&EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/2-80-078
August 1980
Air
Evaluation of Contribution
of Wind Blown Dust From
the Desert to Levels of
Particulate Matter in
Desert Communities
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EPA-450/2-80-078
Evaluation of Contribution of Wind Blown
Dust From the Desert to Levels of Participate
Matter in Desert Communities
by
Frank A. Record and Lisa A. Baci
GCA Corporation
Bedford, Massachusetts
Contract No. 68-02-2607
Task No. 41
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
August 1980
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This report is issued by the Environmental Protection Agency to report technical data of
interest to a limited number of readers. Copies are available - in limited quantities - from
the Library Services Office (MD-35), U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711; or, for a fee, from the National Technical Infor-
mation Service, 5285 Port Royal Road, Springfield, Virginia 22161.
Publication No. EPA-450/2-80-078
11
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ABSTRACT
This report uses existing data and studies to assess the impact of wind-
blown desert dust on the attainment of TSP standards in major cities situated
in desert environments in the Southwestern U.S. Primary emphasis is placed
on four cities: Phoenix and Tucson, Arizona; and Las Vegas and Reno, Nevada.
It is concluded that: (1) the contribution of wind-blown dust from the
undisturbed desert floor to particulate levels in desert communities is very
small and should be considered as part of the background; (2) if human activi-
ties repeatedly break up the desert crust, local violations of the 24-hour
standards are likely; (3) there is substantial agreement on the principal
source categories of fugitive dust contributing to the nonattainment problem
and the characteristics of urban areas most affected by each category.
It is recommended that additional field programs be carried out to define
the level and sources of the inhalable fraction of suspended particulates.
iii
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CONTENTS
Abstract
Figures v
Tables viii
1. Introduction and Summary 1
Major Findings 1
Conclusions and recommendations 7
2. Analytical Techniques 8
Introduction 8
Analysis of temporal or spatial patterns of suspended
particulates 8
Analysis of particulate emissions 9
Chemical, elemental, and morphological analysis 9
Meteorology and suspended particulates 10
Overview 11
3. Background Suspended Particulates 13
Background concentrations 13
Characteristics and sources 20
4. Urban Particulates Levels 32
Particulate levels in and around Las Vegas 32
Particulate levels in and around Reno 38
Particulate levels in and around Tucson 43
Particulate levels in and around Phoenix 52
5. Urban Particulates: Characteristics and Sources 60
Particle size distributions 60
Particulate sources 63
Other studies 80
References 92
Appendix
A. Background Station Information 95
iv
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FIGURES
Number Page
1 Approximate bounds of study area 2
2 1976 annual geometric mean TSP concentrations from National
Aerometric Data Bank 15
3 1976 geometric mean TSP concentrations observed by Four
Corners Ambient Air Monitoring Network operated by
Ute Research Laboratories 16
4 Frequency distribution of annual geometric mean TSP
concentrations at 45 rural and remote sites in
Southwestern U.S. 18
5 1976 second-highest 24-hour TSP concentrations from
National Aerometric Data Bank 21
6 1976 second-highest 24-hour TSP concentrations observed
at Four Corners Ambient Air Monitor Network operated
by Ute Research Laboratories 22
7 Frequency distributions of 24-hour TSP concentrations at
45 rural and remote sites in Southwestern U.S 23
8 Volume distributions observed in the Mojave Desert, California,
and Fort Collins, Colorado 25
9 Particle settling/suspension regimes 26
10 Volume distribution as a function of height 28
11 Percentage distribution of measured chemical species on
respirable particles in the atmosphere at the
Research Ranch 31
12 Crustal enrichment factors of species measured on
respirable particles in the atmosphere at the
Research Ranch 31
13 The Clark County APCD sampling network for TSP 33
14 Annual mean TSP concentrations versus distance from
urban core 35
v
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FIGURES (continued)
Number Page
15 Plots of 24-hour TSP concentrations at 12 sites ordered
by distance from city center (Las Vegas) ........... 37
16 The Washoe County DEP sampling network for TSP ......... 39
17 Spatial distribution of TSP concentrations and land
use in and around Reno .................... 41
18 TSP monitoring network in Tucson and vicinity ......... 44
19 Annual geometric mean TSP concentrations in
and around Tucson in 1977 .................. 47
20 Average TSP concentration versus distance from the
urban core .......................... 48
21 Hi-vol monitoring sites within the Phoenix area ........ 53
22 Expected annual geometric means in yg/m3 ............ 56
23 Expected maximal 24-hour concentrations in ug/m3 ........ 57
24 Effect of wind speed on ambient suspended particulate
levels ............................ 59
25 Average daily dust emissions from unpaved roads, 1975 ..... 68
26 Average daily street dust emissions entrained by motor
vehicles on paved streets, 1975 ............... 69
27 Average daily dust emissions from construction
activities, 1975 ....................... 70
28 Emissions of fugitive dust arising from wind erosion,
average daily emissions, 1975 ................ 71
29 Fugitive dust emissions arising from wind erosion of dis-
turbed soil surfaces, first quarter, daily average, 1975 . . 73
30 Particulate fugitive emissions arising from wind erosion of
undisturbed desert in Phoenix area, first quarter, daily
average, 1975 ........................ 74
31 Dendogram of feature clustering for desert urban
particulate matter ...................... 77
32 Dendogram of feature clustering for desert background
particulate matter ...................... 78
vi
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FIGURES (continued)
Number Page
33 Enrichment factors for species in desert background and
34
35
36
37
A-l
A-2
1975 Las Vegas particulate emission density, ton/mi2/yr . . .
Location of 25 TSP monitoring stations shown in the
Monitor locations for National Aerometric Data Bank data . .
Monitoring site locations
83
84
87
90
98
100
vii
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TABLES
Number Page
1 Primary Techniques Used by Studies Relied on in this
Report ............................ I2
2 TSP Concentrations at Selected Background Sites in
New Mexico, Arizona, and Nevada ............... 1?
3 TSP Concentrations at Selected Background Sites in
Arizona ........................... 19
4 Estimated Background TSP Concentrations for Selected
AQCR's in Colorado and Utah ................. 19
5 Site Location Descriptions for Las Vegas Monitors ....... 34
6 Number of Exceedences of the Secondary Standards and
Emission Densities at Selected Sites ............. 38
7 Site Location Descriptions for Reno Monitors .......... 40
8 TSP Concentrations in Reno and Vicinity on Days when
the Secondary Standard was Exceeded ............. 42
9 Site Location Descriptions for Tucson Monitors ......... 45
10 TSP Concentrations in Tucson and Vicinity on Days when
the Secondary Standard was Exceeded in 1977 ......... 49
11 Wind Conditions on Days with the Greatest Number of
Violations in Tucson ..................... 51
12 Site Location Descriptions for Phoenix Monitors ........ 54
13 Average TSP Concentrations for Six Site Environments ...... 58
14 Height Variation of Particulate Concentrations from
Andersen Sampler Data .................... 61
15 Particle Size Distribution for Suspended Particulates
Measured in Phoenix, September 27 and November 14, 1975 ... 61
16 Particle Size Information from Phoenix Sampling Program .... 62
viii
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TABLES (continued)
Number Pago
17 TSP Concentrations Measured by Hl-voln ;m
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SECTION 1
INTRODUCTION AND SUMMARY
Several large cities located in the southwestern United States have not
yet attained the primary and/or secondary national ambient air quality stan-
dards (NAAQS) for total suspended particulates. These cities are located in
desert environments; their major economic activities tend to be tourism, agri-
culture, or provision of services, rather than heavy manufacturing. As would
be expected, studies of several of these cities have shown that these areas
experience relatively little pollution from industrial point sources; however,
widespread fugitive dust problems do exist.
At present, there are differing opinions concerning the contributions of
fugitive dust from human activities and of wind-blown dust from the surrounding
desert to this nonattainment problem. To help resolve this issue, GCA was
asked to review existing data and studies and assess the impact of wind-blown
desert dust on particulate levels within such cities.
Figure 1 indicates the approximate study area considered. It includes
the semi-arid regions of the southwestern states and extends from the Sacra-
mento and San Joaquin valleys in California to central Texas and Oklahoma.
Although information was reviewed for nonattainment sites throughout the
region, studies of Phoenix and Tucson, Arizona, and Las Vegas and Reno, Nevada
contained the most useful information for the purposes of the required assess-
ment. For this reason, this report focuses on these four cities.
The report is organized into five sections. This section provides an
introduction, summarizes the major findings, and presents conclusions and
recommendations. Section 2 describes the principal analytical techniques used
in the studies reviewed. Section 3 summarizes annual and 24-hour concentration
data from remote and rural sites throughout the southwest. It also discusses
chemical and physical properties of background particulates. Section 4 exam-
ines the distribution of particulates in and around the four study cities and
compares the distributions with patterns of land usage and human activities.
Section 5 discusses characteristics and sources of urban particulates, focus-
ing on the contribution of wind-blown desert dust. It includes a summary of
particle size measurements that emphasize the inhalable size fraction.
MAJOR FINDINGS
The authors of this report have reviewed numerous published documents
and some recent air quality data in an attempt to define the contribution of
wind-blown desert dust, and its inhalable fraction, to the TSP nonattainment
problem in large cities set in desert surroundings. From this review, a
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Figure 1. Approximate bounds of study area.
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concensus emerges that the part played by dust blown in from the undisturbed
desert is very small, and can safely be ignored when developing control strat-
egies. With the principal exception of contributions during widespread dust
storms - one of the occasional natural phenomena the effects of which may be
disregarded in control strategy development - its impact is contained within
the low background levels of approximately 25-30 yg/m3 found throughout the
Southwest. When major duststorms do occur, they are fed principally by emis-
sions from disturbed surfaces. These emissions increase rapidly near urban
areas as a result of increasing construction, agriculture, and similar activ-
ities. Severe duststorms occur perhaps once or twice a year in the study
area during periods of sustained high winds; their frequency can be much
higher in the agricultural regions of the Great Plains, particularly during
drought conditions.
In this summary discussion, the major findings of the reviewed reports
have been organized around the four principal analytical techniques described
in Section 2. Although the findings are sometimes taken directly from the
reports, they more often represent a condensation and integration of ideas
by the GCA reviewers. The description of TSP and land use relationships is
based on an analysis carried out by GCA for this report. Emphasis is placed
on the interpretation of the air quality data; information provided by the
remaining techniques is considered supportive, but not conclusive. Through-
out the summary, reference is made to more complete discussions of the various
findings provided within the body of the report.
The particle size data that were available were too limited and incon-
clusive to be of much help in defining the inhalable particulate levels
either in the desert or within the urban areas.
TSP and Land Use Relationships
The analysis of TSP concentrations in and around Phoenix, Tucson, Las
Vegas and Reno presented in Section 4 shows a close relationship between the
spatial distribution of concentration and land use and its associated human
activities. Generalizing, annual geometric mean concentrations increase
steadily as one progresses from remote and rural regions to the urban core.
The increase in concentration roughly parallels an increase in the emission
density of fugutive dust. In leaving the remote area one first encounters
areas with increasing amounts of dust generated by traffic on unpaved roads
and by agricultural activities. Pockets of urbanization, both residential
and commercial, are reached next with an accompanying increase in vehicular
traffic; construction activities become significant sources. In drawing
closer to the urban core, the density of residential and commercial property
continues to increase, and with it vehicular associated emissions, including
direct tail pipe emissions and entrained street dust.
The overall effect of changing land use patterns and increasing emission
density on concentration is shown by the following average values derived
from the concentration fields around the four cities:
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Site Characteristics Average Concentration
Remote or rural 30 pg/m3
Suburban/residential, commercial 81 yg/m3
Center city/commercial 124 yg/m3
Considerable variation in concentration does occur within areas having the
same general land use classification, however, as a result of differences in
the intensity of the associated human activities plus differences in small-
scale site characteristics. For example, a direct relationship exists between
the average center city concentration found within each of the four cities and
the city's population, as shown below:
Reno Las Vegas* Tucson Phoenix
Population 82,500 201,300 301,200 684,500
Mean concentration, ug/m3 77 100 133 184
This relationship is further evidence that the particulate emissions leading
to nonattainment within the cities are generated by urban activity.
The overall behavior of 24-hour concentrations in and around the urban
areas agrees closely with that of the annual averages; that is, violations of
the secondary standard rarely occur in the outlying areas surrounding the
cities, but do occur with increasing frequency as the proportion of disturbed
soil surfaces and the amount of vehicular traffic increases. Although details
differ from city to city due to differences in the physical setting of the
cities and in the distribution of urban activities, the occurrence of high
concentrations typically fall into two patterns. One pattern is associated
with light winds and low mixing heights which severely limit the dispersion
of particulates. Under these conditions, wind-generated emissions are absent
and high concentrations develop within the central city and the immediately
adjacent area where human activity peaks. Under prolonged stagnating condi-
tions, high concentrations become more widespread.
The second pattern is associated with strong winds during which wind-
generated fugitive dust plays a significant and sometimes dominant role.
Such periods are of relatively short duration (hours rather than days). Maxi-
mum concentrations on strong wind days are generally found in areas with the
greatest amount of exposed, disturbed surface. In the case of Phoenix, the
largest urban area studied, the observed maximal 24-hour concentrations (1973-
1975) at sites classified as rural/residential and surrounded by fugitive
sources were approximately twice the maximal values observed within the cen-
tral city.
One additional feature of the air quality data is of major significance.
Site by site comparisons of annual and 24-hour concentrations observed either
within or near the urban core of the larger cities disclose large differences.
Including North Las Vegas.
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Some of the differences among proximate sites are attributable to differences
in monitor height; others are judged to be a reflection of the distribution
of local fugitive dust sources. For example, the 1977 annual geometric means
at four Tucson sites located within a few miles of one another were 122, 158,
68 and 119 ug/m3; the heights of the monitors were 25, 15, 80 and 18 feet,
respectively. The large concentration gradient shown in the vertical is in-
dicative of ground-level sources of large particulates with relatively short
horizontal travel distances. The difference of 39 yg/m3 between two sites
whose heights differ by only 3 feet is most easily attributed to differences
among local sources. These differences are also reflected in the 24-hour
measurements at the two sites. Out of 57 sampling days In 1977, the number
of exceedances of the secondary standards at the site with a mean concentra-
tion of 119 yg/m3 was 12, while 35 exceedances were observed at the site with
a mean of 158 yg/m3.
Details of these analyses are given in Section 4,
Emission Inventories and Modeling
Emission inventories for particulates have been carried out throughout
the Southwest. These inventories vary in detail from county- or AQCR-wide
estimates to microinventories around specific nonattainment sites. The inven-
tories have been used in dispersion models of different degrees of complexity
in some of the urban areas to calculate the impact of specific categories of
emissions on TSP levels. All of these studies are consistent in stressing
the dominant role played by fugitive dust emissions from unpaved roads, reen-
trained street dust, construction activity and wind erosion from agricultural
fields and other disturbed surfaces. Although total emissions from the undis-
turbed desert are estimated to be substantial, they are distributed over large
areas outside of the urban centers and therefore have little impact on the
urban monitors. Conclusions from several of these studies follow.
An emission inventory and modeling study covering the Phoenix area was
carried out by TRW. TRW concluded that nearly all of the TSP above background
was caused by emissions from unpaved roads, entrained street dust, construc-
tion activities, and wind erosion from agricultural fields, unpaved roads,
undisturbed desert, tailings piles, vacant lots and the like at 12 of the 13
sites studied. Off-road vehicles were considered to be primarily responsible
for violations at the 13th site. The sites most affected by wind erosion were
in rural areas under development. The impacts of the various classes of wind-
erosion sources were not disaggregated in the model results as presented.
Emissions from disturbed soil surfaces were highly concentrated in the urban
portion of the region. In a separate study which developed an emissions in-
ventory for Maricopa County, PEDCo found that wind erosion from agricultural
land was the biggest single contributor to county-wide emissions, followed by
unpaved roads. From another modeling study for the Phoenix area, carried out
by the University of Texas, it was concluded that the high concentrations of
particulates experienced during late fall and winter periods of atmospheric
stability are associated with local fugitive dust sources. Advective trans-
port of dust from the countryside to the urban areas was judged to be
unimportant. Details of these three studies can be found in Section 5, pages
65, 75, and 64, respectively.
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In a study of the Las Vegas and Reno areas, PEDCo developed gridded emis
sion inventories. These inventories showed that emissions in both cities are
concentrated in the more urbanized portions of the study areas. PEDCo con-
cluded that approximately 80 percent of the total emissions in both cities
comes from fugitive dust sources. Unpaved roads were estimated to be the
largest contributor, followed by natural surfaces and paved roads. This study
is discussed more fully in Section 5, p. 80.
PEDCo also studied 35 nonattainment sites in Colorado and Utah, none of
which were in rural locations (see Section 5, p. 85). PEDCo concluded that the
principal sources of particulates in large and moderate sized urban centers
are traffic related. These include reentrained street dust, winter road
sanding, and motor vehicle exhaust. In medium and small urban centers, how-
ever, the major sources were found to be point sources, unpaved roads, con-
struction, and wind-blown dust from agricultural fields and other open areas.
One other related study was reviewed. In this study, Engineering-Science
investigators developed microinventories around five nonattainment sites in
Albuquerque and modeled each site (see Section 5, p. 85). They concluded
that from 42 to 61 percent of the particulates at these sites were from un-
paved roads or driveways, paved roads, fire and exhaust emissions, and un-
paved parking lots.
Chemical, Elemental, and Morphological Analysis
Chemical and elemental analyses coupled with correlation and enrichment
factor techniques showed that approximately 50 percent of the suspended par-
ticulate matter in the Tucson area was composed of soil. The values at 11
sites ranged from 48 to 83 percent, with the lowest estimate being obtained
at the background site. It was not clear that the percentage of soil material
was significantly greater in the urban area than at the background site, but
even if it were not, the much greater absolute TSP concentrations within the
city imply major contributions from urban soil sources. Unfortunately, the
analytical techniques cannot distinguish between wind-blown desert soil and
soil suspended as the result of human activities such as travel on unpaved
roads A description of this analysis begins on p. 72 of Section 5.
Microscopic analyses performed on particulate samples collected in
Phoenix led the participants in another field study (see Section 5, pp. 63-
64) to conclude that the particles were not typical of wind-eroded materials.
It was concluded from this study that vehicular traffic, especially on un-
paved roads, was the primary generator of TSP within the Phoenix area, and
that long-range transport of aerosols by winds from the surrounding deserts
was only a minor source.
The meteorological parameters that most often correlate significantly
with TSP levels are precipitation and wind speed, although the effect of wind
speed is confounded by two opposing phenomena- When emissions remain con-
stant, concentrations decrease with increasing wind speed due to increased
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dilution; on the other hand, once wind speed reaches a critical level, fur-
ther increases lead to an increasing amount of wind-generated dust. In one
of the reports reviewed (see Section 5, pp. 86-92) meteorological relation-
ships were used as the basis for estimating the contribution of wind-blown
dust (not disaggregated by source type) to TSP nonattainment in EPA Region
VI. The importance of wind-blown dust was judged by the degree to which
high TSP concentrations were associated with high winds and low precipitation.
Using the AID decision-tree program as the analytical tool, .it was decided
that wind-blown dust was the primary contributor to high TSP levels at one
of the seven sites (Lubbock, Texas). This technique leads to only very
qualitative evaluations.
CONCLUSIONS AND RECOMMENDATIONS
The review of past studies carried out in the Southwest has led us to
the following conclusions. First, the contribution of wind-blown dust from
the undisturbed desert floor to particulate levels in desert communities is
very small and should be considered as part of the low-concentration back-
ground when developing control strategies. Second, if human activities, such
as the use of off-road vehicles, repeatedly break up the desert crust, local
violations of the 24-hour standards are likely. Third, the contributions of
the various source categories of fugitive dust to the nonattainment problem
cannot be accurately disaggregated with the techniques employed in the re-
viewed reports. However, these techniques can be used to identify the major
contributing source types, and there is now substantial agreement not only on
the major source types but also on the characteristics of the urban localities
mos.t affected by each type.
Thus, there already appears to be sufficient information to serve as a
sound basis for the development of strategies leading to an overall improve-
ment in air quality. The spatial application of control measures can be fine
tuned to some extent on the basis of current observations and microinventories
around problem sites. Special monitoring programs can be used to define the
impact of individual sources if desired.
The one area where additional field programs are needed is in defining
the level and sources of the inhalable fraction of suspended particulates.
The collection of samples over short averaging times (e.g., 1 or 2 hours)
along a line through an urban area and oriented with the prevailing wind
would be invaluable in assessing the relative impacts of locally generated
and transported inhalable particulates. The use of instrumentation providing
respirable, inhalable, and total particulate data is recommended. This detail
would be helpful in evaluating conformance to possible future standards as
well as in assessing source impact.
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SECTION 2
ANALYTICAL TECHNIQUES
INTRODUCTION
This section introduces the analytical techniques used in particulate
studies reviewed for this report. Four types of analysis are discussed:
(1) analysis of temporal or spatial patterns of suspended particulates;
(2) analysis of particulate emissions; (3) examination of chemical, elemental,
or morphological properties of suspended particulates; and (4) examination of
the impact of meteorological conditions on suspended particulates. The dis-
cussion focuses on techniques' strengths and weaknesses in assessing the con-
tribution of wind-blown desert dust to urban particulate concentrations. The
section concludes with an overview of where these techniques were applied
within the study area.
ANALYSIS OF TEMPORAL OR SPATIAL PATTERNS OF SUSPENDED PARTICULATES
This category includes many of the most commonly used techniques in par-
ticulate analysis. Analysis of temporal patterns encompasses techniques such
as trending and examination of seasonal and daily fluctuations in particulate
concentration. Spatial analysis includes comparison of particulate concen-
trations by site environment, inter-site correlations, and mass flux
determinations.
In the type of problem this report deals with, spatial analysis is par-
ticularly important, but temporal analysis also has a role to play. Several
studies reviewed for this report examined seasonal patterns of particulate
concentrations, often in conjunction with analyses of seasonal meteorological
fluctuations. One of these studies concluded that seasonal patterns impli-
cated fugitive dust, rather than wind-blown desert dust, as a major contribu-
tor to the particulate problem in the Phoenix area.*
Spatial patterns play a prominent role in the analysis presented later
in this report. One technique frequently relied on is comparison of particu-
late concentrations by site environment. Comparison of urban and background
particulate concentrations, for example, reveals a great deal about the con-
tribution of wind-blown desert dust to high particulate concentrations in
urban areas. Other spatial analysis techniques also provide information that
is helpful in assessing the contribution of wind-blown desert dust to urban
particulate concentrations. Inter-site correlations, which were relied on in
several studies, can indicate whether geographically disperse sites are in-
fluenced by the same source or type of source. In Tucson, for example,
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concentrations of Al, a soil indicator, at the background location correlated
very poorly with Al concentrations at urban locations.2 This evidence sug-
gests that different sources (or processes) may be responsible for introducing
soil into the atmosphere in urban and background locations. Upwind/downwind
and mass flux analyses were also -used to assess the transport of wind-blown
dust from the desert into urban areas.
ANALYSIS OF PARTICULATE EMISSIONS
The studies reviewed for this report relied heavily on emissions inven-
tories, microinventories, and air quality modeling. The two inventory tech-
niques are similar in many ways; both attempt to identify sources in some
bounded geographic area, then estimate emissions from these sources. The
major difference between the two techniques is the scale of the analysis:
microinventories focus on small geographic areas - often a 1- to 5-mile
radius around a monitor; emission inventories usually encompass a larger
geographic area. Air quality models, which range from very simple to very
sophisticated, translate the emissions documented in inventories into ambient
concentrations.
One drawback of emission inventories/microinventories is that they often
ignore natural emissions such as wind-blown desert dust or treat these emis-
sions in a very cursory manner. Although many of the inventories reviewed
for this report suffered from this flaw, they do give a sense of the magni-
tude of other sources - such as paved and unpaved roads - contributing soil
material to the atmosphere in urban areas. Air quality modeling is poten-
tially very useful in assessing the impact of wind-blown desert dust on urban
air quality since one of its purposes is to estimate source contributions to
ambient concentrations. Its usefulness is limited by the accuracy and com-
pleteness of inventory input, however. Several studies examined in this re-
port relied on air quality modeling.3"7
CHEMICAL, ELEMENTAL, AND MORPHOLOGICAL ANALYSIS
Technological advances have enabled scientists to characterize the chem-
ical, elemental, and morphological properties of suspended particulate matter.
This section deals with a variety of techniques used to analyze this detailed
data including enrichment factors, inter-species correlation and factor
analysis.
Many of these techniques are quite useful in identifying sources of par-
ticulate matter. Inter-species correlations, for example, indicate whether
certain components of particulate matter cluster together; a common source is
usually hypothesized for such clusters. In the Tucson study by Moyers et al.,2
the elements Al, Fe, Si, Ti, Li, Rb, Mg, Na, Ca, K, Mn, and Sr were correlated
with each other. The authors suggested soil or crustal material as a possible
common source for this cluster of elements. Factor analysis is a refinement
of inter-species correlation that serves much the same purpose. Statistical
analysis based on inter-species correlations is used to group elements into
several clusters. The analyst then draws on his experience and knowledge to
hypothesize about the factor - in this case, the source - that generates each
cluster of elements.
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Enrichment factors try to distinguish anthropogenic and "natural" sources
by examining the concentration of elements in suspended particulate matter
relative to their concentration in soil material. An enrichment factor of
one indicates that the element has the same relative concentration in both
air and soil, implying a "natural" soil-related source. An enrichment factor
greater than one indicates that a particular element is more abundant in air
than in soil, suggesting contributions from anthropogenic sources. In the
Tucson study, enrichment factors for the 12 elements suspected of being soil-
related (see list above) were similar, all very close to one. This reinforces
the evidence provided by inter-species correlations that these elements, which
comprise a large part of the particulate matter in the Tucson study, have a
common source, soil.
Most of these techniques are incapable of distinguishing between fugitive
(man-made) dust and natural wind-blown desert dust, although they can indicate
how much these two sources, taken together, contribute to particulate concen-
trations. Several of the techniques discussed earlier, for example analysis
of spatial patterns, can help distinguish between these two sources when
applied to chemical and elemental data. Spatial analysis of soil-related
elements in the Tucson study showed that concentrations of soil-related ele-
ments were much different at urban sampling sites compared to the background
site. The authors concluded from this evidence that much of the suspended
soil material in Tucson is probably due to urban activity. Inter-site corre-
lations in Tucson also indicate that soil concentrations in urban and back-
ground locations were dissimilar.
Morphological analysis can also distinguish between natural and anthro-
pogenic sources of suspended dust particles. A recent study of particulates
in Phoenix,8 for example, used morphological data to distinguish the sources
of mineral material found in particulate samples. They found that the par-
ticle sizes and shapes of most of the mineral particles in the Phoenix sam-
ples were not typical of wind-eroded materials; instead, the particles were
often sharp and angular indicating, according to the authors, vehicle travel
over paved roadways.
METEOROLOGY AND SUSPENDED PARTICULATES
This technique focuses on relationships between meteorological param-
eters, such as wind speed, precipitation, and mixing height, and levels of
suspended particulates. Most studies reviewed for this report relied on
common statistical techniques such as linear regression or correlation co-
efficients to examine the relationship between meteorology and particulate
concentration.
Many of these studies found the complexity of the TSP/meteorology rela-
tionship defied analysis by simple statistical techniques. Several studies,
for example, focused on the relationship between wind speed and particulate
concentrations, hoping to distinguish the relative importance of wind-blown
dust. Most found it difficult to sort out the conflicting influences of
increased wind speed: (1) increased emissions which tend to produce higher
TSP concentrations and (2) greater dilution of pollutants, which results in
10
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lower concentrations. Even studies that focused exclusively on the TSP/
meteorology relationship9 emphasized the qualitative nature of their results
and the inability of the techniques available to distinguish between wind-
blown desert dust and wind-blown dust from construction sites, unpaved roads,
and agriculture sites.
OVERVIEW
Table 1 indicates which techniques were used in the studies relied on
most heavily in the preparation of this report. The table reveals several
noteworthy patterns. Perhaps the most noticeable pattern is the wide variety
of techniques employed by the three studies of Phoenix; techniques from all
four categories are used in these studies. The study of Tucson also used a
large number of different approaches to analyze particulate problems.
The second distinctive pattern is the heavy reliance of the studies on
emissions inventory and modeling approaches. Eight of the eleven studies
utilized these approaches, six exclusively. While some of this information
was very useful in assessing the contribution of wind-blown desert dust to
urban particulate concentrations, many of the inventories suffered from the
flaws discussed above limiting their usefulness.
These two patterns help explain why this report concentrates heavily on
Phoenix and Tucson: a great deal of detailed and useful information about
the nature of the particulate problems in these two cities had already been
compiled. Less information was available in the published reports on other
cities. This study also examines Reno and Las Vegas because the emission
inventory done by PEDCo includes an assessment of the contribution of wind-
blown desert dust.
11
-------
TABLE 1. PRIMARY TECHNIQUES USED BY STUDIES RELIED ON IN THIS REPORT
.. 0)
4-1 J-J
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PS
Analysis of Spatial or Temporal Patterns
Seasonal Patterns
Comparisons by Site Environment X
Inter-Site Correlations
Mass Flux Determinations
Emissions and Modeling
Emission Inventory X
Microinventory X
Air Quality Modeling X X
Chemical, Elemental and Morphological Analysis
Interspecies Correlations
Enrichment Factors
Factor Analysis
Pattern Recognition
Particle Size Analysis
Morphological Analysis
Other Elemental Analysis
Meteorology and Suspended Particulates
Regression Analysis
Other
4-1 * CO X >i
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J CTv>HQtO &OO-HU1 OcO"Cfl4JO > E3"
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-------
SECTION 3
BACKGROUND SUSPENDED PARTICULATES
The expression background suspended particulates, as generally used,
refers to particulates found in the atmosphere in remote or rural places well
removed from obvious anthropogenic sources. Some of these particulates come
from nearby natural sources; others are transported from distant natural and
urban sources; still others are formed within the atmosphere by chemical
action during precursor transport. In this report, background concentration
is considered to be the concentration of particulates that would have existed
throughout the study area had that area remained undisturbed by man. Con-
ceived of in this way, background concentrations represent baseline levels
upon which particulates generated within an urban area are superimposed. The
difference between background and observed concentrations represents the incre-
ment that may be manipulated through the use of local control measures. The
concept is somewhat simplisitc since the background really comprises a dynamic
particulate population continually responding to changing depletion and
replacement rates.
Background concentrations are usually expressed in terms of annual geo-
metric mean concentrations measured in remote or rural areas unaffected by
local sources. In addressing the influence of wind-blown desert dust on the
nonattainment problem in urban areas, however, consideration must also be
given to the magnitude of 24-hour concentrations observed in remote and rural
areas.
This section first summarizes annual and 24-hour concentrations observed
at remote and rural sites throughout the Southwest. It then discusses some
of the physical and chemical properties of particulates in outlying areas in
an attempt to shed light on their origins and probable transport distances.
Topics discussed include: (1) particulate size distributions, (2) the genera-
tion of wind-blown dust, and (3) chemical constituents of suspended particu-
lates. This information, when compared with that presented for urban areas
in Sections 4 and 5 of this report, will be used in estimating the contribution
of wind-blown dust to the TSP nonattainment problem in large cities set in
desert surroudings.
BACKGROUND CONCENTRATIONS
Background concentration data have been assembled from three sources and
are based principally on measurements made in 1976. Large year-to-year varia-
tions in background concentrations are not expected, however, barring extreme
differences in meteorological conditions. Data obtained from the National
13
-------
Aerometric Data Bank for 24 remote and rural sites throughout the eight south
western states provides the most widespread set of annual and 24-hour concen-
trations. This data set is supplemented by measurements made at 20 sites in
the Four Corners area for EPA by the Ute Research Laboratories.10 In addition,
contractor reports provide estimates of background levels for several specific
urban areas.
Appendix A lists the location of each monitor, the station type as classi-
fied by the SAROAD site identification procedure, elevation above sea level,
and the elevation of the monitor above the ground. Annual geometric mean con-
centrations, and the highest and second highest concentrations for the year,
or period of measurement, are also given. The approximate locations of the
monitors are indicated on maps (Figures A-l and A-2).
Descriptions of the stations operated by the Ute Research Laboratories
can be found in Reference 10. Typically, these stations were located on
either Indian Reservation or National Park land in arid areas with sparse
vegetation and widely scattered homes. Nearby land use was generally restric-
ted to livestock grazing; in a few cases, limited areas were devoted to agri-
culture. The high-volume air samplers were mounted on 4.6 m (15 ft) towers
to minimize the effects of local dust and ground-level obstacles.
Annual Geometric Mean Concentrations
Figure 2 displays the annual geometric mean concentrations obtained from
the National Aerometric Data Bank. At three stations, the 1976 data did not
meet the SAROAD summarization criteria for the calculation of annual means,
and 1977 means were substituted; these three 1977 values have been placed in
parentheses. The results from special monitoring programs conducted in north-
eastern Utah and northwestern Colorado are given as ranges. In each case,
the results from four monitors were combined.
Although the results show no sharply defined pattern, the lowest values
tend to be found in northern Utah and Colorado. At lower latitudes, concentra-
tions of 50 yg/m3 were measured in central Oklahoma and central Texas, perhaps
reflecting regional differences in land use and agricultural practices. The
only concentration that exceeded federal ambient standards, 84 yg/m, was
measured at the Kern Wildlife Refuge in the San Joaquin Valley airshed in
California. Examination of long-term trends at this site11 suggests an improve-
ment in air quality since 1976; in 1978, the annual geometric mean was 62 yg/m3.
Neither of these values, however, is representative of background concentrations.
Figure 3 displays geometric means observed by the Ute Research Laboratories
monitoring metwork. Activation dates for the monitors ranged from 12 January
1976 to 6 May 1977 (see Appendix A, Table A-l). The values plotted in Figure 3,
however, were calculated using 1976 data from sites where observations were
available for at least three seasonal quarters. As the figure shows, the moni-
tors stretched along an east-west belt 50-100 km wide that extended for a
distance of about 380 km. Geometric means within the network ranged from 12 to
56 yg/m3.
14
-------
Figure 2.
1976 annual geometric mean TSP concentrations from National
Aerometric Data Bank. Values in parentheses are 1977
concentrations. Ranges are shown for closely located
sites in Utah and Colorado.
-------
0 50 100 miles
1 1 1
1 1 1
0 80 160 km
QR1CHFIELD
UTAH
.56
«
.26 .26
18 *16 290
29
18 .
22 24*
32 .17
ARIZONA
n FLAGSTAFF
QGRAND JUNCTION
COLORADO
.23 ^ .23
12
.24 .45
.31
NEW MEXICO
D GALLOP
Figure 3. 1976 geometric mean TSP concentrations observed by Four Corners
Ambient Air Monitoring Network operated by Ute Research Laboratories.
-------
The means shown In Figures 2 and 3 have been combined and summarized as
a frequency distribution, Figure 4, that distinguishes the data by site type;
i.e., remote or rural. In this sample, on the average, rural sites experi-
enced a mean concentration of 38 yg/m3 in contrast to the 24 yg/m3 experienced
by remote sites. Because of the small size of the rural-site sample, this
difference may not be significant, but it suggests that the impact from rural
activities at these sites is in the vicinity of 10-20 ug/m3-
Estimates of background concentrations can also be obtained directly from
a number of particulate studies. Background concentrations, taken from three
of these studies are listed in Tables 2, 3 and 4. PEDCo used the data contained
in Table 2 to develop the following relationships between vegetative cover in
the Southwest and background particulate levels: forest-woodland, 15-20 yg/m3;
southern desert scrub, 25-30 yg/m3; northern desert scrub, 20-30 yg/m3; and
grassland, 22-27 yg/m3. The values in Table 3 were used by TRW to determine
a weighted average background concentration of 30 yg/m3 for Phoenix, Arizona.
The local health departments suggested 35 yg/m3 and 25 yg/m3 as appropriate
background values for Las Vegas and Reno, respectively. In addition to these
estimates that are based directly on observations, PEDCo estimated background
concentrations for sites in Colorado and Utah from the y-intercepts of emis-
sion density versus air quality, and modeling analyses. These esitmates are
presented in Table 4.
TABLE 2. TSP CONCENTRATIONS AT SELECTED BACKGROUND
SITES IN NEW MEXICO, ARIZONA, AND NEVADA
State
Sampling site location
Annual geometric
mean, yg/m3
New Mexico Albuquerque - NASN
Bernalillo County-Radar Stn.
Dona Ana County
White Rock
Arizona Organ Pipe Cactus Nat'l
Monument
Grand Canyon
Davis Dam
Page
Nevada White Pine - NASN
Las Vegas - Marina
Boulder City
Las Vegas - Civil Defense
Building
Reno
22
32
13
32
26
21
29
17
14
35
30
34
31
Source: Table 3-7, pg. 3-26, Reference 4.
17
-------
zo
1 C
CO
z
O 14
H
OBSERVA
O t\>
NUMBER OF
P> Cft CD
o
-
M
-
:£:'?:
- ' '.
': '
.' ' ' '
'.'' :
(AVE.= 24)
ri.'v-y:.*:.: RURAL
ti-'-vV-'i (AVE. s 3fl)
kFRM RPPIIftP
1
sra; v
m^i(m \ i
0-9 10-1920-2930-3940-4950-5960-6970-7980-8990-99
TSP CONCENTRATION,
Figure 4. Frequency distribution of annual geometric
mean TSP concentrations at 45 rural and
remote sites in Southwestern U.S.
18
-------
TABLE 3. TSP CONCENTRATIONS
AT SELECTED BACK-
GROUND SITES IN
ARIZONA
Annual geometric
mean, yg/m3
Site
Grand Canyon
Petrified Forest
Organ Pipe
Montezuma
Average
1973
22
26
34
28
28
1974
17
23
23
27
23
1975
N/A
N/A
31
34
32
Source: Table 4-1, pg. 4-1,
Reference 3.
TABLE 4. ESTIMATED BACKGROUND TSP CONCENTRA-
TIONS FOR SELECTED AQCR's IN
COLORADO AND UTAH
Estimated annual
State
Colorado
Utah
geometric mean
AQCR yg/m3
Denver
Pawnee
San Isabel
Colorado Springs
Pueblo
Other sites
Yampa
Grand Mesa
Wasatch Front
40-45
45
30-35
45
40-45
20
40
40
Source: Table 2-2, pg. 2-8, Reference 12.
19
-------
Twenty-four Hour Concentrations
Figures 5 and 6 display the second highest 24-hour TSP concentrations for
1976 in the same fashion used for the geometric means. Again, substituted 1977
concentrations are indicated by parentheses, and a range of values is given
for samplers in geographic proximity. In Figure 5, one concentration exceeds
the primary standard and five others exceed the secondary standard, with two
of the five being observed in northwestern Colorado. In Figure 6, two concen-
trations exceed the primary standard and nine others exceed the secondary
standard.
These 24-hour, second-highest, concentrations have been combined as a
single frequency distribution in Figure 7a. In this case, there appears to be
no significant difference between the averages shown at rural and remote sta-
tions. A similar frequency distribution of the maximum 24-hour concentrations
has been plotted In Figure 7b, and again there appears to be no tendency for
the highest concentrations to occur more frequently at rural stations than at
remote stations.
Finally, inspection of the two sets of maps reveals no obvious relation-
ship between geometric means and the magnitude of the second-highest 24-hour
concentration. The lack of strong relationship was confirmed by a linear
correlation between the two sets of data of 0.42. Although this is significant
at the 0.01 level with 45 pairs, only 17 percent (R2) of the variation is
common.
CHARACTERISTICS AND SOURCES
An understanding of the physical and chemical nature of background partic-
ulates provides insight into their probable sources and likely transport dis-
tances. This discussion briefly reviews particle-size distribution information
and some of the generally accepted concepts pertaining to the generation of
wind-blown desert dust. It also summarizes the results of recent studies that
have investigated the chemical species present in desert dust and interrela-
tionships among these species. Much of this latter work was carried out on
samples collected at the Research Ranch approximately 60 miles to the south-
east of Tucson, Arizona.
Particle Size Distribution
Very few measurements covering the complete size range of particles
collected by the standard high-volume sampler have been reported in the litera-
ture for desert atmospheres. Furthermore, it is rather widely conceded that
the details of observed distributions are dependent upon the collection devices
and experimental techniques employed. (See Lundgren and Paulus,13 and Farmer
and Hornkohl,14 for example). Nevertheless, recent studies have contributed
substantially to knowledge of airborne particulates in a variety of environ-
ments, and this information can be used to supplement the limited desert
measurements to obtain the most significant features of particle size distri-
butions in background, desert atmospheres.
20
-------
Figure 5.
1976 second-highest 24-hour TSP concentrations from National
Aerometric Data Bank. Values in parentheses are 1977 con-
centrations. Ranges are shown for closely located sites in
Utah and Colorado.
-------
0
h
50
H-
80
100 miles
-H
160 km
QRICHFIELD
UTAH
360
196
so
86
138
90
'353
124
ie
155
ARIZONA
FLAGSTAFF
QGRAND JUNCTION
COLORADO
8I
70
171
171
NEW MEXICO
DGALLOP
Figure 6. 1976 second-highest 24-hour TSP concentrations observed at Four Corners
Ambient Air Monitor Network operated by Ute Research Laboratories.
-------
20
_
0
16
v>
O <4
S 12
K
Ul
£ 10
O
U. o
o 8
i 4
n
REMOTE
(AVE.= 138)
RURAL
(AVE. = 139)
0- 75- ISO- 225- 300-1375^ 450-525-600- 675-
74 149 224 299 374 |449 1524 |599 | 674 1749
CONCENTRAT ION , yu.g An3
0)SECOND HIGHEST CONCENTRATION
20
18
16
14
12
10
S 8
i REMOTE
(AVE. = 217)
i..,....i RURAL
-..-- 170)
0- 75- ISO- 225- 300- 375- 450- 525- 600- 675-
74 149 224 299 374 449 524 599 674 749
CONCENTRATION,
b) MAXIMUM CONCENTRATION
Figure 7- Frequency distributions of 24-hour TSP
concentrations at 45 rural and remote
sites in Southwestern U.S.
23
-------
The picture that emerges is of a volume, or mass, distribution that is
bimodel. One mode is comprised of fine particles in the range from 0.1 ym to
roughly 2 ym, and the other mode is comprised of larger particles, with a peak
that depends on soil characteristics, meteorological conditions and height
above ground. The bimodel form of the distribution over the range from 0.1 to
10 ym is illustrated in Figure 8, taken from a paper by Sverdrup, Whitby and
Clark.15 Five of the distributions are based on observations made at Goldstone
in the Mojave Desert, California. The sixth distribution represents conditions
at Fort Collins, Colorado on a day when there was little evidence of local con-
tamination from dust. The aerosol particle size distribution was measured with
four on-line instruments over a particle size range from approximately 0.003
to 40 ym. A description of the instrumentation is given in Whitby
et al.16
Particles in the fine-particulate mode remain suspended in the atmopshere
for long distances unaffected by gravitational forces. Estimates by Esmen and
Corn,17 for example, indicate that the residence time for particles 1 ym in
diameter in the absence of precipitation is of the order of 100 hours. At an
average transport speed of 5 m/sec (11.2 mph) this represents a travel distance
of 1800 km (1118 mi). Thus, many of the particles in this mode reflect emis-
sions from distant sources, some of which are anthropogenic and others natural.
This fine particulate mode was named the "accumulation mode" by Willeke and
Whitby18 to reflect the fact that aerosol particles that grow into this range
from smaller sizes by coagulation or condensation tend to remain in this size
range.
The other mode is comprised of larger particles whose primary source
is the underlying ground surface. Under average meteorological conditions and
uniform surface conditions, TSP measurements suggest that a quasi steady state
develops in which the resuspension of soil particles from the desert floor is
roughly balanced by the removal rate over a 24-hour period. During any 24-
hour period, however, marked variations in the resuspension rate occur as a
result of major changes in the turbulent characteristics of the wind field
and in the amount of convection.
Evidence that resuspension occurs in puffs of short duration (less than
or equal to 2 minutes) has been presented by Porch.19 Dust devils are a
visual indication of convective adjustment in which a large size range of
particles are injected into the lower atmosphere. The next section discusses
the generation processes for desert dust in more detail, but common experience
illustrates relationships between wind speed, soil conditions and the injec-
tion of particulate material into the atmosphere. Once injected, the residence
time of the particles in a dry atmosphere depends upon the initital height
reached by the particles, the gravitational settling rate, atmospheric turbu-
lence, and ground cover.
Figure 9, developed by MRI,20 relates particle diameter to three settling/
suspension regimes at wind speeds up to 18 mph. The area labeled "suspension"
represents particles that have the potential for long range transport. The
area labeled "unimpeded settling" represents particles with terminal veloci-
ties sufficient to largely overcome the effects of turbulence and horizontal
transport. Particles in the "impeded settling" area respond to atmospheric
motions while settling.
24
-------
e
*
|
H 4
<
MITT]
NUN NO. DATE* TIME
O Bl OCT. l»72l3'30-l6'BOb
0 Ktr 2 NOV. 1972 OOOO-OI«Oh
I I Illlj
OXM
I
D., tan
O
A comparison of the background volume distributions during a very clean period
and an evening with higher total volume.
so
tf
f«
O GOLOSTCNE
A FT. COLLINS
i i i | i ill] i ill
MM NO. TME MTE
KM OHJO-02-OOH I NOV. «9I j
1-32 0»S9-O7^«Oti (AIM. I
A comparison of the volume distributions of background aerosols sampled at
Goldstone and Fort Collins, Colorado.
Figure 8.
!
I I I | llll|
GOLDSTONE
4 NOV. I9T2
O 05'000
A OB'40h
O 07<90«
TTTT
0.01
D,,
Incursion of aged aerosol from the south coast basin.
Volume distributions observed in the Mojave Desert, California,
and Fort Collins, Colorado (from Sverdrup, Whitby, and Clark,15
pp. 489 and 490).
25
-------
200 i-
4 6 8 10 12
REFERENCE WIND SPEED (mph)
14 16
18
Figure 9. Particle settling/suspension regimes.
26
-------
Because of the complicated relationships alluded to above, the modal peak
due to ground level sources can be expected to vary with desert location and
sampling height. An example of the shift in the peak toward greater particle
diameter as the sampling height decreased from 30 m to 0.3 m is shown in
Figure 10 taken from Schmel.21 (Derivations of the lines "A" and "B" are given
in Schmel's paper). The observations used in preparing this figure were made
during a dry, spring period in a semi-arid and sparsely vegetated region of the
Atomic Energy Commission's Hanford reservation. The upwind terrain was undis-
turbed for several miles and included a region without sage bush that extended
about 200 feet upwind. Particles in the respirable size range were determined
using 20 cfm cascade particle impactors; the larger particles were collected
by deposition within a wind-direction self-orienting attachment to the
impactors.
Generation of Wind-blown Dust
The generation of dust begins at a wind speed great enough for aerodynamic
forces to overcome the forces holding individual particles in the soil.
Although a considerable amount of theoretical and experimental work has been
carried out on idealized systems Csee for example, Chepil,22 Greeley et al,23
Marshall2** and Lyles and Allison25), few studies of wind-generated fugitive
dust have addressed natural soil surfaces and man's impact upon these surfaces.
As a result, current understanding of the mechanisms by which desert soil
becomes entrained is largely qualitative.
Two important aspects of soil structure are the distribution of particle
sizes and the aggregate structure of the soil. The undisturbed desert soil
surfaces in much of the southwest are composed of a silt aggregate and a thin
crust of gravel and sand, (.see Richard et al.1 for a description of soil charac-
teristics in the Phoenix area). This surface crust is sometimes referred to
as the desert pavement. It is easily broken up by human activities and is
particularly vulnerable to vehicular travel. Where loose sand particles exist,
moderate wind speeds may be sufficient to initiate sandblasting of the sur-
face soil, resulting in the release of soil fines and the suspension of
particulates.
Under sufficiently strong winds, severe dust storms may develop, particu-
larly in regions where the soil surface has been disturbed as a result of
man's activities. For example, on February 23, 1977 central Oklahoma experi-
enced the worst dust storm in more than 20 years with 24-hour average TSP con-
centrations up to 5800 yg/m3.26 The paths of dust were clearly evident in
photographs prepared from satellite data. Reported surface winds were 30 to
40 knots in the dust swaths and 20 to 30 knots in the clear area. Oklahoma
had another severe storm on March 2, 1977. The photographs show very strikingly
that in each case the western limit of the dust coincides approximately with the
Texas-New Mexico border, apparently because of changing soil characteristics
and agricultural practice in the vicinity of the border. Rangeland is pre-
dominant on the New Mexico side of the border, and cropland on the Texas side.
Dust storms are typically associated with sustained wind speeds of 20 to
30 knots produced by major weather systems. In a study of dust storms in the
27
-------
AIR SAMPLING
t- HEIGHT, m
O 0.3
105
|
103
'I
APRIL 4-26,1972
Q 3
O 10
A 30
°0
//» \
///w \
10 102
PARTICLE DIAMETER, (Dl, |ini
Figure 10. Volume distribution as a function of height.21
28
-------
Great Plains,27 Hagen and Woodruff found that the average duststorm lasted 6.6
hours and the median concentration during the period of the storm was 4850 yg/m3,
In this study, particulate concentrations were calculated from National Weather
Service visibility data using the relationship
C6 " TTZF mg m~3
developed by Chepil and Woodruff.28 In this expression GS is the dust concen-
tration 6 feet above the surface and V is the horizontal visibility in kilo-
meters. The data analyzed for each station were from 10-year period beginning
in either 1949 or 1950. In a related study, Hagen and Woodruff29 roughly esti-
mated that the median size of the duststorm covered an area of about 188 * 188
miles square. The average number of days per year with dust reported at 19
stations distributed throughout Texas, New Mexico, Oklahoma and Colorado ranged
from 1.3 at Grand Junction, Colorado to 47.5 at Lubbock, Texas. The mass
median particle diameter during duststorms has been reported by Whitby et al30
as 50 ym.
Chemical Constitutents
The information provided here has been taken largely from a paper by Korte
and Moyers31 that describes the results of a measurement program conducted
between September 1975 and October 1976 at the Research Ranch. The Research
Ranch is a protected land laboratory comprising 7,840 acres of private, state
and federal land, generally high desert grassland. It is situated in the
transition zone between the Sonoita Plains and the Hauchuca Mountains. The
nearest town is Elgin (population 50) approximately 5 miles to the north.
Thirty-two size fractionated samples were collected during the sampling
period as part of a larger program described by Moyers et al.2 Sampling was
performed using Sierra 230 two-stage, high-volume slotted Cascade Impactors.
Particle separation using this system was about 2 ym aerodynamic diameter.
Elemental analysis was performed on digested filters by atomic absorption
spectrometry. Analyses for ammonium, nitrate and sulfate ions were also
carried out.
The data were evaluated using statistical correlations, particle size
distributions, and comparison of particle composition with the composition of
suspected source materials. In calculating the crustal enrichment factor,
aluminum was chosen as the reference element since soil is considered to be
the sole source of aluminum in this region.
It is concluded on the basis of this and the previous work by Moyers et al
that wind blown soil materials dominate the mass concentration of large parti-
cles (greater than 2 ym) and all measured species except Cd, Zn, Pb, Cu, 80^=,
N03- and NHtt+. On the other hand, the smaller particles are composed of soil
material, gaseous oxidation products, and species apparently from distant
anthropogenic or natural sources. The small particle sulfate, nitrate, and
ammonium ions are the result of gas-to-particle conversion from gaseous SOa ,
NOx, and NHs released into the atmopshere from natural sources such as decaying
vegetation, and anthropogenic sources such as smelters, agriculture, power
29
-------
plants and urban areas. Previous work by Moyers et al32 estimated that the
contribution of soil material to the total atmospheric burden of particulate
matter at the Research Ranch is 50 percent.
Figures 11 and 12 taken from the paper by Korte and Moyers,31 and the
linear correlation coefficients calculated between chemical species that are
presented in the paper, support these conclusions. Figure 11 shows the per-
centage distribution of the individual species on the respirable (less than
2 ym) particles, while Figure 12 is a plot of the crustal enrichment factors
for the respirable particles. Species with enrichment factors near unity
(from 0.5 to 5) are attributed to airborne soil material, while species with
enrichment factors greater than about 50 are attributed to sources other than
the injection of crustal weathering products into the atmosphere.
More general information concerning the magnitude and distribution.of
sulfates and nitrates is being obtained from an expanded monitoring network
of high-volume samplers within the Western Energy Resource Development Area.33
Preliminary summaries of data, collected before major expansion of the net-
work occurred, show sulfate concentrations in the 1 to 3 yg/m3 range in north-
ern Arizona, southern Utah, northwestern New Mexico, and southeastern Colorado.
With the exception of southern Arizona where values from 3 yg/m3 to greater
than 15 yg/m3 were reported, the region lies in the range from 1 to 6 yg/m3.
This is in agreement with the mean value of 2.6 yg/m3 reported for rural areas
in the West by Greeley et al34 and Altshuller,35 Better definition of regional
differences will be available from the expanded network. Nitrate data from
the early network is less complete and shows greater variability than the
sulfate data. Mean values generally range from 1 to 5 yg/m3 throughout the
region, with the lower values being found in the rural areas.
30
-------
100-
5
s -
RESEARCH
SEPT 1975 - OCT 1976
Ct Si Cl II III CD Ml Ti Ft K M| li A I, A nlj
Figure 11. Percentage distribution of measured chemical species on
respirable particles in the atmosphere at the Research
Ranch. (Korte and Moyers31)
10'-
Ruiti $mu PuriciE
ElllCIIWIIT FtCTOIS
Ft Sr Ci fi Hi m Si Mg K Rb Ni Li Cr 2n Pb Cu S0,= NO, NH|
Figure 12. Crustal enrichment factors of species measured on respirable
particles in the atmosphere at the Research Ranch. (Korte
and Moyers31)
31
-------
SECTION 4
URBAN PARTICULATES LEVELS
This section examines the distribution of particulates in and around four
major urban areas located in dry, arid regions of the southwest. The review
is based in large part on published reports summarizing 1975 TSP data, but is
supplemented in some cases by more recent observations. The objective is to
analyze the relative contributions made by particulates arriving from outside
the urban area, and those that are generated or reentrained within the area
to violations of the standards by comparing spatial particulate patterns with
land usage and associated human activities. The four urban areas studied are
Las Vegas and Reno, Nevada, and Tucson and Phoenix, Arizona.
PARTICULATE LEVELS IN AND AROUND LAS VEGAS
Las Vegas is situated near the center of a broad desert valley which runs
from northwest to southeast. The valley floor slopes gradually upward on each
side towards the surrounding mountains. The climate is charactrized by low
humidity, abundant sunshine, mild winters and hot dry summers. The prevailing
winds at McCarran Airport, 7 miles south of downtown Las Vegas are from the
west through south-southwest. Precipitation averages about 4 inches per year.
Las Vegas has grown very rapidly over the last 20 years, with the population
of the metropolitan area reaching 361,100 in 1977. 6 The tourist industry
dominates. Agriculture is carried out on a small scale.
The following discussion is based on information provided in a 1977
report by PEDCo5 prepared for the U.S. Environmental Protection Agency. In
this report, TSP data from 12 sites are presented and analyzed. Figure 13
shows the sampling locations and their relationship to Las Vegas. In terms
of physical setting, the sites range from center city/commercial to rural/
recreational. Table 5 lists site location information provided in the PEDCo
report, plus monitor heights.
The concentration data analyzed covers the 12-month period from October
1974 through September 1975. Mean concentrations for this period are plotted
against distance from a central point in the Las Vegas business district (CBD),
Fire Station No. 1, Site E. The data cover three distance intervals, The
first interval contains 5 monitors centrally located within the heart of the
urban area. (Sites C, I, F, H, and E). The second interval contains 4 moni-
tors that ring the urban area from the McCarran International Airport to the
south to the Nellis Air Force Base to the northeast; the distances of these
monitors from Site E range from about 10 to 14 km. The third interval contains
3 monitors located from 20 to 24 km from Site E. As shown in Figure 14, two
of these monitors (B and D) are located within the city of Henderson (1977
32
-------
KEY
A LAS VEGAS AIRPORT
B BASIC SCHOOL
CLARK COUNTY HEALTH DEPT.
HENDERSON POST OFFICE
LAS VEGAS FIRE DEPT. No.
LAS VEGAS FIRE DEPT. No.
NELLIS AIR FORCE BASE
NORTH LAS VEGAS
SAHARA HOTEL
LAS VEGAS STADIUM
SUNRISE POWER PLANT
LAS VEGAS WASH
Figure 13. The Clark County APCD sampling network for TSP (after PEDCo).5
33
-------
TABLE 5. SITE LOCATION DESCRIPTIONS FOR LAS VEGAS
MONITORS
Site
designator
A
B
C
D
E
F
G
H
I
J
K
L
Site
Las Vegas Airport
Basic School
Clark County Health
Department
Henderson Post Office
Las Vegas Fire
Department No. 1
Las Vegas Fire
Department No. 2
Nellis Air Force Base
North Las Vegas
Sahara Hotel
Las Vegas Stadium
Sunrise Power Plant
Las Vegas Wash
Site type
Suburban/
commercial
Suburban/
commercial
Center city/
commercial
City/industrial/
commercial
Center city/
commercial
Center city/
commercial
Suburban/
commercial
City/commercial
Center city/
commercial
Suburban/
commercial
Suburban/
industrial
Rural/
recreational
Monitor
height
(ft)
25
30
25
30
35
25
25
25
30
10
25
25
34
-------
120
no
100
90
*»E 80
E
z ?0
o
| 60
z
uj
« 50
O
o
a. 40
30
20
10
c
\
G
X
INCREASING URBANIZATION
HENDERSON
0
\°
POST OFFICE
BASIC
SCHOOL
Figure 14. Annual mean TSP concentrations
versus distance from urban core
(Las Vegas).
X L
6 8 10 12 14 16 18 20 22 24
DISTANCE FROM URBAN CORE, km
35
-------
population of 20,100)36 southeast of Las Vegas. These monitors are therefore
subject to particulates generated by activities within that city. Eliminating
these two monitors, and averaging the concentrations within the other two
intervals gives the following results as one approaches the Las Vegas CBD from
the largely undisturbed rural/recreational area to the east: (1) background
concentration - 32 yg/m3, (2) outlying concentration - 69 yg/m3, and (3) down-
town concentration - 100 yg/m3- The dashed line in Figure 14 connects the
central values (open circles) of the three groups.
Plots of the 24-hour concentrations at each of the 12 sites are shown in
Figure 15. The individual frequency distributions have been arranged from
left to right in order of distance from the city center (Site E). Several
features of this figure are of note. Most striking are the very high concen-
trations joined by the solid lines. These were observed on June 17, 1975 and
clearly show the effect of regionwide blowing dust. This was the only TSP
observation day during the 12-month period when blowing dust was reported in
the 3-hourly local climatological data summaries for the McCarran International
Airport. On this date, visibility at the airport dropped from 20 mi at 1300
PST to 2 mi at 1600 PST, was still only 2 mi at 1900 PST, and had only
increased to 4 mi by 2200 PST. During this dusty period winds blew from the
southwest at about 20 mph. The only site not affected was the topographically
protected Las Vegas Wash site in the National Recreational Area east of the
city.
The two other most extreme concentrations occurred at the Sahara Hotel
site on April 24, 1975 (895 yg/m3) and at the Power Plant site on January 12,
1975 (793 yg/m3) . Both of these were isolated violations and must be attri-
buted to local and perhaps non-reoccurring sources. On April 24th, the next
highest concentration observed was 129 yg/m3 at Nellis Air Force Base; on
January 12, 1975, the next highest concentration was 87 yg/m3 at the Las Vegas
Fire Department No. 2.
Also of interest is the changing nature of the distributions as one pro-
gresses from the relatively undisturbed area represented by Site L west to
the center of Las Vegas (Site E). The distributions appear to reflect the
influence of the city of Henderson, particularly at Site D. At the Stadium
(Site J), concentrations are generally quite low, but five values exceed the
standards. (No attempt has been made to relate these exeedances to stadium
events, but a relationship could be expected). Concentrations are low at the
Nellis Air Force Base (Site G), but the number of exceedances of the secondary
standard increase thereafter in moving toward the city center until the Sahara
Hotel is reached. After that, the number of exceedances decrease rather
steadily, reaching 6 at Sites C and E.
It is tempting to associate the improvement in air quality as one pro-
gresses inward toward the CBD from the Sahara Hotel with a decrease in fugitive
dust emissions from disturbed soil surfaces, unpaved roads, and the like, and
this may well be the case. Such a hypothesis does not agree well with the
emission densities determined by PEDCo for the various sites, as shown in
Table 6, however.
36
-------
1200
1100
1000
900
BOO
10
E
* 700
4
o
Q.
at
600
400
300
200
100
6/IT/7S
FIRE
OEPT
C H
HEALTH NORTH
OEPT. LAS
VAGAS
FI KAGJDBL
FIRE SAHARA POWER AIRPORT NELLIS STADIUM HENOER- BASIC LAS VEGAS
OEPT HOTEL PLANT AFB P.O. SCHOOL WASH
Figure 15. Plots of 24-hour TSP concentrations at 12 sites ordered
by distance from city center (Las Vegas).
37
-------
TABLE 6. NUMBER OF EXCEEDENCES OF THE SECONDARY STANDARDS
AND EMISSION DENSITIES AT SELECTED SITES
Site Number of
designator Site exceedences
I
F
H
C
E
Sahara Hotel
Fire Department No. 2
North Las Vegas
Health Department
Fire Department No. 1
15
11
9
6
6
a
Emission density
(tons/mi2 /day)
251
75
85
210
163
a
Contributed by fugitive dust.
PARTICULATE LEVELS IN AND AROUND RENO
Reno is located on the semiarid eastern slope of the Sierra Nevada Moun-
tain Range. The Truckee River flows from the Sierras in California eastward
through Reno to Wadsworth on the eastern edge of the study area, and then
turns northward to drain into Pyramid Lake. Temperatures are mild and sun-
shine is abundant throughout the year. Annual precipitation averages around
7 inches, more than half of which occurs from December through March largely
as mixed rain and snow. The prevailing winds at the International Airport
are from the west. The approximate 1977 population of Reno is 82,500, and
that of Sparks roughly three miles to the east of the Reno CBD, is 33,800.36
This discussion is also based on information provided in the 1977 PEDCo
report5 in which data from 12 sites are presented for the period from October
1974 through 1975. The site types range from city/commercial in downtown
Reno and Sparks to rural sites on the western and eastern edges of the study
area. Figure 16 shows the approximate locations of the monitors; Table 7
lists the site location information provided in the PEDCo report, plus moni-
tor heights when available.
Figure 17 shows the similarity in the spatial patterns of annual mean con-
centration and number of observations exceeding 150 yg/m3 in the vicinity of
Reno and Sparks. Comparison of these patterns with the site-type map at the
top of the figure indicates a strong relationship between the level of parti-
culates and the pattern of land use and its associated human activities. The
highest concentrations occur in the busiest, most commercial areas, while the
lowest concentrations occur in the suburban/residential areas to the west.
Farther to the west at Lake Tahoe and Verdi, the mean concentrations were 22
and 18 yg/m3, respectively. Concentrations for different site types can be
generalized as follows: background concentration (Sites I and J), 20 yg/m3;
suburban/residential and rural (Sites C, E, F, and L), 46 yg/m3; suburban/
residential/commercial (Site G), 58 yg/m3; and city/commercial and suburban/
commercial (Sites B, H and A, D), 77 yg/m3. On 15 of the 61 sampling days
during the 12-month period, concentration exceeded 150 yg/m at one or more
of the Reno-Sparks sites. Table 8 lists the concentrations observed at the
9 sites on each of these days. On 8 of the 15 days, the concentration
38
-------
KEY
10
15km
vo
WASHOE COUNTY HEALTH DEPT.
CAL-NEVA CLUB
JESSIE BECK SCHOOL
RENO AIRPORT
NEVADA FISH AND GAME
MAMIE TOWLES SCHOOL
GREENBRAE SCHOOL
SPARKS NUGGETT
LAKE TAHOE
VERDI SCHOOL
WADSWORTH FIRE DEPT.
SEWER PLANT
10 ml
Figure 16. The Washoe County DEP sampling network for TSP
(after PEDCo5).
\
/
-------
TABLE 7. SITE LOCATION DESCRIPTIONS FOR RENO MONITORS
Site
designator Site
A Health Department
B Cal-Neva Club
C Jessie Beck School
D International Airport
E Nevada Fish and Game
F Mamie Towles School
G Greenbrae School
H Sparks Nugget
I Lake Tahoe
J Verdi School
K Wadsworth Fire Department
L Sewer Plant
Site type
Suburban/
commercial
City/commercial
Suburban/
residential
Suburban/
commercial
Suburban/
residential
Suburban/
residential
Suburban/
residential/
commercial
City/commercial
Suburban/
commercial
Rural/residential
Rural/agricultural
Rural/agricultural
Height of
monitor
Cft)
15
50
20
15
20
20
15
35
___
15
35
40
-------
SUB/RES/COM
SITE TYPE
0 I 2 3 mi
58*6 \
0123
ANNUAL GEOM WEAK
NUMBER
OF OBSERVATIONS
Figure 17. Spatial distribution of TSP concentrations and
land use in and around Reno.
41
-------
TABLE 8. TSP CONCENTRATIONS IN RENO AND VICINITY ON DAYS WHEN
THE SECONDARY STANDARD WAS EXCEEDED (10/74-9/75)
Site
Date
H
A
B
G
D
Concentration
10/02/74
10/20/74
10/26/74
11/07/74
11/13/74
11/19/74
12/19/74
01/12/75
01/18/75
01/24/75
01/30/75
02/11/75
03/01/75
04/24/75
06/17/75
No. >
150 yg/m3
134
174a
100
154a
197a
152a
137
170a
152a
206a
95
142
298a
161a
71
9
-
186a
94
113
182a
107
204a
144
166a
234a
165a
200a
156a
73
69
8
134
121
82
86
110
84
162a
139
140
154a
98
202a
132
87
66
3
128
366a
187a
71
161a
125
135
120
105
139
60
77
96
74
53
3
173a
181a
99
121
128
100
100
118
124
124
58
-
114
86
200a
3
E
yg/m3
130
153a
86
81
189a
111
149
105
108
149
68
124
87
73
41
2
C F
103
87
54
54
65
56
96
78
85 -
64
52
64
49 -
36 38
38 2
0 0
L
88
106
64
52
96
48
-
52
55
59
26
39
50
-
82
0
No. >
150 yg/m3
1
5
1
1
4
1
2
1
2
3
1
2
2
1
1
28
a
Concentrations greater than the secondary standard.
42
-------
exceeded the standard at only one site. The greatest number of simultaneous
exceedances was 5 on October 20, 1974, followed by 4 on November 13, 1974.
Thus on the occasions when high concentrations did occur, they were almost
always confined to small geographic areas.
On October 20th, wind speeds were light but increased to about 15 mph
early in the afternoon and remained near this level for the balance of the
day. The maximum wind speed reached during the day was 24 mph. In contrast,
on November 13th the winds were very light throughout the day with the fastest
mile of wind reported at the airport being 3 mph. Although high wind speed may
have contributed to the high concentrations observed on October 20th, this is
not the case on November 13th. It is of interest to note that a large high
pressure system that had dominated the Great Basin for several days was just
beginning to weaken on the 13th. This suggests a regionwide accumulation of
the finer particulates, a possibility supported by the fact that five of the
Las Vegas sites also exceeded the standard on that day. Using a Chi Square
analysis PEDCo designated November 13th as a high regionwide concentration
day in both Reno and Las Vegas.
PARTICULATE LEVELS IN AND AROUND TUCSON
Tucson is a moderately large city (1977 population of 301,200)36 located
in a desert valley that runs northwest-southeast between the Santa Catalina
and Rincon Mountain ranges to the northeast and east and the Tucson Mountains
to the west. The climate is characterized by abundant sunshine and a long
hot summer extending from April to October. Precipitation averages about 11
inches per year. Roughly half of the precipitation occurs during summertime
showers (July-September); the balance is distributed throughout the year,
with a secondary maximum during December and January. Surface winds are
generally light and frequently undergo a diurnal change in direction as a
result of the daily heating and cooling cycle of the mountain slopes and chan-
neling by the local topography. Early morning winds are usually from the
southeast quadrant; during the day the winds become northwesterly. Tucson has
no heavy industry and is supported primarily by tourism, agriculture and gov-
ernment services. Copper mining and refining is extensive, but is removed
from the immediate metropolitan area.
The air quality data reviewed in this section come from two sources.
The first, a report by the University of Arizona (Moyers et al2), contains
averages of 24-hour concentrations measured at 11 sites from September 1975
to October 1976 under a program sponsored by the Electric Power Research
Institute (EPRI). The second is the National Aerometric Data Bank (NADB)
which provides 1977 annual geometric means and individual 24-hour observations.
The monitoring network used in obtaining the two sets of data is shown in
Figure 18 and described in Table 9. The EPRI network comprised the sites
numbered from 1 through 11, as designated in the report; the NADB network
comprised all sites from 1 through 16 except for the remote site at the
Research Ranch (Site 11). Note that the monitor at Sites 10 and 14 are at
heights of 47 and 80 feet respectively, while the remaining heights range
from 6 to 25 feet.
43
-------
4
115
'16
CORONA DE TUCSON
GREEN VALLEY
5
km
mi
10
20
i
10
RESEARCH
RANCH
Figure 18. TSP monitoring network in Tucson and vicinity.
44
-------
TABLE 9. SITE LOCATION DESCRIPTIONS FOR TUCSON MONITORS
Designator Site address
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
7920 E. Tanque Verde
7901 E. Scarlett
Route 7 (Corona
De Tucson)
Davis Mountain Air
Force Base
245 West Esperanza
(Green Valley)
1810 S 6th Ave.
(S. Tucson)
1970 W Ajo Rd.
1019 Prince Rd.
Magee Rd.
Florence Highway
University of Arizona,
2nd and Palm
Research Ranch
Orge Gr Rd. and
El Camino De Terra
(Tucson)
3915 E Ft. Lowell Rd.
151 W Congress
2400 Harrison Rd.
Nogales Highway and
Hughes Access Rd .
Height of
monitor
Site type (ft)
Suburban/residential
Suburban/residential
Remote
Suburban/ indus tr ial
Suburban/ commer c ia 1
Center City/commercial
Suburban/ res id ent ial
Center City/commercial
Rural/near urban
Center City/commercial
Remote
Suburban/residential
Suburban/ commer c ial
Center City/commercial
Suburban/residential
Rural/near urban
16
18
13
14
13
18
18
25
6
47
6
15
80
6
6
45
-------
Figure 19 displays the 1977 annual geometric means on the site map. Two
features of the spatial distribution are of special interest. The first is a
progressive increase in mean concentration as the urban core is approached;
the second is the large variation in concentration observed within the urban
core itself. A significant part of the latter variation appears to be related
to differences in the height of the monitors. In particular, the low concen-
trations that appear to be nonrepresentative of the urban core at Sites 10
and 14 are quite likely due to the greater measurement heights at those loca-
tions. Reports reviewed for this study do not contain sufficient siting
information to speculate upon the reasons for other large differences between
proximate monitors (Sites 1, 2, and 15, for example).
Some comment should be made, however, on the difference in concentration
observed at Sites 3 and 5, located more than 40 kilometers from the center of
Tucson. Site 3 is located in a retirement community with a population of
about 1,000 and no through traffic. Site 5 is in a somewhat larger retirement
community (population of about 5,000) located on an interstate highway with
moderate amounts of through traffic. There are also two large copper mines
within five miles to the north.
Figure 20 is a plot of annual concentration versus distance from Site 14
in downtown Tucson. The EPRI data are represented by open circles and the
NADB data by filled circles. Sites 10 and 14 have been omitted from the
figure. If, as suspected, the relatively high concentration at a distance of
52 km is due to the impact of local sources, then the figure suggests that
background levels are reached within 40 km of the center of Tucson.
Averaging mean concentrations for similar site types provides the follow-
ing relationships: background concentration, (Sites 3 and 11), 26 yg/m3;
rural/near urban, (Sites 9 and 16), 61 yg/m3; suburban/residential (Sites 12,
1, 15, and 7), 72 yg/m3; suburban/industrial, (Site 4), 76 yg/m3; and center
city/commercial (Sites 6, 8, and 13), 133 yg/m3. In calculating these aver-
ages, Sites 10 and 14 were omitted because of their greater monitoring heights,
Site 2 was omitted because data were available only from Januray through July,
Site 13 was considered to be center city rather than suburban because of its
proximity to Sites 8 and 10 both of which were classed as center city in the
NADB, and Site 5 was omitted because it was considered to be a special situa-
tion outside of the urban influence of Tucson, but with local source impact.
Except for the inclusion of Site 11 data, the averages were calculated from
1977 NADB concentrations.
Examination of the 24-hour observations for 1977 shows that the secondary
standard of 150 yg/m3 was exceeded at one or more of the sites on 39 of the 61
sampling days; Table 10 lists the concentrations at all of the sites on these
39 days. The sites have been arranged in the table so that the number of
exceedances per site (and degree of urbanization) decreases from left to right.
Site 13, at the left of the table, experienced the greatest number of exceed-
ances by far. There were, in fact, only two days out of the 39 when the con-
centration at 'Site 13 was observed to be below the standard; on the two other
days, concentration was not reported. Furthermore, on 19 of the days when
the concentration exceeded the standard at Site 13, all other reported values
throughout the monitoring network were below the standard. Clearly, a local
46
-------
76
(63)
50
CORONA DE TUCSON
(23)
GREEN VALLEY
o
kini
mi o
10
20
5
10
29
RESEARCH-
RANCH
(9/75-1
10/76)
Figure 19. Annual geometric mean TSP concentrations (yg/m3) in
and around Tucson in 1977. Values in parentheses are
derived from incomplete record.
47
-------
160
140
o 1977 GM (NADB)
( ) INCOMPLETE RECORD
O EPRI STUDY AVERAGE
120
O
*> '00
o
I-
ir
t-
z
UJ
o
z
o
o
Q.
H
80
. O
60
40
20
20 40 60 80
DISTANCE FROM URBAN CORE, km
100
120
Figure 20. Average TSP concentration versus distance from
the urban core. (Site 14, Tucson).
48
-------
TABLE 10. TSP CONCENTRATIONS IN TUCSON AND VICINITY ON DAYS WHEN THE
SECONDARY STANDARD WAS EXCEEDED IN 1977
Site
Date
13
8
6
9
12
2
7
4
Concentration
01/13/77
01/19/77
02/06/77
02/12/77
02/18/77
02/24/77
03/02/77
03/08/77
03/14/77
03/20/77
04/01/77
04/07/77
04/13/66
04/25/77
05/07/77
05/13/77
05/19/77
05/25/77
05/31/77
06/18/77
06/24/77
06/30/77
07/06/77
07/12/77
182a
239a
250a
28 3a
301a
-
225a
227a
204a
179a
174a
202a
189a
191a
157a
-
186a
177a
170a
231a
161a
169a
158a
117
122
144
143
257a
211a
204a
156a
155a
146
133
76
129
98
111
93
124
-
108
112
132
126
108
97
123
101
103
111
206a
168a
2233
136
141
135
98
66
104
140
80
92
160a
124
112
117
132
120
110
91
154a
39
57
55
82
108
111
-
113
92
99
39
114
89
71
81
191a
104
98
109
68
124
105
86
77
66
-
-
-
152a
2153
112
177a
103
89
52
89
76
79
87
-
84
72
103
115
96
124
76
129
127
135
110
-
154a
1853
123
89
117
-
90
88
93
92
121
210a
98
86
96
100
75
116
-
71
47
79
171a
122
113
122
104
113
95
119
39
65
85
58
65
64
73
65
105
77
67
77
71
107
75
74
71
102
99
I82a
116
96
111
62
58
69
88
76
49
74
83
57
68
66
74
72
61
147
14
(Ug/m3)
67
69
69
108
109
135
109
114
110
66
38
63
74
64
54
82
75
58
82
72
83
77
63
92
1
65
-
89
93
130
60
101
115
85
70
47
84
90
53
58
87
83
67
72
93
73
85
75
63
16
41
62
52
66
69
95
85
107
80
59
33
52
48
53
48
88
55
43
70
61
59
63
-
-
10
65
83
69
111
124
89
99
113
101
78
52
81
77
86
51
115
71
65
83
82
83
85
80
65
15
-
-
-
-
-
121
110
58
85
73
48
64
64
46
68
102
69
66
86
84
70
74
61
55
5
56
66
62
90
72
73
119
78
92
59
50
56
44
57
43
66
59
58
81
75
12
88
57
47
3
-
-
-
-
-
-
-
-
-
-
23
28
24
30
24
40
35
25
41
43
40
38
-
3.1
No. >
150 ug/m3
1
1
2
3
5
5
2
3
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
1
(continued)
-------
TABLE 10 (continued)
Ul
o
Site
Date
13
8
6
9
12
2 7
4
Concentration
08/05/77
08/29/77
09/28/77
10/04/77
10/16/77
10/22/77
10/28/77
11/03/77
11/15/77
11/21/77
11/27/77
12/03/77
12/09/77
12/15/77
12/21/77
No. >
150 yg/m3
179a
161a
191a
160a
102
216a
202s
19la
2613
2793
1833
222a
413a
322a
204a
35
108
153a
118
100
208a
-
198a
204a
177a
175a
1703
247a
331a
228a
209a
16
110
-
84
87
119
131
-
-
407&
159a
177a
305a
661a
352a
624a
12
61
110
119
162a
81
86
131
184a
119
145
56
107
2903
158a
189a
6
88
-
82
67
85
93
132
90
-
Ill
102
149
1923
133
196a
5
63
73
50
60
-
70
91
84
84
83
147
119
112
121
- 5913
3 2
74
93
-
-
75
84
80
107
112
114
55
70
149
109
308a
2
14
(Pg/m3)
68
82
62
54
79
75
-
86
96
102
73
17
141
86
223a
1
1
-
-
76
52
67
-
78
100
35
104.
_
-
1783
130
117
1
16
63
50
44
39
61
52
64
47
75
58
38
63
81
51
261a
1
10 15
72 67
89 64
72
-
61
92
61
_
79
91
64
90
99
107
66
0 0
5
64
71
51
41
58
62
75
78
96
-
46
63
120
143
214a
1
3
27
29
26
14
42
28
13
20
32
27
17
20
23
22
84
0
No. >
150 ug/m3
1
2
1
2
1
1
2
3
3
3
3
3
6
4
10
85
Concentrations greater than the secondary standard.
-------
problem exists at this site. Note also that the two sites with the next
highest number of exceedances, (16 and 12, respectively) are city center
sites No. 8 and No. 6.
Table 11 contains wind speed and direction data for the four days with
the greatest number of exceedances. The day with the most widespread problem
was December 21, 1977, when 10 of the 13 sites reporting exceeded the stan-
dard. The sustained high winds observed throughout the day suggest that this
is a classic case of wind-generated fugitive dust (see Section 3, p. 27).
Winds were from the southeast and exceeded 20 mph for much of the day; the
highest wind speed reported at the airport was 42 mph. Based on afternoon
and evening wind speeds, it is also likely that wind-generated dust contri-
buted heavily to the high levels observed on February 24, 1977; of the 61
sampling days, February 24th experienced the second highest average wind
speed (13.5 mph). On the other hand, airport wind speeds suggest that wind-
generated dust was probably not a major factor on either February 18, 1977,
or December 9, 1977. On December 9th, two concentrations in excess of
400 yg/m3 were observed but the highest wind speed was only 13 mph and the
wind speed for the day averaged only 6.5 mph.
TABLE 11. WIND CONDITIONS ON DAYS WITH THE GREATEST NUMBER
OF VIOLATIONS IN TUCSON
No. > Hour
150 ug/m3 Date (MST)
5 02/18/77 02
05
08
11
14
17
20
23
5 02/24/77 02
05
08
11
14
17
20
23
6 12/09/77 02
05
08
11
14
17
20
23
10 12/21/77 02
05
08
11
14
17
20
23
Wind
direction
(deg)
140
140
140
160
320
360
250
160
160
140
00
320
250
220
240
300
140
140
140
150
00
40
160
140
130
120
120
120
110
120
120
120
Fastest mile
LM nH ^
winu ^^^^^^^^^^^^^^^^^
speed Speed
(knots) (mph) lrecti°n
7 14 SE
10
9
3
5
6
5
6
6 34 SW
6
0
8
20
25
15
14
8 13 S
9
8
5
0
4
5
6
25 42 SE
16
23
23
18
16
16
13
Average
speed
9.4
13.5
6.5
21.6
Notes: 1 knot - 1.15 mph - 0.515 m/sec
Wind speed tabulated under "fastest mile" is a measure of the max-
imum wind speed during the 24-hr period. It Is calculated from
the length of time required for one mile of wind to pass the anemo-
meter. The direction tabulated under "fastest mile" is the direc-
tion measured during this period.
-------
PARTICULATE LEVELS IN AND AROUND PHOENIX
Phoenix is located on the broad, nearly flat plain of the Salt River Valley.
The Salt River runs from east to west through the valley, but is almost always
dry. Mountains rise in nearly every direction, the closest being the South
Mountains to the south and the larger Phoenix Mountain Range to the north and
northeast. The metropolitan area of Phoenix, with a population of over one >
million, is the largest of the four urban areas studied. In addition to the
city of Phoenix, it includes the cities of Scottsdale, Tempe and Mesa to the
east, and Glendale to the northwest. In 1977 these cities had the following
populations: Phoenix - 684,516; Scottsdale - 81,458; Tempe - 98,146; Mesa -
110,079; and Glendale - 73,730.36 The unincorporated area of Sun City lies
farther to the northwest, roughly 10 miles beyond Glendale. The centralized
urban area is surrounded by pockets of urban development, particularly in the
extensive agricultural areas to the west and southeast. These include Avondale,
Goodyear, Litchfield Park, Tolleson and Cashion to the west, and Chandler and
Mesa to the southeast. Manufacturing and tourism also contribute substantially
to the economy of the area.
The climate is desert-like with low annual rainfall (about 7 inches),
high summertime daytime temperatures, and low humidity. Rainfall is centered
on two seasons of the year. The first is from November to March when occa-
sional storms from the Pacific reach the area, and the second is during July
and August when Arizona is subjected to widespread thunderstorm activity.
May and June are the driest months and frequently experience no significant
precipitation. The valley floor is rather free of wind. During the spring
months southwest and west winds associated with the passage of low pressure
troughs predominate. During the thunderstorms season local gusty winds often
occur, usually from an easterly direction. Because of the topography and pre- .
dominance of weak pressure gradients, mountain-valley wind circulations are
common. Typically, downslope east-to-west flow is established about 8 p.m.
and lasts until early morning; the flow reverses about noon and lasts until
after sunset.
The principal basis for the following discussion is Volume I of the series
of four support documents prepared for EPA by TRW Environmental Engineering
Division entitled "An Implementation Plan for Suspended Particulate Matter in
the Phoenix Area."1 The air quality data analyzed in this document came from
17 monitoring sites operating throughout all or part of 1973 through 1975.
Figure 21 locates these sites with respect to the center of Phoenix, and Table
12 provides site type and additional location data.
The duration of the sampling periods at the various sites was inconsis-
tent. However, TRW used the available distributions to calculate the annual
geometric means and maximum 24-hour concentrations that would have been expec-
ted under a 60-sample per year measurement program. This was usually done by
fitting a log-normal distribution to the data; in three cases the actual dis-
tribution appeared to seriously over predict concentrations at the high end,
and an adjustment to the log-normal fit was made. Comparison of expected with
actual concentrations showed good agreement in the case of annual means; the ex-
pected maximal 24-hour values were generally higher than measured maximal val-
ues, however. This would be expected for those cases where fewer than 60
52
-------
Carefrte Alrocrt
Ul
CO
Paradise Valley north Sefltt«d«l*/P«r«iHM v«n»v
l St..Johns
Figure 21. Hi-vol monitoring sites within the Phoenix area (TRW).x
-------
TABLE 12. SITE LOCATION DESCRIPTIONS FOR PHOENIX MONITORS
Ul
Site
designator
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Site
St. Johns
Litchfield Park
Sun City
Glendale
West Phoenix
North Phoenix
Paradise
North Scottsdale/
Paradise Valley
Carefree
Scottsdale
South Phoenix
Guadalupe
Chandler
Mesa
Downtown Phoenix
Arizona State
Central Phoenix
Site type
Rural/residential
(Indian Reservation)
Suburban/residential
(growth in progress)
Suburban/residential
Suburban-rural/
Residential-Agri-
cultural
Suburban/residential
Suburban/residential
Suburban/residential
(development)
Rural/residential-
commercial
Remote
Suburban/ residential
Urban/residential-
commercial
Rural/residential
Suburban/residential
Suburban/residential-
commercial
Urban/ commercial
Suburban/residential
Urban/residential
Representativeness
Site specific
Site specific
Area wide
Area wide
Area wide
Area wide
Site specific
Area wide
Area wide
Area wide
-
Area wide
Area wide
Area wide
Site specific
Site specific
Area wide
Area wide
Monitor
height
(ft)
15
10
25
20
5
5
5
5
5
15
36
5
21
5
23
15
22
-------
observations were made per year. In part, the differences may be due to a
failure of the log-normal distribution to properly fit actual TSP data at the
high concentration end of the distribution.
The expected annual geometric means and expected maximal 24-hour TSP con-
centrations are shown on site maps in Figures 22 and 23, respectively. TRW
concluded that the lack of a consistent spatial pattern in both figures was due
to the influence of local fugitive dust sources and hence related to the site
environment. For example, sites in rural/residential areas are frequently
surrounded by numerous vacant fields and unpaved roads. Also, construction
activities, frequent in such areas, disturb the soil surface, making it sus-
ceptible to suspension by wind. Other rural/residential sites were surrounded
by improved property lacking obvious fugitive dust sources.
Table 13 presents average concentrations for the site categories developed
by TRW. Data for the individual sites within each category can be found in
Table 5-1 of the TRW report. Because of the influence of fugitive dust, it is
very likely that monitor height is a complicating factor. Note in Table 12
that height ranges from 5 to 36 feet above the ground. No attempt was made
to factor in monitor height in preparing Table 13, however. Although the
highest annual average concentration occurs in the central city/residential-
commercial environment, the highest 24-hour concentrations occur outside the
city in rural/residential environments surrounded by fugitive dust sources.
Closer examination of the data reveal that meteorological conditions and
the ambient particulate distributions associated with high TSP concentrations
fall into two patterns. One is primarily a wintertime phenomenon characterized
by low wind speeds and low mixing heights. Under these conditions, high con-
centration centers around the city monitoring sites and often at Paradise
Valley. Concentrations also increase at other stations throughout the region,
although to a lesser degree. The other pattern occurs most frequently from
March to August during periods with strong wind gusts from the southeast or
west and above average wind speeds during the day. Under these circumstances,
concentrations are highest at the rural and suburban residential sites. These
responses of the particulate field to meteorological conditions support the
following two-part hypothesis put forth by TRW:
1. "Human activity, which is most densely focused in the
city area, is responsible for suspension of substan-
tial fugitive emissions. These emissions are of higher
density than those released at the rural sites and this
is reflected by the higher concentrations produced dur-
the stable atmospheric conditions of winter."
2. "Because vast expanses of agricultural land, unpaved
roads, and unimproved (but disturbed) soil surfaces
surround the rural sites, suspension of dust by soil
wind erosion is very likely a dominant factor affect-
ing high particulate levels during gusty winds in the
rural areas. Soil erosion by wind is of less conse-
quence in the more developed areas."
55
-------
41) Cartfr** Airport
t_n
Paradise Valley
9?
[143JNorth Scottsdale/Paradlse Valley
U.Srg
>tesa U.S.-60. U.S.-80
(124)
U.S.- 89
indltr
Figure 22. Expected annual geometric means in ug/m3 (TRW).1
-------
69) Carefree Airport
Ul
528)North Scottsdale/Paradise Valley
State \~/|Downtown Phoenix
Figure 23. Expected maximal 24-hour concentrations in pg/m3 (TRW).1
-------
TABLE 13. AVERAGE TSP CONCENTRATIONS FOR SIX SITE ENVIRONMENTS (AFTER TRW) x
Ul
oo
Site environment category
Central City/Residential-Commercial
(Surrounded by fugitive dust sources)
Central City/Residential
(No sources)
Rural/Residential
(Surrounded by fugitive dust sources)
Suburban/Residential
(Surrounded by fugitive dust sources)
Rural/Residential
(No sources)
Remote
Expected
annual
geometric
mean
Sites (ug/m3)
11, 15 184
5, 16, 17 168
1, 7, 8, 12 160
6, 13, 14 129
3, 4, 10 97
9 41
Expected
maximal
24 -hour
level
(pg/m3)
438
487
638
362
250
169
Observed
maximal
24 -hour
level ,
1973-1975
(Ug/m3)
481
436
1099
380
256
277
-------
The relationships between wind speed and concentration leading to the two par-
ticulate patterns are illustrated qualitatively in Figure 24. Human-activity-
related emissions result in high concentrations when dilution is minimal as a
result of light winds; in contrast, the contribution from wind erosion is
insignificant during light winds, but can be of overiding importance in areas
with disturbed soil surfaces when wind speeds are high.
c
o
in
in
O
O)
Suspension by Wind
Suspension by Human Activity
Wind Speed
c
o
re
i-
»-»
C
01
o
c
_o
Dust Storm
Resultant
Concentration
ontribution
from
Human Activi
Contribution
from
Wind Erosion
Wind speed
Figure 24. Effect of wind speed on ambient suspended particulate
levels (TRW).:
59
-------
SECTION 5
URBAN PARTICULATES: CHARACTERISTICS AND SOURCES
This final section discusses the characteristics and sources of urban
particulates in the Southwest, focusing on the contribution of wind-blown desert
dust. It begins with a summary of particle size measurements that emphasizes
the inhalable size fraction. Next, the discussion turns to the sources of par-
ticulates in several urban areas including Phoenix and Tucson, Arizona, and Las
Vegas and Reno, Nevada. The section concludes with a brief review of the con-
tribution of wind-blown desert dust to high TSP levels in Colorado, Utah,
Western Arizona, Texas and New Mexico.
PARTICLE SIZE DISTRIBUTIONS
Particle size distribution data from the reviewed reports have been
assembled in this section in an attempt to estimate the impact of dust from
desert areas on levels of inhalable particulates in urban areas. The data
are very limited and unfortunately are somewhat contradictory. The most use-
ful data appear to be those obtained in Phoenix in 1975 (IITRI).8
In the Phoenix study, particle size information was acquired by three
techniques: (1) the use of fractionating samplers, (2) sizing by microscopy,
and (3) the use of dichotomous samplers. Data were obtained on five sampling
days at several heights and at upwind, downwind, and centrally located sites.
Table 14, derived from material presented in the TRW report3 but based on the
IITRI study, presents cross-city averages for heights of 3, 10, and 30 meters
for two wind speed conditions. These concentrations were measured by Andersen
samplers. Two features of data are of interest. First, on the day with a
wind speed of 4 m/sec the total concentration decreases only slightly with
height, while on the very light wind or calm days the concentration at 30 meters
has dropped to about half of the value at 3 meters. This drop is also accom-
panied by a decrease in the proportion of particles greater than 15 ym. Second,
the percentage of the particulates that are inhalable (defined as less than
15 ym in aerodynamic diameter) is higher on the light wind days than on
November 18th. The average values for the 3-m and 10-m heights, for example,
are 44 percent inhalable on November 18th, and 59 percent inhalable on the
other three days. These results agree qualitatively with expectations since
mixing is enhanced by increasing wind speed and the principal sources of the
larger particles subject to gravitational setting are at ground level.
Particle size analysis of hi-vol filters from three heights were also
carried out by IITRI by microscopy. Table 15, taken directly from Volume 3
of the TRW report,3 shows the results for one windy day (average wind speed
of 4.4 m/sec) and one calm day. Over this smaller height interval, no
60
-------
TABLE 14. HEIGHT VARIATION OF PARTICIPATE
CONCENTRATIONS FROM ANDERSEN
SAMPLER DATA (TRW,3 IITRI8')
November 18,
wind = 4 ra/sec
November 17, 21, 25,
wind = 1 m/sec
Height
above Total Total
ground concentration Percent concentration Percent
(m) (yg/m3) <15 ym (yg/m3) <15 ym
3
10
30
112
107
105
46
42
38
149
90
79
52
66
66
Note: Data from five sites were used to compile these
averages.
TABLE 15. PARTICLE SIZE DISTRIBUTION FOR
SUSPENDED PARTICULATES MEASURED
IN PHOENIX, SEPTEMBER 27 AND
NOVEMBER 14, 1975 (TRW3)
Percent of particles
(by weight) in size range
2 ym 2-8 ym 8-20 ym >20 ym
September 27 (windy)
Monitors
Monitors
Monitors
November
Monitors
Monitors
Monitors
at
at
at
14
at
at
at
20
15
5
feet
feet
feet
.07
.06
.05
2
2
2
.8
.2
.0
32
33
28
.2
.0
.3
65
64
69
.0
.6
.7
(calm)
20
15
5
feet
feet
feet
.14
.14
.13
2
2
2
.8
.5
.7
32
29
34
.4
.5
.9
64
67
62
.7
.9
.6
61
-------
significant differences were found in the particle size distributions with
either height or wind speed. On both occasions, approximately 65 percent of
the particulates were greater than 20 ym in diameter. If, as a rough approxi-
mation, half of the particulates in the 8-20 pm size range were less than
15 ym, only 18 percent of the particulates found on these filters would have
been classed as inhalable. Note that optical micorscopy generally does not
account for particles smaller than about 1-2 ym; consequently, this technique
may severly underestimate the percent of particulates that are inhalable.
The third summary prepared from the IITRI data, Table 16, compares results
obtained from dichotomous samplers with results obtained by the microscopic
analysis of hi-vol filters. The data for each day listed in Table 16 are
average values from all available measurements; however, only 11 pairs of
dichotomous sampler hi-vol observations from the same location (site and
height) are contained in the data set. Table 17 lists the concentrations from
the collocated samplers. The average concentrations measured by the two devices
on these 11 occasions were almost identical: 232 yg/m3 by dichotomous sampler
and 228 yg/m3 by hi-vol. There were some very large discrepancies, however,
but no consistent bias. Linear correlation between the two sets of data,
shown in Table 17, results in a correlation coefficient of + 0.66, which is
significant at the 5 percent level.
TABLE 16. PARTICLE SIZE INFORMATION FROM PHOENIX SAMPLING PROGRAM
(IITRI8)
Dichotomous sampler
High-volume sampler*
Number
of
Date samples
Number
of
<3.5 ym >3.5 ym samples
<5 ym 5-15 ym >15 ym
(Mass Percent)
11/17/75
11/18/75
11/21/75
11/23-24/75
11/25/75
Average
5
6
4
5
5
-
35
28
32
45
32
34
65
72
68
55
68
66
5
4
6
6
6
-
11
5
17
15
13
12
42
35
41
52
45
43
47
60
42
33
42
45
* Estimated by optical microscopy.
62
-------
TABLE 17. TSP CONCENTRATIONS MEASURED BY HI-VOLS AND DICHOTOMOUS
SAMPLERS
Concentration, yg/m3
Concentration, yg/m3
Dichotomous
Date sampler
11/17/75
11/17/75
11/18/75
11/18/75
11/18/75
11/21/75
253
210
460
136
499
149
Hi-vol
221
206
441
287
257
108
Dichotomous
Date sampler
11/21/75
11/23-24/75
11/23-24/75
11/25/75
11/25/75
Average
250
122
106
170
197
232
Hi-vol
315
142
116
258
157
228
Although a direct comparison between the results obtained by the two
techniques, is impossible, it is instructive to note that the percent found
to be less than 5 ym by microscopy is consistently much less than the percent
found to be less than 3.5 ym by use of the dichotomous sampler. Also note
that microscopy indicates that, on average, 55 percent (12 plus 43) of the
particulates are inhalable.
A small amount of information is available from the PEDCo study of Las
Vegas and Reno. In this report results are presented for three sites in or
near each city where size distributions were determined by microscopy. When
averaged within each city, 30 percent by weight of the particulates were found
to be less than 15 ym. In this analysis, the particles collected on sections
of the glass-fiber, hi-vol filters were resuspended in distilled water with the
use of an ultrasonic bath and refiltered onto a membrane filter prior to sizing.
In IITRI's analysis, particles were counted as collected on the filter through
the use of immersion oil.
The data summarized above are too limited and the estimates cover too
broad a range to be of much help in defining inhalable particulate levels
within the urban areas. Further, no information was found on the proportion
of incoming particulates that is less than 15 ym. Thus, it appears that a
comprehensive measurement program will be required before the impact of dust
from desert areas on the levels of inhalable particulates within the cities
can be reliably ascertained.
PARTICULATE SOURCES
Phoenix
Several studies of Phoenix reviewed for this report examined the contri-
bution of wind-blown dust from the desert to high levels of TSP in urban loca-
tions. Two of these studies concluded that high particulate levels should not
be attributed to wind-blown dust from the undisturbed desert region surrounding
63
-------
Phoenix and its suburbs. Instead they implicated anthropogenic sources as the
prime contributors to the TSP problem. Several of the other studies present
evidence that supports this conclusion.
The first two studies relied on different techniques to reach very similar
conclusions. IITRI's Aerosol Sampling and Analysis8 used several analytical
techniques to characterize Phoenix particulates including mass flux determina-
tions, particle size and morphological analysis, and elemental analysis. The
second report, Dust Transport in Maricopa County,7 relied exclusively on the
emissions inventory/modeling approach.
The purpose of the IITRI study was to determine whether high TSP levels
in Phoenix are due to human activities within the Phoenix area or to long-range
transport from the surrounding desert. To answer this question, authors of
the study designed a sampling program to collect and measure aerosols both
upwind and downwind of Phoenix. This sampling program took into account the
typical diurnal pattern of wind direction in Phoenix: day wind from the west,
night wind from the east. Microscopic and elemental analysis was used to
determine the physical and chemical characteristics of the particulate samples
collected.
The study found that the sizes and morphologies of the majority of mineral
particles found in the Phoenix samples were not typical of wind-eroded materials.
Instead of being frosted, indicating tumbling and collision with finer parti-
cles, particle surfaces tended to be scratched with fine particles embedded
suggesting mechanical wear. In addition, TSP concentrations were not signifi-
cantly higher in a day when the wind-speed increased to 5 m/sec compared to
other sampling days when wind speeds averaged 1 m/sec. The report concluded
that "wind is not the primary source for suspension of particles" and "long-
range transport of aerosols by winds from the surrounding deserts is only a
minor source for suspended particulates."
The report went on to state that "vehicular traffic, especially on unpaved
roads is the primary generator of suspended particles." According to the
authors, the appearance of smooth-surfaced, worm-shaped, rubber tire particles,
fine carbonaceous particles, and sharp, angular mineral fragments indicate
vehicle travel over paved roadways while torn, rough-surfaced rubber tire par-
ticles and fine carbonaceous particles, together with rounded clay coated
minerals indicated vehicle travel over unpaved roads and shoulders.
The report cautions that agricultural activity could also produce the
round, clay-coated mineral fragments attributed to vehicle travel over unpaved
roads. The authors felt, however, that the relative absence of plant or fer-
tilizer materials in the samples suggested that agricultural activity generated
less suspended particulate matter than vehicular traffic.
The second report, Dust Transport in Maricopa County, Arizona relies on
a behavioral model of suspended particulate dynamics to analyze the contribu-
tion of dust, including wind-blown desert dust, to high urban particulate
levels in and around Phoenix. Three major categories of dust emissions were
considered: (1) traffic dust from unpaved roadways and off-roadway vehicle
64
-------
emissions, (2) "diurnal dust" - windblown desert dust and agricultural and
construction emissions and (3) "constant dust" consisting of tailing piles,
cattle feed lots, and vacant soil emissions. The analysis is limited to the
late fall, a period characterized by fairly light winds, when - according to
the study - high ambient particulate concentrations are usually observed.
The report concluded that: "observed high particulate concentrations in
Maricopa County urban areas during late fall and winter periods of atmospheric
stability are associated with local fugitive dust sources. Because of light
drainage winds prevalent during these periods, advective transport of dust
from countryside to the urban areas is not an important contribution to urban
supermicrometric particulate concentrations,"
Several other studies also examined TSP nonattainment in the Phoenix
metropolitan area. TRW Environmental Engineering Division produced a study
for EPA that focused on the development of control strategies for total sus-
pended particulates in the Phoenix area. As part of this study, TRW developed
an emission inventory37 that included estimates of emissions from wind-blown
desert dust, then used this inventory to model air quality in the Phoenix area.
The TRW study relied on both the Climatological Dispersion Model (COM)
and the Linear Rollback model (LR) to simulate the relationship between emis-
sions and ambient air quality in the Phoenix area. The study assumed that
particulates smaller than 20 pm aerodynamic diameter could be adequately
modeled with the COM model, and those greater than 20 ym could be adequately
treated in the context of the LR modeling concept. Particle size distributions
for emissions were estimated from a number of different sources.
The model predicts that nearly all the TSP level (excluding background)
at 12 of the 13 sites monitoring in 1975 was caused by emissions from unpaved
roads, entrained street dust, construction activities, or wind erosion. Wind-
erosion includes emissions from agricultural fields, unpaved roads, undisturbed
desert, tailings piles, and vacant lots. Table 18 indicates that undisturbed
desert and disturbed soil are by far the largest sources of these emissions -
roughly equal in magnitude. At the Sun City site however off-road vehicles
were responsible for most of the TSP levels. Table 19 indicates the relative
importance of these four types of sources at each of the 13 sites; in all but
a few cases, the contribution of wind-erosion is modest relative to the contri-
bution from unpaved roads and entrained street dust. "Monitors which were
most dramatically affected by wind-erosion emissions tended to be located in
the rural areas under development, such as the Paradise Valley and North Scotts-
dale/Paradise Valley sites. (Figure 21 indicates the location of the 13 moni-
toring sites while Table 12 provides a brief description of the site environ-
ments.) Unfortunately, the impacts of the various classes of wind-erosion
emissions on TSP levels were not disaggregated in the report.
Figures 25 through 28 display 1975 emissions from the four major sources.
Although these figures provide a vivid picture of the spatial distribution of
emissions, the reader is cautioned not to use them to compare emissions from
different types of sources since all the figures use slightly different scales
to measure emission magnitudes. These figures show that emissions from all
four sources, even wind erosion, are much greater in the more urbanized portion
of the study area. In Figure 28, wind erosion emissions include those from
65
-------
agricultural fields, unpaved roads, undisturbed desert, tailings piles, and
disturbed soil. (The monitors roughly define the urbanized portion of the
study area; Figure 21 shows the location of each monitor.)
TABLE 18. 1975 TOTAL PARTICULATE EMISSION INVENTORY FOR PHOENIX STUDY
AREA (TONS/DAY) (AFTER TRW3)
Source category
Stationary Sources
Area Sources
Mobile Sources
Aircraft
Agricultural Tilling
Venicles on Unpaved Roads
Aggregate Piles
Cattle Feed Lots
Off-Road Vehicles
Construction
Paved Streets
Wind Blown Agriculture
Wind Blown Unpaved Roads
Wind Blown Undisturbed Desert
Wind Blown Disturbed Soil
Tailing Piles
Total
1st
quarter
22
1.4
11
.4
22
1281
.10
6
71
100
248
4.1
1.4
160
161
1.4
2091
2nd
quarter
22
1.4
11
.4
30
1365
.10
6
71
100
248
4.0
2.1
244
248
1.4
2354
1975
3rd
quarter
22
1.4
11
.4
1
1365
.10
6
71
100
248
3.8
2.7
321
323
1.4
2478
4th
quarter
22
1.4
11
.4
17
1086
.10
6
71
100
248
4.0
3.8
450
456
1.4
2478
Annual
average
22
1.4
11
.4
20
1281
.10
6
71
100
248
4.0
2.5
294
297
1.4
2360
66
-------
TABLE 19. IMPACT OF MAJOR SOURCES ON TSP LEVELS (AFTER TRW3)
Contribution of
major
Monitor site
Central Phoenix
South Phoenix
Arizona State
Glendale
North Phoenix
North Scottsdale/Paradise Valley
Scottsdale
Mesa
Downtown
St. Johns
Sun City
Paradise Valley
Chandler
TSP
in 1975
112
144
169
101
121
. 149
115
117
200
145
88
184
119
Unpaved
roads
25
75
35
30
26
24
27
32
42
93
15
42
64
suspended particulates from four
sources (vg/m3)
Entrained
dust
31
20
59
17
28
8
33
35
70
2
12
14
10
Construction
activities
4
2
7
7
7
14
6
8
8
0
3
17
7
Wind
erosion
19
15
33
15
28
71
16
10
40
18
2
78
5
Percentage of TSP
level contributed
from four major
sources & background
96.3
98.2
96.4
97.2
97.8
98.3
96.5
97.7
94.1
98.3
55.2
98.1
96.6
-------
Figure 25. Average daily dust emissions from unpaved roads, 1975. (TRW37)
-------
Figure 26. Average daily street dust emissions entrained by motor vehicles on paved streets, 1975. (TRW37)
-------
Figure 27, Average dally dust emissions from construction activities, 1975. (.TRW37)
-------
X, o
o
o
Figure 28. Emissions of fugitive dust arising from wind erosion, average daily emissions, 1975. (TRW37)
-------
Figures 29 and 30 depict emissions from the two most significant wind-
erosion sources: disturbed soil surfaces and undisturbed desert. Figure 29
illustrates that emissions from disturbed soil surfaces are highly concentrated
in the urban portion of the region. For these calculations, the vulnerable
soil surfaces were considered to be vacant lots, parking lots, and dirt resi-
dence yards. Emissions from the undisturbed desert, which are similar in aver-
age daily magnitude, are distributed over a much larger area to the north and
south of Phoenix.
PEDCo Environmental Inc. examined major sources of fugitive dust in the
Phoenix - Tucson AOCR, as well as in five other AQCR's in New Mexico, Arizona,
and California.1* Table 20 shows PEDCo's emission estimates for the Phoenix-
Tucson AOCR. In Maricopa County, where Phoenix is located, agriculture is by
far the largest source of emissions, followed by unpaved roads. The report does
not estimate emissions from paved roads or undisturbed desert.
PEDCors conclusion that wind-erosion from agricultural lands is the pri-
mary source of emissions in Maricopa County differs from the conclusions of
other studies examined for this report that unpaved roads are the principal
source of emissions. Although it is difficult to resolve this discrepancy,
the TRW report provides some evidence that might explain the magnitude of agri-
cultural emissions in the PEDCo study. TRW notes that PEDCo assumed that agri-
cultural soils experienced the same low moisture levels as native soils; they
conclude that neglecting the effect of irrigation on agricultural soil losses
has probably resulted in emissions estimates which were substantially over-
stated in the PEDCo inventory.
Tucson
A study done by the University of Arizona for the Electric Power Research
Institute (EPRI),2 discussed earlier, utilizes many techniques to examine
sources of particulates in the Tucson area. Some of these techniques, chemical/
elemental analysis and examination of spatial patterns for example, were used
in the studies of Phoenix discussed above. Others, such as enrichment factors,
inter-species correlations, and pattern recognition are used almost exclusively
by the Tucson study.
The evidence compiled in the study indicates that a great deal of the par-
ticulate matter in Tucson is soil. Table 21 shows that more than 50 percent
of the particulate matter was composed of soil at 9. of the 11 sites studied.
Site locations may be found in Figure 18 of Section 4. The contribution of
soil to particulate concentrations ranges from 82.7 percent at a suburban/
commercial site to 48.2 percent at Site 11, the "background" location. Examin-
ing all the sites, however, the report concluded that there appears to be per-
haps no significant differences in the relative amounts of soil-like material
in Tucson and the background location.
Since the soil is composed of many elements, it cannot be measured direc-
tly; the analysts had to rely on several indirect techniques to determine the
soil content of their particulate samples. They used correlation analysis to
discover which elements appeared to cluster together in each sample; they found
that the elements Al, Fe, Si, Ti, Li, Rb, K, Ca, Mg, Na, Mn, and Sr were corre-
lated with each other at both urban and background locations*. (Tables in the
original report list the inter-species correlation coefficients, r, for the
72
-------
Figure 29. Fugitive dust emissions arising from wind erosion of
disturbed soil surfaces, first quarter, daily average,
1975. (TRW37)
-*?
-------
Figure 30. Particulate fugitive emissions arising from wind erosion of undisturbed desert in Phoenix
, first quarter, daily average, 1975. (TRW37)
area
-------
TABLE 20. PHOENIX-TUCSON AQCR SUMMARY SHEET, ESTIMATED ANNUAL EMISSIONS FROM
FUGITIVE DUST SOURCES (PEDCo1*)
Aggregated Cattle County
Unpaved roads Agriculture Construction Tailings piles storage feedlots emission
Vehicle Emission Emission Acres Emission Emission 103 Emission 103 Emission Total,
County mi/day tons/yr Acres tons/yr per/yr tons/yr Acres tons/yr tons tons/yr head tons/yr tons/yr
Gila 13,266 1,300 - 1,785 30
9,200 50 - 5,430 90 - 14,770
Maricopa 121,758 408,500 3,775 - 552 235
82,200 175,000 62,440 - 1,590 250 321,470
Pima 45,530 50,700 1,440 2,680 212 13
34,910 8,900 24,160 9,430 540 20 77,960
Final 58,936 238,000 - 1,100 120 230
39,750 126,500 - 7,100 340 1,010 174,700
SCruz 9'258 1'400 - - 75 -
6,250 50 - - 220 - 6,520
AQCR
Activity
Total 249,104 699,900 5,215 5,565 989 451
AQCR
Emissions
Total 172,310 310,500 86,590 21,960 2,780 1,280 595,420
-------
TABLE 21. SOUTHERN ARIZONA ATMOSPHERIC PARTICULATE
MATTER, PERCENT COMPOSITION OF MAJOR
COMPONENTS AT EACH LOCATION (EPRI2)
Location Soil SO^ - NH^ NOa Pb Zn - Cu - Cd
1
2
3
4
5
6
7
8
9
10
11
81
52
61
60
82
65
57
49
54
61
48
.8
.8
.7
.9
.7
.2
.9
.6
.2
.4
.2
4
2
5
4
4
2
4
3
4
3
16
.1
.7
.9
.4
.2
.9
.1
.5
.1
.5
.4
2.
1.
2.
1.
1.
1.
2.
1.
1.
1.
2.
2
7
6
8
6
5
0
8
8
4
9
0
0
0
0
0
0
0
0
0
0
0
.74
.38
.10
.48
.32
.61
.58
.45
.28
.51
.08
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
38
15
30
26
33
26
30
22
18
55
47
background location as well as a "typical" urban site." Figures 31 and 32 use
cluster analysis, a form of pattern recognition, to display the information
conveyed by the correlation coefficients more vividly. The height of the lines
connecting elements is proportional to 1-r; thus short vertical lines designate
element pairs that are highly correlated, long lines, pairs that are more weak-
ly correlated.
The authors observe that the clustering of these elements suggests a com-
mon source (or type of source) for these species and that a likely source for
many of these elements would be soil material. To test this hypothesis they
examined the enrichment factors of each element. Enrichment factors, E, are
defined as:
Air Concentration of Element
E _ Air Concentration of Reference Element
Crustal Concentration of Element
Crustal Concentration of Reference Element
An enrichment factor of one indicates that the relative concentration of a
given element is the same in both air and soil, supporting the hypothesis that
soil is the primary source. An enrichment factor significantly greater than
one provides tentative evidence that another source besides soil is contribut-
ing the element to the atmosphere. In this study the authors use Al, the sec-
ond most abundant crustal element, as the reference element.
As Figure 33 shows, enrichment factors for Fe, Si, Ti, Li, Rb, K, Ca, Mg,
Na, Mn, and Sr are all close to one lending credibility to the hypothesis that
soil is the source of these elements. Unfortunately, this technique does not
76
-------
HIERARCHICAL CLUSTERING - LOCATION 2
NH^SC^CU CD ZN PB NO^ Nl CO CS CA K FE MG NA CR RB Tl AL SI SR LI MN MS
Figure 31. Dendogram of feature clustering for desert urban
particulate matter, (EPRI2)-
77
-------
HIERARCHICAL CLUSTERING - LOCATION 11
NH*SO^CU CD PB ZN NOj MG SR LI MN NA Nl CO CA AL FE RB SI Tl CR CS K MS
Figure 32. Dendogram of feature clustering for desert background
particulate matter, (EPRI2).
78
-------
Enrichment Factors
10-
Tucson
A Background
A
-1 f 1 1 1 T-
Mg Sr Fe Na Mn Cr Si K Co Ti Ni Rb Ca Li Cs Zn Cu SO; Tl Cd NO^ Bi In NH4 Pb
Figure 33. Enrichment factors for species in desert background
and urban particulate matter, (EPRI2).
79
-------
distinguish between wind-blown desert soil and soil material suspended as the
result of human activities such as travel on unpaved roads.
Urban-background concentration ratios shed some light on the possible
sources of soil-related particulate matter. As Table 22 shows, urban-background
ratios exceed one for all the soil-related elements at all urban and suburban
sites. These ratios typically are higher for the sites within Tucson, lower
for sites 3 and 5 which lie between Tucson and Research Ranch, the background
site. Although this evidence does not reveal specific urban sources, the
authors of the study conclude that it does implicate urban activity as an
important source of soil and other particulate matter in the Tucson area.
Las Vegas and Reno
In a report prepared for the U.S. Environmental Protection Agency,5 PEDCo
Environmental Inc. estimated emissions, including emissions from natural sur-
faces for both the Las Vegas and Reno areas. Tables 23 and 24 summarize their
emission estimates for 1975. Approximately 80 percent of the total emissions
in both cities come from fugitive dust sources. The data indicates that natural
surfaces are an important but not predominant source of fugitive dust emissions.
In Las Vegas, unpaved roads are the largest source of emissions, followed by
natural surfaces; paved streets and cleared areas also generate large amounts
of particulate emissions. In Reno, unpaved roads contribute more than a third
of all emissions. Natural surfaces and paved roads are also major sources of
fugitive dust.
Figures 34 and 35 show the distribution of 1975 particulate emissions in
Las Vegas and Reno; these figures do not include emissions from natural sur-
faces. As was the case with Phoenix, emissions in both cities are concentrated
in the more urbanized portion of the study area. (Note, for example, the mag-
nitude of emissions at points within the city boundaries where interstate high-
ways intersect). In Las Vegas, many of the outlying grids with high emission
densities are the location of large point sources. In Reno, the three grids
north of the city with high emission densities all experience a large contri-
bution to emissions from unpaved roads.
OTHER STUDIES
The conclusion that emerges from the studies of Phoenix, Tucson, Las Vegas,
and Reno is that fugitive dust from urban activities, rather than wind-blown
desert dust, appears to be responsible for the high particulate concentrations
observed in those cities. Evidence from studies of other areas in the southwest
provide some support for this conclusion, although this evidence is not as
complete or detailed as that available for the four cities already discussed.
One study38 compiled emission inventories for the two counties that form
Arizona's western border: Mojave and Yuma. Table 25 summarizes the inventories
for both counties. Although they do not contain estimates of emissions from
undisturbed desert areas, these inventories do indicate the magnitude of other
fugitive dust sources in the region. Fugitive dust sources account for approxi-
mately 98 percent of all emissions in both counties. In Mohave County, the
principal sources of fugitive dust are unpaved roads and vehicle travel on
80
-------
TABLE 22. URBAN/BACKGROUND CONCENTRATION RATIOS (EPRI2)
Site
Element
Pb
Ca
K
Sr
Mg
Li
Rb
Si
Al
Mn
Na
Fe
Mass
Ti
Cs
In
Tl
Co
NO;
Ni
NflJ
Zn
sol;
Cd
Cr
Cu
Bi
1
10.7
5.8
4.9
4.7
4.4
3.9
3.7
3.7
3.5
3.5
3.9
3.4
2.2
2.9
2.2
3.8
3.3
2.8
2.0
2.0
1.3
1.7
1.3
1.3
1.3
1.9
1.0
2
12.1
6.2
5.8
5.4
5.3
5.2
4.4
4.3
4.3
4.3
4.3
4.1
3.7
3.1
3.0
2.9
2.8
2.8
2.5
1.9
1.6
1.6
1.5
1.5
1.4
1.4
1.1
3
1.4
1.7
1.5
1.9
1.7
1.9
1.7
1.3
1.3
1.4
1.8
1.4
1.2
1.2
1.1
2.7
2.9
2.2
1.5
1.2
1.0
1.3
1.3
0.7
0.5
1.2
0.9
4
10.4
5.1
4.6
4.6
4.5
3.7
3.8
3.3
3.4
3.3
3.7
3.5
3.1
2.7
2.1
4.1
3.0
2.8
2.5
2.8
1.6
1.8
1.6
3.9
2.0
1.3
1.1
5
5.5
3.4
3.1
4.3
3.3
3.2
3.8
3.3
3.3
3.0
3.7
3.0
2.3
3.2
2.0
3.0
3.0
2.8
1.5
1.1
1.0
1.3
1.1
0.9
1.0
1.9
0.7
27
11
5
13
8
5
5
4
5
4
5
5
4
3
2
5
6
4
2
2
1
2
1
2
2
3
1
6
.0
.7
.9
.8
.9
.9
.0
.9
.3
.9
.5
.0
.2
.9
.7
.1
.0
.4
.7
.8
.5
.2
.6
.4
.4
.3
.3
7
10.5
5.4
2.8
4.3
3.8
3.5
2.6
2.6
2.8
3.0
2.8
2.6
2.6
2.2
1.6
3.8
3.7
2.2
2.1
1.4
1.4
1.6
1.5
0.8
1.1
1.9
1.0
8
18.0
6.2
4.4
5.7
5.2
4.0
3.8
3.6
3.5
3.5
4.5
3.7
3.7
2.7
2.3
4.7
4.2
3.1
2.3
2.3
1.8
1.5
1.8
2.4
1.6
2.0
1.0
9
10.3
2.1
4.0
2.8
2.2
2.8
3.1
2.8
2.8
2.4
3.5
2.4
2.6
2.2
1.7
2.3
2.5
2.9
1.8
1.6
1.3
1.2
1.5
1.3
1.0
0.9
1.0
10
15.7
6.0
3.5
6.0
4.5
3.7
3.5
3.5
3.5
2.9
3.2
3.0
3.2
2.5
1.9
3.5
3.2
2.4
2.0
2.7
1.2
1.6
1.2
4.4
2.0
10.9
0.8
81
-------
TABLE 23. LAS VEGAS PARTICIPATE
EMISSION INVENTORY SUM-
MARY, TONS/YEAR (AFTER
PEDCo5)
Source category
1975
Fuel Combustion:
Residential 37.2
Commercial/Institutional 134.4
Industrial 55.8
Industrial processes 2986.0
Burning 51.9
Mobile Sources:
Aircraft
Railroad
Auto exhaust
Off-highway
Fugitive Dust Sources:
Construction
Normal paved streets
Dirty paved streets
Unpaved roads
Sand and gravel pits
Agriculture
Cleared areas
Heavy equipment storage
Playgrounds
Unpaved parking lots
Road shoulders3
Railroad right-of-ways
Horse corrals
Natural surfaces
Total
71.8
13.5
795.7
206.8
620.0
2122.7
43.7
5818.0
711.0
180.0
2309.9
27.6
5.0
38.5
202.9
51.0
5591.7
22074.3
a
TABLE 24. RENO PARTICULATE EMIS-
SION INVENTORY SUMMARY,
TONS/YEAR (AFTER PEDCo5)
Source category
Fuel combustion
Industrial processes
Burning
Mobile Sources:
Aircraft
Railroad
Auto exhaust
Off -highway
Fugitive Dust Sources:
Construction
Normal paved streets
Dirty paved streets
Unpaved roads
Sand and gravel pits
Agriculture
Street sanding
Cleared areas
Heavy equipment storage
Playgrounds
Unpaved parking lots
Road shoulders
Railroad right-of-ways
Horse corrals
Natural surfaces
Total
1975
388.2
23.0
1099.5
10.7
24.7
437.3
85.5
814.0
1034.1
20.6
3969.0
460.0
121.0
140.0
40.1
3.4
50.9
38.8
2.8
35.6
9.0
2323.2
11131.2
Road shoulder emissions included
with unpaved parking lot emissions,
82
-------
4020 to
4010 km
4000 k»
3990 U
3980 ta
650 k»
660
670 km
0 L
SCALE
KILOMETERS
680 km
10
MILES
1 ? ? 1
690 bi
I I 0-49 ton/mi2/yr
tg-tag* 50-99 ton/mi2/yr
HIIIIIIIIIIIIIH 100-149 ton/miVyr
BBI150-199 ton/mi2/yr
>200 ton/mi2/yr
Figure 34. 1975 Las Vegas participate emission density, ton/mi /yr.
(After PEDCo5). Excludes emissions from natural surfaces.
83
-------
242.5 (a EAST
100.000 rt. lAit
HI.4M ft. mni
' 43M 4 » HOOTH
43M.Z If (OCX
IU.M n. Htm
uo.oot rv IMT
24!.3 IK CASr
4353.7 t. MOTH
tM.OM ft. Mm
1M.4t» ft. IAJT
HI.» tt (AST
0-49 ton/mi2/yr
50-99 ton/mi2/yr
100-149 ton/mi2/yr
150-199 ton/mi2/yr
>200 ton/mi2/yr
Figure 35. 1975 Reno participate emission density, ton/mi2/yr.
(After PEDCo5). Excludes emissions from natural surfaces.
84
-------
off-road surfaces. In Yuma County, travel on off-road surfaces is the primary
source of emissions, followed by unpaved roads and exposed surfaces. The
latter category consists of agricultural land and land cleared for development.
TABLE 25. 1976 TOTAL EMISSIONS BY SOURCE
CATEGORY, (TONS/YR) (AFTER
PEDCo38)
Mohave Yuma
Source category county county
Point Sources 631 924
Traditional Area Sources 736 3,968
Fugitive Dust Sources:
Paved Roads 2,134 4,374
Unpaved Roads 105,830 66,045
Off-road Vehicles 99,375 183,425
Construction Activity 986 1,422
Agricultural Activity 26 8,172
Exposed Surfaces3 360 14,414
Total 210,078 282,744
alncludes emissions from agricultural sur-
faces and land cleared for development.
Does not include emissions from undistrubed
desert.
Other studies relied on the microinventory technique to analyze particu-
late problems. One such study prepared by Engineering Science for the U.S.
Environmental Protection Agency,6 analyzed particulate problems at five non-
attainment sites in the Albuquerque, New Mexico area. The study inventoried
all sources within a one-mile radius of the nonattainment monitors including
fugitive dust sources such as paved and unpaved roads, areas subject to wind-
erosion, and aggregate storage piles. The study utilized the Air Quality Dis-
play Model (AQDM) to relate emissions to ambient air quality. The report
concluded that four anthropogenic fugitive dust sources - unpaved roads or
driveways, paved roads, tire and exhaust emissions, and unpaved parking lots-
contributed 42 to 61 percent of the TSP concentration at these five sites.
Another study12 compiled microinventories for 35 nonattainment sites in
Colorado and Utah as well as 8 nonattainment sites in Montana, Wyoming, and
North Dakota. The authors concluded that "in general, the sources associated
with nonattainment areas in the large urban centers of Region VIII such as
Denver, Salt Lake City, Colorado Springs, and Pueblo were traffic-related
reentrained dust from streets, winter road sanding, and motor-vehicle exhaust).
In some moderate sized cities such as Grand Junction and Rapid City, traffic
related emissions also appeared to be a major cause of high concentrations.
However, in most of the medium and small cities, the major sources were point
sources, unpaved roads, construction, and/or wind-blown dust from agricultural
and open areas. None of the nonattainment sites were in rural locations."
85
-------
Finally, a study by Technology Service Corporation9 analyzed TSP/meteor-
ology relationships in order to examine the contribution of wind-blown dust
to TSP nonattainment in EPA Region VI. The study covered 25 nonattainment
sites in four states: Arkansas, Oklahoma, Texas, and New Mexico. Seven of
the sites, located in New Mexico as well as Western Texas and Oklahoma, fall
into the study area for this report which is designated by the cross-hatched
area in Figure 36. The discussion which follows focuses on these seven sites
for which site descriptions are provided in Table 26.
The authors of the study used a variety of techniques to relate meteor-
ological variables and TSP concentrations. One of the simpler analyses in
the study assesses the contribution of wind-blown dust on days when measured
TSP concentrations exceed the 24-hour primary or secondary NAAQS. In this
analysis, the authors classify TSP concentrations according to the wind speed
and precipitation observed on or before the day of the measurement. If viola-
tions of the 24-hour NAAQS at a site are associated with high winds and low
precipitation, the authors conclude that wind-blown dust is a major contribu-
tor to high TSP concentrations at that site; if violations are usually asso-
ciated with low winds and moderate to high precipitation, the authors conclude
that wind-blown dust is only a minor contributor. Table 27 lists the classi-
fication of each of the seven sites in the study area.
TABLE 26. CLASSIFICATION OF
SITES ACCORDING
TO IMPORTANCE OF
WIND-BLOWN DUST
Location Class
Albuquerque (No. 1), NM III
Albuquerque (No. 2), NM III
Dona Ana, NM II
Las Cruces, NM II
Raton, NM II
Roger Mills Co., OK II
Lubbock, TX III
Class II - wind-blown dust is a
significant but not the major
contributor, or there is uncer-
tainty as to wind-blown dust
contributions
Class III - wind-blown dust is the
major contributor.
86
-------
oo
AQCR Boundary
State Boundary
Particulate Data Site
Surface Weather Site
orpus Christi
Brownsville
Figure 36. Location of 25 TSP monitoring stations shown in the regional map of AQCRs. (Numerals
in parentheses indicate the number of stations in a same city. After Tech. Ser. Corp9)
-------
TABLE 27. SUMMARY OF SITE CHARACTERISTICS (.AFTER TECH. SER. CORP.9)
00
00
AQCR
152
153
154
187
211
Site
Albuquerque, NM
Albuquerque, NM
Dona Ana, NM
Las Curces, NM
Raton, NM
Roger Mills, OK
Lubbock, TX
SAROAD
site
type
CC/C
S/C
R/C
CC/C
S/C
R/A
S/C
Countrywide
emission
density I
High
High
Low
Low
Moderately Low
Low
Moderate
Climatology
'recipitation Humidity
Low
Low
Low
Low
M. Low
M. Low
M. Low
M. Low
M. Low
Low
Low
Moderate
Moderate
M. Low
Wind
speed
Moderate
Moderate
M. High
M. High
Moderate
High
High
Elevation
Heating of monitor
degree above ground
days (ft)
M. High
M. High
Moderate
Moderate
M. High
Moderate
Moderate
29
13
12
50
15
12
14
-------
Although this analysis implicates wind-blown dust as a significant con-
tributor at all seven sites in the study area, the authors of the report had
some reservations about this conclusion. Results of a more detailed analysis,
described below, indicated that man-made sources played a greater role in
high TSP concentrations than wind-blown dust at most of the sites listed in
Table 27. The authors suggested two possible explanations for this discrep-
ancy. (1) Both conclusions may be correct. The simpler analysis deals
only with days when TSP concentrations exceed primary or secondary standards.
The authors speculated that wind-blown dust from desert pavement, agricultural
lands, construction sites, etc., may play a greater role on such days than on
more typical days. (2) The results of one of the analyses may be incorrect.
The authors expressed greater confidence in the more detailed analysis
described below, noting that it relied on all the sampling days rather than
just a few and used many more variables to explain variations in TSP concen-
trations. The detailed analysis used the AID (Automated Interactive Decision)
decision-tree program developed at the University of Michigan Institute for
Social Research. This program accounts for the variance in the dependent
variable (TSP) by splitting the data according to ranges in the independent
(meteorological) variables, each time choosing the split that maximizes the
variance explained in the dependent variable. The study examined the 18
meteorological variables listed in Table 28 to explain the variance in
24-hour TSP concentrations at the 25 study sites.
Figure 37 illustrates the output from the AID decision-tree program for
a site in Raton, New Mexico. The output indicates that seasonal fluctuations
account for most of the variance in TSP concentrations at this site; TSP
concentrations average 27.9 yg/m3 during January and February compared with
52.5 vig/m3 during the rest oi the year. Other important explanatory variables
at this site include temperature, wind direction, and wind speed. Higher
TSP concentrations are associated with high temperatures (greater than 40°F),
winds from the east, and low average wind speed (less than 7 knots).
To assess the contribution of wind-blown dust, the analysts drew con-
clusions based on their interpretation of the meteorological variables that
are important at each site. At the Raton, New Mexico, site, for example, they
concluded that man-made sources, mostly to the east, were the primary contri-
butors to high TSP concentrations. As Table 29 indicates, the authors of the
study concluded that man-made sources - including some fugitive dust sources
- were the principal contributors to high TSP concentrations at all five of
the sites in New Mexico and at the Roger Mills site in Oklahoma. Wind-blown
dust, which includes dust from construction activities and agricultural lands
as well as dust from undisturbed desert areas, was the primary contributor
at Lubbock, Texas, and was listed as a potential contributor at the other
six sites as well.
89
-------
TABLE 28. SUMMARY OF METEOROLOGICAL
VALUES
Variable
Month of the Year
Daytime Average Visibility
Number Observations Blowing Dust
Arithmetic Average Wind Speed
Vector Average Wind Direction
Average Relative Humidity
Wind Variability
A.M. Mixing Height
A.M. Average Wind Speed Through Mixing Layer
P.M. Mixing Height
P.M. Average Wind Speed Through Mixing Layer
Maximum Temperature
Minimum Temperature
Amount of 1-Day Precipitation
Maximum Wind Speed
3-Day Accumulated Precipitation
Number of Days Since Last Precipitation or
Snow Cover
Number of 1-Day Precipitation Observations
90
-------
1 < Month of the Year 52 3 < Month of the Year < 12
Maximum Temperature < 1(0 Maximum Temperature > 1(0
\ '
ISO ? Vector Average Wind Direction < 360 0 < Vector Average Wind Direction < 180
/ X
Y 1(8.2
N 38
Y 59.*
N = 36
^ \
5 < Month of 35 Month of
the Year S 12 the Year 5 It
'_ \
Arithmetic Average Arithmetic Average
Wind Speed > 7 Wind Speed < 7
Y <(1(.
N = 33
Y 72.6
N = 5
Y = 55.1
N - 33
Y 106.3
N = 3
Average Relative Average Relative
Humidity > 65 Humidity < 65
Y" = 25.0
N = 3
P.M. Average Wind Speed P.M. Average Wind Speed
thru Mixing Layer < 3-5 thru Mixing Layer > 3.5
Y - 29.0
N = k
Wind Variability < 2 Wind Variability > 2
Y
N
31.2
It
Y 1(8.8
N - 26
Y 53.7
N = 29
0 < Vector Average 135 S Vector Average
Wind Direction < 135 Wind Direction < 180
Y
N
53. *
20
Y - Average TSP Level
N Sample Size
Figure 37. Example of AID output.
91
-------
TABLE 29. SUMMARY OF CONCLUSIONS FROM THE INTERPRETATION OF THE AID DECI-
SION TREES
Location
Conclusion
Albuquerque (No. 1), NM
Albuquerque (No. 2), NM
Dona Ana, NM
Las Cruces, NM
Raton, NM
Roger Mills Co., OK
Lubbock, TX
Man-made sources (mostly dust related). Also,
a major contribution from wind-blown dust.
Man-made sources, mostly dust related. Also
wind-blown dust. Wind-blown dust sources and/
or man-made dust sources may be concentrated
toward the southeast.
Man-made dust sources, possibly concentrated
toward the northeast. Possibly some minor
contributions from wind-blown dust.
Man made sources. Also, significant contribu-
tions from wind-blown dust. Dust sources may
be most intense during winter and spring
(possibly agriculture related).
Man-made sources, mostly to the east. Also a
possibility of wind-blown dust. Dust sources
may be most intense in spring and least intense
in winter (possibly agriculture related).
Man-made sources, mostly dust related. Also a
possibility of major contributions from wind-
blown dust.
Substantial contributions from wind-blown dust.
Significant dust sources (wind-blown or man-
made) toward the west.
92
-------
REFERENCES
1. Richard G., and R. Tan. An Implementation Plan for Suspended Particulate
Matter in the Phoenix Area. Vol. 1, Air Quality Analysis. EPA-450/3-77-
021a. TRW Environmental Engineering Division. Redondo Beach, California.
November 1977.
2. Moyers, J.L. Identification and Analysis of Urban Air Quality Patterns.
Final Report. EPR1 EA 487, Project 438-1. University Analytical Center.
University of Arizona. Tucson, Arizona. December 1977.
3. Richard, G., J. Avery, and L. Baboolal. An Implementation Plan for
Suspended Particulate Matter in the Phoenix Area. Vol. 3, Model Simula-
tion of Total Suspended Particulate Levels. EPA-450/3-77-021c. TRW
Environmental Engineering Division. Redondo Beach, California.
August 1977.
4. Jutze, G., and K. Axetell. Investigation of Fugitive Dust. Vol. 1,
Sources, Emissions, and Control. EPA-450/3-74-036a. Vol. 2, Control
Strategy and Regulatory Approach. EPA-450/3-74-036b. PEDCo Environmental
Specialists, Inc. Cincinnati, Ohio. June 1974.
5. Jutze, G.A., J.M. Zoller, K. Axetell, and R. Livingston. Neveda Particu-
late Control Study for Air Qaulity Maintenance Areas. Reno and Las Vegas
Urban Areas. EPA-909/9-77-001. PEDCo Enviornmental, Inc. Cincinnati,
Ohio. March 1977.
6. Engineering-Science. Arcadia, California. Fugitive Dust Emission Study
for the City of Albuquerque. EPA-906/9-79-002. February 1979.
7. Suck, S.H., B.C. Upchurch, and J.R. Brock. Dust Transport in Maricopa
County. Arizona. Atmos. Environ. Vol 12, No. 12, 2265-71. 1978.
8. Graf, J., R.H. Snow, and R.G. Draftz. Aerosol Sampling and Analysis.
Phoenix, Arizona. EPA-600/3-77-015. ITT Research Institute. Chicago,
Illinois. February 1977.
9. Trijonis, J., Y. Horie, and D. Bicker. Statistical Analysis of TSP and
Meteorological Data in EPA Region VI. Preliminary Draft-Final Report.
EPA Contract No. 68-02-2828. Technology Service Corp. Santa Monica,
California. May 1978.
10. Smith, D.E., O.K. Spencer, J. Richards, and G. Peterson. The Environ-
mental Protection Agency Four Corners Ambient Air Monitoring Network.
EPA-600/7-79-135. ute Research Laboratories. Ft. Duchesne, Utah.
June 1979.
93
-------
11. PEDCo Environmental, Inc. Kansas City, Missouri. Technical Assistance
in Developing Nonattainment Plans for Selected Areas in California.
Vols. 1 and 2. Draft Final Report. EPA Contract No. 68-02-2535, Task
Order No. 9.
12. PEDCo Environmental Specialists, Inc. Cincinnati, Ohio. Characterization
of Particulate Sources Influencing Monitoirng Sites in Region VIII Non-
attainment Areas. EPA Contract No. 68-02-1375, Task Order No. 30.
13. Lundgren, D.A., and H.J. Paulus. The Mass Distribution of Large Atmos-
pheric Particles. JAPCA Vol. 25, No. 12. December 1975.
14. Farmer, W.M., and J.O. Hornkohl. Environmental Aerosol Measurements
Using an Airborne Particle Morphokinetometer. EPA-600/3-76-087. Spec-
tron Development Labs. August 1976.
15. Sverdrup, G.M., K.T. Whitby, and W.E. Clark. Characterization of Cali-
fornia Aerosols - II. Aerosol Size Distribution Measurements in the
Mojave Desert. Atmos. Environ. Vol. 9, pp. 483-494.
16. Whitby, K.T., W.E. Clark, V.A. Marple, G.M. Sverdrup, G.J. Sem, K. Willeke,
B.Y.H. Liu, and D.Y.H. Pui. Characterization of California Aerosols - I.
Size Distributions of Freeway Aerosol. Atmos. Environ. Vol. 9, pp. 463-
482.
17. Esmen, N.A., and M. Corn. Residence Time of Particles in Urban Air.
Atmso. Environ. Vol. 5, pp. 571-578.
18. Willeke K., and K.T. Whitby. Atmospheric Aerosols: Size Distribution
Interpretation. JAPCA. Vol. 25, No. 5. May 1975.
19. Porch, W.M. Recent Studies of the Suspension of Desert Dust and Resuspen-
sion of Toxic Aerosol Due to Wind. University of California. Livermore.
ASME Paper. July 1974.
20. Cowherd, Jr. C., K. Axetell, Jr., C.M. Guenther, and G.A. Jutze. Develop-
ment of Emission Factors for Fugitive Dust Sources. EPA-450/3-74-037.
Midwest Research Insitute. Kansas City, Missouri. June 1974.
21. Sehmel, G.A. Influence of Soil Erosion on the Airborne Particle Size
Distribution Function. Battelle, Pacific Northwest Laboratories.
Richland, Washington. APCA Paper No. 73-162. June 1973.
22. Chepil, W.W. Properties of Soil which Influence Wind Erosion, 4, State
of Dry Aggregate Structure. Soil Sci. 72, pp. 387-401.
23. Greeley, R., J.D. Iverson, J.B, Pollack, N, Udovich, and B. White. Wind
Tunnel Studies of Martian Aeolian Processes: NASA. Tech. Mem. 62. 1973.
24. Marshall, J. Drag Measurements in Roughness Arrays of Varying Density
and Distribution. Agr. Meteor. Vol. 8, pp. 269-292.
94
-------
25. Lyles, L. and B. Allison. Wind Erosion: The Protective Role of Simulated
Standing Stubble. Trans, or the ASAE, Vol. 19, pp. 61-64. 1976.
26. Kessler, E., D.Y. Alexander, and J.F. Rarick. Duststorms from the U.S.
High Plains in Later Winter 1977 - Search for Cause and Implications.
Proc. Okla. Acad. Sci., Vol. 58, pp. 116-128. 1978.
27. Hagen, L.J. and N.P. Woodruff. Air Pollution from Duststorms in the
Great Plains. Atmos. Environ. Vol. 7, pp. 323-332. 1973.
28. Chepil, W.S. and N.P- Woodruff. Sedimentary Characteristics of Dust-
storms - II. Visibility and Dust Concentration. Am. J. Sci. Vol. 255,
pp. 104-114. 1957.
29. Hagen, L.J. and N.P- Woodruff. Particulate Loads Caused by Wind Erosion
in the Great Plains. U.S. Department of Agriculture. Manhattan, Kansas.
APCA Paper No. 73-102. June 1973.
30. Whitby, K.T., A.B. Algren, R.C. Jordan, and J.S. Annis. The ASHAE Air-
borne Dust Survey. Heating, Piping, Air-conditioning, pp. 185-192.
November 1957.
31. Korte, N.E., and J.L. Moyers. The Concentration of Inorganic Species in
Airborne Respirable Particulate Matter in Rural Southern Arizona. J. of
Ariz-Nev. Acad. of Sci., Vol. 13, pp. 79-83. October 1978.
32. Moyers, J.L., L.E. Ranweiller, S.B. Hopf, and N.E. Korte. Evaluation
of Particulate Trace Species in Southwest Desert Atmosphere. Environ.
Sci. and Tech., Vol. II, pp. 789-795. August 1977.
33. Pearson, M.J., M. Pitchford, and R. Snelling. Western Energy Sulfate/
Nitrate Monitoring Network Progress Report. EPA-600/7-79-074. Environ-
mental Monitoring and Support Laboratory. Las Vegas, Neveda. March 1979.
34. Greeley, R.S., R.P. Ouellette, J.T. Stone, S. Wilcox. Sulfates and the
Environment A Review. Mitre Corporation. MTR-6895. March 1975.
35. Altshuller, A.P. Atmospheric Sulfur Dioxide and Sulfate. Distribution
of Concentration at Urban and Nonurban Sites in United States. Environ.
Sci. and Tech., Vol. 7, pp. 709-712. August 1973.
36. Current Population Reports. Population Estimates and Projections.
Individual State Reports. U.S. Department of Commerce. Bureau of the
Census.
37. Richard, G., R. Tan, and J. Avery. An Implementation Plan for Suspended
Particulate Matter in the Phoenix Area. Vol. 2, Emission Inventory.
EPA-450/3-77-021b. TRW Environmental Engineering Division. Redondo Beach,
California. December 1977.
38. Ungers, L.H. Comprehensive Emission Inventory for Mohave and Yuma Counties,
Arizona. Vols. I and II. EPA-909/9-78-003. PEDCo Environmental.
Cincinnati, Ohio. July 1978.
95
-------
APPENDIX A
BACKGROUND STATION INFORMATION
96
-------
TABLE A-l. 1976, 1977, AND 1978 TSP CONCENTRATIONS AT 33
(FROM NATIONAL AEROMETRIC DATA BANK)
SITES
VO
Elevation
(ft)
State
Arizona
Nevada
California
Oklahoma
Texas
New Mexico
Colorado
Utah
Denotes a
County
Yavapai
Pirns
Coconino
Plraa
Clark
Kern
Tulsa
Oklahoma
Jeff. Davis
Tom Green
Los Alamos
Bernallllo
La Plata
Montezuma
Rio Blanco
Rio Blanco
Rio Blanco
Rio Blanco
Uintah
Uintah
Uintah
Uintah
Kane
Kane
value derived
Site location
Camp Verde
Org. Pipe Cact. Nat. Hon.
Grand Canyon Village
Corona de Tucson
Las Vegas Wash-Marina
Kern Wildlife Refuge
Bixby
Draper Lake
Mt. Locke
Fish Hatchery No. 1
White Rock
West Mesa Radar Station
Red Mesa
Mesa Verde
Tract C-A, Site 1
Tract C-A, Site 2
Tract C-A, Site 3
Tract C-A, Site 4
Tracts UA+UB, Site A7
Tracts UA+UB, Site A6
Tracts UA+UB, Site A4
Tracts UA+UB, Site A3
Glen Canyon
Glen Canyon
Site code
030940002F03
030620005F03
030370001703
030620008G03
29008001 1G03
053480001103
373020133F03
372200020F03
452740003F03
455200001F03
3207 20001 F03
320140031H03
061 300001 F03
061530003F03
061860001J03
061860002J03
061860003J03
061860004J03
461 200007 J03
461200006J03
461 200004 J03
461200003J03
460400002F03
4604 00001 F03
from data which do not meet SAROAD sum
Note: Concentrations for 1976, 1977, and 1978 are
tabulated In
Abov«
MSL
3381
1661
6955
3225
1300
0215
0918
1290
6791
1864
6265
6003
6520
7060
7360
7360
6600
6300
5360
5250
5717
5320
3890
3750
Abovs
ground
4
4
4
13
25
4
18
15
4
15
15
29
10
15
197
33
33
33
20
20
20
20
5
5
Ststion type
Remote
Remote
Remote
Remote
Rural -Unqualified
Remote
Rural-Near Urban
Rural -Agricultural
Rural -Agricultural
Rural-Near Urban
Rural -Unqualified
Rural-Unqualified
Rural -Agricultural
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
arlzatlon criteria of OAQPS Guideline
Number of OBS
52/30/33
48/42/31
36/37/9
52/45/29
52/52/20
48/36/34
19/62/61
59/56/61
42/51/40
21/53/32
59/61/25
60/57/58
61/53/
77/57/77
103/6/
121/10/
124/10/
121/10/
60/3/~
61/2/~
61/3/
61/3/
202/340/156
272/326/
1.2-040, Vol.
Highest
64/68/49
139/83/98
69/82/27
51/84/40
115/79/92
390/196/450
87/110/98
147/3094/116
221/99/66
391/191/154
147/134/172
238/314/235
189/280/
132/125/38
81/6/-
57/10/-
281/14/
182/39/
7S/22/
101/31/
64/15/
39/20/
118/661/156
120/423/
Second
highest
59/65/49
83/78/49
58/42/27
42/45/33
91/78/71
222/157/203
76/95/91
138/162/105
131/71/44
94/127/98
123/104/38
236/116/132
172/188/
102/92/38
80/5/
57/6/
210/8/
173/9/
42/20/
72/23/-
60/12/--
36/16/--
114/322/143
US/258/
Geometric
mean
30/29a/24a
33/34a/3l"
14/20a/14a
5/25a/17a
37/38/Z43
84/76a/62
33a/38/40
50/51/47
20/18/18
56a/50/48a
30/32/223
37/27/19
43/34a/
13/15/12
11/43/-
ll/4B/~
17/3a/
14/5a/
14/17a/
20/273/
15/3l"/
12/15a/~
23a/24/ll
IS/17/
3, Sec. 2.3.0.
chronological order, separated by slashes.
-------
vo
00
Monitor Locations
1. Kern Wildlife Refuge (near Corcoran Rd)
2. Park Service Bldg Las Vegas Wash-Marina
3. Glen Canyon Nat. Rec. Area (Maintenance Garage)
4. Glen Canoyn Nat. Rec. Area (Fish 6 Game Office)
5. Grand Canyon Village (Visitor Center)
6. Hontezuma Castle Nat. Park (Camp Verde)
7- Organ Pipe Cactus Nat. Monument (Pump Station)
8. Corona de Tucson
9. White River Shale Project - Tracts UA+UB (Sites 3, *. 6, 7)
10. RBOSC - Tract C-A (Sites 1, 2, 3, It)
11. Mesa Verde Nat. Park (Fire Lookout Station)
12. Red Mesa CGI lien Dairy)
13. White Rock (Treatment Plant)
14. West Mesa (Radar Station)
15. Mt. Locke (McDonald Observatory)
16. Tom Green County (Fish Hatchery, No. 1)
17. Draper Lake (Ranger Station)
18. Bixby (Water Plant)
Figure A-l. Monitor locations for National Aerometric Data Bank data
-------
TABLE A-2. 1976 TSP CONCENTRATIONS AT 26 SITES OPERATED BY UTE RESEARCH LABORATORIES
1C
VO
Elevation
(ft)
State County
Arizona Navajo
Conconino
Coconino
Coconino
Coconino
Mohave
Apache
Apache
Coconino
Coconino
Colorado La Plata
La Plata
Montezuma
New Mexico San Juan
San Juan
Rio Arriba
San Juan
Utah San Juan
Washington
Garfield
Kane
Garfield
San Juan
San Juan
Washington
Site Location
Bacobi
Bodaway
Coppermine
Kaibito
Lee's Ferry
Piute
Redrock
Teec Nos Pos
Tsa Schizzi
Tuba City
Ignacio
Redmesa
Towaoc
Burnham
Chaco Canyon
Dulce
Huerfano
Aneth
Boom ing ton
Escalante
Glen Canyon
Kenrieville
Navajo Mtn.
Oljato
St. George
Site code
030520003K03
03020001 2K03
03 020001 1K03
03020001 OK03
030200007K03
030500009K03
030040000K03
03004 0001K03
63020001 3K03
03020001 4K03
061300003K03
061300002K03
061600004K03
321 00001 2K03
32100001 1K03
320920003K03
321000007K03
46096003K03
46128001K03
460300002K03
460400003K03
460300003K03
460960001K03
460960002K03
461280002K03
Above Above Station
MSL ground type
6300
5960
6050
6000
3190
4880
6110
4990
5550
5170
6550 ,
6460
5740
5610
6190
7220
6140
4590
2520
5755
4040
5905
6050
4810
2880
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Remote
Number
of
OBS
137
76
93
152
61
151
155
141
67
99
131
121
113
83
75
153
118
157
152
141
59
143
13
150
62
Highest
208
370
663
253
481
193
128
473
102
305
188
80
110
569
113
207
174
144
123
592
36
308
99
207
57
Second
highest
155
353
90
216
256
134
125
171
57
124
171
70
81
185
111
171
171
138
86
360
34
196
56
193
46
Geometric
mean
17
22
18
29
21
18
24
29
16
32
23
24
23
24
31
12
45
30
26
56
15
42
22
26
16
-------
UTAH
Gre*n Rlwr
Capitol Reef \
Canyonlands,'
.C^cit, Bryce Canyon
\' :"
\>" "^ f
. BU^n.
20
..
*28
COLORADO
Grind Junction
Cortei Pagoia Spr«.
' " Du"no°
IT-
9*
*4
'"'W
19
\
ARIZONA
Canyon de C'helly
Chaco Canyon
FUoMilT
NEW MEXICO
^indicates Ute Research Laboratories' monitoring stations:
1 Babcobi, AZ
2 Bodaway, AZ
3 Coppermine, AZ
4 Kaibito, AZ
5 Lechee, AZ
6 Lee's Ferry, AZ
7 Piute, AZ
8 Red rock, AZ
3 Teec Nos Pos, AZ
10 Tsa Schizzi,
11 Tuba City, AZ
12 Ignacio, CO
13 Redmesa, CO
14 Towaoc, CO
15 Burnham, NM
16 Chaco Canyon, NM
17 Dulce, NM
18 Huerfano, NM
19 Navajo Farm Proj., NM
20 Aneth, UT
12 Bloomington, UT
22 Escalante, UT
23 Glen Canyon, UT
2k Henrieville, UT
25 Huntington Canyon, No. 1.
26 Huntington Canyon, NO. 2.
27 Navajo Mountain, UT
28 Oljato, UT
29 St. George, UT
UT
UT
Figure A-2. Monitoring site locations (from EPA-600/7-79-135,
p. 5, Reference 10).
100
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TABLE A-3. ACTIVATION DATES FOR SITES OPERATED BY UTE RESEARCH
LABORATORIES
Monitoring
site
Bacobi, AZ
Bodaway , AZ
Coppermine , AZ
Kaibito, AZ
Lechee, AZ
Lee's Ferry, AZ
Piute, AZ
Redrock, AZ
Teec Nos Pos, AZ
Tsa Schizzi, AZ
Tuba City, AZ
Ignacio, CO
Redmesa , CO
Towaoc, CO
Burnham, MM
Activation
date
02/27/76
06/21/76
02/02/76
01/22/76
05/22/77
10/05/76
01/27/76
01/12/76
01/20/76
04/02/76
01/16/76
01/19/76
04/19/76
04/29/76
05/17/76
Monitoring
site
Chaco Canyon, NM
Dulce, NM
Huerfano, NM
Navajo Farm Project, NM
Aneth, UT
Blooming ton, UT
Escalante, UT
GLen Canyon, UT
Henrieville, UT
Huntlngton Canyon, No. 1,
Hunt ing ton Canyon, NO. 2,
Navajo Mountain, UT
01 j a to, UT
St. George, UT
Activation
date
06/30/76
05/17/76
04/13/76
02/06/77
02/11/76
02/02/77
01/24/76
10/13/76
01/24/76
UT 01/18/77
UT 05/06/77
01/30/77
01/23/76
07/14/76
Note: No uniform sampling schedule was in use in 1976, but sampling
was required for three 24-hour periods each week.
101
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
\. REPORT NO.
EPA 450/2-80-078
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Evaluation of Contribution of Wind Blown Dust From
the Desert to Levels of Particulate Matter in
Desert Communities
7. AUTHOR(S) ~ ~~
5. REPORT DATE
August 1980
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
Frank A. Record and Lisa A. Baci
9. PERFORMING ORGANIZATION NAME AND ADDRESS
GCA Corporation
Bedford, Massachusetts
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-2607
(Work assignment no. 41)
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report uses existing data and studies to assess the impact of
windblown desert dust on the attainment of TSP standards in major cities
situated in desert environments in the Southwestern U.S. Primary emphasis
is placed on four cities: Phoenix and Tucson, Arizona; and Las Vegas and
Reno, Nevada. It is concluded that: (1) the contribution of windblown
dust from the undisturbed desert floor to particulate levels in desert
communities is very small and should be considered as part of the back-
ground; (2) if human activities repeatedly break up the desert crust,
local violations of the 24-hour standards are likely; (3) there is
substantial agreement on the principal source categories of fugitive
dust contributing to the nonattainment problem and the characteristics
of urban areas most affected by each category.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
^.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Fugitive Dust
TSP
Desert
8. DISTRIBUTION STATEMENT
Limited Availability
:LASS (This Report)
21. NO. OF PAGES
108
:LASS (This page)
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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