THE QUALITY - University of...

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


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


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.


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)



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.


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)



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)



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)



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


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



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


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



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


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


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


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


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


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^


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.

REFERENCES

Ahlquist, N. C. and R. J. Charlson, 1968: Measurements of the

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Bevington, P. R. 1969: Data Reduction and Error Analysis

for the Physical Sciences. McGraw-Hi ll Inc. New York,

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Effects of a coal-fi red power plant and other sources on

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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.

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