2 and NOx
from
dispersed
transportation
systems--namely,
p r i v a t e automobiles.
F u g i t i v e d u s t from unpaved
r o a d s and e o l i a n s o i l s a l s o c o n t r i b u t e t o t h e
p a r t i c u l a t e loading.
P o l l u t a n t s from w i t h i n f o r e s t s o u r c e s a l s o
i n c l u d e emission from w i l d f i r e , p r e s c r i b e d f i r e ,
unpaved r o a d s , e o l i a n s o i l s , c o n c e n t r a t e d recreat i o n , and second-home developments, Chief e m i s -
E f f e c t s of t h e above p o l l u t a n t s , p a r t i c u l a r l y
smoke, f l o r a , fauna, and s o c i a l v a l u e s a r e poorly
understood. Documented e f f e c t s range from reduced
p h o t o s y n t h e t i c a c t i v i t y through blockage of s o l a r
radiation t o t i s s u e necrosis.
E f f e c t s on microorganisms range from i n h i b i t i o n of some s p o r e s and
fungi t o i n c r e a s e d germination of one fungus.
E f f e c t s of smoke on fauna a r e documented, but without e x p l a n a t i o n .
p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r
P o l l u t a n t s on Mediterranean and Temperate F o r e s t
Ecosystems, J u n e 22-27, 1980, R i v e r s i d e ,
C a l i f o r n i a , U.S.A.
2 ~ r o j e c tLeader, F o r e s t and Brushland Meteorology, P a c i f i c Southwest F o r e s t and Range Experiment
S t a t i o n , F o r e s t S e r v i c e , U.S. Department of Agric u l t u r e , Berkeley, C a l i f . , s t a t i o n e d a t R i v e r s i d e ,
C a l i f . ; and G e o l o g i s t , Los Padres N a t i o n a l , F o r e s t ,
F o r e s t S e r v i c e , U.S.
Department of A g r i c u l t u r e ,
Goleta, C a l i f .
V i s i b i l i t y i s both a physical and s o c i a l v a l u e .
V i s i b i l i t y can be q u a n t i f i e d i n terms of v i s u a l
range and a b i l i t y t o d e f i n e d e t a i l s a t s p e c i f i e d
distances.
V i s i b i l i t y is a l s o a personal v a l u e
based on p a s t and expected experiences.
A recent
popular c o u n t r y and western song (McCall and o t h e r s
One of t h e guys from New York
1976) goes
s a i d 'Hey, look a t t h e smog i n t h e sky, smog c l e a r
out h e r e i n t h e s t i c k s ' .
Someone s a i d , 'Hey J o e ,
".....
t h a t ' s not smog, t h a t ' s t h e Milky Way', J o e had
never s e e n t h e Milky Way
Contrast Joe's
r e a c t i o n t o t h a t of a r e s i d e n t of t h e Four Corners
a r e a of Utah v i s i t i n g any urban a r e a i n t h e world
on a c l e a r a i r day. Local r e s i d e n t s would comment
on t h e c l a r i t y of t h e a i r , but t h e v i s i t o r would
n o t i c e t h e impairment of v i s i b i l i t y
Although C02 i s n o t a p o l l u t a n t a s such, C02 i s of
c o n s i d e r a b l e i n t e r e s t i n a n a l y s i s of t h e g l o b a l
h e a t balance.
Carbon d i o x i d e emissions range from
1000 kg per m e t r i c t o n of f u e l t o 1750 kg per
m e t r i c t o n of f u e l (Ryan and McMahon 1976), w i t h
extreme v a l u e s n e a r 1830 kg per m e t r i c t o n (Vines
and o t h e r s 1971).
The r e l a t i o n s h i p between a s o u r c e of p o l l u t i o n
and t h e ef f e c t of t h a t p o l l u t a n t on Mediterranean
and temperate f o r e s t ecosystems is through disp e r s i o n of t h e p o l l u t a n t between t h e s o u r c e and t h e
r e c e p t o r point. Nearly a l l d i s p e r s i o n c a l c u l a t i o n s
a r e based on t h e Gaussian model i n which t r a n s p o r t
is t r e a t e d through d e f i n i t i o n of a mean windspeed
and d i r e c t i o n and t u r b u l e n t d i f f u s i o n i s based on a
t r a n s f o r m a t i o n of t h e t u r b u l e n c e s t r u c t u r e t o a
Gaussian s t a t i s t i c a l d i s t r i b u t i o n (Turner 1969).
V a l i d i t y of t h e c o e f f i c i e n t s used i n t h e Gaussian
model a r e u n c e r t a i n i n s i t u a t i o n s where t e r r a i n
f e a t u r e s a r e complex.
I n p a r t i c u l a r , winds a r e
known t o c o n t a i n a high degree of s p a t i a l and
temporal v a r i a b i l i t y (Fosberg and o t h e r s 1980) and
3
t h e turbulence i n t e n s i t i e s a r e highly anisotropic.
Because much of t h e Mediterranean and temperate
f o r e s t ecosystems a r e found i n complex t e r r a i n
throughout t h e world, t h e d i s p e r s i o n o r d e l i v e r y
system of
p o l l u t a n t s from t h e s o u r c e t o t h e
r e c e p t o r must account f o r complex t e r r a i n atmospheric processes.
Carbon monoxide emissions from f i r e a r e h i g h l y
dependent on can bust i o n e f f i c i e n c y .
Values r a n g e
from 17 t o 98 kg per m e t r i c t o n (Sandberg and
Martin 1975, Darley and o t h e r s 1966, G e r s t l e and
Kemnitz 1967).
The U.S. Environmental P r o t e c t i o n
Agency (1978) recommends a v a l u e of 4 5 kg per
m e t r i c t o n from hemlock, Douglas-f i r , and c e d a r and
98 kg per m e t r i c t o n from ponderosa pine.
Inef f id e n t combustion f o r smoldering damp f u e l s have
r e s u l t e d i n emissions a s high a s 250 kg per m e t r i c
t o n of f u e l (Ryan and McMahon 1976). Emissions a s
high a s 250 t o 400 kg per m e t r i c t o n of f u e l have
been reported when energy r e l e a s e from f i r e i s less
t h a n 750 w a t t s per s q u a r e meter (Sandberg and
Martin 1975).
...."
.
An understanding of each p h y s i c a l and b i o l o g i c a l
process i s necessary but not s u f f i c i e n t t o develop
management p l a n s f o r a i r r e s o u r c e s w i t h i n f o r e s t s
and brushlands. A c t s , laws, r e g u l a t i o n s , and codes
e s t a b l i s h e d by Congress down through l o c a l county
r e g u l a t o r y agencies s p e c i f y g o a l s and o b j e c t i v e s
f o r a i r q u a l i t y and f r e q u e n t l y s p e c i f y t h e methods
i n which a i r q u a l i t y o b j e c t i v e s w i l l be met.
As
example, o r g a n i c a c t s of most Federal a g e n c i e s i n
t h e United S t a t e s r e q u i r e t h a t t h e agency p r o t e c t
o r p r e s e r v e , o r meet a i r q u a l i t y o b j e c t i v e s . The
Clean A i r Act of 1977 (U.S. Congress 1977) s p e c i f ic a l l y r e q u i r e s t h a t a i r q u a l i t y o b j e c t i v e s be met
through emissions c o n t r o l .
Because i t is not
f e a s i b l e t o i n s t a l l s c r u b b e r s on p r e s c r i b e d f i r e ,
emission c o n t r o l is achieved through emissions
d e n s i t y planning.
Each of t h e following s e c t i o n s a d d r e s s e s t h e
s p e c i f i c t o p i c s of emission c h a r a c t e r i z a t i o n , disp e r s i o n i n complex t e r r a i n , e f f e c t s of smoke on
f l o r a , fauna, s o c i a l v a l u e s , and a i r r e s o u r c e
management
.
EMISSIONS FROM WITHIN FOREST SOURCES
Major emissions from w i l d f i r e and p r e s c r i b e d
CO, hydrocarbons, and p a r t i c u l a t e s .
f i r e a r e CO
2'
anh ham,
Lucy M.
1980.
Wintertime d i s p e r s i o n
p r o c e s s e s i n t h e Lake Tahoe Basins.
Proc. 2nd
Conf. o n A p p l i c a t i o n of A i r P o l l u t i o n Meteorology.
Amer. Meteorol. Soc.
[ i n press]
Hydrocarbon emissions range from 2 t o 7 kg p e r
m e t r i c t o n of f u e l (U.S. Environmental P r o t e c t i o n
Agency 1978) although emissions a s high a s 20 kg
per m e t r i c t o n have been r e p o r t e d (Ryan and McMahon
1976, Darley and o t h e r s 1966).
S p e c i a t i o n of
hydrocarbons ( f i g . 1) shows s a t u r a t e d hydrocarbons
(mostly methane) comprise about 30 p e r c e n t a t peak
f i r e i n t e n s i t y and about 1 5 percent a t low f i r e
intensities
(Sandberg and o t h e r s
1979).
Low
molecular weight o l o f i n e s make up about 17 percent
of t h e emission from flaming f i r e and 3 p e r c e n t
from smoldering f i r e (Sandberg and o t h e r s 1979).
Bnissions of
SO
and N O a r e n e g l i g i b l e .
x Most
f u e l c o n t a i n s l e s s t h a n 0.2 percent s u l f u r and comb u s t i o n temperatures a r e low, p r e v e n t i n g formation
of NOx.
P a r t i c u l a t e emissions from f i r e a r e g i v e n a s 2
t o 6 kg per m e t r i c t o n of f u e l (U.S. Environmental
P r o t e c t i o n Agency 1978). A range of emissions a r e
given i n t a b l e 1. P a r t i c u l a t e s i z e s a r e mainly i n
t h e submicron diameter c l a s s e s with o n l y a few
p a r t i c l e s l a r g e r t h a n a micron ( f i g . 2).
Particul a t e s i z e s a r e dependent on combustion e f f i c i e n c y
(Schaefer 1976) with t h e most e f f i c i e n t f i r e producing s i z e s i n t h e r e s p i r a b l e range.
National emissions of p a r t i c u l a t e s from pres c r i b e d f i r e s and w i l d f i r e s a r e shown i n f i g u r e 3.
Prescribed f i r e c o n s i s t s of less t h a n 20 percent of
a l l f i r e emissions n a t i o n a l l y .
Emissions of t h e
major p o l l u t a n t s , p a r t i c u l a t e s , CO, and hydrocarbons by S t a t e and r e g i o n s a r e given i n t a b l e 2
f o r p r e s c r i b e d burning.
I n a d d i t i o n t o w i l d f i r e and p r e s c r i b e d f i r e ,
c o n c e n t r a t e d r e c r e a t i o n and second-home developments c o n t r i b u t e smoke through f i r e p l a c e burning
and more i n c r e a s i n g l y through use of wood f o r home
heating
.
100-
80
IOOM GLASS SCOT OV-101
20-230'Cat 4Ymln
I.Sml/mIn H i
-
iz
=m
-
-u
60-
w
TIME (MINUTES)
PEAK
2
28
zc
3
3A
30
4A
48
7
8
8A
9
10
15
16
17
20
21
22
23
24
COMPOUND
homw
1-pentun
furon
n-pentaw
isoprene
ocetorr
iwpropanol
cyclopç"t<"lhn
diacet~l
I-hexw
methyl vinyl k à § t
2-methylfuran
n-hexone
2,4- h e x a d h
1.3.5-hexatrlç
3-methylbutanal
benzene
cyclohexom
4 - methylpentaw
214-dlmethylixf;t(~
I-trans-2-dimethylcyclopentone
F i g u r e IÑChromatogra
McMahon 1976).
Table I--Summary
PEAK
24A
26
26A
27
29
31
32
36
39
40
41
42
44
49
SO
50A
52
53
PEAK
COMPOUND
54
n-maw
5 4 ~ 2- lsopro~>lfuran
5s
anlwlÃ
56
2-mathyl-5-IÇÈprÃ
m y If uron
57
cumene
58
n-decone
60
n-propyltfnzew
59
camphena (tçnl.
COMPOUND
Wbotdihyd* ( t i l t )
2.5-dlmethylfuran
n-haptone
a - 2 - htptanÃ
2-vinylfuran
2 3-dimçlhyl-2
Pcntona
2.4-dlmçthylhtxo
tOllWM
I-octene
2.3- dimçthylhçi
1.4-diem
n- octane
2.3.5-trimtliylfuron
furfurol
ethyl benzene
p-aybne
2-propionylfuranftfrtJ
styrene
Q-XYI~W
61
62
66
67
71
72
77
78
an
m-ethyltoluene
p- ethyltoluiw
I-deceni
benzofuron
m-diethylhzme
.lne
p-a-dlrnethylçtyrç
n-undccane
n-dodecona
of o r g a n i c vapors i n l o b l o l l y p i n e smoke
(from Ryan and
of p a r t i c u l a t e emission y i e l d s r e p o r t e d from w i l d l a n d f u e l s
(from Sandberg and o t h e r s 1979)
P a r t i c u l a t e s (kg per m e t r i c t o n
of f u e l burned)
Fuel t y p e
Logging r e s i d u e s
(Western)
Lablfield
experiment
Field
Type of f i r e
Heading
Backing
14-53
Laboratory
Grass burning
Field
Live u n d e r s t o r y
(Australia)
Field
(Southern)
Pine l i t t e r
(Southern)
~
Reference
Sand berg (1974)
Laboratory
Field
Laboratory
Landscape r e f u s e
-
Sandberg (1974)
Radke and o t h e r s (1978)
F r i t s c h e n and o t h e r s (1970)
12
8
F e l d s t e i n and o t h e r s (1963)
Boubel and o t h e r s (1969)
Vines and o t h e r s (1971)
Laboratory
Field
Laboratory
7-15
12-49
Vines and o t h e r s (1971)
Ward and o t h e r s (1976)
Ryan (1974)
Field
22-27
Ward and o t h e r s (1976)
Laboratory
Laboratory
3-1 4
11-63
Ryan and McMahon (1976)
Ryan and McMahon (1976)
99.99
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NUMBER
DISTRIBUTION
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PARTICLE DIAMETER, MICRONS
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PARTICLE DIAMETER, MICRONS
(B)
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LOW CONCENTRATION
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PARTICLE DIAMETER, MICRONS
.I
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I t
.2 .3 . 4 . 5 6
(C1
F i g u r e 2--Particle s i z e d i s t r i b u t i o n : (A) S i n g l e f i r e i n f o u r f u e l t y p e s ; (B)
Grand Average, a l l f u e l t y p e s ; and (C) Normalized d i s t r i b u t i o n , number, s u r f a c e
a r e a , and volume f o r a high and low c o n c e n t r a t i o n (from Ryan and McMahon 1976).
a r e a l s o e m i t t e d from
x
t r a n s p o r t a t i o n systems and p r i v a t e v e h i c l e s i n
r e c r e a t i o n a l and second-home developments.
fungi (Panneter and Uhrenholt 1975a, b).
Effects
of smoke on p h o t o s y n t h e s i s a t low dosages reduces
t h e p h o t o s y n t h e t i c r a t e by d i r e c t blockage of s o l a r
radiation.
Increased C O c o n c e n t r a t i o n s , however,
F u g i t i v e d u s t from unpaved roads and e o l i a n
s o i l s occasionally contribute substantially t o the
p a r t i c u l a t e l o c a t i o n of p o l l u t a n t s , but t h i s h a s
n o t been completely q u a n t i f i e d (Singer 1980).
could i n c r e a s e carbon f i x a t i o n and p h o t o s y n t h e t i c
a c t i v i t y (Green and Wright 1977).
Some hydrocarbons and NO
EFFECTS OF SMOKE ON FORESTS
Few s t u d i e s e x i s t t h a t c l e a r l y d e f i n e t h e
e f f e c t s of smoke and f o r e s t b i o t a .
E f f e c t s of
smoke on micro-organisms s u g g e s t t h a t smoke reduced
growth of s p o r e germination of s e v e r a l fungal
pathogens, but i n c r e a s e d s p o r e germination on one
E f f e c t s of smoke on s o c i a l v a l u e s , p r i m a r i l y
v i s i b i l i t y , a r e not c l e a r l y defined.
Although
p h y s i c a l a s p e c t s of v i s i b i l i t y ; t h a t i s , v i s u a l
range, maximum d i s t a n c e a n o b j e c t can be s e e n , and
d i s c r i m i n a t i o n of d e t a i l s on a d i s t a n t o b j e c t can
be defined q u a n t i t a t i v e l y (Malm 1979). perceived
psychological b e n e f i t s (Driver and o t h e r s 1979) of
v i s i b i l i t y a r e i n t e r r e l a t e d with o t h e r demands on
t h e sensory system. Paraphrasing D r i v e r and o t h e r s
(1979) a l i t t l e n o i s e p o l l u t i o n , a l i t t l e l i g h t
LEGEND:
SEASON
1 JAN
2 APR
3 JULY
4 OCT
FIRE TYPE:
-
-
- MAR
- JUNE
- SEPT
- DEC
R - WILDFIRE
- PRESCRIBED FIRE
REGIONS AND SEASONS
F i g u r e 3--Forest
f i r e p a r t i c u l a t e production by r e g i o n and season
Ward and o t h e r s 1976).
p o l l u t i o n , a l i t t l e l o s s of open s p a c e , awareness
of water p o l l u t i o n , nonbiodegradable s u b s t a n c e s ,
a e r o s o l cans and c a n c e r , change expected v a l u e s of
visibility.
R e f e r r i n g t o t h e quote from a popular
song used i n t h e i n t r o d u c t i o n of t h i s paper, we can
a s k , d i d J o e ' s a t t i t u d e s toward v i s i b i l i t y change
o n h i s v i s i t t o Colorado, and how would t h o s e
changes i n f l u e n c e h i s view of t h e New York s k y l i n e ?
The p o i n t D r i v e r and o t h e r s (1979) a r e emphasizing
is t h a t t h e perceived v a l u e s a r e t h e r e a l v a l u e s
and t h a t t h e p h y s i c a l l y measurable v a l u e s of v i s i b i l i t y a r e i n d i c e s of t h e v a l u e s .
In particular,
s c a t t e r i n g and a t t e n u a t i o n of l i g h t i s n o t a s o c i a l
value.
DISPERSION PROCESSES I N
COMPLEX TERRAIN
Wind p a t t e r n s i n complex t e r r a i n a r e h i g h l y
v a r i a b l e i n t i m e and space.
Local mountain and
v a l l e y c i r c u l a t i o n s f r e q u e n t l y mask t h e l a r g e - s c a l e
p a t t e r n s such t h a t a mean t r a n s p o r t wind f o r poll u t a n t movement i s d i f f i c u l t t o d e f i n e (Fosberg and
o t h e r s 1976a, b; Fosberg and Fox 1978).
Spatial
v a r i a b i l i t y of winds i s c l e a r l y i l l u s t r a t e d i n
f i g u r e 4 over t h e Oregon Coast Range and over t h e
Cascade Mountains. C o n t r a s t t h i s v a r i a b i l i t y with
t h e u n i f o r m i t y of winds over t h e P a c i f i c Ocean and
w i t h i n t h e Willamette Valley.
I n a d d i t i o n t o mean t r a n s p o r t of p o l l u t a n t s ,
t u r b u l e n t d i f f u s i o n i s important i n d i s p e r s i n g a i r
(from
pollutants.
The most f r e q u e n t l y used method of
q u a n t i f y i n g t h e d i s p e r s i o n process is through t h e
so-called Gaussian d i s p e r s i o n model (Turner 1969)
Downwind c o n c e n t r a t i o n s , X , a r e r e l a t e d t o emission
Q by
.
where u i s t h e mean windspeed and
Here, o and a a r e t h e v a r i a n c e s i n t h e GaussY
i a n s t a t i s t i c a l d i s t r i b u t i o n ; y and z a r e t h e d i s t a n c e of t h e p o l l u t a n t element from t h e plance
c e n t e r l i n e . The v a r i a n c e o i s r e l a t e d t o t h e t u r bulence s t r u c t u r e through
2Kx
o2 = u
(3)
i n which K i s t h e eddy t u r b u l e n c e c o e f f i c i e n t and x
i s t h e d i s t a n c e downwind from t h e s o u r c e . Tradit i o n a l i n t e r p r e t a t i o n s of atmospheric processes
t h a t were developed f o r l e v e l ground suggest t h a t
t h e K ' s be defined through a n a l y s i s of t h e i n e r t i a l
subrange of t u r b u l e n c e and t h a t t h i s mean wind is
c o n s t a n t over s u b s t a n t i a l d i s t a n c e s , t h i s i s , 1 0 ' s
of km. Such assumptions a r e extremely d i f f i c u l t t o
s a t i s f y i n complex t e r r a i n .
Table 2 ~ S u m m a r yof p r e s c r i b e d f i r e a c r e s burned and t o n s of c r i t e r i a p o l l u t a n t e m i t t e d (by geographic
r e g i o n , annual b a s i s ) (from Sandberg and o t h e r s 1979)
S t a t e s by
Region
Area
hectares
Fuel consumed
Metric
Metric
tonslha
tons
Particulates
8 kglmetric
tons
Carbon monoxide
10 k g l m e t r i c
tons
Hydrocarbons
5 kglmetric
tons
California
Oregon
Washington
Total
ROCKY MTN
Arizona
Colorado
Idaho
Montana
New Mexico
North Dakota
Total
N. CENTRAL
Michigan
Minnesota
Wisconsin
Total
EASTERN
Delaware
New J e r s e y
Total
SOUTHERN
A1a bama
Arkansas
Florida
Georgia
Louisiana
Mississippi
N. C a r o l i n a
S. C a r o l i n a
Texas
Virginia
Total
USA Tot a1
.
An a1 t e r n a t i v e method of d e f i n i n g t h e v a r i a n c e s
f o r complex t e r r a i n i s mathematically i d e n t i c a l but
does n o t r e q u i r e t h a t t h e t u r b u l e n c e l i e i n a
p a r t i c u l a r p o r t i o n of t h e energy spectrum (Fosberg
and o t h e r s 1976b, Fosberg and Fox 1978).
I n part i c u l a r , a mean wind i s d e f i n e d s t a t i s t i c a l l y over
t h e d i s p e r s i o n d i s t a n c e of i n t e r e s t .
D e v i a t i o n of
wind about t h i s mean, whether i n t h e t u r b u l e n t
i n e r t i a l subrange o r produced by organized flows of
s c a l e s m a l l e r t h a n t h e averaging d i s t a n c e s , a r e
The
t r e a t e d mathematically as components of K.
d e v i a t i o n s about t h e s t a t i s t i c a l l y d e f i n e d mean
wind a r e u'.
The K ' s a r e t h e n defined by
i n which t h e l i n e over t h e s q u a r e of t h e d e v i a t i o n s
i s t h e a v e r a g i n g o p e r a t o r . The time c o n s t a n t T i s
r e l a t e d t o t h e averaging t i m e and space. These K ' s
do n o t r e p r e s e n t t u r b u l e n c e .
I n s t e a d , t h e K's
d e f i n e t h e wind v a r i a b i l i t y a t s c a l e s s m a l l e r t h a n
t h o s e used t o d e f i n e t h e mean wind.
MANAGEMENT OF AIR RESOURCES
Emission c o n t r o l is r e q u i r e d t o meet a i r q u a l i t y
o b j e c t i v e s (U .S. Congress 1977).
Because d i r e c t
l i m i t s on emission from open burning can be
achieved o n l y by l i m i t i n g t h e mass of f u e l burned
a t any given time, a model f o r a i r r e s o u r c e a l l o c a t i o n was developed. The A i r Resource A l l o c a t i o n
Model (ARAM) i s based on t h e Gaussian d i s p e r s i o n
model d e f i n e d i n e q u a t i o n 1. Because t h e i n t e n t i s
t o l i m i t emissions, e q u a t i o n 1 i s r e a r r a n g e d t o
Q = X-"L
G
(5
The c o n c e n t r a t i o n X is i n t e r p r e t e d h e r e a s t h e
increment of a i r q u a l i t y a v a i l a b l e f o r p r e s c r i b e d
Table 3--Change
i n annual burn ( i n h e c t a r e s by p o l l u t a n t )
C.O.
Basin
1
T.S.P.
1
H.C.
Monterey Ranger D i s t r i c t
1. L i t t l e Sur
2. Big Sur
3. Carmel
4. Arroyo Seco
5. Ocean Front
6. San Antonio
7. Nacimiento
Santa Lucia Ranger D i s t r i c t
8. S a l i n a s (A)
9. S a l i n a s (B-)
10. Lopez Canyon
11. Cuyama (A)
12. Sisquoc
Mount Pinos Ranger D i s t r i c t
13. Cuyama (B)
14.
Joaquin Val l e y
15. P i r u
an
Ojai
16.
17.
18.
Ranger D i s t r i c t
Sespe
~ a n t aPaula
Ventura
20,500
6,200
25,500
170
-17
-7 0
2,700
no d a t a
no d a t a
S a n t a Barbara Ranger D i s t r i c t
19. Santa Ynez
20. Santa Barbara Front
ARAM i s based on e a r l i e r development on
burning.
emission l i m i t s f o r s i n g l e sources, s i n g l e receptor
r e l a t i o n s d e f i n e d i n t h e TAPAS model (Fosberg and
Fox 1976, Fox and Fosberg 1976). ARAM d i f f e r s from
TAPAS i n t h a t ARAM c o n s i d e r s m u l t i p l e s o u r c e s and
m u l t i p l e r e c e p t o r s i t e s and c o n t a i n s improvements
i n c h a r a c t e r i z a t i o n of t h e d i s p e r s i o n p r o c e s s e s .
R e l a t i o n s between m u l t i p l e s o u r c e s and m u l t i p l e
r e c e p t o r s i t e s a r e d e f i n e d through m a t r i x a l g e b r a
as
Here
x,
,
ARAM h a s been a p p l i e d on one National F o r e s t i n
C a l i f o r n i a , t h e Los Padres, i n support of use of
p r e s c r i b e d f i r e i n v e g e t a t i o n management.
Current
a i r quality regulations i n California recognize
t h a t prescribed f i r e is an a l t e r n a t i v e t o w i l d f i r e
f o r v e g e t a t i o n management.
In particular, the
r e g u l a t o r y a g e n c i e s accept t h e concept t h a t a t o n
of f u e l burned i n p r e s c r i b e d f i r e can be used t o
o f f s e t a t o n of f u e l burned i n w i l d f i r e .
and s o on a r e t h e increments of
p o l l u t i o n allowed a t r e c e p t o r s i t e s 1, 2, and s o
on; Q,,
Q2,
a r e t h e a l l o w a b l e emissions a t
...
s o u r c e sites 1, 2,
relation
The g e n e r a l i z e d form of ARAM expressed i n e q u a t i o n
5 is t h i s
...
and Gll
is the dispersion
between s o u r c e 1 and r e c e p t o r 1; G
21 is
t h e d i s p e r s i o n r e l a t i v e between source. 2 and
r e c e p t o r 1, and s o on.
Expressing e q u a t i o n 6 i n
m a t r i x format
I n t h e following example, t h e increment f o r
p r e s c r i b e d burning is d e f i n e d a s t h e incremental
d e p a r t u r e from t h e e x i s t i n g emission from pres c r i b e d f i r e and w i l d f i r e s .
T h i s approach circumv e n t s t h e d i f f i c u l t i e s a s s o c i a t e d with development
of a complete regionwide e m i s s i o n i n v e n t o r y base.
The assumption h e r e i s t h a t t h e e x i s t i n g emission
from p r e s c r i b e d f i r e and w i l d f i r e a r e d e f i n e d
w i t h i n t h e S t a t e Implementation Plan.
The followi n g c a l c u l a t i o n s t h e n r e p r e s e n t a n a n a l y s i s of
where p r e s c r i b e d burning can be i n c r e a s e d and where
burning must be reduced.
The a i r q u a l i t y database
i s t h e C a l i f o r n i a A i r Resources Board (1977) ThreeYear Summary of A i r Quality.
Nearly a l l t h e a i r
q u a l i t y monitoring s t a t i o n s a r e i n urban a r e a s and,
t h e r e f o r e , do n o t n e c e s s a r i l y r e f l e c t c o n d i t i o n s i n
t h e wildlands.
The following c a l c u l a t i o n s a r e
c o n s e r v a t i v e e s t i m a t e s because of t h e b i a s i n t h e
d a t a b a s e . The m e t e o r o l o g i c a l d a t a b a s e i s from t h e
N a t i o n a l F i r e Weather L i b r a r y (Furman and Brink
1975).
T h i s d a t a b a s e i s t h e o n l y r e a d i l y access i b l e d a t a b a s e f o r wildlands.
Plume r i s e c a l c u l a t i o n s were made through t h e e q u a t i o n s developed by
Craig and Wolf (1980) f o r p r e s c r i b e d burning.
T h r e e c r i t e r i a p o l l u t a n t s were e v a l u a t e d .
These
p o l l u t a n t s were p a r t i c u l a t e s , hydrocarbons, and
carbon monoxide.
The p h y s i c a l s e t t i n g of t h e Los Padres National
F o r e s t i s along t h e C a l i f o r n i a Coast extending from
n e a r Monterey i n t h e n o r t h , around Point Concept i o n , t o n e a r Santa Barbara i n t h e ~ a l i f o r n i a
Bight. The Los Padres National F o r e s t l i e s w i t h i n
t h e C a l i f o r n i a Coast Range and, t h e r e f o r e , can be
broken up i n t o a s e r i e s of small a i r s h e d s .
In
20 a i r s h e d s were defined.
Several
particular,
Emissions
C l a s s I w i l d e r n e s s a r e a s a r e included.
i n each of t h e a i r s h e d s were converted t o h e c t a r e s
through a f u e l s i n v e n t o r y of t o n s of f u e l per
h e c t a r e and t h e emission c h a r a c t e r i s t i c s defined i n
t h e second s e c t i o n of t h i s paper.
Calculated
changes i n combined emissions of p r e s c r i b e d and
w i l d f i r e s a r e defined by t h i s l e a s t a c r e s f o r
i n c r e a s e o r l a r g e s t n e g a t i v e numbers f o r d e c r e a s e
A s a n example, a l l a i r from c u r r e n t emissions.
sheds on t h e Monterey D i s t r i c t a r e l i m i t e d by
p a r t i c u l a t e p o l l u t a n t s ( t a b l e 3 ) . Most a i r s h e d s on
t h e Los Padres National Forest could s u s t a i n minor
i n c r e a s e s i n p r e s c r i b e d burning.
Only t h r e e a i r sheds show a need t o decrease t h e combined pres c r i b e d f i r e , w i l d f i r e emissions.
A l l three airsheds a r e h e a v i l y populated, and t h e F o r e s t must
compete with numerous o t h e r p o l l u t a n t s o u r c e s f o r
t h e a i r resource.
WASHINGTON
F i g u r e 4a--Location of weather s t a t i o n s i n northwest
Oregon used t o c a l c u l a t e wind p a t t e r n s shown i n
f i g u r e 4b.
F i g u r e 4 b à ‘ C a l c u l a t e wind p a t t e r n s . Mesh l e n g t h i s 4 km by 4 km. Windspeed is p r o p o r t i o n a l t o l e n g t h of arrows. Note t h e u n i f o r m i t y of wind
d i r e c t i o n and speed over t h e P a c i f i c Ocean and w i t h i n t h e Willamette
Valley. Winds i n complex t e r r a i n , t h e Coast Range, and t h e Cascade Range
show a h i g h d e g r e e of speed and d i r e c t i o n v a r i a b i l i t y .
.
LITERATURE CITED
E. F. Darley, and E. A. Schuck.
Boubel, R. W.,
1969. Emissions from burning g r a s s s t u b b l e and
straw.
J. A i r P o l l u t . Control Assoc. 19:497520.
C a l i f o r n i a A i r Resources Board.
1977.
Three year summary of
q u a l i t y d a t a . 346 p.
California
air
C r a i g , C. D . , and M. A. Wolf.
1980.
F a c t o r s i n f l u e n c i n g p a r t i c u l a t e concent r a t i o n s r e s u l t i n g from open f i e l d burning.
Atmos. Environ. 14:433-443.
Darley, E.
Middleton,
1966.
waste
Pollut
F., F. R. Burleson, E. H. Mateer, J. T.
and V. P o s t e r l i .
C o n t r i b u t i o n s of
burning a g r i c u l t u r a l
t o photochemical a i r p o l l u t i o n . J. A i r
Control Assoc. 16:685-690.
.
D r i v e r , B. L., Donald Rosenthal , and Lynn Johnson.
1979. A suggested r e s e a r c h approach f o r quantif ying t h e psychological b e n e f i t s of a i r v i s i bility.
Proc. Workshop i n V i s i b i l i t y Values.
USDA F o r e s t Serv. Gen. Tech. Rep. 18, p. 100105.
F e l d s t e i n , M . , S. Duckworth, H. C. Wohlers, and B.
Lusky
1963.
The c o n t r i b u t i o n s of t h e open burning of
land c l e a r i n g d e b r i s t o a i r p o l l u t i o n .
J. A i r
Pol l u t Control Assoc. 13: 542-545, 564.
.
.
Fox, Douglas G. , and Michael A. Fosberg
1976. Estimating r e g i o n a l a i r p o l l u t i o n impact.
Int.
I n Proc. 4 t h I n t . Clean A i r Congress.
Union of A i r P o l l u t . Control Assoc.
p. 229301.
F r i t s c h e n , Leo, Harley Bovee, Konrad B u e t t n e r ,
Robert Charlson, Lee Monteith, Stewart P i c k f o r d ,
James Murphy, and El 11s Darley.
1970.
Slash f i r e atmospheric p o l l u t i o n .
Res.
Paper PNW-97, 42 p.
P a c i f i c Northwest F o r e s t
and
Range
Exp.
Stn.,
U. S.
Dep.
Agric.,
P o r t l a n d , Oreg
.
Furman, R. William, and Glen F. Brink.
1975. The f i r e weather l i b r a r y : what i t is and
how t o use i t .
Gen. Tech. Rep. m-19, 8 p.
Rocky Mountain F o r e s t and Range Exp. Stn.,
Forest Serv., U.S. Dep. Agric., F o r t C o l l i n s ,
Colo.
G e r s t l e , R. W., a n d D . A. Kemnitz.
1967.
Atmospheric emissions from open burning.
J. A i r P o l l u t .
Control Assoc.
17:324-327.
Green, Kathleen, and Robert Wright.
1977.
F i e l d response of p h o t o s y n t h e s i s t o CO 2
enhancement i n ponderosa pine.
Ecology 58:
687-692.
Malm, William.
1979. V i s i b i l i t y : a physical p e r s p e c t i v e . Proc.
Workshop i n v i s i b i l i t y Values.
USDA F o r e s t
Serv. Gen. Tech. Rep. 18, p. 56-68.
McCall. C. W.. B i l l F r i e s . and Chip Davis.
Fosberg, Michael A., and Douglas G. Fox.
1976.
~ u r o r a ~ o r e a l i s on
'
record a1 bum Wilder1976. An a i r q u a l i t y index t o a i d i n determining
ness,
PD-1-6069.
Polydor Inc.,
New York.
mountain land use planning.
I n Proc. 4th
N a t i o n a l Conf on F i r e and F o r e s ~ ~ e t e o r o l o ~ ~ .
Parmeter, J. R. , and B. Uhrenhol t
USDA F o r e s t Serv. Gen. Tech. Rep. RM-32, p.
1975a.
E f f e c t of smoke on pathogens and o t h e r
167-170.
fungi.
Proc. T a l l Timbers F i r e Ecology Conf
No. 14:299-304.
Fosberg, Michael A., W. E. M a r l a t t , and Lawrence
Krupnak.
Panneter, J. R. , and B. Uhrenholt
l976a.
Estimating a i r f l o w p a t t e r n s over complex
1975b.
Some e f f e c t s of p i n e n e e d l e s o r g r a s s
terrain.
Res. Paper RM-162, 16 p. Rocky Mounsmoke on fungi. Fhytopathol 65:28-31.
t a i n F o r e s t and Range Exp. S t n . , F o r e s t Serv.,
U.S. Dep. Agric., F o r t C o l l i n s , Colo.
Radke, L. F., J. L. Smith, D. A. Hess, a n d P . V.
Hobbs
Fosberg, Michael A., Douglas G. Fox, E. A. Howard,
1978. Airborne s t u d i e s of p a r t i c u l a t e and g a s e s
and J a c k Cohen.
J. A i r P o l l u t . Control
from f o r e s t f i r e s .
1976b.
Non-turbulent
dispersion processes i n
Assoc. 28: 30-34.
complex t e r r a i n . Atmos. Environ. 10:1053-1055.
.
.
.
.
.
.
Fosberg, Michael A . , and Douglas G. Fox.
1978.
Reply: non-turbulent d i s p e r s i o n processes
i n complex t e r r a i n .
Atmos. Environ. 12:976.
Ryan, P. W.
1974. The q u a n t i t y and q u a l i t y of smoke produced
by s o u t h e r n f u e l s i n p r e s c r i b e d burning operations.
B u l l . h e r . Meteor01
Soc. 55: 70.
Fosberg, Michael A., C h a r l e s D. C r a i g , and Marshall
P. Waters, 111.
1980.
A p p l i c a t i o n of i n f r a r e d d a t a from a geosynchronous m e t e o r o l o g i c a l s a t e l l i t e i n s u r f a c e
on F i r e and
wind modeling.
Proc. 6 t h Conf
F o r e s t Meteorology.
Soc. Amer. For.
p. 265275.
Ryan, P. W., and C h a r l e s K . McMahon.
1976. Some chemical and p h y s i c a l c h a r a c t e r i s t i c s
of emissions from f o r e s t f i r e s .
Paper No.
76-2.3 p r e s e n t e d a t t h e 6 9 t h Annual Meeting of
t h e A i r P o l l u t i o n Control A s s o c i a t i o n [June
1, 1976, P o r t l a n d , Oregon], 15 p.
22-July
.
.
Hydrocarbon Emissions from vegetation1
David T. Tingey Walter F. ~ u r n s ~
Abstract: A wide range of volatile organic compounds may be
emitted by vegetation. The identified emittants, however,
are mainly terpenoid in nature. Their emission rates are
controlled primarily by the physical/chemical processes that
regulate hydrocarbon vapor pressure. Emission rates vary
between species and are influenced by environmental factors
such as light and temperature. Regional emission estimates
indicate that vegetation may emit as much as 30 kg of hydrocarbons k w 2 day-l. The measured atmospheric concentrations
are in reasonable agreement with the estimated emission
rates. Within the atmosphere, these hydrocarbons may participate in photochemical reactions leading to aerosol
production and the consumption or formation of ozone. High levels of ozone have been measured in
rural and remote locations far from significant
anthropogenic sources of oxidant precursors.
These elevated concentrations may have resulted
from long distance transport and/or the photooxidation of locally-produced biogenic hydrocarbons. Robinson (1978) proposed that ambient
hydrocarbon concentrations were governed by both
long distance transport and local production.
Volatile organics, including monoterpenes and
isoprene, have been detected in the atmosphere
(Rasmussen and Went 1965; Schjoldager and Watine
1978; Whitby and Coffey 1977; Arnts and Meeks 1980; Lonneman and others 1977) and in laboratory studies shown to produce ozone (Arnts and Gay
1979), suggesting that they may contribute to ambient ozone concentrations.
Plants contain a number of potentially volatile
organic compounds including monoterpenes, isoprene, aldehydes, alcohols, and ketones (Meigh
Presented at the Symposium on Effects of Air
Pollutants on Mediterranean and Temperate Forest
Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.
Plant Physiologist, Office of Research and
Development, U.S. Environmental Protection Agency,
Corvallis, Ore.; and Chemist, Northrop Services, Inc., Corvallis, Ore. 1955; Rasmussen 1972; Zimmerman 1979a).
Individ-
ual species have relatively distinctive emission profiles. For some species, only one or a few compounds dominate the emission profile; however, other species have a diffuse emission profile with no dominant compounds (Rasmussen 1972; Zimmerman 1979a).
Despite the wide range of potentially volatile compounds, only isoprene, monoterpenes, and a few aromatics have been conclusively identi- fied as emission products from vegetation (Rasmussen 1972; Zimmerman 1979a), hence they form the basis for further discussion. METHODS FOR ESTIMATING EMISSION RATES A variety of experimental methods have been used to estimate emission rates. A tree branch or a few small plants were enclosed in a large Teflon bag to estimate biogenic hydrocarbon emission rates in the field (Zimmerman 1979a, l979b). The bag was sealed, evacuated and refilled with hydro- carbon-free air. A small gas-exchange rate was maintained through the bag. After an accumulation period, the head space was sampled to determine the gas phase concentration. Vertical gradients of temperature, water, and a-pinene, both within and above the canopy of a loblolly pine (Pinus taeda L.) plantation were measured and used to calculate emission rates (Arnts and others 1978). Sandberg, D. V.
1974. Measurement of p a r t i c u l a t e emissions from
f o r e s t r e s i d u e s i n open burning experiments.
Ph. D. t h e s i s , Univ. of Washington.
165 p.
Sandberg, D. V., and R. E. Martin.
1975.
P a r t i c l e s i z e s i n s l a s h f i r e smoke. Res.
Paper PNW-199, 7 p.
P a c i f i c Northwest F o r e s t
and Range Exp. S t n . , F o r e s t Serv., U.S. Dep.
A g r i c . , P o r t l a n d , Oreg.
Sandberg, D. V., J. M. P i e r o v i c h , D. G . Fox, and E.
W. Ross.
1979. E f f e c t s of f i r e on a i r . Gen. Tech. Rep.
WO-9,
40 p.
F o r e s t Serv., U.S. Dep. Agric.,
Washington, D.C.
Schaef e r , Vincent J.
1976. The p r o d u c t i o n of optimum p a r t i c l e smokes
in forest fires.
Proc. A i r Q u a l i t y and Smoke
from Urban and F o r e s t F i r e s . National Academy
of
Science-Nat i o n a l
Research
Council.
p.
27-29.
S i n g e r , Michael J .
1980.
Climate v a r i a b l e s i n s o i l e r o s i o n processes.
Proc. of t h e N a t i o n a l Weather S e r v i c e
A g r i c u l t u r a l Meteorology T r a i n i n g Conf , Univ.
Davis.
Atmos. S c i . Paper 19, p.
of C a l i f
75-87.
.,
.
Turner, D. Bruce.
1969. Workbook of atmospheric d i s p e r s i o n e s t i mates.
U.S.
Dep.
Health,
Education,
and
N.
Welfare
Public
Health
Service
Publ.
999-AP-26.
84 p.
U.S. Congress.
1977. Clean A i r Act Amendment of 1977.
685, 42 U.S.C. 7401 of seq.
91 S t a t .
U.S. Environmental P r o t e c t i o n Agency.
1978.
Compilation of a i r p o l l u t a n t emission
AP 42.
f a c t o r s , 3d ed., Supplemental No. 8.
Vines, Robert G., L. Gibson, A. B. Hatch, M. K.
King, D. A. MacArthur, D. R. Packhan, and R. J.
Taylor.
1971. On t h e n a t u r e , p r o p e r t i e s , and behavior of
brush-fire smoke.
CSIRO, Div. of Appl. Chem.
Tech. Paper 1. 32 p.
Ward, D. E., C. K. McMahon and R. W. Johansen.
1976.
An u p d a t e on p a r t i c u l a t e emissions from
forest fires.
Paper No. 62-2.2.
6 t h Annual
Meeting of A i r P o l l u t . C o n t r o l Assoc.
1 4 p.
Hydrocarbon Emissions from Vegetation
David T. Tingey Walter F. ~ u r n s ~
Abstract: A wide range of volatile organic compounds may be
emitted by vegetation. The identified emittants, however,
are mainly terpenoid in nature. Their emission rates are
controlled primarily by the physical/chemical processes that
regulate hydrocarbon vapor pressure. Emission rates vary
between species and are influenced by environmental factors
such as light and temperature. Regional emission estimates
indicate that vegetation may emit as much as 30 kg of hydrocarbons k w 2 day-l. The measured atmospheric concentrations
are in reasonable agreement with the estimated emission
rates. Within the atmosphere, these hydrocarbons may participate in photochemical reactions leading to aerosol
production and the consumption or formation of ozone. High levels of ozone have been measured in
rural and remote locations far from significant
anthropogenic sources of oxidant precursors.
These elevated concentrations may have resulted
from long distance transport and/or the photooxidation of locally-produced biogenic hydrocarbons. Robinson (1978) proposed that ambient
hydrocarbon concentrations were governed by both
long distance transport and local production.
Volatile organics, including monoterpenes and
isoprene, have been detected in the atmosphere
(Rasmussen and Went 1965; Schjoldager and Watine
1978; Whitby and Coffey 1977; Arnts and Meeks 1980; Lonneman and others 1977) and i n laboratory studies shown to produce ozone (Arnts and Gay
1979), suggesting that they may contribute to ambient ozone concentrations.
Plants contain a number of potentially volatile
organic compounds including monoterpenes, isoprene, aldehydes, alcohols, and ketones (Meigh
Presented at the Symposium on Effects of Air
Pollutants on Mediterranean and Temperate Forest
Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.
Plant Physiologist, Office of Research and
Development, U.S. Environmental Protection Agency,
Corvallis, Ore.; and Chemist, Northrop Services, Inc., Corvallis, Ore. 1955; Rasmussen 1972; Zimmerman 1979a).
Individ-
ual species have relatively distinctive emission profiles. For some species, only one or a few compounds dominate the emission profile; however, other species have a diffuse emission profile with no dominant compounds (Rasmussen 1972; Zimmerman 1979a).
Despite the wide range of potentially volatile compounds, only isoprene, monoterpenes, and a few aromatics have been conclusively identi- fied as emission products from vegetation (Rasmussen 1972; Zimmerman 1979a), hence they form the basis for further discussion. METHODS FOR ESTIMATING EMISSION RATES A variety of experimental methods have been used to estimate emission rates. A tree branch or a few small plants were enclosed in a large Teflon bag to estimate biogenic hydrocarbon emission rates in the field (Zimmerman 1979a, 1979b). The bag was sealed, evacuated and refilled with hydro- carbon-free air. A small gas-exchange rate was maintained through the bag. After an accumulation period, the head space was sampled to determine the gas phase concentration. Vertical gradients of temperature, water, and a-pinene, both within and above the canopy of a loblolly pine (Pinus taeda I,.) plantation were measured and used to calculate emission rates (Arnts and others 1978). Semi-quantitative estimates of emission rates were made using static gas-exchange chambers containing either detached leaves, twigs or whole plants (Rasmussen 1970; Rasmussen 1972; Sanadze and Kalandadze 1966a).
Within these chambers carbon dioxide may be elevated or depleted depend- ing on light intensity. This may modify plant metabolism and the stomatal aperture; humidity will increase; and high concentrations of hydro- carbon gases will build up within the chamber reducing diffusion gradients. These factors can lead to an underestimation of emission rates. Dynamic mass-balance gas-exchange chambers and leaf cuvettes which simulate the gaseous environ- ments of plants in the field have also been used to estimate hydrocarbon emissions (Kamiyama and others 1978; Tingey and others 1979 and 1980; Tyson and others 1974).
These chambers may be used to determine the influence of environmental factors on emission rates. MECHANISM OF HYDROCARBON VOLATILIZATION Terpenoid Biosynthesis Knowledge of the mechanism and sites of terpenoid biosynthesis aids in understanding the factors
controlling emission rates. Terpenoid biosynthesis starts with the conversion of carbon dioxide
to sucrose with its subsequent metabolism to
acetyl-CoA and mevalonic acid to form isopentenyl
pyrophosphate. The hemiterpene, isoprene, (Cg) is
formed from isopentenyl pyrophosphate; monoterpenes (Clo) are formed from a condensation of
dimethylallyl pyrophosphate and isopentenyl pyrophosphate. Subsequent additions of isopentenyl
pyrophosphate units form higher homologs in the
terpenoid series (Loomis and Croteau 1980). The conditions that promote isoprene biosynthesis indicate that it is likely synthesized within
the chloroplast.
Isoprene biosynthesis
is
affected by metabolic inhibitors that regulate
photorespiration (Loomis and Croteau 1980). Monoterpenes appear to be ubiquitous in higher plants (Loomis and Croteau 1980). The accumula- tion or secretion of significant quantities of monoterpenes is associated with the presence of secretory structures such as glandular hairs or trichromes, oil cells, resin ducts or glandular epidermises, and lysogenous spaces. It is gener- ally assumed that monoterpenes are synthesized within the secretory cells, although this point has not yet been conclusively demonstrated (Loomis and Croteau 1980). tion gradient. The larger the concentration gradient, the larger the hydrocarbon flux; con- versely, the larger the resistance to mass trans- fer, the smaller the flux (Nobel 1974). Only hydrocarbons with appreciable vapor pres- sures at ambient temperatures will be emitted at significant rates. The vapor phase concentration of hydrocarbons within the leaf is controlled by the liquid phase concentration, vapor pressure, and solubility. The vapor pressure of terpenoid compounds increases exponentially with the temper- ature (Jordan 1954).
Monoterpene emission rates from black sage (Salvia mellifera Greene) and slash pine (Pinus elliottii Engelm.) also exhibit an exponential increase with temperature (Dement and others 1975; Tingey and others 1980), indi-
cating that vapor pressure is a significant factor in controlling emissions. Emission rates from dead slash pine needles and black sage leaves are similar to emission rates from live tissue (Tingey and others 1980; Dement and others 1975), support- ing the concept that the volatilization is primar- ily a physical process. Hydrocarbons with chain lengths greater than Clo generally have low vapor pressures and will not have a large emission rate. When monoterpenes occur in high concentrations in resin ducts, oil cells or glandular trichomes, their emission rates are essentially independent of concentration. Large pools of isoprene, how- ever, have not been detected. Below 35OC (the boiling point for isoprene), the emission rate is closely linked to its synthesis rate. Above 35OC, the emission rate is diffusion-limited (Tingey and others 1979). Monoterpenes have a low aqueous solubility (hydrophobic) and higher vapor pressures than similar, more hydrophilic compounds. Therefore, monoterpenes would be emitted at a higher rate than similar oxygenated compounds at equal concen- trations within the tissue. Similarly, if the concentration exceeds its aqueous solubility limit, then vapor pressure and emissions are independent of tissue concentrations. Resistance to mass transfer can occur along either a stomatal or cuticular pathway (Nobel 1974). Either one or both pathways may be signif- icant, depending on the species. Stomata are apparently the main pathway for diffusion of monoterpenes (Hanover 1972), isoprene and other compounds synthesized within the leaves. However, for plants with glandular trichomes or glandular cells in the epidermis, such as in the Labiatae and Solanaceae, the cuticular pathway is the main one for diffusion. Hydrocarbon Diffusion from Plants BIOGENIC EMISSIONS Gaseous diffusion between the plant and its
environment is controlled by the chemical potential gradient between the inside and the outside
of the leaf and the resistance to mass transfer
along the diffusion pathway. The chemical potential gradient can be approximated by a concentra-
Emission Rates Emission rates for several plant species are shown in table 1. Total non-methane hydrocarbon and monoterpene emission rates are similar among Table 1--Biogenic hydrocarbon emission rates estimated at 30°C TNMHC1
Species
Isoprene Monoterpenes References [g dry weightl-I hr-l-
fg
4.1
7.3
13.6
14.2
Slash Pine
Longleaf Pine
Sand Pine
Cypress
Slash Pine
Loblolly Pine
Cryptomeria
Laurel Oak
Turkey Oak
Bluejack Oak
Live Oak
Live Oak
Willow
Saw Palmetto
22.1
11.5
Mean 7 Hardwood
Trees--Isoprene
20'0 12.6
26.5
56.4
10.8
2.6
5.6
11.0
8.1
6.4
3.7
3.0
10.0
23.4
43.9
9.1
41.2
12.4
8.6
Flyckt and others 1980 Zimennan 19798 Zimerman 1979a Zimerman 1979a Zimnerman 1979a Zimerman, l979a Zimnennan, 1979a Wax Myrtle
Persimon
Orange
Grapefruit
Red Maple
Hickory
Mean 10 Hardwood
Trees--Nm-Isoprene
Zimerman 1979a Zitmerman 1979a Zimerman 1979a Zimerman 1979a Tingey and other? 1980 Arnts and others 1978 Kamiyama and others 1978 Zimerman l979a Zimmerman 1979a Zimerman 1979a Zimnennan 1979a Tingey and others 1980 Zimerman 1979a Zimmerman 1979a 1
7'3 Emission factors were developed to characterize the various biomes in the United States: Emission Rate (mg w2hr-l) Flyckt and others, 1980 Biome :
Total non-methane hydrocarbons the conifers and as much as 50 percent less than
emission rates from hardwoods that emit isoprene.
Monoterpenes account for 50 to 75 percent of the
total non-methane hydrocarbon emissions in conifers. Similarly, isoprene accounts for 60 to 90
percent of total non-methane hydrocarbon emissions
from isoprene emitters. Plants whose emissions
were not dominated by either isoprene or a few
monoterpenes had emission rates roughly similar to
the conifers. Total non-methane emission rates were estimated at several locations in the United States on similar vegetation types: Vegetation Type
and Location:
Hydrocarbon emission rates/unit tissue multi- plied by biomass density yield emission factors. Emission factors for the Tampa-St.Petersburg, Florida, area (Zimmerman 1979a), indicate that 92 percent of the total non-methane hydrocarbon emis- sions occur in the following four land use types: evergreen forests (35 percent); citrus groves (22 percent) ; pasture and rangeland (19 percent) ; and
residential areas (16 percent).
The remaining 8 percent was distributed among crop lands, decid- uous forests, mangroves, freshwater, marine, and barren lands. Emission factors for trees were approximately 6 mg m-2 hr-l; shrubs, 2.0 mg m-2 hr-l; pastures, mud flats and other land use types were less than 0.1 mg m-2 hr-I .
Emission Rate1 (ye [g dry weight]-I hr-l) Night
0.2 1.4 9.4 2.7 2.7 0.7 0.4 Data from Zimmerman Daytime biome emission factors ranged from a low
of 0.3 mg m-2 hr-I for grasslands to a high of
10.7 for temperate rain forests. Nighttime emissions were 10 to 60 percent lower reflecting, in
part, the absence of isoprene emissions. Environmental Influences on Emission Rates Isoprene production is light dependent, and persists for only a few minutes when plants are darkened (Rasmussen and Jones 1973; Sanadze and Kalanadze
1966b).
Emissions increase with increasing light intensity until a maximum is reached and then remain constant (Sanadze and Kalandadze 1966a; Tingey and others 1979); similar to a light saturation curve for photosynthesis. Isoprene emissions are light saturated at moderate light intensities (Sanadze and Kalandadze 1966a; Tingey and others 1979). In contrast, monoterpene emissions from slash pine, black sage, and several other plant species, are similar in the dark and light (Tingey and others 1980; Dement and others 1975; Rasmussen 1972). Conifers Washington Florida Texas Oaks California Florida Texas Non-Conifers, Non-Isoprene Emitter Washington
7.8 California
4.1 Florida
4.7 Texas
0.2 Data from Zimmerman 1979b and c. Emission rates for the conifers, oaks and nonconifer, non-isoprene emitting vegetation are
similar within each vegetation type. This indicates an apparent high uniformity in emission
rates among locations using the same estimation
technique. Grassland
Sclerophyll Scrub
Temperate Rain Forest
Deciduous Forest
Coniferous Forest
Desert
Tundra, Alpine Fields
Isoprene emissions increase sigmoidally with temperature; low emissions occur at 18-20° and increase exponentially between approximately 20 and 35OC, then plateau. At higher temperatures (between 43 and 47OC), depending upon the species, there is the large, precipitous decline in iso- prene emissions (Sanadze and Kalandadze 1966a; Rasmussen and Jones 1973; Tingey and others 1980). The increase in isoprene emissions with temperature is greater at high light intensities than
low (Tingey and others 1979).
Isoprene emissions
from several hardwood trees and live oak (Quercus
virginiana Mill.) increased at approximately 20
and 16 percentI0C (20-35OC), respectively (Flyckt
and others 1980; Tingey and others 1979). Monoterpene emissions from conifers, black sage and hardwood trees increase exponentially with the temperature (Arnts and others 1978; Kamiyama and others 1978; Rasmussen 1972; Flyckt and others 1980; Dement and others 1975; Tingey and others 1980).
The relative percent increase per degree temperature varies between species and ranges from approximately 6 to 20 percent/OC. In conifers, extensive genetic variations in monoterpene pools (Hanover 1972) may explain the lack of an exponen- tial relationship between temperature and emission rates in some field studies (Flyckt and others 1980). Typical diurnal emission patterns for isoprene and monoterpenes and environmental conditions for an average of summer days in Tampa, Florida, were used to illustrate the interaction of light and temperature on terpenoid emissions (Tingey and others 1979, 1980). During early morning and late afternoon, when the leaves are not light-saturated and the temperature is moderate, light would be the main factor controlling isoprene emissions from live oak. However, during most of the day, the leaves of the canopy are light-saturated; thus varying air temperature would control emission rates. More than 80 percent of the isoprene emissions were expected to occur after mid-
morning, ceasing in the evening. Monoterpene emission rates . from slash pine increase after
sunrise, peaking during early afternoon, and declining to a minimum shortly before sunrise. Approximately 55 percent of the total daily mono- terpene emissions occurred during daylight hours (0600-1800) with an additional 25 percent emitted between sunset (1800) and midnight (2400). Seasonal emission patterns were estimated for
individual ponderosa pine and red oak trees
(Flyckt 1979).
Monoterpene emissions from ponderosa pine were sinusoidal, at a maximum during
late spring (May and June), declining to a minimum
around November, and then gradually increasing.
In contrast, isoprene emissions from red oak were
maximum during July and August and decreased
during the fall.
No isoprene emissions were
detected during the winter; emissions reappeared
in the spring with the initiation of new leaves.
It is not clear whether seasonal emission changes
were due solely to changes in environmental conditions or were, in part, due to changes in terpenoid pools. In addition to changes in the emission
rates, there were also qualitative changes in the
monoterpene emissions throughout the year (Flyckt
and others 1980). Table 2"-Estimated emissiops for biogenic hydrocarbons. Location
Emissions
---metric tons-
World
1.75 x 10'/year
World
4.38 x lo8/year
World
8.30 x 108/year
United States 0.23-4.64 x lo7/year
United States
6.5 x lo7/year
Florida
157.0lday
(81 x 60 km) Texas
32.4ldav
. .
(38 x 31 to) Pennsvlvania
3.580.0/day
1
Emission Factor*
kg km-x day-' 32.3
References Went 1960
Rasmussen
Zimwrnan
Rasmussen
Zimeman
Zimeman
and Went 1965 1979b 1972 1979b 1979a 27.5
Zimeman 1979~
30.7
Flyckt and others 1980 Regional Emissions Biogenic hydrocarbon emission rates for a variety of plant species and biomass estimates, were used to estimate emissions for various areas (table 2).
The emission rate estimates for vari- ous estimation scales (world, United States, or regional) were approximately similar. The close agreement between the emission estimates from the three regional studies may have occurred because the same experimental approach was used. Emission estimates for Pennsylvania and the Tampa-
St.Petersburg, Florida, area indicate that bio- genic emissions range from 12 percent greater to 20 percent less than anthropogenic emissions (Flyckt and others 1980; Zimmennan 1979a; Wayne and Kochis 1978). Relationship Between Primary Productivity and Emission Rates A relationship between biogenic hydrocarbon
emissions and primary productivity should exist
because they are ultimately derived from photosynthetically fixed carbon dioxide. Measurements
of the ratio of carbon lost as volatile terpenoids
to primary productivity for several tree species
indicated loss rates of 0.2 to 2 percent for
isoprene and 0.06 to 0.4 percent for monoterpenes
(Sanadze 1969; Tingey and others 1979, 1980; Tyson
and others 1974).
The relationship between primary productivity and biogenic hydrocarbon emissions could be used to delineate geographic areas
where emissions would tend to be high. Based on
the work of Leith (1975), primary productivity is
highest in the Southeast, followed by the
Mississippi Valley area and the central part of
the United States and lowest in the Great Basin
and the Southwest. Zimmennan (1979b) estimated
that 45 percent of the total national biogenic
hydrocarbon emissions occurred in the South, an
area with the highest primary productivity in the
United States (Leith 1975). AMBIENT CONCENTRATIONS OF TERPENOIDS Biogenic hydrocarbons were measured in the
atmosphere over several vegetation types. The
average isoprene concentrations varied from 10 ppb
carbon for an oak forest to 0.1 ppb carbon for a
pine forest. The average monoterpene concentrations ranged from 24 ppb carbon in the coniferous
forest in Norway to 2.7 ppb carbon in the conifer- ous forest in Idaho (Schjoldager and Watine 1978; Arnts and Meeks 1980; Coffey and Westberg 1978). Measured ambient concentrations of biogenic hydro- carbons and ambient concentrations predicted from biogenic emission rates are in reasonable agree- ment (Zimmerman 1979c; Flyckt and others 1980; Scully, 1979; Coffey and Westberg, 1978). Atmospheric hydrocarbon concentrations are
dependent on emission rates, mixing height, and
the reactivities (photolysis and ozonolysis) of
the individual components. Peterson and Tingey
(1980) used a box model to estimate ambient air
concentrations of isoprene and monoterpenes. The
predicted isoprene concentrations increased during
the daylight hours, reaching a maximum at midafternoon and then disappearing during the early
evening when isoprene emissions ceased. Predicted
ambient monoterpene concentrations were the lowest
during mid-day when atmospheric dilution, photooxidation, and ozonolysis, were the highest,
despite the fact that monoterpene emissions were a
maximum. In contrast, monoterpene concentrations
were the largest during the evening and early
morning hours because monoterpenes are emitted at
night when atmospheric mixing is low and hydrocarbon decay reactions are slow, permitting an
accumulation of monoterpenes.
This predicted
monoterpene profile was verified by field measurements (Arnts and Gay 1979). ATMOSPHERIC FATES OF TERPENOIDS There are several atmospheric fates for the
biogenic hydrocarbons, including conversion to
aerosols, carbon monoxide formation, and photochemical reactions, both forming and consuming
oxidants. Went (1960) attributed the blue haze
found over many coniferous forests to the conversion of terpenes to aerosols. When limonene, a
monoterpene, was reacted with NO and 03, greater
than 50 percent of the limonenexwas converted to
aerosols within 2.5 hours (Schuetzle and Rasmussen
1978).
The aerosols contained both mono- and
dimeric alcohols, aldehydes and acid-substituted
products. Zimmerman and others (1978) suggested that
atmospheric isoprene and monotepenes could be
oxidized in the atmosphere to CO with a yield of
60-80 percent. Based on biogenic emission estimates, they concluded that natural hydrocarbons
may be the largest contributor to the United
States carbon monoxide budget. Nitrogen oxides in the presence of solar radiation form OH radicals (Cleveland and Graedel
1979).
Hydroxyl (OH) radicals react with hydrocarbons, forming peroxy radicals, which in turn
convert NO to NO2, perturbing the photostationary
state releasing a free oxygen, forming ozone and
other oxygenated products. The exact mechanisms
are not clearly delineated because of competing
secondary reactions with hydrocarbons, 03, N O ,
and OH radical. Arnts and Gay (1979) reported
ozone, PAN, formic acid, acetone, aldehydes, CO, and Coy formation when terpenes were irradiated in
the presence of nitrogen oxides. The amount of ozone formed depended on the C / N O ratio. At a low C/NO ratio, 1 ppb C from terpenoids produced 2-4 ppb ozone. However, when the ratio was large, 1 ppb C produced 0.3 to 0.1 ppb ozone, suggesting that terpenoids also consume ozone. Eschenroeder (1974) and Coffey and Westberg (1978) concluded that emissions of biogenic hydrocarbons did not significantly alter ambient ozone concentrations through scavenging reactions. Zimmerman (1979~) suggested that photooxidation
of isoprene from forests could contribute 22 ppb
ozone to the ambient concentration. Similarly,
Coffey and Westberg (1978) suggested that emissions from coniferous forests could react to add 1
to 5 ppb ozone to the ambient air. LITERATURE CITED Arnts, R.R., R.L. Seila, R.L. Kuntz, F.L. Mowry, K.R. Knoerr, and A.C. Dudgeon. 1978. Measurements of a-pinene fluxes from a loblolly pine forest. In Proc. 4th Joint Conf. on Sensing of Environmental Pollutants. Amer. Chem. Soc.
Washington, D.C., p. 829-833. Arnts, Robert R., and Bruce W. Gay, Jr. 1979. Photochemistry of some naturally emitted hydrocarbons. EPA-600/3-79-081, U.S. Environ- mental Protection Agency, Research Triangle Park, North Carolina. Arnts, Robert R., and Sarah A. Meeks. 1980. Biogenic hydrocarbon contribution to the
ambient air of selected areas: Tulsa, Great
Smoky Mountain, Rio Blanco County, Colorado.
EPA-600/3-80-023, U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina. Cleveland, William S., and T.E. Graedel. 1979. Photochemical air pollution in the north- east United States. Science 204(4399):1273- 1278. Coffey, P. E. and H. Westberg. 1978. The issue of organic emission. Inter-
national Conference on Oxidants, 1976. Anal-
ysis of Evidence and View Points. Part IV. EPA-600/3-77-116, U.S. Environmental Protec- tion Agency, Research Triangle Park, North Carolina. Dement, William A., Bennett J. Tyson, and Harold A. Money. 1975. Mechanism of monoterpene volatilization in Salvia mellifera. Phytochem. 14(12):2555- 255-7
Eschenroeder, Alan. 1974. Reaction and diffusion of natural hydro- carbons in the atmosphere over forests. General Research Corporation, Santa Barbara, California. Flyckt, Donald L. 1979. Seasonal variation in the volatile hydro- carbon emissions from ponderosa pine and red oak. Masters Thesis. Washington State Uni- versity, Pullman. Flyckt, D.L., H.H. Westberg, and M.W. Holdren. 1980. Natural organic emissions and their impact on air quality.
Preprint 80-69.2 Annual Meeting Air Pollution Control Associa- tion. [June 22-27, 1980, Montreal, Canada]. Peterson, Ernest W., and David T. Tingey. 1980. Contributions of biogenic sources to airborne hydrocarbon concentrations. Atmos. Environ. 14(1):79-81. Rasmussen, Reinhold A. 1970. Isoprene: Identified as a forest type emission to the atmosphere. Environ. Sci. Tech. 4(8):667-671. Rasmussen, Reinhold A. 1972. What do the hydrocarbons from trees contribute to air pollution? J. Air Poll. Con. Assoc. 22(7):537-543. Rasmussen, R.A., and C.A. Jones. 1973. Emission isoprene from leaf discs of Hamamelis. Phytochem. 12(1):15-19. Hanover, James W. 1972. Factors affecting the release of volatile chemicals by forest trees. Mitteilungen der forstlichen
Bundes-Versuchanstalt
Wien. 97:625-644. Rasmussen, Reinhold A., and F.W. Went. 1965. Volatile organic material of plant origin in the atmosphere. Proc. Nat. Acad. Sci. 53(1):215-220. Jordan, T. Earl. 1954. Vapor pressure of organic compounds. 266 p. Interscience Publishers, Inc., New York. Robinson, Elmer. 1978. Hydrocarbons in the atmosphere.
Appl. Geophys. 116(2/3):372-382. Kamiyama, K., T. Takai, and Y. Yamanaka. 1978. Correlation between volatile substances released from plants and meteorological condi- tions. & Proc. Inter. Clean Air Conf. E.T.
White, P. Hetherington, B.R. Thiele, eds. Brisbane, Australia. p. 365-372. Sanadze, G.A.
1969. Light dependent excretion of molecular isoprene. Progress in Photosynthesis Res. 2:701-706. Lieth, Helmut. 1975. Historical survey of primary productivity research.
Primary productivity of the biosphere.
Helmut Leith and Robert H. Whittaker, eds. p. 7-16. Springer-Verlag, Berlin. Lomeman, William A., Robert L. Seila, and Sarah
A. Meeks. 1977. Preliminary results of hydrocarbon and other pollutant measurements taken during the 1975 Northeast Oxidant Transport Study. In Proc. Symp. 1975 Northeast Oxidant Transport Study. EPA-600/3-77-017, U.S. Environmental Protection Agency, p. 40-53. Loomis, W. David, and Rodney Croteau. 1980.
Biochemistry of terpenoids.
In The biochemistry of plants. P.K. Stumpf and E.E. Conn, eds. 4:363-415. Academic Press, New York. Meigh, D.F. 1955. Volatile alcohols, aldehydes, ketones and ester. In Modern Methods of Plant Analysis. K. ~ a e c h a n d M.V. Tracey, eds. 2:403-443. Springer-Verlag, Berlin. Nobel, Park S. 1974. Introduction to Biophysical Plant Physi- ology. 448 p. W.H. Freeman and Co., San Francisco. Pure Sanadze, G.A., and A.N. Kalandadze. 1966a. Light and temperature curves of the evolution of Ccfia. Sov. Plant Physiol. 13(3):411-413. Sanadze, G.A., and A.N. Kalandadze. 1966b. Evolution of the diene CsHc by poplar leaves under various conditions of illumina- tion. Dokl. Bot. Sci. 168:95-97. Schjoldager, J., and B.M. Watine. 1978. Preliminary study of hydrocarbons in forests. Norwegian Institute for Air Quality Studies, Lillestrom, Norway. Schuetzle, Dennis, and Reinhold A. Rasmussen. 1978. The molecular composition of secondary aerosol particles formed from terpenes. J. Air Poll. Con. Assoc. 28(3):236-240. Sculley, Robert D. 1979. Correspondence to the editor.
Sci. Tech. 13(3):234-235. Environ. Tingey, David T., Marybeth Manning, Louis C. Grothaus, and Walter F. Burns. 1979. The influence of light and temperature on isoprene emission rates from live oak. Physiol. Plant 47(2) :112-118.
Tingey, David T., Marybeth Manning, Louis C. Grothaus, and Walter F. Burns. 1980. The influence of light and temperature on monoterpene emission rates from slash pine. Plant Physiology 65 (in press). Tyson, Bennett, William A. Dement, and Harold A. Mooney .
1974. Volatilization of terpenes from Salvia mellifera. Nature 252(5479):119-120. Zimmerman, P.R. 1979a. Determination of emission rates of hydrocarbons from indigenous species of vege- tation in the Tampa/St. Petersburg, Florida, area. Appendix C. Tampa Bay Area Photochem- ical Oxidant Study. EPA-904/9-77-028. U.S. Environmental Protection Agency, Region IV. Atlanta, Georgia. Zimmerman, Patrick R. 1979b. Testing of hydrocarbon emissions from vegetation, leaf litter and aquatic surfaces, and development of a methodology for compiling biogenic emission inventories. EPA-450/4-79-
004. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina. Went, F.W. 1960. Organic matter in the atmosphere, and its possible relation to petroleum formation. Proc. Nat. Acad. Sci. 46(2):212-221. Zimmerman, Patrick. 1979c. Natural sources of ozone in Houston: natural organics. & Proc. APCA Houston
Specialty Conference on Ozone Oxidants. Houston, Texas. p. 299. Wayne, L.G., and P.C. Kochis. 1978. Assessment of the anthropogenic hydrocarbon and nitrogen oxide emissions in the
Tampa Bay area. EPA 904/9-77-016, U.S. Environmental Protection Agency, Region IV.
Atlanta, Georgia. Whitby, Robert A., and Peter E. Coffey. 1977. Measurement of terpenes and other organ- ics in an Adirondack Mountain pine forest. J. Geophys. Res. 82(37):5928-5934. Zimmerman, Patrick R., Robert B. Chatfield, Jack
Fishman, Paul Crutzen, and Phillip L. Hanst.
1978. Estimates of the production of CO and Hz
from the oxidation of hydrocarbon emissions
from vegetation. Geophys. Res. Let. 5(8):679- 682. Background Levels of Trace Elements in
Forest Ecosystems1
G. Bruce Wiersma and Kenneth W. ~ r o w n ~
Abstract: This study was conducted as part of a project to develop a pollutant monitoring system for biosphere reserves. Sampling was carried out in the Great Smoky Mountains National Park and Olympic National Park. Results are reported for copper, lead, manganese, aluminum, calcium and phosphorus. Olympic National Park had much lower levels of lead and copper than Great Smoky Mountains National Park. Moss appeared to be a good collector for lead and copper. Results indicate that reference levels for trace elements can be established for remote areas, although they cannot be considered true background levels. Introduction
Biosphere reserves are remote, pristine areas
set aside in perpetuity. A pollutant monitoring
system is being developed for implementation on
the reserves (Wiersma and others 1978a; Wiersma
and others 1979). Purpose of monitoring pollutants on these areas are:
1. to serve as locales for background
reference levels of certain pollutants .
2. to provide a frame of reference against
which changes in impacted areas can be measured
3. to reflect changes of a global nature
before such changes are obvious in more impacted
areas.
-presented at the Symposium on Effects of Air
Pollutants on Mediterranean and Temperate Forest
Ecosystems, June 22-27, 1980, Riverside,
California, U.S.A.
2~coloqist,U. S. Environmental Protection Agency, Environmental Monitoring Systems
Laboratory, U.S. Environmental Protection Agency,
Las Vegas, Nevada; Botanist, U.S. Environmental
Protection Agency, Environmental Monitoring
Systems Laboratory, U.S. Environmental Protection
Agency, Las Vegas, Nevada.
The reserves are areas that can be used to mon- itor the behavior of pollutants that have long range transport characteristics such as trace elements (Zoller and others 1974; Duce and others 1975; Thrane 1978; Weiss and others 1971; Scheslinqer and others 1974; and Chow and Earl 1970). Since many trace elements have the potential for long-term transport the question becomes, in a monitoring program for background areas, what elements should be of prime interest. Two
parameters can be used to estimate potential for long-term transport. First, elements that have a high vapor pressure, and second, elements that would have a significant small particle (1.0 p or
less) association. There is evidence that these two phenomena may work in conjunction. Ondov and others (1977a) analyzed the relationships existing between particle size and elemental composition in power plant emissions. They stated that elements with low vapor pressures tended to be associated with larger particle sizes. In a subsequent paper Ondov and others (1977b) listed several elements as having significant small particle association including manganese, lead and copper. Kyser and others (1978), using a variety of microprobe analytical techniques, found that arsenic, cadmium, cobalt, chromium, manganese, nickel, lead, sulphur antimony, selenium, thallium, vanadium and zinc were present on particles primarily as surface material. This lends further support to the hypothesis that elements with high vapor pressure tend to condense on smaller particles. Methods Analytical This paper will present data for trace element levels in vegetation and forest litter. The ana- lytical procedure used was spark source emission spectroscopy (SSES) which determines 26 elements per sample. The analytical procedure has been previously described by Alexander and others ( 1975).
Every tenth sample submitted was a quality assurance sample, alternating between known value samples and replicated samples. Samples were sub- mitted in a set order. The analytical laboratory was required to analyze the samples in the order submitted. 1 Air
T Water
0 Vegetation-Soil
Figure 2-Sampling locations in the Olympic National Park Biosphere Reserve. Field Sampling Two biosphere reserves, the Great Smoky Mountains and Olympic National Park, have been sampled as part of a pilot research project to develop a cost effective pollutant monitoring system. Great Smoky Mountains National Park was originally sampled in the fall of 1977 and again in 1978. The results of this effort have been reported by Wiersma and others (1979). Olympic National Park was sampled in the summer of 1979. Figures 1 and 2 show sample site locations for the Great Smoky and Olympic National Parks respectively. Details of the Olympic study design are presented by Brown and Wiersma (1979). Results and Discussion Trace Element Selection The 26 trace elements analyzed by SSES are given in table 1. Table l~elementsand detection limits for spark source emission spectroscopy. Element
PPm
Element
PPm P Na K ca M9 Zn cu Fe Mn B A1 Si Ti *Â
Sampled Autumn, 1977
Sampled Spring, 1978
Figure 1--Sampling locations in the Great Sknoky Mountains Biosphere Reserve. Using this listing and selection criteria previously described, we are limiting our presentation in this paper to copper, lead and manganese. Also included are two biologically essential elements, calcium and phosphorus and one non-essential element, aluminum, which also is not one of the elements which has the potential for long-term transport. Quality assurance results are shown in table 2. Good agreement exists between the analytical results and certified levels. In addition, the replicated samples, which were analyzed sequen- tially, showed no drift and had acceptable reproducibility. Table 2--Quality assurance results for elements from Great Smoky Mountains. malytical results for QA samples Phosphorus
1,950
2,000 to
2,200
Not significant
44
Not significant
Lead
44.7
Copper
12.0
11.0 to
13.0
Not significant
Manganese
92.4
87 to 95
Not significant
Calcium
2.1
2.1 3
Not significant
~luminum~
-
-
Not significant
'AS determined by 95 pet. correlation coeffi- cient of replicated samples and site numbers analyzed in order with site number 2 ~ standard
o 3pct. by weight Table 3 shows elemental levels for seven species of vegetation collected in the Great Smoky Mountains in the spring of 1978. Lead levels are highest in moss samples. Copper levels tend to be higher in wood fern and witch hobble, while manganese appears to be higher than previously re- ported for agricultural crops (Hemphill 1972). However, Romney and others (1977) report manganese levels for desert vegetation ranging from approxi- mately 20 ppm to 220 ppm. Van Hook and others (undated) report manganese values in chestnut oak and hickory on the walker Branch water shed ranging up to 1,000 ppm. Grodzinska (1978) reported manganese levels in moss from Poland ranged from 79 to 880 ppm. Therefore, the levels of manganese reported appears reasonable when compared to other studies, particularly from forested areas. Calcium and phosphorus levels appear to be equal to or slightly below calcium levels reported for agricultural crops (Hemphill 1972). Table 4 presents the results for the second sampling that occurred in the fall of 1978. There was a large increase in lead levels in moss samples, but the rest of the vegetation samples reflected a slight decline in lead levels. A
similar relationship was shown for copper. Studies using vegetation, particularly for those elements where root uptake is small, as indicators of airborne pollution have ranged from interception phenomenon of vegetative surfaces for modeling purposes (Shreffler, 1978; Davidson and others 1976) to the use of individual species as collectors of airborne pollutants. Smith (1977) has reviewed the probability of urban vegetation filtering out airborne particulates. He reported that fine hairs on vegetative surfaces increase particle trapping phenomenon. Carlson and others (1976) and Wedding and others (1975) found in controlled studies that rough, pubescent leaves entrap seven times more particles than smooth nonpubescent leaves and the particle load increases with leaf area sometimes by a factor of 10. Removal of particle from vegetation surface appears to be through solubilization in rain and not physical impaction from droplets (Carlson and others 1976). Compounding this phenomenon is data reported by Harris and others (1976) which states "...all elements are in a far more soluble phase in the ambient aerosol (and are associated with particles retained by biological and inert surfaces) than in fly ash collected from in stack deflector plates..
.".
From the above discussion, plants with large leaf surface areas, or those with very rough pubescent surfaces (ferns, witch hobble) should collect larger particulate loads, but because of wash off, they probably cannot be expected to increase the particle load throughout a growing season unless another phenomena were at work. This is shown in table 4 by a decrease for lead and copper concentrations for ferns and witch hobble when compared to the results in table 3. Manganese, however, does not follow this pattern. Tyler (1972) states that mosses, via passive ion exchange, can accumulate a variety of airborne elements. If this is the case then solubilization of surface material will not be an important removal process and fall moss samples should have higher levels than spring, particularly for copper and lead. Data in tables 3 and 4 tends to support this hypothesis. The forest floor of the Great Smoky Mountains was sampled in the spring of 1978. Two types of samples were collected, the first was the unin- corporated organic material and the second was the partially decomposed material of the fermenta- tion layer. The results are shown in table 5. Except for manganese, significant differences existed between the litter and fermentation layer for all trace elements. The fermentation layer showed an increase in lead, copper, phosphorus, aluminum, and a significant decrease in calcium. Site to site correlations for each element, excluding aluminum, were significant between unincorporated organic matter and the fermentation layer. Table 3--Average concentration of selected elements for samples collected in the Great Smoky Mountains biosphere reserve, spring 1978. ^9/9
Lead
Cop&= r
^9/9
Manganese
^9/9
Moss
42.3
13.4
368
Yellow birch
Betula allegheniensis 12.2
13.2
2,090
Calcium
pet.
Phosphorus
~919
Aluminum M9/9 0.32
1,430
1,410 1.38
2,540 165 Red maple Acer rubrum --
New York fern Thelypteris novaborecensis Wood fern Dryopteris spinulosa Witch hobble Viburnum alnifolium Fraser fir Abies fraseri Table &-Average concentration of selected elements for samples collected in the Great Smoky Mountains biosphere reserve, fall 1978. Lead
~ / l
CoPPr
~ / 9
Manganese
P3/9
Calcium
pet.
Phosphorus
Id9
Aluminum ~-9/<3 Moss
Yellow birch
10.5
2,370
1.50
2,360
154
6.6
1,070
1.14
1,920
66
1
9.9
3.9
1,000
0.68
854
2,040
5.3
11.5
1,350
0.50
2,200
424
I
13*3
9.2
2,800
1.50
1,700
426
0.2
3.8
915
0.30
2,680
375
Red maple
New York fern
Wood fern
Witch hobble
Fraser fir
1
Reiners and others (1975) found lead levels in
New Hampshire in litter increase with altitude.
At extreme elevations, a slight decrease was noted. The levels of lead in litter ranged from 35 to 336 ppm. The fir forest sites had the
highest lead concentrations. Figure 3 shows a
similar relationship from our data for lead in the
Smoky Mountains. This relationship did not.exist
for any of the other elements. Previous work by
Wiersma and others (1978b, 1980) indicate that the probable source of this lead is from anthropogenic activities. Some data are available from samples collected in the summer of 1979 in Olympic National Park. The forest floor was not sampled by the method previously used in the 1978 Smoky Mountains study. With the modified technique, unincorporated Table 5 ~ C o m p a r i s o nof elemental l e v e l s i n unincorporated organic m a t e r i a l and t h e fermentation l a y e r ,
Great Smoky Mountains biosphere r e s e r v e , s p r i n g 1978.
Unincorporated
organic m a t e r i a l
Fermentation
layer
Coefficient
correlation ( 8 df)2
Manganese yg/g
calcium p e t .
1
0.89
0.58
I
1,980
5,420
-5.22
0 .W4
Phosphorus p e t .
Aluminum M / g
Paired
'Element
'95 p e t .
'99 p e t .
Not Calculated
"T" t e s t
i n unincorporated organic m a t t e r v e r s u s element i n fermentation l a y e r .
confidence
conÂidence
Copper l e v e l s i n moss i n t h e G reat
averag e about 3 t i m e s g r e a t e r than
National Park.
Lead l e v e l s i n t h e
a r e 7 t o 19 times g r e a t e r than t h e
National Park.
Smoky Mountains
i n t h e Olympic
Smoky Mountains
Olympic
A similar relationship exists for the forest
f l o o r samples:
Comparison of f o r e s t f l o o r samples from
Olympic National Park and Great Smoky
Mountains National Park.
(yg/g)
01ympic
litter
30'00
35'00
40'00
4500
5000
55'00
6000
Elevation (Feet)
Figure 3--Relationship between l e a d r e s i d u e s and
a l t i t u d e i n t h e Great Smoky Mountains Biosphere
Reserve.
Smokys
unincorporated
organic m a t t e r
s p r i n g 1978
Smokys
fermentation
s p r i n g 1978
organic m a t e r i a l s were sampled along with t h e
fermentation l a y e r .
Copper and l e a d l e v e l s i n moss and l i t t e r a r e
compared f o r t h e two biosphere r e s e r v e s :
Comparison of moss samples from Olympic
National Park and Great Stooky Mountains
National Park.
(pg/g)
Copper
Moss-Olympic
Moss-Smoky Spring
Moss-Smoky F a l l
4.4
13.5
15.3
Lead
-
5.7
42.4
108.0
True "background" l e v e l s f o r many t r a c e
elements a r e probably impossible t o determine.
Lead l e v e l s f o r moss i n t h e Smoky Mountains appear
high b u t i n l i n e with v a l u e s r e p o r t e d i n t h e
literature.
For example Ruhling and Tyler (1968)
analyzed museum samples of moss.
They found
samples c o l l e c t e d a f t e r 1950 had l e a d concentrat i o n s of 80 t o 90 ppm.
Samples c o l l e c t e d around
1860 contained average l e a d l e v e l s of 20 ppm.
These r e s e a r c h e r s believed t h a t t h e 20 ppm l e v e l
did not represent "natural" lead levels.
They
suspected " n a t u r a l " l e a d l e v e l s might be
considerably lower.
The moss samples from Olympic
National Park averaged 5.7 ppm lead with some remote sites having average lead levels of 0.4 ppm and 2.2 ppm. Hirao and Patterson (1974) estimated for a remote site on the high sierra crest that 97 percent of the lead detected was from anthro- pogenic sources. Therefore, even for sites as remote as the high Dosewallips/High Quinault (over 13 miles from the nearest road) in a park that primarily receives wind off the Pacific Ocean, it may not be appropriate to consider the lead levels natural background levels. It is our opinion that reference levels can be established in vegetation in remote areas for a variety of trace elements. Sites should be regionally representative and sampling should be repetitive through time, at least once a year, preferably twice a year. Biosphere reserves are ideal places to use because of their protected nature and the fact that they are selected to be representative of various biological systems. Monitoring systems can and should be estab- lished in these reserves for the purposes listed. Literature Cited Alexander, G. V., D. R. Young, D. J. McDermott, M. J. Sherwood, A. J. Mearns, and 0. R. Lunt. 1975. Marine organisms in the Southern California bight as indicators of pollution. In International Conference on Heavy Metals in the Environment. [1975. Toronto, Canada], p. 955-972. Brown, K. W. and G. B. Wiersma. 1979. Pollutant monitoring in Olympic National Park biosphere reserve. In Proc. Second
Conference on Scientific Research in the National Parks. [Nov. 28-30, 1979, San Francisco, Calif.] 12 p. Carlson, R. W., F. A. Bazzaz and J. J. Stukel and J. B. Wedding. 1976. Physiological effects; wind reentrainment and rainwash of Pb aerosol particulate deposited on plant leaves. Environmental Science and Technology 10(12):1139-1142. Chow, T. J., and J. L. Earl. 1970. Lead aerosols in the atmosphere: increasing concentrations. Science l69:577-580. Davidson, C. I., S. V. Herring and S. IS.
Friedlander. 1976. The deposition of ~b-containing particles from the Los Angeles atmosphere. In Proc. International Conference on Environmental Sensing and Assessment. [Sept. 14-19, Las Vegas, Nevada] pp. 6-3 to 6-4. Duce, R. A., G. L. Hoffman, and W. H. Zoller. 1975. Atmospheric trace metals at remote northern and southern hemisphere sites Pollution or natural? Science 187:59-61. Grodzinska, Krystyna. 1978. Mosses as bioindicators of heavy metal pollution in Polish national parks. Water, Air and Soil Pollution 9:83-97. Harris, W. F., B. S. Ausmus, G. J. Dodson, Sidney Draggan, G. K. Eddlemon, Cyrus Feldman, J. M.
Giddings, J. W. Huckabee, D. R. Jackson, S. A. Janzen, M. J. Levin, S. E. Lindberg, L. K. Mann, E. G. OINeill, R. V. OINeill, Cheryl B. Phillips, B. M. Ross, W. J. Selvidge, D. S. Shriner, R. R. Turner, P. Van Voris, Martin Witkamp. 1976. Environmental behavior of trace contaminants. The role of vegetation aerosol scavenging. ORNL-5257. Environmental Sciences Div. Annual Progress Report. Oak Ridge National Laboratory, Oak Ridge, Tennessee. Hemphill, D. D. 1972. Availability of trace elments to plants with respect to soil-plant interaction. Annals New York Academy of Sciences 199:46-61. Hirao, Y., and C. C. Patterson. 1974. Lead aerosol pollution in the high sierra over-rides natural mechanisms which exclude lead from a food chain. Science 184:989-992. Keyser, T. R., D. F. S. Natusch, C. A. Evans, Jr.
and R. W. Linton. 1978. Characterizing the surfaces of environmental particles. Environmental Science and Technology 12(7):768-773. Ondov, J. M., R. C. Ragaini, R. E. Hett, G. L. Fisher, D. Silberman and B. A. Prentice. 1977a. Interlaboratory comparison of neutron activation and atomic absorption analyses of size-classified stack fly ash. Preprint UCRL-78194. Lawrence Livermore Laboratory, Livermore, Calif. Ondov, J. M., R. C. Ragaini, A. H. Bierman, C. E. Choquette, G. E. Gordon and W. H. Zoller. 1977b. Elemental emissions from a western coal fired power plant: preliminary report on concurrent plume and in-stack sampling. Preprint UCKL-78825. Lawrence Livennore Laboratory, Livermore, Calif. 7 p. Reiners, W. A., R. H., Marks and P. M. Vitousec. 1975. Heavy metals in subalpine and alpine soils of New Hampshire. OIKOS 26(3):264-274. Romney, E. M., A. Wallace and G. V.
1977. Boron in relationship to a
power plant. Communications in
and Plant Analysis 8(9):803-807.
Alexander. coal-burning Soil Science Ruhling, Ake and Germund Tyler. 1968. An ecological approach to the lead problem. Bot. Notiser 121:338-341. Schlesinger, W. H., W. ,A. Reiners and D. S.
Knupman
1974. Heavy metal concentrations and deposition in bulk precipitation in montane ecosystems of New Hampshire, U.S.A. Environmental Pollution 6:39-47. .
Shreffler, J. H. 1978. Factors affecting dry deposition of so2 on forests and grasslands. Atmospheric Environment 12:149-153. Smith, W. H. 1977. Removal of atmospheric particulates by urban vegetation. Implications for human and vegetative health. The Yale J. of Biology and Medicine 50: 185-197. Thrane, K. E. 1978. Background levels in air of lead, cadmium, mercury and some chlorinated hydrocarbons measured in south Norway. Atmospheric Environment 12:1155-1161. Tyler, G. 1972. Heavy metals pollute nature, may reduce productivity. AMBIO 1(2):52-59 Van Hook, R. I., W. F. Harris, G. S. Henderson and D. E. Reichle. Undated. Patterns of trace element distribution in a forested watershed. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee. Wedding, J. B., R. W. Carlson, J. J. Stukel and F. A. Bazazz. 1975. Aerosol deposition on plant leaves. Enviornmental Science and Technology 9(2) :151-153. Weiss, H. V., M. K. Koide, and E. D. Goldberg. 1971. Mercury in the greenland icesheet: evidence of recent input by man. Science 74:692-694. Wiersma, G. B., C. W. Frank, K. W. Brown and C. I. Davidson
1980. Lead particles in the Great Smoky ~ountainsBiosphere Reserve. EPA-600/ 4-80-002. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Las Vegas, Nevada. .
Wiersma, G. B. 1979. Kinetic and exposure commitment analyses of lead behavior in a biosphere reserve. MARC Report 15. 41 p. Monitoring and Assessment Research Center, Chelsea College, Univ. of London, London, U.K. Wiersma, G. B., and K. W. Brown. 1979. Recommended pollutant monitoring system for biosphere reserves. In Proc. Second Conf. on Scientific Research inthe National Parks. [Nov. 26-30, 1979, San Francisco, Calif.] 19 p. Wiersma, G. B., K. W. Brown, R. Hermann, C. Taylor and J. Pope. 1979. Great Smoky Mountain preliminary study for biosphere reserve pollutant monitoring. EPA-600/4-79-072. Environmental Monitoring Systems Laboratory, U. S. Environmental Protection Agency, Las Vegas, Nevada. Wiersma, G. Bruce, Kenneth W. Brown and Alan B. Crockett
1978a. Development of a pollutant monitoring system for biosphere reserves. EPA-600/ 4-78-052. Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency, Las Vegas, Nevada. 114 p. .
Wiersma, G. B., K. W. Brown and A. B. Crockett. 1978b, Development of a pollutant monitoring system for biosphere reserves and results of the Great Smoky Mountains pilot study. In Proc. 4th Joint Conference on Sensing of- Environmental Pollutants [1978, New Orleans, Louisiana], p. 451-456. Zoller, W. H., E. S. Gladney and R. A. Duce. 1974. Atmospheric concentration and sources of trace metals at south pole. Science 183:198-200.