United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas NV 89114
Research and Development
EPA-600/S4-84-060 Aug. 1984
8€PA Project Summary
Visibility Investigative Experiment
in the West (VIEW)
Robert N. Snelling, Marc Pitchford, and Ann Pitchford
In response to the growing concern
over impairment of visibility in parklands
of the West and requirements of the
Clean Air Act of 1977, the U. S. Envi-
ronmental Protection Agency's (EPA's)
Environmental Monitoring Systems
Laboratory. Las Vegas, in cooperation
with the National Park Service (NPS),
established the VIEW (Visibility Investi-
gative Experiment in the West) program.
Regional scale monitoring networks
were established to measure visibility
and airborne particle composition and
concentrations. Statistical and case
study analyses are being applied to
these data. This summary presents a
brief discussion of preliminary results
from these analyses. Highlights include
a significant decline in summer visibili-
ties in the south-west, well-defined
seasonal cycles, a determination of the
relative contribution of fine and coarse
particulates and of the relative contri-
bution of fine sulfur to visibility impair-
ment, and the significant contribution
of copper smelter emissions to south-
west regional visibility impairment.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
project that is fully documented in two
separate reports (see Project Report
ordering information at back).
Introduction
During the past decade, there has been
growing concern over the impairment of
visibility in the western national parks
due to man-made pollutants. The West
enjoys extremely good visibility compared
to other regions of the country, with an
annual median standard visual range
exceeding 140 kilometers (km) over a
large geographical area (Figure 1).
Because of its relatively clear air, this
region is also particularly sensitive to
future visibility impairment. Concern has
been heightened by anticipated energy
resource development that may signifi-
cantly increase airborne pollution con-
centrations in the region.
Congress, in the Clean Air Act of 1977,
established as a national goal "the
prevention of any future, and the remedy-
ing of any existing, impairment of
visibility in mandatory class I federal
areas which impairment results from
man-made air pollution." Mandatory
class I areas include International Parks,
National Wilderness Areas and National •
Memorial Parks exceeding 5000 acres,
and National Parks exceeding 6000
acres. Subsequent regulations (40 CFR
Part 51) defined visibility impairment as
"any humanly perceptible change in
visibility (visual range, contrast, colora-
tion) from that which would have existed
under natural conditions." Under these
regulations, certain states are required to
develop and implement programs to
address the congressionally declared
goal. Visibility monitoring is required for:
1. Identification of visibility impact
from existing sources.
2. Visibility assessment for new source
review.
3. Demonstration of progress towards
achieving the national goal.
In response to the congressional man-
date, in 1977 the EPA's Environmental
Monitoring Systems Laboratory in Las
Vegas inititated a cooperative research
program with the National Park Service
(NPS) known as the Visibility Investigative
Experiment in the West (VIEW). The
program has had the following monitoring
objectives.
1. Development and evaluation of
improved visibility monitoring ap-
-------
XXX Median Standard Visual Range (Km)
f/VJ Station Number
\Nu Selected for Intensive Analysis
Figure 1. Regional visibility monitoring network, showing median standard visual range.1
N
preaches.
2. Characterization of the temporal and
spatial dynamics of visibility impair-
ment in the West.
3. Identification of major sources of
visibility impairment in the West.
A regional scale monitoring program was
established which included visibility and
atmospheric paniculate monitoring.
These data are now yielding significant
insight into the sources and nature of
visibility impairment in the West.
Procedure
The study of visibility and its relation-
ship to meteorology and atmospheric
aerosol content is a complex and, in many
cases, a semi-quantitative science.
Traditionally, visibility has been defined
in terms of visual range: the maximum
distance from an object at which the
contrast between that object and some
appropriate background is perceptible,
i.e., above threshold contrast. Threshold
contrast refers to the smallest difference
between two stimuli that the human eye
can distinguish. The measurement of
these quantities depends on the nature
of the observer, his or her physical health,
and his or her mental attitudes of
attention or distraction due to effects
such as boredom and fatigue.
Although visibility defined in terms of
visual range of a distant target is a
meaningful definition, visibility also
includes being able to appreciate the
details of line, texture, color, and form of
vistas at shorter distances. Therefore, it is
not reasonable or even possible to define
visibility in terms of any one physical
variable. It is necessary to measure a set
of variables that: 1) relate directly to
what the eye-brain system perceives, 2)
can be monitored directly, and 3) can be
related to the atmospheric constituents
controlling visibility.
Improving Visibility Monitoring
Methods
Evaluation of methods to characterize
visibility was one of the earliest tasks of
the VIEW program. Initially, an extensive
review was made of instruments that can
measure optical parameters in the
atmosphere. This review led to establish-
ment of research stations employing
several types of visibility monitoring
devices. The basic measurement tech-
niques utilized included:
photography - documents perceived
visual air quality;
multiwavelength telephotometer -
measures apparent contrast between
target and horizon or other objects
and is useful over long path, up to 50
to 100 km;
transmissometer - measures trans-
mission and extinction of light over a
fixed path, 10 to 20 km;
nephelometer - measures light scatter-
ing by particles at a single point and
estimates extinction coefficient.
The use of these and other instruments in
the field served the dual purpose of
building a valuable visibility data base
while allowing the instruments and
procedures to be evaluated and improved.
Visibility Baseline
To characterize visibility throughout
the western United States, a regional
network of visibility monitoring stations
was established. The network was
operated by the Visibility Research Center
of the John Muir Institute with field
support from the NFS. The network
consisted of 23 stations, shown in Figure
1 and listed in Table 1. Three additional
stations were operated outside the VIEW
network (Olympic National Park, Wash-
ington, Shenandoah National Park,
Virginia, and Acadia National Park,
Maine). Visibility measurements were
made at each station using a teleradi-
ometer, measuring the light received
from a 'target' (i.e., a point on a distant
mountain) and from the adjacent sky at
four wavelengths: 405 nanometers (nm),
-------
Table 1. Regional Visibility Monitoring Network, Standard Visual Range (km): Seasonal Geometric Mean and Station Median'
Station
Number Location
1
2
3
4
5
6
7
9
10
11
12
13
14
15
16
17
18
19
21
22
24
28
30
Is/and in the Sky, UT
Grand Canyon, AZ
Canyonlands, Hans Flat, UT
Bryce Canyon, UT
Capital Reef, UT
Dinosaur, CO
Mesa Verde, CO
Wupatki, AZ
Navajo, AZ
Chaco Canyon, NM
Bandelier, NM
White Sands, NM
Carlsbad, NM
Big Bend, TX
Theodore Roosevelt, ND
Wind Cave. SD
Colo. Nat'l Mon.. CO
Rocky Mt. N.P.. CO
Chiricahua, AZ
Grand Tetons, WY
Capulin, NM
Death Valley, CA
Yellowstone, WY
1978
S F
172
178
190
192
207
166
192
187
172
118
157
148
200
208
208
215
ND
185
122
191
203
155
125
179
130
W
251
248
259
ND
205
ND
188
ND
ND
226
190
245
212
1979
S S
169
159
136
144
171
168
153
201
160
188
284
143
151
163
120
123
189
178
166
170
175
177
182
159
164
198
148
114
139
154
113
145
F
190
194
176
195
189
192
184
162
175
198
149
115
142
146
154
179
W
194
276
206
289
216
ND
189
215
264
298
186
159
206
174
230
ND
250
1980
S S
182
130
151
129
164
102
139
141
145
176
174
132
197
168
100
111
137
171
190
159
158
138
164
151
176
158
168
180
164
119
128
131
163
177
157
152
139
145
F
206
219
180
223
206
203
201
180
230
213
176
139
146
195
194
204
239
172
207
235
W
241
264
174
280
159
209
235
165
256
257
221
177
208
211
209
235
278
273
294
1981
S S
192
180
192
204
166
190
170
192
177
187
141
183
130
185
190
221
180
204
165
138
159
160
145
153
140
152
163
147
112
139
115
159
171
193
145
147
160
142
177
F
205
203
206
207
ND
172
176
218
208
176
133
143
135
128
183
199
244
151
201
220
161
Median
173
162
163
174
165
160
158
147
162
175
149
117
144
126
122
137
173
134
138
137
155
145
141
ND = No Valid Data.
F = Fall, W = Winter, S = Spring or Summer.
Blanks signify no data available.
Seasonal geometric mean calculated from edited data.
Median derived from cumulative frequency graph.
(violet), 450 nm (blue), 550 nm (green),
and 630 nm (red). The wavelengths were
chosen to cover the visible spectrum and
avoid the strong reflection beyond 650
nm from vegetation. Up to six targets were
sighted, in a variety of directions, at each
observation station. Where possible, the
targets were selected at distances
between 10 and 75 percent of the
estimated mean visual range. Within
these distances apparent contrast (per-
ceived contrast of an object against its
background) is particularly sensitive to
changes in air quality. Measurements
were made three times a day (9:00 am,
noon, and 3:00 pm local time). Measure-
ments are expressed as standard visual
range. Standard visual range is visual
range normalized to a reference Rayleigh
scattering coefficient of 0.01 km"1.
Rayleigh scattering is that caused by air
molecules in an unpolluted atmosphere.
At a Rayleigh scattering coefficient of 0.01
km"1, the visual range is 391 km. In
addition toteleradiometer measurements,
color photographs were taken.
Figure 1 depicts median standard
visual range for stations with a minimum
of one full year of data. Table 1 summarizes
available data for the study period and
indicates seasonal geometric mean
visual range. Data for individual stations
are available in a variety of formats.
Examples of data for Grand Canyon
National Park are shown in Figures 2 and
3.
Particulates
In addition to visibility monitoring, a
networkfor airborne particulatesampling
400-
300-
sual Range (km)
NJ
o
o
1
is
"S
1
S
700-
0-
I— I — Geometric Mean
H 90% Confidence Interval
Z
2
i
I
i
_i
J JA SOND
1978
!
I
g
a
%
z
Z
Z
Z
,
'
I
JFMAMJJASONC
^P
1
^
%
i
\
%
2
rr
R
4
I
I
^
J F M AMJ J ASOND
1979
Month
2
I
3
rn aa
*±
S
S
__
2
J FMAMJJASON
1980 1981
Figure 2. Grand Canyon National Park, monthly standard visual range, geometric mean (km).^
3
-------
600-
500'
400-
300-
200-
700-
80-
1
to 60-
40'
30-
20'
Percent SVR (Km)
10 88
50 162
90 299
10 50
Cumulative Frequency (%)
I
90
99
Figure 3.
Grand Canyon National Park, cumulative frequency of standard visual range (km),
July 1978 through November 1981.^
was also established. The network is
shown in Figure 4. Station names and
data are listed in Table 2. The network
was operated by the Air Quality Group of
the University of California at Davis, with
field support from the NPS and other
agencies. Although the paniculate
network covered a larger area than the
visibility network, paniculate samplers
were colocated with visibility stations
where possible.
Particulates were samples with a
stacked filter sampler which separates
particles into two size ranges: less than
2.5 pm diameter and 2.5 to ] 5 fjm. The
samplers were operated for 72 hours,
twice per week. This sampling scheme
yielded data representing six of every
seven days. All samples were analyzed
gravimetrically and by particle-induced x-
ray emission (PIXE) for elements heavier
than sodium. The trace elements analysis
allows the association of visibility
impairment with types of sources through
case studies and statistical analyses.
Sampling began at some sites in
August 1979 and the network was fully
operational by October 1979. Sampling
ended on October 1, 1981. Eighty-eight
percent data recovery was obtained over
the network for the study period. Table 2
summarizes the average coarse and fine
mass and fine sulfur for the study period.
Figure 4 depicts the average fine sulfur
concentration over the network for the
entire sampling period.
Quality Assurance
A rigorous quality assurance program
was instituted to assess the performance
of visibility and paniculate measurement
techniques. The program consisted of
both systems audits and performance
audits. Annual systems audits were
intended to ensure the application of
documented operating and maintenance
procedures and to evaluate the reliability
of the data handling and reporting
system. Semi-annual performance audits
served to evaluate the accuracy and
precision of monitoring instruments and
laboratory analyses.
Results
These data were analyzed to identify
the major causes of visibility impairment
and to establish the relationships between
visibility impairment and particulates. At
the same time the monitoring techniques
themselves were evaluated. Both statis-
tical and case study approaches have
been applied.
Monitoring Methods
It has become clear that several types
of instruments are needed to determine
visibility impairment and to relate such
impairment to sources.4 Optical instru-
ments are essential for the characteriza-
tion of visibility impairment. Instruments
to measure particulate composition and
concentration are critical in source
identification. A measurement of appa-
rent vista contrast, which relates well to
human perception of visual air quality,
can be converted into ground level
extinction coefficient (a measure of the
light attenuation characteristic of a
parcel of air) or fine particulate concen-
tration only with restrictive assumptions
concerning uniform concentrations along
horizontal sight paths. Conversely, a
measurement of ground level fine partic-
ulate concentration or extinction coeffi-
cient will not allow an accurate computa-
tion of visual air quality in terms of target
contrast. However, when site intercom-
parisons are required (such as for
establishing regional trends) it is useful to
use visual range as a normalizing
variable. Also, because of its historical
popularity, it remains a useful concept to
indicate atmospheric 'clarity' to the lay
person.
Experience gained from the VIEW
program led to the publication of "Interim
Guidance for Visibility Monitoring."5The
recommended minimum visibility moni-
toring program is shown in Table 3.
Results from the quality assurance
program indicated a standard error for
teleradiometer measurements ranging
from 5.87% for high contrast targets to
24.2% for low contrast targets.6Standard
Error is defined as the deviation about
zero for the difference in measured
contrast between paired measurements.
Flow audits for particulate samplers
showed that 60% of the samplers had an
absolute percent difference between
sampler and audit flows of 15%, with 80%
of the flows being within 25%. Audits of
gravimetric analysis over the period of
study showed an average absolute
percent difference between measured
and audit weights of 0.08%. Filter trace
element analysis audits showed a preci-
sion of ±8.0% for PIXE analysis. Interlab-
atory agreement on split samples was
generally within ±20% for all elements.
Visibility Baseline
Nine stations (12 targets) were selected
from the network for more intensive
analysis. These stations are shown in
Figure 1 as shaded circles. Target
selection was based on the following
criteria:
1. Data available from the summer
1978 through September 1981.
2. Optimum target distance of between
45 and 75 km.
-------
Table 2. Western Fine Paniculate Monitoring Network3
Average Concentration
Station
Number
1
2
3
4
5
6
7
8
9
JO
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Location
Murphy Lake, MT
Malta Airport, MT
Medicine Lake NWR. MT
Upper Souris NWR, ND
Belt Creek Ranger Station, MT
Jordan Airport, MT
Theodore Roosevelt NMP, ND
Bald Hill Dam. ND
Big Hole Valley, MT
Bluewater Fish Hatchery, MT
Charlie Odelfs Ranch. MT
Lake Hiddenwood State Park, SO
Yellowstone NP, WY
Buffalo Airport, WY
Mount Rushmore MN, SD
Lake Andes NWR. SD
Lander Airport, WY
Fort Laramie NHS, WY
Fossil Butte NW. WY
Saratoga, WY
Fish Springs NWR. UT
Brown's Park NWR, CO
Rocky Mountain NP, CO
Cedar Mountain. UT
Delta County Airport, CO
La Junta, CO
Bryce Canyon NP, UT
Canyonlands NP, UT
Great Sand Dunes NM, CO
Grand Canyon NP, AZ
Chaco Canyon NM, NM
Fort Union NM. NM
Montezuma Castle NM. AZ
Petrified Forest NP. AZ
Grand Quivira, NM. NM
Organ Pipe Cactus NM, AZ
Tonto NM, AZ
Gila Cliff Dwelling NM. NM
Carlsbad Caverns NP, NM
Fort Bowie NHS. AZ
Coarse Mass
/jg/m3
4.3
8.9
8.2
13.0
3.3
19.3
8.7
13.1
3.0
5.9
10.8
8.9
2.4
8.7
4.8
13.7
8.9
8.7
5.5
5.0
6.1
4.5
3.5
4.9
10.2
7.7
4.1
4.5
5.7
3.4
4.9
4.2
8.2
3.8
5.8
9.4
6.8
4.2
7.4
7.4
Fine Mass
fjg/m3
4.7
3.2
3.9
4.5
2.3
4.5
4.1
4.1
2.0
2.7
2.8
3.7
1.6
2.9
2.7
5.1
3.9
3.7
3.4
2.5
2.4
2.6
2.5
2.8
3.7
4.0
2.7
2.6
2.4
2.2
2.5
2.7
4.0
2.9
2.9
4.6
4.4
3.5
3.3
4.3
Fine Sulfur
ug/m3
0.271
0.216
0.330
0.315
0.169
0.280
0.352
0.275
0.155
0.275
0.222
0.327
0.123
0.214
0.273
0.403
0.216
0.321
0.291
0.214
0.198
0.242
0.250
0.288
0.182
0.304
0.320
0.299
0.223
0.262
0.304
0.273
0.412
0.365
0.368
0.586
0.596
0.472
0.389
0.664
ALL
7.0
3.3
0.306
NWR - National Wildlife Refuge. NMP - National Memorial Park. NP - National Park, NM - National
Monument, NHS - National Historic Site.
3. Target inherent contrast at 550 nm
equal to or greater than 0.7 for all
times of day.
In order to satisfy the assumption of data
independence for statistical testing, the
data set was randomly sampled. A
temporal plot of seasonal arithmetic
mean visual range for a random sampling
of the nine stations shows several major
characteristics (Figure 5). The most
obvious is the seasonal cycle showing
lower visibility during the summer and
greater visibility during the winter
months. Figure 2 shows this cycle more
clearly for Grand Canyon. This same cycle
is seen with paniculate sulfate data
(Figure 6). Less obvious, but more impor-
tant, is the apparent decrease in summer
visibility over the four-year study period
(Figure 5). Analysis of variance (Student-
Newman-Keuls Stepwise Multiple Re-
gression) shows that the trend in summer
data is significant at the 95%'confidence
level. There is no significant trend
discernable for the other seasons within
the period of the study although signifi-
cant differences are noted between
seasons for different years. The fall of
1980, for example, shows significantly
greater visibility than 1979 or 1981. This
may indicate the impact of the copper
smelter strike of 1980 (discussed in a
later section).
It is important to note that although
the decreasing trend in summer visibility
is statistically significant, the cause for
the trend is not understood at this time.
Further investigation is required.
Paniculate
Analysis of paniculate data shows that
coarse particulate makes up, on the
average, 67% of the total mass sampled.3
The correlation coefficient between total
coarse mass and soil-derived mass is
0.90, indicating that the coarse fraction is
soil related.
Fine particulate (i.e., less than 2.5 //m)
constituted 33% of the total mass and
was dominated by sulfur and soil compo-
nents. Ammonium sulfate accounted for
38% of the fine mass while fine soil con-
tributed 23% (Figure 7). Estimated smoke
mass (from K/Fe ratios) was 9% with light
elements making up approximately 30%.
The light elements are those below the
atomic number of sodium. These are not
detected by PIXE analysis or accountedfor
as assumed oxides.
Eighty-eight percent of the sulfur
collected was on the fine stage. A
temporal plot of sulfate for selected
stations is shown in Figure 6. Although
significant spatial and temporal variabil-
ity are apparent, a coherent regional fine
sulfur pattern still emerges (Figure 4).
Visibility Particulate
Correlations
A regression analysis was performed
on visibility and particulate data from
seven selected stations for which both
visibility and particulate data were
available. This analysis indicates that the
coarse and fine particle data explain more
than 75% of the variations in the particle
extinction coefficient and that coarse
particle's may contribute from.30% to as
much as 80% of the particle extinction
coefficient.7 In general, it is found that
coarse particles are more dominant in
summer than in winter. Data from Grand
Canyon are shown in Figure 8. Principle
component analysis indicates that fine
sulfur also shows a significant correlation
with visibility.8
It should be noted that data from other
regions in the United States show signifi-
cantly different extinction budgets. Data
from Lake Tahoe were collected in a
separate study and indicated negligible
coarse particulate contribution to extinc-
tion.
Case Studies
The statistical analyses cited above
treat the data sets in their entirety and
may tend to obscure or ignore some of the
available information. For this reason an
objective case study approach to data
interpretations is also being undertaken.
Trajectory analysis using National
Weather Service upper air measure-
-------
Tables. Recommended Minimum Visibility Monitoring Program5
Instrument Parameter
Frequency
ELECTRO-OPTICAL MEASUREMENT
Manual or continuous multi-
wavelengths teleradiometer
Camera (color photography)
Integrating nephelometer
SUPPLEMENTAL MEASUREMENTS
Paniculate samples
Meteorological sensors
Target and sky radiance
Vista appearance
Scattering coefficient
Mass concentration of
particulates, elemental
constituents, in two
size ranges
Wind speed and direction,
humidity
Manual: three measure-
ments/day
Continuous:
daylight hourly
averages
Three photographs/
day
Continuous (hourly
average)
Two samples/week
Continuous (hourly
average)
ments and the Air Research Laboratory
Atmospheric Transport and Dispersion
(ATAD) model is being applied to episodal
periods. Figure 9, for example, shows
wind trajectories for the 11 worst
visibility days at Grand Canyon between
September 1978 and October 1979. The
time extent of the trajectory in hours is
shown at the origin of the trajectory path
along with the date of arrival at Grand
Canyon. The trajectories indicate trans-
port from southern California, Arizona,
New Mexico and western Texas, raising
the question of copper smelter emission
impact on regional visibility. Fine sulfur
and silicon concentrations for these
periods were in the top 10 percent and 20
percent of annual values measured,
respectively.9
Time series analysis is also being used
to evaluate the network data. Preliminary
analysis indicates that visibility and
paniculate concentrations sometimes
behave in unison over large regional
areas, whereas during other periods
unique site specific episodes are apparent.
Figure 6 shows a long-term temporal plot
of sulfate data for several selected
stations. Of particular interest is the
impact of the copper smelter strike from
July through September of 1980. Table 4
shows the maximum and average sulfate
levels for stations within 650 km of major
smelters for 1979, 1980, and 1981.10
During the strike, sulfate concentrations
at remote sites throughout Arizona,
western New Mexico, and southern Utah
were less than one-half of the maximum
levels of the non-strike summers of 1979
and 1981. Statistically significant changes
in the summer mean concentrations
were observed within 600 km. Using the
mean levels of 1980 to estimate the non-
smelter background, it appears the
smelters increased the mean sulfate
levels 2 to 3 g/m3at sites within 100km
and about 1 g/m3 at sites between 200 km
and 600 km. On the average, the smelters
may have been responsible for about 70%
of the sulfate at near sites and 50% of
the sulfate throughout the rest of the
region. An analysis of meteorological
parameters concluded that surface winds
were nearly identical for the summers of
1980 and 1981. For the two months in
1979 when samples were collected,
winds from the southeast were more
frequent than they were in 1980 and
1981. This may account for the higher
smelter contributions in 1979 compared
to 1981.
Conclusions
1. Visibility in the Four Corners re-
gion of the Southwest averages
above 140 km, with standard
visual ranges commonly approach-
ing the Rayleigh limit of 391 km.
2. Summer visibility in the Southwest
decreased from 1978 through
1981. No visibility trend is evident
for the other seasons.
3. Trajectory analysis for the Grand
Canyon area shows the worst
visibility conditions occurring with
winds from the south and south-
west, indicating possible particu-
late transport from southern Cali-
fornia, Arizona, New Mexico, and
western Texas.
4. Both visibility and particulate
concentrations show a well-defined
seasonal cycle. The coarse particles
are more prevalent in the sumrrfer
as compared to winter.
5. Fine particulate (<2.5 fjm) consti-
tuted approximately 33% of the
Table 4. Summer Sulfate Concentrations and Smelter Contributions (ug/m3)
Site
Ft. Bowie
Tonto
Gila Cliff Dwelling*
Montezuma Castle
Organ Pipe Cactus
Petrified Forest
Gran Quivira
Chaco Canyon
Grand Canyon
Bryce Canyon
Canyonlands
Ft. Union
Average uncertainty
Km to
major
smelter
80
100
110
200
220
250
350
400
400
600
650
550
Maximum Sulfate
Concentration
1979 1980 1981
5.8
5.8
-
6.0
4.4
5.2
4.8
3.7
3.8
6.1
5.0
1.6
2.4
1.3
2.2
2.1
2.4
2.1
2.2
1.5
2.3
2.2
1.8
1.5
5.9
5.7
5.9
4.5
4.2
4.5
4.2
1.9C
3.3
4.3
2.0
1.5
Mean Sulfate
Concentration
1979 1980 1981
3.3
3.9
.
2.8
2.5
2.2
2.2
2.2
2.1
.
-
-
0.3
1.3
0.6
1.1
1.1
1.1
1.0
1.0
0.7
0.6
0.9
0.7
1.0
0.1
3.4
2.5
2.4
1.9
2.1
1.5
1.5
1 .2C
1.1
1.5
1.0
1.0
0.2
Mean Smelter Contribution'
Concentration Percentage
1979 1981 both 1979 1981 both
2.1
3.3
1.7
1.3
1.2
1.2
1.5
1.4
.
-
-
0.3
2.1
2.0
1.3
0.8
1.0
0.5
0.5
0.5
0.4
0.6
0.3
0.0
0.2
2.1
2.5
1.1
1.1
0.8
0.8
1.1
0.8
0.9"
0.5"
-
0.2
62
86
61
54
54
57
68
70
_
-
-
13
62
78
55
42
46
31
35
41
42
41
30
1
14
62
82
51
49
43
59
45
57
52"
44
-
11
"Mean during 1979, 1981 or both 1979 and 1981 minus mean during 1980.
b/Vo samples July-September 1979.
cCollected less than 50% of possible samples in 1981.
"Mean for both summers include 3 samples in late September 1979.
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XXX Fine Sulfur tng/m3)
^"^
N I Station Number
Figure 4. Western Fine Paniculate Network, average fine sulfur concentration (ng/m3/3.
total mass (<15 um) for the desert
Southwest and northern Great
Plains.
6. Coarse paniculate was primarily
soil material.
7. Twenty-three percent of the fine
particulate was soil material.
8. Sulfate accounts for approximately
38% of the fine particulate mass
in the Western Fine Particulate
Network. Eighty-eight percent of
the particulate sulfate is found in
the fine fraction.
9. Coarse and fine particulate explain
more than 75% of the variation in
particle extinction coefficient.
Coarse particulate accounts for 30
to 80% of the particle extinction
coefficient for the southwest
desert.
10. Mean sulfate concentrations mea-
sured at locations throughout the
Southwest during July through
September of 1979 and 1981
ranged from 1.0 to 3.9 /yg/m3. A
detailed analysis of the impact of
the copper smelter strike during
July through September, 1980
indicates that the smelters may be
responsible for at least 50% of the
sulfate measured throughout the
Southwest during that period.
Recommendations
Although data from visibility and fine
particulate monitoring are yielding
significant insight into the nature and
causes of visibility impairment in the
West, further analysis is required to
better characterize the cause and effect
relationships.
Because'decreasing trends in summer
visibility in the Southwest are evident,
continued monitoring is required to
confirm and define the cause of the trend.
Additional monitoring is required to
identify the light element component of the
fine particulate mode in order to fully
define the total extinction budget.
Standardized methods are required for
measurements and data analysis of
visibility.
References
1. Western Regional Visibility Moni-
toring: Teleradiometer Monitoring
Network. EPA-600/4-84-058, U.S.
Environmental Protection Agency,
Environmental Monitoring Sys-
tems Laboratory, Las Vegas, 1982.
2. Malm, W.C. and Walther, E.G. A
Review of Instrument-Measuring
Visibility-Related Variables. EPA-
600/4-80-016, U.S. Environment-
al Monitoring Systems Laboratory,
Las Vegas, 1980.
3. Cahill, T.A., Flocchini, R.G., Eldred,
R.A. and Feeney, PJ. EPA-600/4-
84-059, Western Particulate Char-
acterization Study. U.S. Environ-
mental Protection Agency, Envi-
ronmental Monitoring Systems
Laboratory, Las Vegas, 1982.
4. Malm, W.C., Pitchford, M.L, and
Pitchford, A. Site Specific Factors
Influencing the Visual Range
Calculated from Teleradiometer
Measurements. Atmospheric En-
vironment, 1 6, (5), 1982.
5. Interim Guidance for Visibility
Monitoring. EPA-450/2-80-082,
U.S. Environmental Protection
Agency, Office of Air Quality
Planning and Standards, 1980.
6. McDade, C.E. VIEW/WFP Quality
Assurance. U.S. Environmental
Protection Agency, Environmental
Monitoring Systems Laboratory,
Las Vegas, 1982 (unpublished).
7. Pitchford, M.L. The Relationship of
Regional Visibility to Coarse and
-------
Fine Particle Concentration in the
Southwest. Journal of Air Pollution
Control Association, 32,(8), 1982.
8. Flocchini, R.G., Cahill, T.A., Pitch-
ford, M.L., et al. Characterization
of Particles in the Arid West.
Atmospheric Environment, 15(10/
11), 1981.
9. Pitchford, A., Pitchford, M.L.,
Malm, W., et al. Regional Analysis
of Factors Affecting Visual Air
Qualfty. Atmospheric Environment,
15, (10/11), 1981.
10. Eldred, R.A., Ashbaugh, L.L., Cahill,
T.A., and Flocchini, R.G. Sulfate
Levels in the Southwest During
the 1980 Copper Smelter Strike.
Journal of Air Pollution Control
Association, 33, (2), 1 983.
Summer Visibility Trend
Winter = Dec. -Feb.
Spring = Mar. -May
Summer = June-Aug.
Fall = Sept. -Nov.
= 55% Confidence Interval for Mean
S \ F
1978
I W I
S I S |
1979
F
\w |
S
I S | F
1980
\ W I
I
S
I s I
1981
F
\ W \
1
100
Season
Figure 5. Mean seasonal visibility (km) for selected stations.
-------
A \S\0\N\D \J\f\M\A\M\ J\ J
1979 | 1980
t DIJ \F\Mt A'M' J*J
1981
Figure 6. Time plot of fine sulfate at selected stations.3 Summer periods are bracketed by
dashed lines.
-------
Figure 7. Average composition of fine paniculate mass for the Western Fine Particle
Network.
100-\
90-
80-
70'
SO-
SO-
20-
10-
Aug. Sept. Oct. Nov. Dec.
1979
Jan. Feb. Mar. Apr. May June July Aug. Sept.
1980
10
Figure 8. Monthly percent contribution to particle extinction coefficient by coarse particles for
Grand Canyon National Park7
*USGPO: 1984-759-102-10655
-------
° Cities
O Length of Trajectory in Hours
igure 9. Wind trajectories back in time for days of low visual air quality at Grand Canyon
National Park.9
The EPA authors, Robert N. Snelling. Marc Pitchford (also the EPA Project
Officer, see below), and Ann Pitchford are with Environmental Monitoring
Systems Laboratory, U.S. Environmental Protection Agency, Las Vegas, NV
89114.
This Project Summary covers the following two reports:
"Western Regional Visibility Monitoring: Teleradiometer and Camera
Network" authored by staff of John Muir Institute for Environmental
Studies. Inc., 743 Wilson Street, Napa. CA 94558,"(Order No. PB 84-211
192; Cost: $13.00. subject to change).
"Western Paniculate Characterization Study" authored by T. A. Cahill, R.
G. Flocchini, R. A. Eldred, and P. J. Feeney who are with Crocker Nuclear
Laboratory, University of California, Davis, CA 95616 (Order No. PB 84-211
200; Cost: $13.00, subject to change).
The above reports will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89114.
11
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