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THE EFFECTS OF A COAL-FIRED POWER PLANTON REGIONAL AIR QUALITY
by
Wi ll iam R. Poteet, Dean A. Hegg andPeter V. Hobbs
Supplemental Annual Report toSouthern Cal ifornia Edison Company
for P.O. Number B2618901
December 1983
SUMMARY
Data col lected over a three year period both in the plume and in the vici
nity of the plume from the Mohave power plant have been util ized to evaluate the
nfluence of the power plant on regional visibi lity. Whi le of a preliminary
nature, this study has yielded the fol lowing information.
Ai rborne measurements of bgcat* ^2 concentrations and particle size
distributions have shown that with southerly wi nds the Mohave plume is
restricted to the wel l-defined region of the Colorado River Val ley
before it reaches the "mi xing bowl (the Lake Mead Basin) located 70 km
north of the Mohave power pl ant. After entering the "mixing bowl ", the
plume spreads to widths of 24 km and sometimes splits at the gap in the
Black Mountains.
In southerly winds the Mohave plume has been tracked as a distinct
entity, by visual and real-time ai rborne measurements of the light-
scattering coefficient (bscat) ^ concentrations and particle size
distributions, up to distances of -139 km downwind of the plant and out
to widths of ~25 km. Attempts to track the plume in real time to
greater distances were not successful At the larger downwind
distances, the plume was detected by instrument rather than visual ly.
Particle volume distributions in the Mohave plume peaked at 1.1 urn
diameter. The location of the peak in the particle volume distribution
in the "ambient" ai r varied. The "ambient" ai r of an older ai rmass
(such as on August 28, 1979) was more likely to have been influenced by
the Mohave plume than the "ambient" ai r of a new ai rmass (such as on
August 31, 1979)
SUMMARY (Continued)
Values of bgcgt i n the "ambient" ai r of the Colorado River Val ley
generally increased downwi nd of the Mohave plant. For southerly winds,
the maximum value of b^cat n the "ambient" ai r occurred in the "mixing
bowl (-70 to 200 km north of the Mohave plant). With southerly winds,
the Mohave plume affected the characteristi cs of the "ambient" ai r up
to at least 140 km downwind of the plant.
On August 23 and August 27, 1979, S02 concentrations and b^at were
higher in the "ambient" ai r on the west side of the "mixing bowl than
on the east side. Thus the Las Vegas area could have been a source of
pollution in the "mixi ng bowl
Regional haze in southeastern Cali fornia, southern Nevada and western
Arizona appears to be caused more by brushfi res and possibly by the Los
Angeles urban plume, than by the Mohave plume or pol lution from Las
Vegas. Al so, visi bi lity in the Colorado Ri ver Val ley (up to ~140 km)
appears to be affected more by regional haze than by the Mohave plant.
n
TABLE OF CONTENTS
Page
List of Figures. iv
List of Tables. viii
CHAPTER I BACKGROUND AND SCOPE OF STUDY
1 1 Introductory Remarks. l
1 2 Topography of the Area and Its Effectson the Mohave Plume. 5
1 3 Primary Measurements. 7
1. 4 Data Sources. 10
1. 5 Scope of Study. 11
CHAPTER II INSTRUMENTATION
2. 1 Introductory Remarks 13
2 2 Instrumentation on the B-23 Research Aircraft. 13
CHAPTER III PRESENTATION OF THE DATA
3 1 Introductory Remarks. 30
3 2 Methods of Data Analysis. 30
3 3 Regional Extent of the Plume fromthe Mohave Power Plant. 32
3 4 Summary. 86
-m
TABLE OF CONTENTS-continued.
CHAPTER IV: DISCUSSIONS OF THE DATA
4. 1 Introductory Remarks. 91
4. 2 Channeling of the Mohave Power Plant Plume. 92
4. 3 Variations in the Peak of the Particle VolumeDistributions in the Plume and in the"Ambient" Air. 96
4.4 The Variations in the "Ambient" Air of theRegion Impacted by the Mohave Plume. 100
4 .4.1 The 1.1/0. 55 Ratio. 101
4 .4. 2 The Correlation Matrix. 101
4. 5 Effects on Visibility. 121
CHAPTER V: SUMMARY AND RECOMMENDATIONS
5. 1 Summary of Results. 124
5. 2 Recommendations for Future Research. 126
REFERENCES. 128
APPENDIX 133
iii a
LIST OF FIGURES
PageFigure 1 .1 Location of the Mohave power plant
in relation to the National Parks 4
Figure 1 .2 Topography of the region surrounding theMohave power plant. 6
Figure 2. 1 Research instruments on the B-23 aircraft. 21
Figure 2. 2 Instrumentation details. 24
Figure 2. 3 Schematic of air sample inlet systems. 25
Figure 3 .1 Maximum values of b measured onAugust 23 1979 .5ca. 33
Figure 3. 2 Maximum S0~ concentrations measured onAugust 23, 1979 35
Figure 3. 3 Particle volume-to-number ratiosmeasured on August 23 1979 37
Figure 3 .4 Particle size distributions measuredat 0 5 km from the Mohave power planton August 23 , 1979. 38
Figure 3 5 Particle size distributions measuredat 65 km from the Mohave power plant
Figure 3 6 Particle size distributions measuredat 102 km from the Mohave power planton August 23 , 1979 41
Figure 3 7 Particle size distributions measuredat 130 km from the Mohave power planton August 23 , 1979 42
IV
LIST OF FIGURES-continued.
PageFigure 3 .8 Maximum values of b measured on
August 27, 1979 45
Figure 3. 9 Maximum S0 concentrations measured onAugust 21 -1979 47
Figure 3 .10 Vertical distribution of SO., and bon August 27, 1979 .. .sca-. 48
Figure 3 11 Particle volume-to-number ratios measuredon August 27, 1979. 50
Figure 3 12 Particle size distributions measuredat 0. 5 km from the Mohave power planton August 27, 1979 51
Figure 3 13 Particle size distributions measuredat 81 km from the Mohave power planton August 27, 1979. 52
Figure 3 15 Maximum values of b measured onAugust 28 , 1979 .?"". 56
Figure 3 16 Maximum SOy concentrations measured onAugust 28 , 1979 58
Figure 3 .17 Vertical distributions of
SO^ and b^
on August 28 , 1979 59
Figure 3 18 Particle volume-to-number ratiosmeasured on August 28, 1979 61
Figure 3 19 Particle size distributions measuredat 0 .5 km from the Mohave power planton August 28 , 1979 62
v
LIST OF FIGURES-continued.
PageFigure 3 20 Particle size distributions measured
at 93 km from the Mohave power planton August 29 1979 63
Figure 3 21 Particle size distributions measuredat 139 km from the Mohave power planton August 28 1979. 65
Figure 3 .22 Maximum values of b_ measured onAugust 31 , 1979 66
Figure 3 23 Maximum SOy concentrations measured onAugust 31, 1979 68
Figure 3 24 Particle volume-to-number ratiosmeasured on August 31 1979 69
Figure 3 25 Particle size distributions measuredat 0 .5 km from the Mohave power planton August 31 1979 70
Figure 3 26 Particle size distributions measuredat 93 km from the Mohave power planton August 31, 1979 72
Figure 3 27 Maximum values of b measured onAugust 11 , 1980. .sca. 73
Figure 3 28 Maximum SOy concentrations measured onAugust 11 , -1980. 75
Figure 3. 29 Particle volume-to-number ratiosmeasured on August 11 1980 76
Figure 3 .30 Particle size distributions measuredat 0. 5 km from the Mohave power planton August 11 1980. 77
VI
LIST OF FIGURES-continued.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
3 31
3 .32
3 33
3 34
3 35
4 1
4. 2
4 3
Particle size distributions measuredat 37 km from the Mohave power plant onon August 11 , 1980
Maximum SOy concentrations measured onDecember 20, 1978.
Particle volume-to-number ratios
Particle size distributions measuredat 9 km from the Mohave power planton December 20 1978
Particle size distributions measuredat 46 km from the Mohave power planton December 20, 1978
Surface analysis at 1200 GMT onDecember 18, 1978
Surface analysis at 0300 GMT onAugust 30, 1979.
Surface analysis at 1500 GMT onAugust 15, 1980.
Page
70
0
Q 7
0 1
QC
107
111
117
vii
LIST OF TABLES
Page
Table 2 1 Specifications of research instrumentaboard the University of Washington’ sB-23 aircraft. 14
Table 4 1 Altitudes of the Mohave plume. 93
Table 4. 2 Widths of the Mohave plume. 94
Table 4 3 Particle diameters at which the particlevolume distributions in the Mohave plumeand in the "ambient" air reachedpeak values 97
Table 4 4 Parameters used in the correlations matrix. 102
Table 4 5 Correlations of the 1 1/0 55 ratiowith various parameters. 104
Table 4. 6 The time event parameter and the 1 1/0. 55ratio (700 flight series) 108
Table 4 7 The time event parameter and the 1 1/0. 55ratio (800 flight series) 113
Table 4 8 The time event parameter and the 1 1/0. 55ratio (900 flight series) 118
Vlll
CHAPTER I
BACKGROUND AND SCOPE OF STUDY
1 .1 Introductory Remarks
Good visibility in the southwestern United States
is critical to maintaining the aesthetic appeal of the
national parks in the region. Concern over the
possibility of visibility impairment due to increased
industrial and urban emissions of certain trace gases and
particulates has led to several studies of the sources of
pollution in the Southwest and their effects on
visibility (Marians and Trijonis, 1979; Bhardwaja et al
1981; Blumenthal et al 1981; Cahill et al , 1981;
Hering et al 1981; Macias et al 1981; Malm et al
1981 Pitchford et al , 1981)
Copper smelters were identified by Trijonis (1979)
as being a major contributor to visibility degradation in
the Southwest. However, emissions of sulfur dioxide from
smelters have decreased by a factor of three since the
late 1960s (Marians and Trijonis , 1979 ; Larson and
Bil lings, 1978) During the period from 1970 to 1977,
sulfur dioxide and nitrogen oxide emissions from power
plants in Arizona, New Mexico, Utah, Colorado and Nevada
increased due to the construction of new power plants and increases in
capacity of existing plants (Hering et a1 1981) The effects of
these increases in emissions on visibi lity in the region have not been
clearly established.
Project VISTTA (risibility Lupai rment due to Sulfur Transport
and Transformation in the Atmosphere) was carried out to investigate
the effects on visibi lity of emi ssions from coal-fi red electric power
plants (Blumenthal et a1 1981) Preliminary results indicate that
reductions in visibi lity near Page, Arizona, due to pollutants from
southern California and from brushfi res near Prescott, Arizona (150
km to the southwest) exceeded those due to the emissions from the
Navajo coal-fi red electric power plant near Page, Arizona.
Several workers have studied the effects of long-range transport
of pol lutants from southern California on visibi ity in the south-
western United States. Cahil et a1 (1981) li nked reduced visibi lity
n the region encompassing northern Arizona and southern Utah to the
urban plume from southern California. Glantz (1982) documented the
movement of the Los Angeles urban plume across the Mojave Desert
for distances up to 500 km. Hotter et a1 (1981) described a meteorological
-3-
flow pattern that resulted in the long-range transport of the Los
Angeles urban plume into the Mohave Desert and the Grand Canyon,
Bryce and Zion National Parks. However, they could not quantitatively
ink this episode to visibi ity impai rment in the region.
In December 1978, August 1979 and July-August 1980, the Cloud and
Aerosol Research (CAR) Group at the University of Washington carried
out ai rborne studies of the effluents from the Mohave coat-fi red
electric power station. This plant is located near Bullhead, Arizona,
n the Colorado Ri ver Val ley, 120 km southeast of Las Vegas (Fig. 1.1)
The plant burns coal consisting of 10% dry ash, with a moisture content
of 12% and a sulfur content of 0.5% (i nformation provided by Southern
Cali fornia Edison).
The 1978 and 1979 CAR studies were concerned primari ly with the
plume from the Mohave power plant, whi le the 1980 study was concerned
both with this plume and the Los Angeles urban plume and thei r
effects on ai r qual ity in the southwestern United States. Glantz
(1982) described some of the data from the 1980 field study, with
particular emphasis on the Los Angeles urban plume and its effect
on regional visibi ity. The present study is concerned with the
effluents from the Mohave power plant and thei r effects on regional
visibi lity.
.4-
0 50 km
The location of the Mohave power plant in relation to theGrand Canyon, Bryce and Zion National Parks (outlined bydashed lines) Cities are represented by squares, smalltowns by dots and the Grand Canyon Visitors Center (V.C.by a cross.
-5-
1.2 Topography of the Area and Its Effects on the Mohave Plume
The topography surrounding the Mohave power plant is depicted in
Fig. 1.2. Immediately north of the plant there is a north-south
oriented valley, 70 km long and 15 to 25 km wide. Mountai ns bordering
this valley rise to over 1500 m above mean sea level (MSL). The
Colorado Ri ver itself has an elevation of only 200-300 m MSL 1n
this valley.
Si xty-five ki lometers north of the plant, a gap in the Black
Mountains forms a saddle, with the lowest elevation being 892 m MSL.
In the presence of southwest winds, the plume from the Mohave plant
general ly moves northeast through the gap in the Bl ack Mountai ns
toward the point where the Colorado Ri ver leaves the Grand Canyon
National Park.
Approximately 70 km north of the pl ant, the mountains enclosing
the Colorado Ri ver give way to a large basin encompassing Las Vegas
to the west, the entrance to the Grand Canyon to the east, and Lake
Mead. The dimensions of this basin are ~130 km from west to east and
~130 km from north to south. It is in this basin, or "mixing bowl ,"
that the plume from the Mohave power plant can readi ly mix with ai r
Topography of the region surrounding the Mohave powerplant. Terrain over 915 m is indicated by the slantedlines. Specific elevation points are indicated bydots. Cities are indicated by squares.
-7-
from other large sources of pol lution, including the Las Vegas metropo-
itan area and the Los Angeles urban plume.
However, the Mohave plume does not always flow northward into the
"mixing bowl With northerly winds which commonly occur in winter,
or which may accompany the passage of a cold front, the plume moves
south through the Mohave Val ley (which is not as confining as the chan-
nel north of the Mohave power plant) The only major source of pol lu-
tion south of the plant is Needles, California, which is located 37 km
south of the plant in the Mohave Val ley.
1.3 Primary Measurements
A major objecti ve of the present study was to determine the hori
zontal and vertical dimensions of the plume from the Mohave power
plant. The parameters used in the present study to differentiate the
plume from the ambient ai r are: particle size di stributions, the
extinction coefficient of light scattered by particles and gas
molecules, sulfur dioxide concentrations, and the ratio of cumulative
particle volume concentrations to cumulati ve particle number
concentrations. Each of these parameters is discussed briefly below.
The instruments used to measure these parameters are described in
Chapter II
-8-
(a) Particle Size Distributions
The principal features of atmospheric particle size distri butions
are the nucleation, accumulation and coarse parti cle modes (Wi lleke and
Whitby, 1975). The nucleation mode is composed of particles <0.1 urn in
diameter. The accumul ation mode includes particles between 0.1 and 2.0
pm in diameter. The coarse particle mode includes particles >2.0 urn in
diameter.
Particles in the accumulation mode have the longest (up to a week
or more) average residence time. Particles in the accumulation mode
are also most efficient in scattering light and therefore in affecting
visi bi lity (Friedlander, 1977).
(b) The Extinction Coefficient
The extinction coeffi cient of light is inversely related to
visual range (Koschmieder, 1924; Mi ddleton, 1952; Johnson, 1954;
Waggoner et al 1981) The visual range (V is given by:Hi
^ tt (1-1 ’where "a" is a constant, and b is the total extinction
coeffi cient of light. The total extinction coeffi cient is given by:
b b- + b + h + b (1.2)ext Rg sp ag ap
where the four components on the ri ght-hand side are,
respectively, Rayleigh scattering due to gases (br,Kgscattering by particles (b absorption by gases (b
sp ag
and absorption by particles (b Li ght scattering byap
particles is usual ly the dominant extinction mechanism
and wi hereafter be referred to as bS CBL
(c) Sutfur Dioxide
Atmospheric visibi lity and particulate sulfate
concentrations are generally considered to be closely related
(Eldred et a1 1983) The conversion of SO,, to fine particulate
sulfate in wel l-aged urban or semi -urban ai r increases the mass
of aerosol with diameters 0.3-1.5 urn. This is the size
of particle most dominant in scattering visible li ght (Hobbs
and Eitgroth, 1981) However, the sulfate mass distribution
in power plant plumes can have substantial fractions above
and below the optically critical size range of 0.3-1.5 urn di ameter
(Hobbs and Eitgroth, 1981) As a power plant plume evolves
downwind, sulfate may accumulate in the optical ly critical size range
via gas-to-particle conversion in the plume or entrainment of sul fate
from the ambient ai r (Hobbs and Eitgroth, 1981)
10
(d) Volume-to-Number Ratio of Particles
By comparing the cumulative particle volume
concentration to the cumulative particle number
concentration in the particle size range 0. 3-1 5 pm
diameter, one can differentiate between plumes and the
ambient air. Generally, this ratio is greater in a plume
than in the ambient air (see Chapter III)
1 .4 Data Sources
Airborne data from all three years of the CAR
Group s Mohave study will be used in this
thesis However, particular attention will be paid to
University of Washington (UW) flight numbers 710, 711,
725 803-810 922-924, 926 928 and 929
UW flights 710 and 725 occurred on December 4 and
December 20 1978 respectively, when the Mohave plume
was advected southward toward Needles , California. UW
flight 711 occurred on December 8 1978 when the Mohave
plant was not operating.
Flights 803-810 occurred from August 23 to
September 3 1979 On these flights the Mohave plume was
moving northward into the Colorado River Valley. On
several of these flights the plume was tracked for a
distance of more than 130 km north of the plant.
Flights 922-924 , 926 928 and 929 occurred from
11
August 8 to August 15 1980 when the plume from the
Mohave power plant was traveling northward through the
Colorado River Valley. Ambient conditions were more
polluted during the 1980 study than the 1979 effort, due
to pol lution from the Los Angeles urban plume and
numerous brush fires (Glantz, 1982)
1. 5 Scope of Study
The Mohave plume can be examined on two different
scales. The smaller scale is determined by the visible
plume. The regional scale extends beyond the range of
the visible plume. By using the parameters described in
Section 1 3 we can identify the plume even if it is no
longer visible.
In this thesis we wil l attempt to define the
regional scale or extent of the Mohave plume. We also
wish to determine the influence of the Mohave plume on
the visibility of the surrounding region. Our region of
concern is the Colorado River Valley, the "mixing bowl"
to the north of the Mohave plant (described in Section
1 2) and the Mohave Valley to the south of the Mohave
plant.
In Chapter II we will describe the airborne
instrumentation relevant to this study. Data analysis,
which is presented in Chapter III focuses on the
12
horizontal and vertical dimensions of the Mohave
plume. Some interpretations of the data are given in
Chapter IV. A summary of this study and recommendations
for future work are presented in Chapter V.
CHAPTER II
INSTRUMENTATION
2 .1 Introductory Remarks
In this chapter we will describe the airborne
data-gathering facilities used in the 1978 1979 , and
1980 Mohave field studies that are relevant to the
measurements discussed in this thesis.
2 2 Instrumentation on the B-23 Research Aircraft
The instrumentation aboard the B-23 aircraft
consists of equipment for particle measurements gas
measurements meteorological measurements and
navigation. The instruments aboard the B-23 aircraft are
listed in Table 2 1. The instrument configuration is
illustrated in Figs 2 1-2 3 The particle and gas
measuring instruments used for obtaining measurements
discussed in this thesis are described below. For
detailed descriptions of the remaining instruments the
reader is referred to Hegg 1976) Eitgroth (1978) Yates
(1981) and Glantz (1982)
(a) Particle Measuring Instruments
Two particle measuring instruments aboard the B-23
TABLE 2. 1 Specifications of research instruments aboardthe University of Washington s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Total airtemperature+
Static airtemperature+
Dew pointt
Pressurealtitutet
True airspeed!
Air turbulence!
Liquid watercontent! ++
Electric field+t
Platinum wireresistance
Computer value
Dew condensation
Variablecapacitance
Variablecapacitance
Differential
Hot wireresistance
Rotary field mill
Rosemount Model102CY2CG + 414 LBridge
In-house
Cambridge SystemsModel TH73-244
RosemountModel 830 BA
RosemountModel 831 BA
MeteorologyResearch, Inc.Model 1120
Johnson-Williams
MeteorologyResearch, Inc.Model 611
-70 to 30C(+/-0 1 C)
-70 to 30C(+/-0 5C)
-40 to 50C(+/-1C)
150 to 1060 mb(+/-0 2%)
0 to 230 m s~1(+/-0. 2%)
0 to 10 cm2^3 s~1(+/-10%)
0 to 2 g m,0 to 6 g m~
-10 to 110 kV m(+/-10%)
(continued)
TABLE 2 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Types and sizesof hydro-meteorst ++
Metal foil impactor MeteorologyResearch Inc.Model 1220A
Detects particle(>250pm)
Ice particle Optical polariza- In-houseconcentrationst ++ tioh technique
0 to 100 S.~1detects particles(>50ym)
Concentration ofcloud condensa-tion nuclei-f-
lee nucleusconcentrationst ++
Ice nucleusconcentrations! -(-+
Concentrations ofsodium-containingparticlesf ++
Altitude aboveterrain+
Light-scattering In-house
NCAR acoustical In-housecounter
Polarizing Mee Industries
Flame spectrometer In-house
Radar altimeter AN/APN22
0 to 5000 cm(+/-10%)
-3
-10. 01 to 500 &
0. 1 to 10, 000 -1
0 to 10, 000 S.(+/-1%)
0 to 6 km(+/-5%)
-1
(continued)
TABLE 2 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Weather radart ++
Aircraft positionand course plotter!
Timet
Timet
Groundcommunication-t-
Light-scatteringcoefficient!
Heading!
Ground speed anddrift angle
5 cm gyro-stabilized
Works off DMEand VOR
Time codegenerator
Radio WWV
FM transceiver
Integratingnephelometer
Gyrocompass
Radio Corp. ofAmerican, AVQ-10
In-house
Syston DonnerModel 8220
Gertsch RHF 1
Motorola
Meteorology Res.Inc. Model 1567(modified forincreased stabilityand better responsetime)
Sperry Model C-2
Bendix ModelDRA-12
100 km
180 km(1 km)
h, min, s(1: 105)
min
200 km
0 tO 2. 5 X lO"4!!!"1or 4 l0 to 10 x 10" m
0 to 360 (+/-2%)
0 to 6 km altitude
(continued)
TABLE 2. 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Ultravioletradiation!
Angle of attackt
Photographs!
Barrier-layerphotoelectric cell
Potentiometer
35 mm time-lapsecamera
Eppley Laboratory,Inc. , Model 14042
RoseihountModel 861
AutomaxModel GS-2D-111
0. 7 J m"^"1(+/-5%)
+/-23(+/-0. 5
1 s to 10 min
Total gaseoussulfurt
FPD flame photo-metric detector
Meloy Model 285 0 5 ppb 1 ppm
Ozonet
NH- NO, NO,,, NO + Chemiluminescence*j ^- x
Size spectrum ofaerosol particlest
Size spectrum ofaerosol particlest
Chemiluminescence
(C^)
(O^)Electrical mobilityanalyzer
90 light-scattering
Monitor LabsModel 8410 A
Monitor LabsModel 8440
Thermal Systems,Inc. , Model 3030
Royco 202(in-house modified)
0 to 5 ppm(+/-7 ppb)
0 to 5 ppm(+/-10 ppb)
0. 0032 to 1. 0 pm
0 3 to 12 ym
(continued)
TABLE 2. 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Size spectrum ofaerosol particles!
Size spectrum ofaerosol particles
Size spectrum ofaerosol particles!
Size spectrum ofaerosol and cloudparticles!
Size spectrum ofcloud particles!!
Size spectrum ofprecipitationparticles!!
Forwardlight-scattering
Diffusion battery
o35-120 light-scattering
Forward light-scattering
Diodeoccultation
Diodeoccultation
Royco 225 1. 5 to 40 ym(in-house modified)
Thermal Systems, 0. 01 0 2 \imInc. Model 3040with in-houseautomatic valves &sequencing
Particle Measuring 0. 09 3. 0 urnSystems, Model (+/-0. 007 urn)ASASP-X
Particle Measuring 1. 5 to 70 pmSystems, ModelASSP100
Particle Measuring 20 to 300 ymSystems, ModelGAP-20OX
Particle Measuring 300 to 4500 pmSystems, ModelOAP-200Y
(continued)
TABLE 2. 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Concentrationsof Aitken nucleit
Concentrationsof Aitken nucleit
Sizes and types ofaerosol particlest
Concentrations ofice nuclei+t
Light transmission General ElectricModel CNC II
Rapid expansion Gardner
Direct impaction Glass slides
Direct impaction Nuclepore/Milliport
102 to 106 cm"3(particles > 0. 001 pm)
2 x 102 to 107 cm ~3
5 to 100 pm
Mass concentration Electrostatic depo- Thermal Systems,aerosol particlest sition onto matched Inc. Model 3205
oscillators
0. 1 to 3000 ug m~3(+/-0. 5 pg m-3)
Particulate SO^ Teflon filtersN03 CL~, Na4’,K+, NH4+++
CXI & Dionex XRFspectroscopy andion exchangechromatography
Thermal Systems,Inc. , Model 3205
0 1 to 50 pg m(for 500 air sample)
(continued)
TABLE 2 1 (continued) Specifications of research instruments aboard theUniversity of Washington’ s B-23 aircraft.
Parameter Instrument type Manufacturer Range (and error) *
Cloud watersamples!+
Size-segregatedconcentrationsof aerosolparticles+t
Centrifuge
Cascade impactor
In-house
Sierra InstrumentsInc.
Collects clouddroplets >3 pmradius with anefficiency >20%
0. 1 3 urn(6 size fractions)
*A11 particle sizes refer to maximum particle dimensions
tData displayed or available aboard the aircraft.
++Not relevant to this study.
21
INSTRUMENT POOMOUNTED ONFORWARD EDGE
Figure 2.1 Research instruments on the University of Washington’sDouglas B-23 aircraft. See following pages for key to symbols.
22
1 Pilot
2 Co-pilot
3 Meteorological Observer
4 Instrumentation Engineer
5 Plight Director
6 Aerosol Scientist
7 Air Chemist
A 5-cm gyrostabilized weather radar
B Rosemount airspeed, pressure altitude and total temperature probes,MRI-turbulence probe and electronics, J-W liquid water probe, angleof attack sensors
C VOR-DME slaved position plotter; research power panel (3 kW 110V 60Hz; 1.6 kW 110V 400 Hz; 150 amps 28V dc) Doppler horizontal winds
D Electronic controls for J-W liquid water indicator, dew pointthermometer, time code generator and time display, WWV time standardreceiver, TAS and T analog computers, signal conditioningamplifiers, audio signal mixers, TSK time-share data multiplexers (63channels) 2-D electric field and turbulence analog readouts
E Minicomputer (16-bit word 16-K word capacity) computer interfaceto instrumentation, remote A-D converter, keyboard and printer,floppy disk
F Hybrid analog/digital tape recorder (7-track, 1/2") and high-speed6-channel analog strip chart recorder
G Inlet for isokinetic aerosol sampling
H Aircraft oxygen, digital readout of all flight parameters, relativehumidity sensor, time code reader and time display, heated aerosolplenum chamber, vertical velocity, Millipore sequential filter system
I Controls for metal foil impactor, PMS-2D image processor anddigital recorder
23
J Aerosol analysis section, generally contains: integrating
nephelometer, mass monitor, diffusion battery, automatic cloud
condensation nucleus counter, Whitby aerosol analyzer, Royco particle
counters, automatic condensation nucleus counter, automatic grab
samplers (28 and 55
K PMS axially scattering spectrometer (small droplet probe)
vertically mounted
L Analog flight parameters and digital cloud physics data display,
color graphics terminal and PMS 2-D image repeater
M PMS 1-D optical array precipitation and cloud particle spectrometer
N 2-D PMS optical array precipitation and cloud particle image probes
0 ultraviolet photometer
P Electric field mill sensor (vertical and horizontal field)
Q Automatic ice particle counter
R Metal foil hydrometeor impactor
S Ion conductivity sensor
T Gas analysis system: SO^, 0^, NO, N0^, NH^, hydrocarbon
U Radar repeater, side-viewing automatic camera, real-time display of
1-D PMS data
V Radar altimeter, 2-D electric field mill electronics, 8-channeltelemetry transmitter, dew point sensor
W Instrument vacuum system (consists of four high-capacity vacuum
pumps, connected individually to the cabin)
X Parachutes, survival gear, life raft
24
AUTOMATIC VALVE SEQUENTIALBAG SAMPLER (FOR OPC 8 EAA)^
-SAMP’LER^ A.TKEN NUCLEUSCOUNTER-
PROBE FORMANUAL BAGSAMPLE (UPTO 3 M3CAPACITY)-FORFILTERS, CASCADEIMPACTORS, ETC.
ELECTRICAL AEROSOLANALYZER (EAA) 8MASS MONITOR
/-INTEGRATING/ NEPHELOMETER/ A--ISOKINETIC__/y^=_) PROBE
Tv sT^\ .5 ^- l1?"’-- STATICm^^-r PRESSURETT L-IY TRANSDUCER
^-SOA HEATEDCHAMBER
GAS ANALYSISSYSTEM (NO.NH,NOz.SOz. AND Os)
OPTICALPARTICLECOUNTERS(OPC i an)
INLET FORD ISOKINETICPROBE
AXIALLYSCATTERINGSPECTROMETERPROBE
openSENSOR
\-ISOKINETIC PUMP
Figure 2.2 More details on instrumentation aboard the University ofWashington’s B-23 aircraft.
25
AIRFLOW
RAM AIRSAMPLETUBE
AIRFLOW
(a (b)
AIRCRAFTOUTER SURFACE
(c
Figure 2.3 Schematic of the air sample inlet system for the (a)Aitken Nucleus Counter, Royco 202 Counter and Electrical
Aerosol Analyzer (EAA) (b) The Royco 225 counter and
Nephelometer, and (c) Sulfur, NO, NO and NO and 0 gasNO and NO and 0A -J
analyzers [from Eitgroth (1978)
26
ai rcraft are particularly relevant to the measurements discussed
n this thesis; they are the Royco 202 and the integrating
nephelometer.
(i Royco 202
The Royco Model 202 Optical Particle Counter measures the
size distribution of particles from 0.3 to 12 urn diameter. Particle
size is determined by measuring the light scattered at 90 from a
collimated beam. The Royco 202 measures the equivalent spherical
diameter of a particle based on the effective light scattering
diameter.
The Royco 202 has fifteen logarithmical ly-equal size channels.
A sixteenth channel records particles with diameter greater than
12 pm. The Royco 202 sampled from a neoprene bag aboard the ai rcraft
(Fi g. 2.1
The theory of the operating technique employed by the Royco 202
s further described by Zinky (1962)
(i Integrating Nephelometer
The Meteorology Research Inc. Model 1567 Nephelometer
measures the extinction coefficient of li ght scattered by both
particles and gas molecules. The theory and operation of the
nstrument have been well documented by Alquist and Charlson (1967)
The particular instrument employed in this study was modified
n-house for increased stabi lity and dynamic range. The ai r
sampled by the nephelometer was provided by the plenum
27
chamber (Fig. 2. 1)
(b) Gas Measurements
Data from a Meloy 285 Sulfur Analyzer and a Monitor
Labs 8410A Ozone Analyzer are presented in this
thesis. Data from the oxides of nitrogen analyzer will
not be presented because the concentrations of the oxides
of nitrogen encountered in the ambient air during the
Mohave field study were below, or only slightly above,
minimum detectable levels.
(i) Sulfur Analyzer
The sulfur analyzer measures the concentration of
total gaseous sulfur. Sample air is carried to the
analyzer through a ram air line exposed to a hydrogen
hyperventilated flame. The squared concentration of
sulfur is proportional to the intensity of light emitted
by excited sulfur molecules when they drop back to a
lower energy state. The detection limit is 0. 5 ppb of
S0~ and the range 1000 ppb.
The sulfur analyzer also detects particulate sulfur
and sulfuric acid droplets , but with a relatively low
detection efficiency. This can lead to a maximum error,
under normal sampling conditions of 1 ppb in the
measured concentration of total gaseous sulfur.
28
(ii) Ozone Analyzer
This instrument detects ozone through the
chemiluminescent reaction between ozone and
ethylene. The sample air is brought to the instrument
through a ram air line and mixed with ethylene gas. The
light emitted from this mixture is proportional to the
concentration of ozone. The minimum detectable ozone
concentration is 5 ppb.
The ozone analyzer was improperly calibrated during
the 1980 Mohave field study, due to a faulty electronic
setting in the analyzer. Measured ozone concentrations
were 1 85 times the actual ozone concentrations The
1 85 factor was determined by testing the B-23 s ozone
analyzer against the properly calibrated University of
Washington Health Science Department ozone analyzer. The
ozone concentrations presented in this thesis from the
1980 Mohave field study have been divided by 1. 85 to
provide correct values
(c) Meteorological and Navigational Instrumentation
The B-23 aircraft is equipped to provide a variety
of meteorological and navigational data. Some of these
parameters include air temperature, dew point, pressure
altitude, turbulence, ultraviolet radiation, aircraft
position (VOR-DME) and radar altitude. A more complete
29
list of measurable parameters , and the instrumentation
involved, can be found in Table 2 1
CHAPTER III
PRESENTATION OF THE DATA
3.1 Introductory Remarks
In this chapter we present horizontal isopleths of
the maximum values of b and SO, concentrations in the
Mohave plume and the surrounding regions based on airborne
measurements obtained on December 20 , 1978, August 23,
August 11 August 28 and August 31, 1979, and August 11,
1980. We also present cumulative particle volume to
cumulative particle number ratios and particle size
distributions for these days. The vertical distributions
of SO^ and b in the plume and in the ambient air are
presented for August 27 and August 28, 1979
3 2 Methods of Data Analysis
To establish the horizontal extent of the plume from
the Mohave power plant, isopleths were drawn of maximum
^cat and S02 concentrations downwind of the plant.
Instantaneous plume values, not time or spatially averaged
averaged values, were used to determine the datum points
for the isopleths. These datum points were the maximum
values of bg-;,*. and S0 concentration that occurred
31
during the crossing of the plume.
In this study, the distinction between the Mohave
plume and the "ambient" air was based upon the
instantaneous data. When sampling took place at ranges
at which the Mohave plume was still visible, the visual
observations of the flight crew supplemented the
instantaneous data. At the farther ranges, when the
Mohave plume was not visible, the flight crew
extrapolated the trajectory of the plume from the last
point at which it was visible on the basis of the
real-time wind data available aboard the B-23
aircraft. Elevated SO- and b signals (relative tosca’c
the running mean signal level detected along these
trajectories were attributed to the Mohave plume. The
plume boundaries were defined by the width of these
elevated signals All measurements taken within the
so-defined plume boundaries were considered plume values,
and those taken outside of these boundaries were
considered "ambient" values. Such a definition of the
plume is equivalent to the instantaneous plume described
by Gifford (1960) This instantaneous plume can meander
back and forth with time, producing a time-averaged plume
of considerably greater extent than the instantaneous
plume. We shall not discuss the time-averaged Mohave
32
plume in detail but simply note that the "ambient" air of
the Colorado River Valley likely contains remnants of the
Mohave plume, due to such meandering.
Thus one might expect the "ambient" air downwind
of the Mohave power plant to be influenced by the
plume. Indeed, "ambient" air in the "mixing bowl" was
on occasions, observed to have different characteristics
from "ambient" air upwind of the plant. By examining
b , SO., concentrations , particle volume-to-numberscat
ratios and particle size distributions differences in
the characteristics of the "ambient" air in the region
become more apparent.
3 3 Regional Extent of the Plume from the Mohave
Power Plant
Five cases with a northward moving plume and one
case with a southward moving plume are described below.
(a) August 23 1979 (UW Flight 803)
0700 to 1200 PDT
On August 23 , 1979 , the plume and "ambient" air
were sampled out to 130 km north of the Mohave
plant. Figure 3 1 shows the b isopleths Values ofsca^
b4.
in the "ambient" air near the power plant weresca’c
lower than the "ambient" b values downwind of thescat
plant, particularly in the "mixing bowl" (^70 to 100 km
33
Maximum values of b (in units of 10 m at thescat
altitude of the centerline of the plume from the Mohave
power plant on 23 August 1979. Measurements in the Mohave
plume are indicated by crosses. Measurements in the
"ambient" air are indicated by circles. Terrain over
915 m is indicated by slanted lines. Specific elevation
points are indicated by dots. Solid isopleths are drawn
where the data points are dense. Dashed isopleths are
drawn where the data points are sparse.
34
north of the plant) Using Eqn. (1 1) we estimated a
value for b at Las Vegas by using the visual range
recorded by the National Weather Service (NWS) office at
Las Vegas Using "a" values in Eqn. (1 1) of 3 .00 and
3 .91 (Middleton, 1952) bg^^ values of 0 36 x 10~4 nT1-4 -1
and 0 48 x 10 m respectively, were obtained for Las
Vegas during the time of UW flight 803 In the "mixing
bowl "b values of 0 33 x 10~4 m"1 and 0 38 x 10~4 m~1were measured in the "ambient" air and in the Mohave
plume, respectively. Winds at Las Vegas were variable,
<3 m s , during the time of the flight.
Figure 3 2 shows the concentrations of b
measured downwind of the plant. Visual observations by
the flight crew indicated that the plume moved to the
northeast through the gap in the Black Mountains (see
Fig. 1 2 for the location of the Black Mountains)
However Figs. 3 1 and 3 2 do not clearly indicate this
path. In Fig. 3 1, the bg,,,*. values in the "ambient" air
on the west side of the "mixing bowl" are equivalent to
the b in the plume on the east side of the "mixing
bowl " In Fig. 3 2 the 10 ppb isopleth cannot
distinguish between the "ambient" S0~ concentrations of
^ 0 to 3 ppb and the SO- concentrations in the plume of
^ 1 to 5 ppb.
35
Maximum SO concentrations (in ppb) downwind of the
Mohave power plant on 23 August 1979. Measurements in theMohave plume are indicated by crosses. Measurements inthe "ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots. Solid isopleths are drawnwhere the data points are dense. Dashed isopleths aredrawn where the data points are sparse.
-36-
Figure 3.3 shows the particle volume-to-number ratios. This ratio
is essential ly the mean value of particle volume. The values of this
quantity were quite distinct in the plume and in the "ambient" ai r
close to the plant. However, unlike the SOg concentrations and fl ight
crew observations, the particle volume-to-number ratios did not show a
distinct plume in the "mi xing bowl ."
Shown in Fi g. 3.4 are the number, surface area and volume
distributions of particles measured in the plume and in the
"ambient" ai r at 0.5 km from the Mohave plant on August 23, 1979.
The particle number di stributions (Fi g. 3.4a) show that there were
many more particles with diameters between ~0.3 and 2.0 urn in
the plume than in the "ambient" ai r. The particle surface area
distribution (Fi g. 3.4b) was bimodal in the plume, with particle modes
at 0.55 urn and 1.1 urn. The particle surface area distribution peaked
at 1.1 urn in the plume and at 0.35 urn in the "ambient" ai r. The
particle volume spectra (Fi g. 3.4c) showed peaks at 1.1 urn in the
plume and 0.55 urn in the "ambient" ai r. The total particle volume
i n the principal visible li ght scattering range of 0.3 to 1.5 urn was
3 -3 3 -362 urn cm in the plume and 1.2 pm cm in the "ambient" ai r.
Shown in Fi g. 3.5 are the number, surface area and
volume distributions of particles measured 65 km
37
A plot of cumulative particle volume to cumulative
particle number ratios (multiplied by 100) downwind of
the Mbhave power plant on 23 August 1979. Measurements in
the Mohave plume are indicated by crosses. Measurementsin the "ambient" air are indicated by circles. Terrain
over 915 m is indicated by slanted lines. Specific
elevation points are indicated by dots.
38
160
10
’ 40CM
^O0
<0
5 100C
0 8090
0
<^ 600
40
2 0
0
T
:a
’"^Ax
110’’ 10 10’DIAMETER (/xm)
10 10 10’DIAMETER (/Am)
b)(a)
Number (a) surface area (b) and volume (c)distributions of particles measured in the ambient air(o) at an altitude of 762 m at 0712 PDT and in theplume (A) at an altitude of 823 m at 0721 PDT at adistance of 0.5 km from the Mohave power plant on 23August 1979.
39
50
45
103 !-
^ 102<->
^ 100
1 o
10’’
DIAME
\ ^A s
o-1
10
Eu
CM
E
0
u>
’c3
0>0
o
10 10’TER (pjn)
40
35
30
25
20
5
10
5
0
DIAMETER (^.m) DIAMETER (^m)
a
\
--l 00-’ 10 10’ 10"’ 10 10’
5.6
4.8
T 4-0
Eu
"e 3-2
0 2.4o>
o
^ 6-0
^ 0.8
<?I
^r(a) b) (c
Figure 3.5 Number (a) surface area (b) and volume (c)distributions of particles measured in the plume (o) atan altitude of 884 m at 0909 PDT and in theambient air (A) at an altitude of 915 m at 0912 PDT at adistance of 65 km from the Mohave power plant on 23August 1979.
-40-
downwind of the Mohave plant on August 23, 1979. Note that the peaks
of the particle surface area and volume distributions in the plume were
0.55 ym, compared to 1.1 urn at the 0.5-km range. The peaks of the
particle surface area and volume distributions in the "ambient" ai r
remained at 0.35 urn and 0.55 urn, respectively. The shapes of the
particle surface area and volume distributions in the plume and in the
"ambient" ai r were simi lar, although the plume had a higher number con-
centration in the range from 0.5 to 2.0 urn. The total particle volume1 3 -3
was 1.7 urn cm" in the plume and 1.3 urn cm in the "ambient" ai r.
Fi gure 3.6 shows the number, surface area and volume distributions
of particles measured 102 km downwi nd of the Mohave plant on August 23,
1979. The peak in the particle surface area distributions (Fi g. 3.6b)
in both the plume and the "ambient" ai r was at 0.35 urn. The peak in
the particle volume distributions (Fi g. 3.6c) in the plume and in
the "ambient" ai r was generally at 0.55 urn. The total particle volume
0 1 3 3was 1.3 urn cm’ in the plume and 1.1 urn cm in the "ambient" ai r.
Figure 3.7 shows the number, surface area and volume
distributions of particles measured 130 km downwind of the
Mohave plant on August 23, 1979. The shapes of the distributions
41
45h <?
40
35
rt
04
25 10
u
(0
4.
4.0
3.2
00>_0D\
(/)D
Q
0>_oo>^>o
2.4
1.6
0.8
0
10’’ 10’10p
DIAMETER ^on)
a)
-l ,010 10’ 10’DIAMETER (^.m)
b)
^1 ^10 10" 10’DIAMETER (^im)
C)
Number (a) surface area (b) and volume (c)
distributions of particles measured in the ambient air
(o) at an altitude of 1220 m at 1003 PDT and in the
plume (A) at an altitude of 1220 m at 1005 PDT at a
distance of 102 tan from the Mohave power plant on 23
August 1979.
42
35
10 30
Q
9_0O
<n
CME 25
20
5
10
4.0i?r
u
M 3.2
^Q 2.4o0
o
^ ’6o
0.8
0
: //
10"’ 10 10’DIAMETER (p.m)
0)
10-’ 10 101DIAMETER (^(.m)
b)
10-’ IQO 10"DIAMETER (p.m)
(0
Number (a) surface area (b) and volume (c)
distributions of particles measured in the plume (o)
an altitude of 762 m at 1032 PDT and in the
ambient air (A.) at an altitude of 762 m at 1056 PDT at a
distance of 130 km from the Mohave power plant on 23
August 1979.
at
-43-
were simi lar to those at the 102-km range (Fi g. 3.6). A discerni ble
di fference existed between the plume and the "ambient" ai r at
130 km downwind of the Mohave plant. The number, surface area
and volume distributions for particles with diameters from
0.3 to 1.2 urn were slightly greater in the plume than in the
"ambient" ai r. The total particle volumes in the plume and In ’fc:
3 -3the "ambient" ai r were 1.3 and 0.8 urn cm respectively.
In summary, on August 23, 1979. the peak in the particle
volume distribution in the "ambient" ai r was at 0.55 urn over
the enti re area covered by the flight. The corresponding peak
in the Mohave plume was at 1.1 urn at 0.5 km from the Mohave plant.
From 65 km to 130 km from the Mohave pl ant, the peak in the
parti cle volume distribution in the pl ume was at 0.55 urn. At
65 km from the plant the shapes of the parti cle size distri butions
were simi lar in the plume and in the "ambient" ai r. Despite this
simi larity, distinct differences existed between the pl ume
and the "ambient" ai r out to a distance of 130 km, as seen in
the SOp concentrations and b data (Fi gs. 3.1 and 3.2).
The peak in the parti cle surface area distri bution
n the "ambient" ai r was at 0.35 urn over the enti re area
44
covered by the flight. The corresponding peak in the
plume was at 1 1 pm at 0 5 km from the Mohave plant. At
65 , 102 and 130 km downwind of the Mohave plant, the
peaks in the particle surface area distributions in the
plume were at 0 .55 0 35 and 0 35 \im, respectively. The
particle surface area distributions in the plume and in
the "ambient" air for the remaining flights were quite
similar to those on August 23 1979 Hence, there will
be no further discussion of the surface area
distributions^
(b) August\27, 1979 (UW Flight 806)
0555 to 13"0< PDT
The plume from the Mohave power plant and the
"ambient" air were sampled from the B-^3 aircraft out to
\/distances of ^ 185 km from the plant on August 27,
1979 Figure 3. 8 shows the bg^at ^-^P16^3 for this
flight. Note the lower values of bg^^ in the "ambient"
air near the plant compared to those downwind
(particularly near Mormon Mesa) The "ambient" bg^^
values in the "mixing bowl" were greater than "ambient"
values closer to the plant.
Using "a" 3 91 in Eqn. (1 1) (Middleton, 1952)
and the measured visual range at Las Vegas a b value
of 0 69 x 10" m was obtained for Las Vegas during the
45
scataltitude of the centerline of the plume from the Mohavepower plant on 27 August 1979. Measurements in the Mohave
plume are indicated by crosses. Measurements in the"ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevation
points are indicated by dots. Solid isopleths are drawnwhere the data points are dense. Dashed isopleths aredrawn where the data points are sparse.
46
period of this flight. This value indicates that bSCd^
increased from the "mixing bowl" (where we measured a
-4 -1value of 0 44 x 10 m toward Las Vegas. The winds
were 3 m s" and from the west at Las Vegas on this day,
indicating that it could have been the source of the high
b values observed in the "mixing bowl "
Figure 3 9 shows the concentrations of S0~ measured
downwind of the Mohave plant. Visual observations by the
flight crew indicated that the plume split near the gap
in the Black Mountains (see Fig. 1 2 for the location of
the Black Mountains) This splitting is not revealed
very wel l in Figs 3 8 and 3 9 since the "ambient" values
of b and SO- on the west side of the "mixing bowl"
are greater than or equal to the plume values on the east
side of the "mixing bowl " The measurement of 30 ppb in
the "mixing bowl" appears abnormally large and may be
indicative of another source of SO-
Figure 3 10 shows the vertical distributions of SO-
and bccat ln the Monave plume and in the "ambient" air at
5.6 28 93 and 185 km downwind of the Mohave plant on
August 27 1979 At these ranges b and SO-SCuU ,
concentrations in the "ambient" air showed very little
variation over the vertical extent of the plume. SOy
concentrations in the plume showed significant vertical
Maximum SO- concentrations (in ppb) downwind
of the Mohave power plant on 27 August 1979. Measurements
in the Mohave plume are indicated by crosses.Measurements in the "ambient" air are indicated bycircles. Terrain over 915 m is indicated by slantedlines. Specific elevation points are indicated by dots.Solid isopleths are drawn where the data points are
dense. Dashed isopleths are drawn where the data pointsare sparse.
bacot (in units of 10 4 m"’
0 1.0 2.0 3.0
928
:o 930E 1; ’scat
- 932R
934 -1 /SOg0-
936Iscot ’SOz
9380 1.50 3.00 4.50
SOg (ppb)
bscot (in units of lO"’1^"1)0 O.I 0.2 0.3 0.4 0.5 0.6 0.7 0.8
bscot (i" units of lO"4 m’1)
0.5 1.0 1-50
920
922-0
E
<u 924
926a.
\. \ \ bsco.SOg bscot928
930100
SOgtppb)0 50
bscaf (i" units of lO^ m’10.2 0.3 0.4 0.5 0.6 0.7 0.80 0.1
150
.0
E906
908
)i/)
&>
a.
912
914
bsco>\
SOg
scot
0 10 15 20 25 30 35 40
SOg (ppb)
910
920.0
E
. 9303
1 9400-
950
960
// bscat
\S02 bscot
0 10 15 20 25 30 35 40
SOz (ppb)
Figure 3,10 SO^ concentrations and b^ in the Mohave pi ume (sol id ines and in the ambient air (dashed inesover the vertical extent of the p lume on 27 August 1979 at (a) 5.6 km, (b) 28 km, (c) 55 km, and(d) 93 km downwind of the Mohave plant. The slanted ines indicate that the concentrations of S02are less than or- equal to the vai up shu.-/n Fxt"’"na1 variances are denoted by the error bars
49
variation up to 185 km from the plant, where
concentrations of SOy in the plume and in the "ambient"
air were ^5 ppb. Values of b in the plume showed
significant variations at the 5 6- and 28-km ranges At
the 93- and 185-km ranges values of b in the plume
did not vary significantly with height.
Figure 3 11 shows the particle volume-to-number
ratios. The differences in the volume-to-number ratios
in the plume and the "ambient" air in the "mixing bowl"
were very smal l
Shown in Fig. 3 .12 are the particle number and
volume concentrations measured in the plume and in the
"ambient" air at 0 5 km from the Mohave plant on August
27 1979 There were many more particles with diameters
between ^ 0. 3 and 4 0 u rn in the plume than in the
"ambient" air (Fig. 3 12a) The particle volume spectra
show peaks at 1 1 and 3 5 \im in the plume and in the
"ambient" air, respectively (Fig. 3 12b) There was a
secondary peak in the particle volume distribution at
1 1 pm in the "ambient" air. The total particle volume
was 245 urn cm in the plume and 4 3 pm cm" in the
"ambient" air.
Figure 3 13 shows the number and volume
concentrations of particles measured in the plume and in
50
Figure 3.11 A plot of cumulative particle volume to cumulative
particle number ratios (multiplied by 100) downwind of
the Mohave power plant on 27 August 1979. Measurements in
the Mohave plume are indicated by crosses. Measurements
in the "ambient" air are indicated by circles. Terrain
over 915 m is indicated by slanted lines. Specific
elevation points are indicated by dots.
51
Q
10
10’
103
10
’E 102
Q
0>_0a
zT3
10’
10’
10 5UE=L’S 40(0
30
Q
20o^.>v 0
10"10 10" 10’DIAMETER (^.m)
0)
f*v->(-rt^tn^010"’ 10 10’DIAMETER (^.m)
b
Figure 3.12 Number (a) and volume (b) distributions of particles measured inthe ambient ai r (o) at an altitude of 762 m at 0606 PDT and inthe plume (A) at an altitude of 762 m at 0610 PDT at a distance of0.5 km from the Mohave power plant on 27 August 1979.
52
27
24
Kl
104 10
E
^15
103 12
ro
’E 102
Q
0>0
0\
z0
10’
lO1
Q
0>0
0
>0
9
6
3
10-I
10- 10’’ 10’DIAMETER (/^.m)
(a)
010’’ 10 10’DIAMETER ^m)
b)
Fi gure 3.13 Number (a) and volume (b) distributions of particles measured inthe plume (o) at an altitude of 945 m at 0821 PDT and in the ambientai r (A) at an altitude of 945 m at 0826 PDT at a distance of 81 kmfrom the Mohave power plant on 27 August 1979.
-53-
the "ambient" ai r at 81 km downwind of the Mohave plant on August 27,
1979. The peak in the particle volume distribution in the plume
remained at 1.1 urn (Fig. 3.13b) The peak in the particle volume
distribution in the "ambient" ai r was at 2.5 urn, with a secondary
peak at 1.1 urn. The total particle volumes in the plume and in the
3 -3 3 -3"ambient" ai r were 7.5 urn cm and 3.8 pm cm respectively.
Figure 3.14 shows the particle number and volume distributions
measured 185 km downwind of the Mohave plant on August 27, 1979.
Whi le there is some evidence of detectable plume at this range, it is
not conclusive. For example, the peak in the particle volume distri-
bution in the plume was at 2.5 urn at 185 km (Fi g. 3.14b) compared
to 1.1 urn at 81 km. The peak in the particle volume distribution in
the "ambient" ai r remained at 2.5 pm, with a secondary peak at 1.1
urn. The total particle volumes in the plume and in the "ambient" ai r
were 3.4 and 3.9 urn cm respectively.
Whi le the particle size di stributions in the plume on August
27, 1979, had the same shape as those in the "ambient" ai r only after
a range of ~185 km downwind of the Mohave plant had been reached on
August 23, 1979, the particle size distributions in the plume had the
same shape as those in the "ambient" ai r at only 65 km downwind of
the Mohave plant. On August 27, 1979, the peak in the particle
54
K)
10’ 10
E^.
15
10’ 12
-r"6 10’
Q
? 10’o^
^ 10
Q
O
’>o
9
6
10-I^010 10" 10’
DIAIVIETER (/^.m)
(0)
010’’ 10" 10’DIAMETER (^m)
b)
Fi gure 3.14 Number (a) and volume (b) distributions of particles measuredin the ambient ai r (o) at an altitude of 854 m at 0957 PDT and in theplume (A) at an altitude of 762 m at 0947 PDT at a distance of 185 kmfrom the Mohave power plant on 23 August 1979.
55
volume distribution in the "ambient" air was located
between 2. 5 and 3 .5 pm, with a secondary peak at
1 1 ym. On August 23, 1979 the peak in the particle
volume distribution in the "ambient" air never varied
from 0. 55 urn. Values of b in the "ambient" air were
slightly higher on August 27 than on August 23
It would seem that the "ambient" air in the
Colorado River Valley had different physical
characteristics on August 27 than on August 23.
(c) August 28 1979 (UW Flight 807)
0548 to 1046 PDT
On August 28 1979 the Mohave plume and in the
"ambient" air were sampled with the B-23 aircraft out to
^ 140 km downwind of the Mohave plant. Figure 3 15 shows
the b isopleths for this flight. As on the previous
day, lower values of b were measured in the "ambient"
air near the stack than in the "ambient" air farther
downwind. Splitting of the plume is evident in
Fig. 3 15 Using the measured visual range at Las Vegas
and taking "a" 3 .91 in Eqn. (1. 1) (Middleton, 1952) a
-4 -1bscat ^l1-1(R) of 0 .48 x 10 m was obtained for Las
-4Vegas In the "mixing bowl , " b values of 0 .28 x 10
-1 -4 -1m and 0 34 x 10 m were measured in the "ambient"
air and in the Mohave plume respectively. Winds at Las
Figure 3.15 Maximum values of b (in unitsscat
altitude of the centerline of the plume from the Mohavepower plant on 28 August 1979. Measurements in the Mohaveplume are indicated by crosses. Measurements in the"ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots. Solid isopleths are drawnwhere the data points are dense. Dashed isopleths aredrawn where the data points are sparse.
57
Vegas were westerly and <5 m s at the beginning of the
flight. They switched to southerly, 8 to 10 m s by
the end of the flight. Therefore, meteorological
conditions were not as favorable for the transport of
pollutants from Las Vegas to the "mixing bowl" on August
28 1979 as on the previous day. Values of bg in the
"ambient" air of the "mixing bowl were lower on August
28 than on August 27
Figure 3 16 shows the concentrations of SOy
downwind of the Mohave plant on August 28 1979 Again
the plume split at the gap in the Black Mountains (see
Fig. 1 2 for the location of the Black Mountains) SO^concentrations in the plume in the "mixing bowl" ranged
from 3 to 13 ppb. SOy concentrations in the "ambient"
air in the "mixing bowl" were 0-1 ppb.
Figure 3 17 shows the SO,, concentrations and b
in the Mohave plume and in the "ambient" air over the
vertical extent of the plume at 5 6 , 28 55 and 93 km
downwind of the Mohave plant on August 28 1979 At
these ranges b and SO., concentrations in the
"ambient" air showed very little variation over the
vertical extent of the plume. SOy concentrations and
b^ -i- showed some vertical variation in the plume at 5 6oCd.’n.
and 28 km downwind of the Mohave plant. The vertical
Figure 3.16 Maximum SO concentrations (in ppb) downwind of the
Mohave power plant on 23 August 1979. Measurements in theMohave plume are indicated by crosses. Measurements inthe "ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots. Solid isopleths are drawnwhere the data points are dense. Dashed isopleths aredrawn where the data points are sparse.
I
bscat (in units of 10-4 m-1)O.I 0.2 0.3 0.4 0,5 0.6 0.7 0.8
942^ (0)
S 944
i^ 9460:=)</)
2 ^ea:a.
950
952
SO;
0
scat
100 200SO (ppb)
300 400
bscat (in units of lO^ m’’)O.I 0.2 0.3
100SO (ppb)
bscot in units of 10’4 m’1 bscat (in units of lO^m’’)
15 20 25SO (ppb)
O.I 0.2 0.3 0.4
886^- (d)
’o 890[r
^ 894
(/)(nLD(ra.
898k
902
906
SO.
SOg ’scat
0 10 15 20 25 30 35 40
SO (ppb)
Figure 3. 17. SO^ concentrations and bscat in the Mohave plume (sol id ines) and in the ambient ai r (dashed ines)over the vertical extent of the plume on 28 August 1979 at (a) 5.6 km, (b) 28 km, (c) 55 km and(d) 93 km downwind of the Mohave plant. The slanted ines indicate that the concentrations of SO^ areless than or equal to the values shown. External variances are denoted by the error bars
-60-
variations of S0 concentrations and b in the plume werec- SCdC
smal at 55 and 93 km.
Figure 3.18 shows the particle volume-to-number ratios on
August 28, 1979. Beyond a range of 8 km, the values of this
ratio were very simi lar in the Mohave plume and in the "ambient"
ai r.
Shown in Fig. 3.19 are the particle number and volume
distributions measured in the plume and in the "ambient" ai r at
0.5 km from the Mohave plant. There were many more particles
with diameters between ~0.3 urn and 3.0 urn in the Mohave plume
than in the "ambient" ai r (Fi g. 3.19a) The particle volume
distributions show a peak at 1.1 urn in the plume and in the
"ambient" ai r (Fig. 3.19b) The total particle volumes in the
plume and in the "ambient" ai r were 201 and 1.7 urn cm"
respectively.
Figure 3.20 shows the particle number and volume distribu-
tions measured in the plume and in the "ambient" ai r at 93 km
downwind of the Mohave plant on August 28, 1979. The peak of
the particle volume distributions remained at 1.1 urn in the
plume and in the "ambient" ai r (Fi g. 3.20b) The total particle
volumes in the plume and in the "ambient" ai r were 1.8 and 1.23 -3urn cm respectively.
61
Figure 3.18 A plot of cumulative particle volume to cumulative
particle number ratios (multiplied by 100) downwind of
the Mohave power plant on 28 August 1979. Measurements in
the Mohave plume are indicated by crosses. Measurements
in the "ambient" air are indicated by circles. Terrain
over 915 m is indicated by slanted lines. Specific
elevation points are indicated by dots.
62
m
u
Q
0_0o
zo
10"’ 10" 10’DIAMETER (/^.m)
(G
DIAMETER (//.m)
(b)
Number (a) and volume (b) distributions of particles measuredin the ambient ai r (o) at an altitude of 640 m at 0601 PDT andn the plume (A) at an altitude of 610 m at 0619 PDT at ’a
distance of 0.5 km from the Mohave power plant on 28 August1979.
63
r0
10
E=t
m
’E 102 e 2.4
Q
0>
o\
zo
10’
100
Q
1.6o’<>’ 0.8
10" 010"’ 10 10’DIAMETER (/im)
G)
10’ 10’i0 10’DIAMETER (/im)
b)
i^ ^i^ ^T^ distn’butions of particles measuredn the ambient ai r (o) at an altitude of 1067 m at 0911 PDT andm the Plume (A at an altitude of 1006 m at 0916 PDT at adistance of 93 km from the Mohave power plant on 28 August 1979.
-64-
Fi gure 3.21 shows the number and volume concentrations of
particles measured at 139 km downwind of the Mohave plant on
August 28, 1979. The peak in the particle volume distributions
in the plume and in the "ambient" ai r remained at 1.1 urn (Fi g.
3.21b) The total particle volumes in the plume and the
"ambient" ai r were 1.6 and 1.3 urn cm" respectively.
On August 28 the peak in the particle volume distribution
was at 1.1 urn in the plume and in the "ambient" ai r for the
enti re fli ght.
(d) August 31. 1979 (UM Flight 809)
1042 to 1317 PDT
On August 31, 1979, the plume and the "ambient" ai r were
sampled for ~26 km downwind of the Mohave plant. Figure 3.22
shows the b isopleths for this fl ight. Using the measuredS CdL
visual range at Las Vegas and putting "a" 3.91 in Eqn. (1.1)-4 -1
(Middleton, 1952) a b value of 0.81 x 10 m was obtained
for Las Vegas, which was much larger than the b values
measured in the "ambient" ai r on this day. Unfortunately, no
b data from the "mixing bowl are avai lable for comparisonS CdL
with the b values at Las Vegas. However, the ai r in the Lass cdL
Vegas area does appear to have had a much higher li ght scattering
65
10
E<->io 4.0E=1.
’S 3.2U)
T10^ E 2.4
Q
0>
o\
Zo
10’
10’-
0
j 1.6o
>" 0.8
10’10"’ 10 10’DIAMETER (^.m)
(0)
0’10-’ 10 10’DIAMETER (/xm)
b)
Fi gure 3.21 Number (a) and volume (b) distributions of particles measuredin the ambient ai r (o) at an altitude of 762 m at 0940 POT andin the plume (A) at an altitude of 762 m at 0946 POT at adistance of 139 km from the Mohave power plant on 28 August1979.
66
Figure 3.22 Maximum values of b (in units of 10"6 m"1) at thescataltitude of the centerline of the plume from the Mohavepower plant on 31 August 1979. Measurements in the Mohaveplume are indicated by crosses. Measurements in the"ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots.
-67-
coefficient than the ai r in the Colorado River Valley
north of the Mohave power plant.
Fi gure 3.23 shows the concentrations of SO? measured down-
wind of the Mohave plant. SO? concentrations in the "ambient"
ai r were generally <3 ppb. Simi lar concentrations of SO?were measured in the "ambient" ai r on August 23 and August 28.
Concentrations of SO? in the plume were well above "ambient"
levels for the enti re flight on August 31.
Fi gure 3.24 shows the particle volume-to-number ratios on
August 31, 1979. These ratios were greater in the plume than
n the "ambient" ai r for the enti re 26-km range of the flight.
Shown in Fi g. 3.25 are the particle number and volume con-
centrations measured in the plume and in the "ambient" ai r at
0.5 km from the Mohave plant on August 31, 1979. The particle
number distributions show that there were many more particles
with diameters between ~0.3 urn and 4.0 urn in the plume than in
the "ambient" ai r (Fi g. 3.25a) The particle volume distribu-
tions show peaks at 1.1 pm in the plume and 3.5 urn in the
"ambient" ai r (Fi g. 3.25b) The total particle volumes in the
3 -3plume and in the "ambient" ai r were 76 and 2.1 urn cm
respectively.
68
Figure 3.23 Maximum SO concentrations (in ppb) downwind of the
Mohave power plant on 31 August 1979. Measurements in theMohave plume are indicated by crosses. Measurements inthe "ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots.
69
Figure 3.24 A plot of cumulative particle volume to cumulativeparticle number ratios (multiplied by 100) downwind ofthe Mohave power plant on 31 August 1979. Measurements inthe Mohave plume are indicated by crosses. Measurementsin the "ambient" air are indicated by circles. Terrainover 915 m is indicated by slanted lines. Specificelevation points are indicated by dots.
70
104
IQ3
ro
’E 10’u
Q
0>0 10o"s
^ 10
10’10"’ 10 10’DIAMETER (^m)
a)
Fi gure 3.25_ Number (a) and volume (b) di stributions of particles measuredn the ambient ai r (o) at an altitude of 640 m at 1056 POT andn the plume (A) at an altitude of 671 m at 1108 PDT at adistance of 0.5 km from the Mohave power plant on August 31L -7 7
71
Figure 3 .26 shows the particle number and volume
concentrations measured in the plume and in the "ambient’
air at 26 km downwind of the Mohave plant on August 31,
1979 The particle volume distributions show peaks at
3. 5 pm in the plume and 0 55 pm in the "ambient"
air. The total particle volumes in the plume and in the
"ambient" air were 2 4 and 1 3 urn cm" respectively.
The S0~ concentrations, b^
and total particle
volume concentrations show the plume and in the "ambient’
air to have been quite distinct over the 26-km range of
UW flight 809 However, the particle volume-to-number
ratios were approximately the same for the plume and in
the "ambient" air at 26 km from the Mohave plant (Fig.
3 24) Figure 3 26 verifies that the shapes of the
particle size distributions in the plume and in the
"ambient" air were similar at 26 km from the Mohave
plant.
(e) August 11, 1980 (UW Flight 924)
0714 to 1148 PDT
On August 11, 1980 , the Mohave plume and the
"ambient" air were sampled from the B-23 aircraft for
37 km downwind of the Mohave power plant. Shown in Fig.
3 27 are the b^
isopleths for this flight. Due to
stagnant meteorological conditions on August 11, 1980
72
10’
10
<-i
r0
E
^103
m
’E 10-
Q
0’0 10’O
^ 10
ao>o 1.6o\
>’ 0.8
10-I
10 100 10’DIAMETER (^.m)
a)
010-’ 10 10’DIAMETER (^m)
(bFi gure 3.26 Number (a) and volume (b) distributions of particles measured
in the plume (o) at an altitude of 793 m at 1226 POT and in theambient ai r (A) at an altitude of 854 m at 1235 PDT at adistance of 26 km from the Mohave power plant on 31 August 1979.
73
Figure 3.27 Maximum values of b (in units of 10" m at thescat
altitude of the centerline of the plume from the Mohavepower plant on 11 August 1980. Measurements in the Mohaveplume are indicated by crosses. Measurements in the"ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots.
-74-
(Hoffer et a1 1981) the values of b in the "ambient"
ai r were much higher than those on August 23, August 27, August
28 and August 31, 1979. Using the measured visual range at Las
Vegas and putting "a" 3.91 in Eqn. (1.1) (Middleton, 1952) we
-4 -1derived a b value of 0.69 x 10 m at Las Vegas. This
SCdu
value is simi lar to those measured in the "ambient" air 1n the
Colorado Ri ver Valley (Fig. 3.27)
Shown in Fig. 3.28 are the measured concentrations of
SO,, downwi nd of the Mohave power plant on August 11, 1980.
"Ambient" values were ~4 ppb at 37 km downwind of the Mohave
plant, whi le the concentrations in the Mohave plume were ~10
ppb.
The particle volume-to-number ratios for August 11, 1980,
are shown in Fi g. 3.29. There was a distinct difference between
the values of this ratio in the plume and in the "ambient" ai r
close to the plant. However, unlike the b values and SOp
concentrations, the particle volume-to-number ratios did not
show a distinct plume at the 37-km range.
Shown in Fi g. 3.30 are the particle number and volume con-
centrations measured in the plume and in the "ambient" ai r at
0.5 km from the Mohave plant. The particle number distributions
75
Figure 3.28 Maximum SO concentrations (in ppb) downwind of the
Mohave power plant on 11 August 1980. Measurements in the
Mohave plume are indicated by crosses. Measurements inthe "ambient" air are indicated by circles. Terrain over915 m is indicated by slanted lines. Specific elevationpoints are indicated by dots.
76
Figure 3.29 A plot of cumulative particle volume to cumulativeparticle number ratios (multiplied by 100) downwind ofthe Mohave power plant on 11 August 1980. Measurements inthe Mohave plume are indicated by crosses. Measurementsin the "ambient" air are indicated by circles. Terrainover 915 m is indicated by slanted lines. Specificelevation points are indicated by dots.
77
m
103
102
Q
J 10’o\
^ 10
10’’10"’ IOC 10’DIAMETER (^.m)
(o
10"’ 10 10’DIAMETER (^.m)
b)Fi gure 3.30 Number (a) and volume (b) distributions of particles measured
in the plume (o) at an altitude of 732 m at 0724 PDT and in theambient ai r (A) at an attitude of 793 m at 0745 PDT at adistance of 0.5 km from the Mohave power plant on 11 August 1980,
-78-
show that there were many more particles with diameters between
~0.3 urn and 3.0 urn in the plume than in the "ambient" ai r (Fig.
3.30a) The particle volume distributions show peaks at 1.1 urn
n the plume (with a secondary peak at 7.0 urn) and 0.55 urn in
the "ambient" ai r (Fi g. 3.30b) The total particle volumes ini i
the plume and in the "ambient" air were 19.7 and 2.4 urn cm .respectively.
Shown in Fig. 3.31 are the particle number and volume con-
centrations measured in the plume and in the "ambient" ai r 37 km
downwind of the plant. The particle volume distributions show a
peak at 0.55 urn in the plume and in the "ambient" ai r (Fig.
3.31b) The total particle volumes in the plume and the
"ambient" ai r were 2.0 and 1.9 urn cm" respectively.
The peak in the particle volume distribution in the
"ambient" ai r was at 0.55 urn for the enti re fl ight. The par-
ticle size distribution in the plume was simi lar to that in the
"ambient" ai r at the 37-km range. However. SO. concentrations,
b and total particle volumes indicated a definable plume at
37 km, even though the particle size distributions and particle
volume-to-number ratios indicated almost no differences between
the plume and in the "ambient" ai r.
79
Kl
Q
0>
_0o\
zo
103
102
10’
lO1
10-I
10 10" 10’DIAMETER (,u,m)
(a
10"’ 10 10’DIAMETER {^m}
b)
Fi gure 3.31 Number (a) and volume (b) distributions of particles measuredin the ambient ai r (o) at an altitude of 808 m at 0942 POT andin the plume (A) at an altitude of 854 m at 0950 POT at adistance of 37 km from the Mohave power plant on 11 August 1980,
80
(f) December 20 1978 (UW Flight 725)
0710 to 1207 PST
On December 20, 1978 the plume and in the
"ambient" air were sampled for ^46 km south of the Mohave
plant. No b data are available for this flight.
Using the measured visual range at Las Vegas and
"a" 3 91 in Eqn. (1 1) (Middleton, 1952) , we estimated
-4 -1a b value of 0 32 x 10 m at Las Vegas during the
sca^
period of UW flight 725
Shown in Fig. 3 32 are the measured concentrations
of S0~ downwind of the Mohave plant. At the 46-km range,
the concentrations were much greater in the Mohave plume
than in the "ambient" air. At 46 km, SO,, concentrations
in the plume and in the "ambient" air were ^16-24 ppb and
1 ppb, respectively.
The particle volume-to-number ratios for December
20 1978 are shown in Fig. 3 33 At the 46-km range,
the ratios in the plume were greater than those in the
"ambient" air. Also, the magnitudes of the ratios in the
"ambient" air were less on this day than those measured
in August 1979 or August 1980
Shown in Fig. 3 34 are the particle number and
volume concentrations measured in the plume and in the
"ambient" air at 8 km from the Mohave plant. The
81
Figure 3.32 Maximum SO- concentrations (in ppb) downwind of the
Mohave power plant on 20 December 1978. Measurements inthe Mohave plume are indicated by crosses. Measurementsin the "ambient" air are indicated by circles. Terrainover 915 m is indicated by slanted lines. Specificelevation points are indicated by dots.
82
Figure 3.33 A plot of cumulative particle volume to cumulativeparticle number ratios (multiplied by 100) downwind ofthe Mohave power plant on 20 December 1978. Measurementsin the Mohave plume are indicated by crosses.Measurements in the "ambient" air are indicated bycircles. Terrain over 915 m is indicated by slantedlines. Specific elevation points are indicated by dots.
83
10
Q
0>
JOo\
zo
102
10’
10
10’10 10- 10’DIAMETER (f-Lm)
a)
10~1 10" 10’DIAMETER (/zm)
b)Figure 3.34 Number (a) and volume (b) distributions of particles measured
in the ambient ai r (o) at an altitude of 442 m at 0748 PST andin the plume (A) at an altitude of 457 m at 0819 PST at adistance of 9 km from the Mohave power plant on 20 December1978.
84
particle number distributions show that there were many
more particles with diameters between ^0 3 and 1. 2 pm in
the plume than in the "ambient" air (Fig. 3 34a) The
number of particles >1. 2 urn diameter were too few to be
accurately counted by the Royco 202 The particle volume
distributions show peaks at 1.1 pm in the plume and
0 35 pm in the "ambient" air (Fig. 3 34b) The total
particle volumes in the plume and in the "ambient" air
were 3 1 and 0. 3 pm cm" , respectively. The total
particle volume in the "ambient" air on this day was less
than that measured on any flight during August 1979 or
August 1980.
Shown in Fig. 3 35 are the particle number and
volume concentrations in the plume and in the "ambient"
air at 46 km downwind of the Mohave plant. The peaks in
the particle volume size distributions remained at 1. 1 ^irn
in the plume and 0 35 pm in the "ambient" air (Fig.
3 35b) The total particle volumes in the plume and in
the "ambient" air were 0 6 and 0 2 pm cm
respectively.
For the entire 46 km downwind of the Mohave plant,
a quantitative difference existed between the plume and
in the "ambient" air, as determined by SO^ concentrations,
total particle volume and the particle volume-to-number
85
10
.6
roE=L |.2
Kl
Q
0>0
O\
ZO
10’
10’
10-I
10-’ 10 10’DIAMETER (/^m)
0.8
o 0.4o>0
O\
>o
0ft10 10" 10’
DIAMETER (fim}
0) ( b)Figure 3.35 Number (a) and volume (b) distributions of particles measured
n the plume (o) at an altitude of 457 m at 0843 PST and in theambient ai r (A) at an altitude of 457 m at 0857 PST at adistance of 46 km from the Mohave power plant on 20 December 1978.
86
ratio. "Ambient" air conditions were much cleaner during
this flight than during any of the flights made in the
summers of 1979 or 1980.
3 .4 Summary
(a) August 23 , 1979
On this day, the NWS at Las Vegas observed haze and
smoke to the northeast through east of Las Vegas during
the time that the flight occurred. The winds at Las
Vegas were variable, <3 m s~ , during this time.
SO- concentrations, b--^ and total particle volume
concentrations all showed distinct differences between
the Mohave plume and the "ambient" air at distances up to
130 km north of the Mohave power plant (Figs. 3 3 and
3 4) SOy concentrations and bg.-.at in the "ambient" air
in the "mixing bowl" increased toward Las Vegas. The
particle volume-to-number ratios were greater in the
plume than in the "ambient" air at distances <65 km from
the Mohave plant. The particle volume-to-number ratios
in the plume and in the "ambient" air were equivalent at
the 65-km range and remained the same thereafter (Fig.
3 .5) The particle size distributions in the plume and in
the "ambient" air differed at distances <65 km from the
Mohave plant, but these distributions were of similar
shape in the plume and the "ambient" air at the 65-km
87
range and remained the same thereafter (Figs. 3 7, 3 8
and 3 .9)
(b) August 27, 1979
On this day, the NWS at Las Vegas observed haze and
smoke through all quadrants during the time that the
flight occurred. The winds at Las Vegas were 3 m s and
from the west.
SOy concentrations b and total particle volume
concentrations all showed distinct differences between
the Mohave plume and the "ambient" air up to distances of
161 km north of the Mohave power plant (Figs 3 .10 and
3 11) As on August 23 1979 b and SO-SCBu
concentrations in the "ambient" air in the "mixing bowl"
increased toward Las Vegas. The particle
volume-to-number ratios were greater in the plume than in
the "ambient" air at distances <161 km from the Mohave
plant. These ratios were equivalent in the plume and in
the "ambient" air at distances 2.161 km from the Mohave
plant (Fig. 3 .12) The particle size distributions in
the plume and in the "ambient" air differed at distances
<185 km from the Mohave plant, but these distributions
were of similar shape in the plume and the "ambient" air
at the 185-km range (Fig. 3 15)
88
(c) August 28 , 1979
On this day, the NWS at Las Vegas observed haze and
smoke to the north through the southeast during the
initial two hours of the flight. During the final two
hours of the flight, the haze and smoke were observed to
the north of Las Vegas Winds at Las Vegas were westerly
and ^5 m s~ at the beginning of the flight. They
switched to southerly, 8 to 10 m s by the end of the
flight.
SO., concentrations, b and total particle volumesca^
concentrations all showed distinct differences between
the Mohave plume and the "ambient" air up to distances of
139 km north of the Mohave power plant (Figs. 3 16 and
3 17) The particle volume-to-number ratios were greater
in the plume than in the "ambient" air at distances <69
km from the Mohave plant. At distances ^69 km from the
Mohave plant, the particle volume-to-number ratios in the
plume and in the "ambient" air were equivalent (Fig.
3. 18) The particle size distributions in the plume and
in the "ambient" air differed at distances <93 km from
the Mohave plant, but the particle size distributions
were of similar shape in the plume and the "ambient" air
at 93 km and beyond (Figs. 3 20 and 3 21)
-89-
(d) August 31. 1979
On this day, the NWS at Las Vegas observed haze and smoke
through all quadrants during the time that the flight occurred.
Minds at Las Vegas were 2 m s and from the north-northeast
through east-northeast. SO? concentrations, b^^ and total
particle volume concentrations al l showed distinct differences
between the Mohave plume and the "ambient" ai r up to distances
of 26 km north of the Mohave power plant (Fi gs. 3.22 and 3.23)
The particle volume-to-number ratios were only slightly greater
n the plume than in the "ambient" ai r at 26 km from the Mohave
plant (Fi g. 3.24) The particle size distributions were of
simi lar shape in the plume and in the "ambient" ai r at 26 km
from the Mohave plant (Fi g. 3.26)
(e) August 11. 1980
On this day, the NWS at Las Vegas observed haze and smoke
through al quadrants during the time that the flight occurred.
Minds at Las Vegas were calm during the initial hour of the
flight, and became variable at <2 m s" during the remainder of
the fl ight. SO? concentrations, b and total particle volume
concentrations al indicated distinct differences between
the plume and the "ambient" ai r at distances up to 37 km
90
north of the Mohave plant (Figs. 3 27 and 3 28) The
particle volume-to-number ratios were greater in the
plume than in the "ambient" air at distances <29 km from
the Mohave plant. These ratios were equivalent in the
plume and in the "ambient" air at 29 km (Fig. 3 .29) The
particle size distributions in the plume and in the
"ambient" air differed at distances <37 km from the
Mohave plant (Fig. 3. 31) but at 37 km these distributions
were of similar shape.
(f) December 20 1978
On this day the NWS at Las Vegas observed no haze
or smoke during the time that the flight occurred. Winds
at Las Vegas were calm during the initial hour of the
flight, and became variable at 2 m s during the
remainder of the flight. SO- concentrations and total
particle volume concentrations both indicate distinct
differences between the plume and the "ambient" air up to
46 km south of the Mohave plant (Fig. 3 32) The particle
volume-to-number ratios also showed a distinct difference
between the plume and in the "ambient" air at 46 km south
of the Mohave plant (Fig. 3 33) The particle size
distribution shapes in the plume and in the "ambient" air
differed at 46 km from the Mohave plant (Figs. 3 34 and
3 35)
CHAPTER IV
DISCUSSIONS OF THE DATA
4. 1 Introductory Remarks
In Chapter III we have presented data on SO.,
concentrations , b and total particle volumescciL
concentrations that show distinct differences between the
Mohave plume and the "ambient" air at distances downwind
of the Mohave plant greater than or equal to the
distances at which the volume-to-number ratios become
equivalent in the Mohave plume and in the "ambient" air.
Furthermore, the data indicated that the "ambient" air of
the region has different characteristics from day to day
and with location in the Colorado River Valley. Also, we
saw in Chapter III that the shapes of the particle size
distributions become similar in the Mohave plume and in
the "ambient" air between 26 and 185 km downwind of the
Mohave power plant. The particle volume-to-number ratios
become equivalent in the plume and in the "ambient" air
between ^ 26 and 161 km downwind of the power plant.
In this chapter we will discuss channeling by
topography of the Mohave power plant plume, examine the
nature of the particle volume distributions in the plume
92
and in the "ambient" air, introduce the 1 1/0 55 ratio in
order to quantify the changing location of the peak in
the particle volume distribution in the "ambient" air,
present the results of a correlation matrix (to provide
information on variations in the peak in the particle
volume distribution in the "ambient" air) , and we will
show how the varying peak in the particle volume
distribution in the "ambient" air correlates with
scat"
4. 2 Channeling of the Mohave Power Plant Plume
Shown in Table 4 1 are the altitudes at which the
Mohave plume was sampled during the six flights described
in Chapter III At ranges of less than 65 km from the
plant, the plume was below 1000 m MSL. Up to 70 km
north of the Mohave power plant, the Colorado River
Valley is enclosed by mountains rising to over 1500 m
MSL, which form a channel for north-south air flow (see
Fig. 1 2 and the description in Chapter I) Hence, in
the five flights in which the plume moved to the north,
for the first 70 km of travel the plume never rose above
the terrain bordering the Colorado River.
Shown in Table 4. 2 are the widths of the Mohave
plume at various distances from the Mohave plant. In all
cases , the plume widths were less than the width of the
-93-
TABLE 4.1 Altitudes of the Mohave Plume
December 21
August 23,
August 27,
August 28,
August 31,
August 11,
3. 1978*
1979
1979
1979
1979
1980
Distance fromStack (km)
9.046.0
0.565.0102.0130.0
0.593.0185.0
0.593.0139.0
0.526.0
0.537.0
Altitude(m, MSL)
457457
82388412201220
762945762
61010061220
671793
732854
* The plume moved to the south on this day but to thenorth on the other days.
94
TABLE 4 2 Widths of the Mohave Plume
D
December4689
August 235
26
130August 27
59
28
93139185
August 285
93139
August 315
11.26
August 115.
112237
ate
20, 1978**
1979
, 1979
1979
, 1979
1980
DistanceStack
9
0
46.65.
102
0
56
0
2856.
0
0
from(km)
000560000056000000560000560056000
1.641.2.3.9385048.9.4.8.
17.1301.56.
11.12022612698
Wi
700973027018986698049695285496294464560422203161760577751695860045
dttkm)
+/-
+/-
+/-
+/-
+/-
+/-
+/-
^+/-
+/-
+/-
+/-
+/-
+/-
+/-
+/-
+/-
+/-
+
+/-
+/-
+/-
+
+/-
4;
+/-
+/-
+/-
I*
01.0.0.0
1.0.5
0132
0.5
10.0.0.2.2.6
00020011
9339911618
089334
12084901
4192741436416480
3581495339956810
*The variances shown are external variances Whereno variance is shown, only one pass occurred atthat altitude and range.
**The plume moved to the south on this day but tothe north on other days.
-95-
Colorado Ri ver Val ley (15-25 km) for distances ~70 km from the
Mohave plant. Thus, for the five cases with a northward moving
plume, the Mohave plume was restricted to a well-defined channel
within the Colorado Ri ver Val ley for up to ~70 km to the north
of the plant.
Beyond ~70 km is the "mixing bowl ," where the plume was
less restricted by topography (see Fi g. 1.2) On August 27 and
August 28, 1979, the Mohave plume spl it at the gap in the Black
Mountains (Fi gs. 3.10, 3.11, 3.16 and 3.17) On those days the
widths of the plume (l isted in Table 4.2) at 93 and 139 km from
the Mohave plant are for the western portion of the Mohave
plume. The widths of the eastern portion of the plume could not
be determined. At 185 km from the Mohave plant on August 27,
1979, the eastern and western portions of the plume may have
merged. It is evident from Table 4.2 that the width of the
Mohave plume general ly increased with distance from the Mohave
plant. The width of the Mohave plume was ~1 km at 0.5 km from
the Mohave plant for the days listed in Table 4.2. At 185 km
from the Mohave plant on August 27, 1979, the width of the Mohave
plume was ~24 km. Note that the measured plume widths did
not always increase with increasing distance downwind of
the Mohave plant (Table 4.2) For example, on August
96
23, 1979 , the Mohave plume seemed to decrease in width at
65 km from the Mohave plant; this was probably because
the B-23 aircraft did not pass through the full width of
the plume. Also, the aircraft may have missed the
instantaneous plume and passed through an aged portion of
the plume at that range.
Table 4 1 shows that the Mohave plume increased in
height (MSL) with distance from the Mohave plant. This
is because the terrain of the Colorado river Valley
increases in elevation north of the Mohave power plant.
4 3 Variations in the Peak of the Particle Volume
Distributions in the Plume and in the "Ambient" Air
On December 20 1978 August 23 August 27, August
28 and August 31 1979 and August 11 1980 , the peak in
the particle volume distributions in the Mohave plume and
in the "ambient" air did not always occur at the same
particle size (Table 4 3)
Table 4 3 shows that in the plume the particle
distributions always peaked at 1 1 pm at 0 5 km from the
Mohave plant. On December 20 1978 and August 28 1979
the peak in the particle volume distribution in the
Mohave plume was at a diameter of 1 1 p m for all ranges
downwind of the Mohave plant (see Table 4 3 and Figs
3 19 3 .20 3 21, 3 .34 and 3 35) On August 23 , 1979
97
TABLE 4 3 Particle Diameters at which the ParticleVolume Distributions in the Mohave Plume and
in the "Ambient" Air Reached Peak Values
Dat.
December 2’
August 23
August 27,
August 28
August 31
August 11
e
0 1978*
1979
1979
1979
1979
1980
Distancefrom
Stack
946
0.565
102130
0 593
185
0 593
139
0 526
0 537
Pf
PI
11
1000
112
111
13
10
arti<or P<Dist]
ume
.1
.1
.1
.555555
11
.5
.1
.11
15
155
;le Diasak inributio
Ambie
00
000.0
3 5 and 1.13 5 and I I3 5 and I I
111
30
0
.meterVo1umeins um)
nt Air
3535
55555555
111
555
55
*The plume moved to the south on this day but to the northon the other days.
A secondary peak in the particle volume distributionoccurred at a diameter of 1 1 \im on this day.
98
and August 11 1980 the peak in the particle volume
distributions in the Mohave plume was at a diameter of
0 .55 urn at ranges greater than 0 5 km from the Mohave
plant (see Table 4 3 and Figs 3 .5 3 6 , 3 7 and
3 .31) On August 27, 1979 , the peak in the particle
volume distribution in the Mohave plume was at 1 .1 pm
diameter at 0. 5 and 93 km downwind of the Mohave plant
(see Table 4 3 and Figs 3 .12 and 3 13) On the same
day, the peak in the particle volume distribution in the
Mohave plume was at 2 .5 ym diameter at 185 km from the
Mohave plant (see Table 4 3 and Fig. 3 14) On August
31 1979 the peak in the particle volume distribution in
the Mohave plume was at 3 5 ijm diameter at 26 km from the
Mohave plant (see Table 4. 3 and Fig. 3 .26) It is clear
from Table 4 3 that, except on December 20 1978 , the
peaks in the particle volume distributions in the Mohave
plume tended to occur at the same particle diameter as
those in the "ambient" air for ranges greater than 0 5 km
from the Mohave plant. The similarity in the locations
of the peaks in the plume and in the "ambient" air
indicate that the Mohave plume was entraining "ambient"
air.
The peaks in the particle volume distributions in
the "ambient" air varied on the days of the UW research
99
flights. On December 20 1978 August 23 1979 and
August 11 , 1980 the peaks in the particle volume
distributions in the "ambient" air were in the
0 .35-0 .55 urn diameter range for all locations downwind of
the Mohave plant (see Table 4. 3 and Figs 3 .4-3 7, 3 30
3. 31, 3. 34 and 3 35) On August 27, 1979 , the particle
volume distributions in the "ambient" air showed a peak
in the coarse particle mode at 2. 15-3 .5 pm diameter for
all locations downwind of the Mohave plant (see Table 4.3
and Figs. 3. 12-3. 14) On August 31 , 1979 , the particle
volume distributions in the "ambient" air peaked at
3 5 urn at 0 5 km from the Mohave plant and at 0 .55 ym at
26 km from the Mohave plant (see Table 4 .3 and Figs 3 25
and 3 26) The source of the coarse particles in the
"ambient" air of the Colorado River Valley could be
windblown dust. However, surface weather observations
from the NWS at Las Vegas showed no evidence of windblown
dust on August 27 or August 31, 1979 A secondary peak
in the particle volume distribution in the "ambient" air
occurred at 1 1 urn on August 27, 1979 (see Table 4 3 and
Figs. 3 12-3 14) On August 28 1979 a peak in the
particle volume distribution in the "ambient" air
occurred at 1 1 Vm for all locations downwind of the
Mohave plant (see Table 4 3 and Figs. 3 .19-3 21) It is
100
clear from Table 4. 3 that the "ambient" air was impacted
by the Mohave plume to a greater extent on August 27 and
August 28 , 1979 than on December 20, 1978 August 23 and
August 31 1979 , and August 11 , 1980. In Section 4.4 we
will investigate the reason (s) for the variations in the
peak in the particle volume distributions in the
"ambient" air.
4. 4 Variations in the "Ambient" Air of the Region
Impacted by the Mohave Plume
We have seen in Section 4 3 that the peaks in the
particle volume distribution did not always occur at the
same particle size in the "ambient" air affected by the
Mohave plume. We also saw that near the power plant the
plume usually had a peak in the particle volume
distribution at 1 1 urn diameter, and the "ambient" air
usually had a peak in the particle volume distribution at
0 35 pm or 0 55 urn diameter. In order to determine the
influence of the Mohave plume on the "ambient" air, we
would like to quantify the changing location of the peak
in the particle volume distribution in the "ambient"
air. Because the coarse particle mode is associated with
windblown dust, we wil l not consider peaks in the
particle volume distribution that occurred in that
mode.
101
4. 4.1 The 1. 1/0 .55 Ratio
To quantify the changing location of the peak in
the particle volume distribution in the "ambient" air, we
will consider the ratio of the increment of particle
volume per increment of the logarithm of particle
diameter evaluated at diameters of 1 1 pm and 0 .55^m.
That is
[dV/d dogD^ ^[dV/d dogDp) ^ ^
This is referred to hereafter as the 1 1/0 55 ratio, or
simply "the ratio. " This ratio is < 1 when the peak in
the particle volume distribution is at 0. 55 pm diameter,
and it is > 1 when the peak in the particle volume
distribution is at 1 1 ym diameter. Thus a 1 1/0. 55
ratio > 1 is indicative of the influence of the Mohave
plume. A 1 1/0 .55 ratio < 1 indicates the Mohave plume is
not influencing the "ambient" air.
4 4 2 The Correlation Matrix
To investigate the factors that affect the 1 1/0 55
ratio in the "ambient" air, we will consider how this
ratio correlates with the seventeen parameters listed in
Table 4 4. All of the measurements to be used in the
102
TABLE 4 .4 Parameters Used in the Correlation Matrix
1 dV/d logD) ratio*
2. Distance from the Mohave plant*
3 Altitude of the measurements*
2/3 -14. Turbulence* (in units of cm s
5. Temperature inversion* (presence or absence of aninversion)
6 Relative humidity* (expressed as a percentage)
7. Time event** (the length of time since a frontalpassage or precipitation event)
8 Plant output (in megawatts) (supplied by SouthernCalifornia Edison)
9 850 mb wind speed**
10 850 mb wind direction**
11 Dew point*
-2 -112 Ultraviolet radiation* (in units of meal cm min
13 SO^* (in ppb)
14 850 mb wind speed** (the average over the 36-hourperiod preceding the flight)
15 850 mb wind direction ** (the average over the36-hour period preceding the flight)
16. 0,* (in ppb)
17. b * (in units of 10~4 m~1)
*Data obtained from measurements taken by the B-23aircraft
**Data obtained from NWS observations
103
correlation matrix were taken in the "ambient" air of the
region affected by the Mohave plant (see Appendix A for a
description of the correlation technique that was
employed) The measurements were taken on December 4 ,
December 8 and December 20 1978; August 23-25, August
27-29 August 31 and September 3 , 1979; and August 8 ,
August 10 August 11 and August 13-15, 1980, which
correspond to UW flights 710 , 711 , 725 , 803-810 , 922-924,
926, 928 and 929 , respectively.
Table 4 .5 shows the correlation of the 1. 1/0.55
ratio with the other parameters. The correlations have
been grouped according to flight series. All but one of
the correlations that are underlined in Table 4 5 have
confidence levels > 60% and will be discussed below. The
correlation of the time event parameter with the 1 1/0 .55
ratio for the 700 flight series was at a confidence level
< 60% but will be discussed because the overall
correlation of these two parameters for the combined
series of flights was > 60%.
The correlation of the distance from the Mohave
plant with the 1 1/0. 55 ratio for the 700 flight series
was 0 75 at the 91% confidence level However, we cannot
suggest a physical basis for this high correlation. In
fact, in the 800 and 900 series there was not a high
TABLE 4.5 Correlation Coefficients of the 1.1/0/55 Ratio with VariousParameters (Confidence Levels in Parentheses)
Parameter
Distance from the Mohave plant
Altitude of the measurements
Turbulence
Temperature inversion
Relative humidity
Time event
Plant output
850 nt) wind speed
850 rob wind direction
Dew point
Ultraviolet radiation
^(continued)
700FlightSeries*
0.75 91%)
0.63 74%)
0.16 (<50%)
-0.59 50%)
-0.30 50%)
0.59 50%)
-0.85 85%)
0.30 (<50%)
-0.65 50%)
-0.79 79%)
0.81 95%)
S
0.19
-0.11
0.23
0.14
0.63
0^85.
0^3
-0.42
-0.14
0.72
-0.07
800Plighteries**
50%)
50%)
(<50%)
(<50%)
64%)
99%)
89%)
(<50%)
50%)
(<50%)
50%)
FSe
-0.16
-0.17
-0.07
-0.48
P.46-0.48
0.16
-0.14
0.16
0.00
900’lightries**’*
50%)
(<50%)
50%)
(<50%)
66%)
(<50%)
50%)
50%)
50%)
(<50%)
cor
0.27
0.17
0.00
0.12
0.02
0.40
0.08
-0.11
-0.21
-0.08
0.10
derailrelations
50%)
50%)
50%)
50%)
(<50%)
83%)
50%)
(<50%)
50%)
50%)
50%)
TABLE 4.5 (continued) Correlation Coefficients of the 1.1/0.55 Ratio with VariousParameters (Confidence Levels in Parentheses)
Parameter , 700 800 900Flight plight Flight pj^i 3/-Series* Series** Series*** Correlations
SO2 -0.18 50%) 0.32 50%) -0.42 50%) -0.14 50%)
36-hour 850 mb wind speed 0.40 50%) -0.35 50%) -0.26 50%) -0.18 50%)
36-hour 850 mb wind direction 0.37 50%) 0.23 50%) 0.02 50%) -0.03 50%)
3 -0.12 50%) -0.48 68%) -0.33 50%) -0.34 50%) ^bscat 0.22 50%) -0.25 50%) -0.52 95%) -0.57 99%)
*Corresponds to UW flights 710, 711 and 725 in December, 1978
^Corresponds to UW flights 803-810 in August-September, 1979
***Corresponds to UW flights 922-924, 926, 928 and 929 in August, 1980
106
correlation between these two parameters (see Table
4.5)
The correlation of the altitude of the measurements
with the 1. 1/0 55 ratio for the 700 flight series was
0 63 at the 74% confidence level Since the altitude of
the measurements generally increased with distance
downwind of the Mohave plant, this high correlation is to
be expected.
The correlations coefficient of the time event
parameter with the 1 1/0 55 ratio was 0 59 for the 700
flight series. Figure 4 1 shows the passage of a cold
front through the region sampled by the B-23 aircraft at
^ 1200 GMT on December 18 , 1978 The 1 1/0 55 ratio
increased in value prior to the cold-frontal passage and
decreased after the cold-frontal passage (Table
4 6) However, because there were only three independent
points in the time event column for the 700 flight
series , the correlation with the 1 1/0 55 ratio was not
significant (Table 4 6)
The correlation of the 1 1/0 55 ratio with the
power output of the Mohave plant was -0 85 at the 85
percent confidence level for the 700 flight series. This
high negative correlation is unexpected, since the 1 .1 urn
particles are a tracer of the Mohave plume and therefore
107
,100
Figure 4. 1 The NWS surface analysis at 1200 GMT on18 December 1978
108
TABLE 4 6 The Time Event Parameter and the 1 1/0 .55Ratio for the 700 Flight Series
1 1/0 55 Ratio Time Event (hours) * Date
0 420 .410 440 860 490. 72
1 491 531 151 521 161 17
0 330 .590. 601 12
596061626263
676868686869
45454748
December 4 , 1978
December 8 1978
December 20 1978
*"Time event" refers to the number of hours since a frontalpassage or precipitation event. A frontal passageoccurred on 18 December 1978
-109-
we might expect the 1.1/0.55 ratio to decrease with decreasing
plant output. The reason for the large negative correlation in
the 700 flight series is the high 1.1/0.55 ratios (>1) on
December 8, 1978 (see Table 4.6) when in fact the Mohave plant
was not operating. This apparent anomaly was due to the fact
that the peak in the particle volume distribution in the
"ambient" ai r on this day was at 0.35 ym rather than 0.55 pm
diameter. Thus, whi le the particle volume at 1.1 urn diameter
exceeded the particle volume at 0.55 urn diameter, and,
therefore, the 1.1/0.55 ratios were >1, the ratio for this case
is not si gnificant. We wi ll see below in the discussion of the
800 flight series that when the 1.1/0.55 ratios were greater
than 1, the Mohave plume was affecting the "ambient" ai r.
The correlation of the dew point with the 1.1/0.55 ratio
was -0.79 at the 79 percent confidence level for the 700
flight series. These parameters are negatively correlated since
relatively low dew point temperatures occurred on December 8,
1978, when the 1.1/0.55 ratios were hi gh. The ratios were high
on this day because the peak in the particle volume was at 0.35
urn rather than at 0.55 urn.
The correlation of ultraviolet radiation with the
-110-
1.1/0.55 ratio was 0.81 at the 95 percent confidence level
for the 700 fl ight series. Several points must be kept in mind
concerning this high positive correlation. Fi rst, the fli ghts
n the 700 series occurred during the morning hours, when
the intensity of ultraviolet radiation general ly increased with time.
As the flights progressed through the morning hours, the intensity of
ultraviolet radiation, the distance from the Mohave plant and the
altitude of the measurements al l increased with time. Thus, these
three parameters were al positively correlated with the 1.1/0.55
ratio. We cannot suggest a physical basis for these positive
correlations. Second, on December 8, 1978, when the 1.1/0.55 ratios
were large, the intensity of ultraviolet radiation was greater, since
the fl ght that day occurred later in the morni ng than the other
fl ights in the 700 series.
The correlation coefficient between the time event
parameter and the 1.1/0.55 ratio was 0.85 at the 99.2
percent confidence level for the 800 fl ight series. Fi gure 4.2
shows the passage of a cold front through the region sampled
by the B-23 ai rcraft at 0300 GMT on August 30, 1979. The
magnitude of the 1.1/0.55 ratios general ly increased up to the time
of the cold-frontal passage and decreased after the cold-frontal
Figure 4 2 The NWS surface analysis at 0300 GMT on30 August 1979 (see Figure 4 1 for stationmodel)
112
passage. As the airmass aged in the region surrounding
the Mohave plant, the 1 1 \im diameter peak in the
particle volume distribution became dominant in the
"ambient" air. After the frontal passage, the "cleaner"
"ambient" air mass in the region surrounding the Mohave
plant showed a peak in the particle volume distribution
at 0 55 pm diameter.
Comparisons of Table 4 6 and Table 4 7 show that
the 1 .1/0 .55 ratios reached higher values during the 800
than during the 700 flight series. The maximum values of
the 1 1/0 .55 ratio for the 800 flight series occurred on
August 11 August 28 and August 29 1979 Table 4. 3 shows
that the peak in the particle volume distribution in the
"ambient" air was at or near a particle diameter of
1 1 pm on August 27 and August 28 , 1979 Table 4 7 also
shows that the time event parameter reached a maximum
value of 234 hours during the 800 flight series , while
Table 4 6 shows that the time event parameter reached a
maximum value of 69 hours during the 700 flight
series. A longer period of time occurred between
cold-frontal passages during August 1979 (the 800 flight
series) than during December 1978 (the 700 flight
series) Thus the impact of the Mohave plume on the
"ambient" air was greater during August 1979 (when the
113
TABLE 4. 7 The Time Event Parameter and the 1 1/0 .55Ratio for the 800 Flight Series
1
0. 490 610. 430 .460. 60
0. 460 530 690 78
0. 800 75
1 631 701 702. 221 842 171 971 591 941 62
1 46
2. 041 871. 691 731 91
1/0.55 Ratio
0.570 640 .49
1 97
Time Event
8989909091919292
112112114114
143144
184184184185185186187187187187
208208208210210210211
(hours) *
August 23 , 1979
August 14, 1979
August 25 , 1979
August 27 1979
Date
August 28 , 1979
(continued)
114
TABLE 4 7 (continued) The Time Event Parameter and the1 .1/0. 55 Ratio for the 800 Flight Series
1. 1/0 55 Ratio Time Event (hours) * Date
2211111
15008881538780
232232232233233234234
August 29 , 1979
0. 760. 940. 800 930 880 70
0. 690 830 92
383939394040
107107107
August 31 , 1979
September 3 1979
*"Time event" refers to the number of hours since afrontal passage or precipitation event. A frontalpassage occurred on 15 August 1980
115
0. 55 ratios were higher and cold-frontal passages less
frequent) than during December 1978 (when the 1 .1/0 .55
ratios were lower and cold-frontal passages more
frequent)
The correlation coefficient of the relative
humidity with the 1 1/0. 55 ratio was 0 63 at the 64
percent confidence level For the 800 flight series, the
relative humidity was an indicator of the difference in
air masses because the 1 1/0 55 ratios changed when a
cold-frontal passage occurred (see Table 4. 7)
The correlation coefficient of the Mohave plant
output with the 1 1/0 55 ratio was 0 53 at the 89 percent
confidence level for the 800 flight series. This is
reasonable, since we expect increases in the output of
the Mohave plant to lead to increases in the total volume
of 1 1 pm particles in the plume.
The correlation coefficient between 0^ and the
1 1/0 55 ratio is -0. 48 at the 68 percent confidence
level for the 800 flight series. There are two possible
reasons for this negative correlation. First, if the
1 1/0 55 ratio is 1 the "ambient" air is likely to
contain a significant volume of particles from the Mohave
plant. Since power plant plumes may be identified by low
0, concentrations (Hegg, 1976) , "ambient" air that
116
contains remnants of the Mohave plume (i.e. large values
of the 1 1/0 .55 ratio) may also have depressed 0,
concentrations. Second, the possibility exists that 0-
may be transported from the stratosphere during periods
of vigorous mixing (Haagensen et al 1981) We have
shown that the 1 1/0 .55 ratio tends to decrease following
a cold-frontal passage. Vigorous mixing may also occur
during cold-frontal passages with the effect of
increasing 0, levels Thus, the 1 1/0. 55 ratio and 0,
concentrations would be negatively correlated.
The correlation coefficient of the time event
parameter with the 1 1/0. 55 ratio was 0 46 at the 66
percent confidence level for the 900 flight
series Figure 4 3 shows the passage of a weak cold
front at ^ 1500 GMT on August 15 , 1980. The 1 .1/0. 55
ratios decreased slightly after this cold-frontal passage
(see Table 4 8)
The time event parameter reached a value of 291
hours during August 1980 (see Table 4 8) which was
greater than the maximum number of hours in the time
parameter during either August 1979 or December
1978 Thus, the cold fronts were less frequent (and the
"ambient" air more stagnant) during August 1980 than
August 1979 or December 1978 The 1 1/0. 55 ratios were
117
The NWS surface analysis at 1500 GMTon 15 August 1980 (see Figure 4 1 forstation model)
118
TABLE 4 8 The Time Event Parameter and the1 1/0 55 Ratio (900 Flight Series)
1. 1/0. 55 Ratio
0 .440 680 621. 170 831 170 .830 .870. 580. 630 .540 530. 460 400 580 570 .560. 570 630 730 730 650 580 360 480 460 460. 500 450 470 .440 43
Time Event
143144145195195195195196196196218219220220266267268268268268268291291
000011223
(hours) *
August 8 1980
August 10, 1980
August 11, 1980
August 13 , 1980
August 14 1980
August 15 1980
Date
*"Time event" refers to the number of hours since afrontal passage or precipitation event. A frontalpassage occurred on 15 August 1980.
119
less during August 1980 (generally <1) than during August
1979 (1 .1/0 55 ratios as high as 2 22) even though
meteorological conditions were more stagnant. The Mohave
plume was not the primary influence on the "ambient" air
during August 1980
Brushfires were burning near Rice, California
(^ 100 km southwest of the Mohave power plant) on August
1, 1980; these brushfires were associated with a peak in
the particle volume distribution at a diameter of
^0.55 ym (Glantz , 1982) Glantz (1982) and Hoffer e^al (1981) documented the movement of the Los Angeles
urban plume into southeastern California and western
Arizona on August 4-6 1980 Glantz (1982) also showed
that the Los Angeles urban air had a peak in the particle
volume distribution at a diameter of ^0 .55 ^m. These
results indicate that brushfires and the Los Angeles
urban plume contributed to a regional haze in
southeastern California and western Arizona during the
period 1-6 August 1980 Furthermore, we know that the
regional haze was associated with a volume size
distribution centered at a particle diameter of
^0 55ym. Our data and those of Hoffer et al (1981)
suggest that meteorological conditions were stagnant
during the August 1980 Mohave field study. Thus the
120
primary influences on the "ambient" air may have been
brushfires and the Los Angeles urban plume, leading to a
regional haze. The 1 1/0 .55 ratios which were < 1
during August 1980 suggest that this was the case (see
Table 4 .8)
The correlation between b and the 1 1/0. 55
ratio was -0 52 at the 95 percent confidence level for
the 900 flight series The two sources mentioned above,
rather than the Mohave power plant, were probably
responsible for the high b values If the Mohave
plume had been responsible for the high bg-t values^
then we would expect a positive correlation between bsca^
and the 1 1/0 55 ratio, because the Mohave plume was
associated with large values of the 1 1/0 55 ratio.
For the combined 700 800 and 900 series of
flights the most significant correlation of the 1 1/0 55
ratio was with b The overall correlation with this
parameter was -0 57 at the 99 2 percent confidence
level
For the combined 700 800 and 900 series of
flights the overall correlation of the 1 1/0 55 ratio
and the time event parameter was 0 40 at the 83 percent
confidence level The lack of a strong correlation with
the time event parameter for the 700 and 900 flight
121
series lowered the overal l correlation. Nevertheless ,
there is a strong indication from the 800 series that the
1 1/0. 55 ratio was affected by the age of the airmass
In summary, two major findings may be gleaned from
the correlation matrix. First, the regional haze present
during the 1980 Mohave field study was probably
responsible for the observed high bg-t values. Thus,
during August 1980 , the regional haze had a greater
impact on the "ambient" air than did the Mohave
plume. Second, the 1 1/0 .55 ratios were affected by the
synoptic weather patterns a change in the airmass was
generally accompanied by a change in the 1 1/0 55
ratios
4 .5 Effects on Visibility
We have shown that the peak in the particle volume
distribution in the "ambient" air affected by the Mohave
plume was often at 0. 55 pm or 1 1 urn. Particles with
diameters of 0. 55 pm and 1 1 mn lie within the Mie
scattering range. From the expression (Friedlander,
1977)
^ext 3_ ^xt dVd (log D 2 D d (log D
where D is the diameter of the particle, k is thes~ GXu
122
scattering coefficient obtained from Mie scattering
theory (van de Hulst, 1957) , and dv is the
increment in particle volume for an increment in the
logarithm of the particle size, we can calculate the
contribution of particles of a particular size to the
extinction coefficient.
We have assumed a value of 1 .5 for the refractive
index and used the appropriate extinction curve, as
calculated by van de Hulst. For particle diameters of
0. 55 urn and 1 1 urn, we obtain contributions to b *. ofSCdw
0 78 x [dV/d (log D and 0 284 x [dV/d log D )]
respectively. Hence, for equal magnitudes of
[dV/d log D (i. e. a 1. 1/0. 55 ratio of 1) the
contribution to bg-^ is 2 7 times greater for particles
diameter 0 55 urn than it is for particles of diameter of
1 1 urn. In the 900 flight series when the regional haze
was present, the 1 1/0. 55 ratios were generally
< 1 Since the 0 55 pm diameter peak was greater than the
l l pm diameter peak in the particle volume distribution,
the contribution to b was greater from the
0 .55pm diameter particles This explains the negative
correlation between b-^ and the 1 1/0 55 ratio.
While the 1 1/0 55 ratio can be used as a tracer of
the Mohave plume, it cannot be used as an indicator of
123
visibility degradation. On August 28 1979 , when the
1 .1/0 .55 ratios were > 1 for all locations in the
"ambient" air in the Colorado River Valley, the bsca^
values were less than on August 11 , 1980 when the
1 .1/0. 55 ratios were < 1 for nearly all locations. The
visibility degradation in the Colorado River Valley was
greater when regional haze was dominant than when the
effluent of the Mohave plant dominated the "ambient"
air.
-124-
CHAPTER V
SUMMARY AND RECOMMENDATIONS
In this thesis we have examined data from seventeen of the
UW-23 research flights flown during the 1978, 1979 and 1980
Mohave field studies. Si x of these fl ights were examined in
detai to determine the isopleths of b * SO? concentrations
and particle volume-to-number ratios, as well as the particle
size distributions in the Mohave plume and the "ambient" air.
Correlations between various meteorological and other parameters
and a "signature" of the Mohave plume have also been
investigated.
5.1 Summary of Results
Ai rborne measurements of b SO,, concentrations
and particle size distributions have shown that with
southerly winds the Mohave plume is restricted to the
wel l-defined region of the Colorado Ri ver Val ley before it
reaches the "mixing bowl " located 70 km north of the
Mohave power plant. After entering the "mixing bowl ," the
plume spreads to widths of 24 km and sometimes splits at
the gap in the Black Mountains.
125
In southerly winds the Mohave plume has been
tracked as a distinct entity, by visual and real-
time airborne measurements of the light-scattering
coefficient (b ^) , S0~ concentrations and
particle size distributions, up to distances of
^139 km downwind of the plant and out to widths of
^25 km. Attempts to track the plume in real time
to greater distances were not successful.
In northerly winds the Mohave plume has been
tracked as a distinct entity, by visual and real-time
airborne measurements of SO- concentrations and
particle size distributions , up to distances of
^90 km downwind of the plant and out to widths of
^6 km.
Particle volume distributions in the Mohave
plume peaked at 1 1 \im diameter. The location of the
peak in the particle volume distribution in the
"ambient" air varied. The "ambient" air of an older
airmass (such as on August 28,, 1979) was more likely
to have been influenced by the Mohave plume than the
"ambient" air of a new air mass (such as on August
31 , 1979)
Values of b in the "ambient" air of the
Colorado River Valley general ly increased downwind of
the Mohave plant. For southerly winds the maximum
126
value of b in the "ambient" air occurred in the
"mixing bowl" (^70 to 200 km north of the Mohave
plant. With southerly winds , the Mohave plume
affected the characteristics of the "ambient" air up
to at least 140 km downwind of the plant.
On August 23 and August 21 1979 SO.
concentrations and b were higher in the "ambient"
air on the west side of the "mixing bowl" than on the
east side. Thus , the Las Vegas area could have been
a source of pollution in the "mixing bowl "
Regional haze in southeastern California,
southern Nevada and western Arizona appears to be
caused more by brushfires and the Los Angeles urban
plume, than by the Mohave plume or pollution from Las
Vegas Also, visibility in the Colorado River Valley
(up to ^140 km) appears to be affected more by
regional haze than by the Mohave plant.
5 2 Recommendations for Future Research
Further studies of the "ambient" air in the
"mixing bowl" need to be made Emphasis should be
placed on determining the impact in this region of
pollution from Las Vegas. Flights should be oriented
along an east-west axis to determine the variations
of b from the western entrance of the Grandsca^
-127-
Canyon to Las Vegas.
More ai rborne sampli ng should be carried out
in the "ambient" ai r upwind of the Mohave plant, in order
to compare it with the "ambient" ai r downwind of the
Mohave plant.
When the Mohave plume is observed to split in
the "mixing bowl ," cross-sections should be obtained in
both portions of the split plume.
When regional haze is believed to be present,
ai rborne sampling should be carried out over a wide
area to determine the extent of the haze. The area of
sampling wil be determined by the extent of the regional
haze. Also, an effort should be made to determine the
source(s) of the haze.
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133
APPENDIX
For the seventeen parameters listed in Table 4.4, we
obtained 94 data entries for each parameter. Thus , the
input data for the correlation matrix consisted of a 17 x
94 array. The computer program, furnished courtesy of
Professor Halstead Harrison, featured a crossed
correlation technique which assumed that all of the data
entries were independent points However, not all of the
data points in the correlation matrix were independent
values Similar magnitudes of the data entries were
grouped together and counted as a single value in order to
determine the number of independent points for a
particular correlation. We then referred to Bevington
(1969) to determine the confidence levels based upon the
number of points.
The wind direction parameters specified in Table 4. 4
were entered into the matrix as a sine function, to avoid
possible discontinuities when the wind direction was near
360.