THE CHEMISTRY FIELD - carg.atmos.washington.educarg.atmos.washington.edu/sys/research/archive/mohave_plume_85.pdf · AN AIRBORNE STUDY OF THE CHEMISTRY AND VISUAL IMPACT OF THE MOHAVE

AN AIRBORNE STUDY OF THE CHEMISTRY ANDVISUAL IMPACT OF THE MOHAVE PLUME:

1983 FIELD PROGRAM

by

David Schutt, Dean A. Hegg, Albert Hendlerand Peter V. Hobbs

Cloud and Aerosol Research GroupAtmospheric Sciences Department

University of WashingtonSeattle, Washington 98195

ANNUAL REPORT FOR 1984 TO SOUTHERN CALIFORNIAEDISON COMPANY FOR P.O. NUMBER B2618901

September 1985

SUMMARY

During the late summer of 1983, airborne measurements of various trace

constituents were made in and around the plume from the Mohave coal-fired

power plant near Laughlin. Nevada. Particular attention was given to simulta-

neous measurement of HNO., and NO,. The NH.,-HNO,-NH.NO, equi ibrium model was

tested and found to be inappl icable in the Mohave region. This would suggest

that particul ate nitrate was not in the form of NH.NO,.

Production of HNO, and NO, was also measured in the plume and compared to

sulfate production. The NO -to-total NO", conversion rate was found to be 0.75%

hr" on average, somewhat lower than the mean SOp-to-SO" conversion rate of 1.3%

hr" A substantial fraction of the NO, was in the form of HNO-. There is some

evidence that the NO, production mechanism differs from the SO" production

mechanism (presumably OH oxidation) and that it may involve particle surfaces as

reaction sites.

Limited data were gathered on "ambient" particle size distributions in and

out of the Colorado River Valley in the region of the Mohave power plant. These

data suggest that the "ambient" particle size distributions in the Valley are

influenced by the Mohave plume.

Optical depths of the plume with respect to both particle scattering and

N0^ absorption were calculated. NO. absorption contributed significantly to the

light attenuation by the Mohave plume, the optical depth for NO. absorption

averaging about 30< of that for particle scattering.

-i-

TABLE OF CONTENTS

SECTION 1: INTRODUCTION

SECTION 2: INSTRUMENTATION AND DESIGN OF FIELD STUDY

2.1 Instrumentation

2.2 Design of the Study

SECTION 3: DATA BASE

3.1 Nitrogen Chemistry

3. 2 Visibil ity Data

SECTION 4; ANALYSES OF NITRATE DATA

4.1 Ambient Measurements

4.2 Plume Measurements

SECTION 5: SUMMARY OF RESULTS AND RECOMMENDATIONS

REFERENCES

APPENDIX A: COMPARISONS OF AMBIENT AEROSOL WITHIN AND OUTSIDE

OF THE COLORADO RIVER VALLEY

-ii-

AN AIRBORNE STUDY OF THE CHEMISTRY AND VISUAL IMPACT OF THE MOHAVE PLUME:

1983 FIELD PROGRAM

SECTION 1

INTRODUCTION

Numerous studies have pointed to the possible effects on regional air

qual ity of emissions from coal-fired power plants (e.g. Davis et al 1974;

Husar et a1 1978; Richards et a1 1981) In an effort to elucidate both the

chemistry and physics of the plumes from such plants, and their effects on

surrounding regions, the Southern Cal ifornia Edison Company is undertaking an

extensive study of the plume from the Mohave coal-fired generating station,

which is located near Laughlin, Nevada, in the Mojave Desert.

In previous reports we have described various aspects of the physics and

chemistry of the Mohave plume (Hegg and Hobbs, 1984) the effects of the plume

on air qual ity in the Colorado River Val ley (Poteet et a1 1983) and the sour-

ces of pol lution affecting the region surrounding the Mohave generating station

(Hobbs et a1 .. 1982). The 1983 Mohave field studies were designed to address a

few selected topics in greater detail than had previously been done. One of

these topics, the nitrogen chemistry of the Mohave plume, is the main subject of

the present report.

Another topic of considerable interest, for which the 1983 field study pro-

vided data, is the comparison of "ambient" air qual ity in the Colorado River

Val ley in the vicinity of the Mohave plant with the ambient air outside of the

Valley. In an earlier study (Poteet et a1 1983) we suggested that "ambient"

air in the Val ley in the vicinity of the Mohave generating station can be

affected by the Mohave plume, albeit marginally. Further data on this topic are

presented in Appendix A.

-2-

SECTION 2

INSTRUMENTATION AND DESIGN OF FIELD STUDY

2.1 Instrumentation

2.1.1 Genera]

AH data to be described in this study, with one exception, were

col lected aboard the University of Washington ’s B-23 research ai rcraft.

The exception is wind velocity data, which were obtained by ai rsonde and

pibals.

The instrumentation available aboard the B-23 ai rcraft is listed in

Table 2.1. A schematic layout of the instrumentation is presented in

Fig. 2.1. The aerosol and trace gas instrumentation used to obtain data

for this study is described briefly below. Detailed descriptions of the

instrumentation have been given by Hobbs et a1 (1976), Hegg et a1

(1976), Hegg and Hobbs (1980) and Radke (1983).

2..1.2 Oxides of Niftrogen Analyzer

Real-time measurements of NO, NO,,, NO and HNO, were made with a^-1 X -J

modi tied’-’Monitor Labs..8840 NO analyzer. With this instrument oxides ofA

nitrogen are detected by the chemi luminescent reaction of NO with ozone.

NO (NO + NO,,) is catalytical ly converted to NO in a heated, molybdenumA

chamber. NO? is obtained as the difference between the NO and NO

signals.

-3-

TABLE 2.1 INSTRUMENTATION ABOARD THE UNIVERSITY OF WASHINGTON’S AIRCRAFT

Parameter Instrument type Manufacturer Range (and error)

(a) Navigational and

Latitude andlongitudeground speed

Ground speed anddri ft angle

True ai rspeed

Heading

Pressurealtitude

Altitude aboveterrain

Ai rcraftposition andcourse plotter

Angle of attackModel 861

VLF: Omeganavi gator

Doppler navi gator

Variablecapacitance

Gyrocompass

Variablecapacitance

Radar altimeter

Works off DMEand VOR (soon tobe integrated withVLF Omega system)

Poflentiometer

Fl ight Character!

LittonLTN-3000

Bendix ModelDRA-12

RosemountModel 831 BA

King KCS-55A

RosemountModel 830 BA

AN/APN22

In-house

Rosemount

sties

0 to 300 m s"1(+/-3.7 km hr-1groundspeedand +/-1drift angle)

0 to 300 m s"1(+/- 1 m s-1 and +/-1

0 to 230 m s-1(< 0.2%)

0 to 360(+/-0.5)

50 to 060 mb(< 0.2%)

0 to 6 km(< 5%)

180 km(1 km)

+/- 23(< 0.5)

(b) Meteorological^.

Total ai rtemperature

Platinum wi reresistance

Rosemount Model -70 to 30C102CY2CG + 414 L (< 0.1 C)Bridge

Static ai rtemperature

Dew point

Computer value

Dew condensation

In-house -70 to 30C(< 0.5C)

Cambridge Systems -40 to 50CModel TH73-244 (< C)

(Continued)

-4-

Table 2. 1. (Continued)


(b) Meteorological (Continued)

Ai r turbulence

Weather radar

Pyranometer(s)(one downward andone upward viewing)

Ultravioletradiation

Photographs

Differential

5 cm gyro-stabil ized

Eppley thermopile

Barrier-layerphotoelectric cel

35mm time-lapsecamera

MeteorologyResearch, Inc.Model 1120

Radio Corp. ofAmerica, AVQ-10

EppleyLaboratory, Inc.Model PSP

EppleyLaboratory, Inc.Model 14042

AutomaxModel GS-2D-111

0 to 10 cm2/3 s-1(< 10%)

100 km

-20 to 1400 W m(-1%)

0-70 J m-2 s-1(< 5%)

s to 10 mi n

(c) Cloud Physics

Concentrations ofcloud condensa-tion nucleusspectrometer

Liquid watercontent

Four verticalthermal diffusionchambers

In-house

Hot wire resistance Johnson-wi liams

0 to 5000 cm-3(< 10%)Simultaneousmeasurementsat 0.2, 0.5,1.0, 1.5%supersaturation

0 to 2 and 0 to6 g m-3

(Continued)

-5-


Parameter

Size spectrumcloud particles

Size spectrumcloud particles

Size spectrum ofprecipitationparticles

Images ofcloud particles

Images ofprecipitationparticles

Instrument type

(c) Cloud PI

Forward light-scattering

Diodeocculation

Diodeoccultation

Diode occulationimaging

Diodeimaging

Manufac

lysics (Con

ParticleSystems,FSSP

ParticleSystems,OAP-200X

ParticleSystems,OAP-200Y

ParticleSystems,OAP-2D-C

ParticleSystems,OAP-2D-P

turer Ra

tinued)

MeasuringModel

MeasuringModel

MeasuringModel

MeasuringModel

MeasuringModel

nge (and error)

2 to 47 urn

20 to 300 urn

300 to 4500 urn

*Resolution25 ym

*Resolution200 urn

Ice particleconcentrations

Electric field

Opticalpolarizationtechnique

Rotary field mil

Ion conductivity. Gerdian

In-house

MeteorologicalResearch Inc. Model611

In-house

0 to 1000 A-1detects particles(> 50 urn)*

0 to 100 kV m-1(<10%)

0 to +/- 4x10’n-1 m-1

-14

n m

(d) Aerosol

Number concentra- Light transmission General Electrictions of particles Model CNC II

102 to 106 cm-3(particles >0.005urn)

(Continued)

* Al particle sizes refer to maximum particle dimensions

-6-



(d) Aerosol (Continued)

Number concentra- Rapid expansiontions Of particles

Mass concentration Electrostatic depo-particles sition onto matched

oscil lators

Sizes and typesof particles

Size spectrum ofparticles

Di rect impaction

Electric aerosolanalyzer

Gardner

Thermal Systems,Inc. Model 3205

Gl ass sl ides

Thermal Systems,Inc. Model 3030

2 x 102 to 107_i *cm

0. 1 to 3000 ug m-3(<0.2 ug m-3)

*5 to 100 urn

0.0032 to 1.0 urn



Size spectrumof particles

90 ight-scattering

Forward ight-scattering

Di ffusion battery

Particle Measuring 0.5 to 11 urnSystem (LAS-200)

Royco 245 1.5 to 40 urn4(in-house modified)

0.01 to 0.2 urnThermal Systems,Inc. Model 3040with in-houseautomatic val ves &sequencing



Size-segregatedconcentrationsof particles

35-120 light-scattering

Forward light-scattering

Cascade impactor

Particle Measuring 0.09 to 3.0 pmSystems, Model (<0.007 urn)*ASASP-X

Particle Measuring 2 to 47 urnSystems, Model FSSP

*Sierra Instruments 0.1 to 3 pmInc. (6 size fractions)

(Continued)

* Al particle sizes refer to maximum particle dimensions.

-7-

TABLE 2.1 (Continued)


(d) Aerosol (Continued)

Light-scatteringcoefficient

Integratingnephelometer

Meteorology Res.Inc. Model 1567(modified forincreased stabilityand better responset i me)

0 to 1.0 x 10-4 m-1or

0 to 2.5 x 10-3 m-1

Number concentra- Flame spectrometer In-housetions of sodium-containing particles

0 to 10,000 A-1(< 1%)

(e) Cloud and Atmospheric Chemistry

Cloud watersamples

Impaction onslotted rods

In-house modifica-tion of ASRC(Mohnen sampler

Bulk cloud water col lec-tion efficiency ~40%based on analysis ofin-house fl ight data

Particulate sulfur

SO^, NOg", C1 ",

Na’1’, K"1’,- NH,’1’

Teflon fi ltersCSI & Dionex XRFspectroscopy andion exchangechromatography

In-house 0.1 to 50 pg m-3(for 500 literai r sample)

SO, Pulsedfluorescence

,,;,-.. -. -’^.-.1-^-.p/^--.1Bn’WMTotal gaseous ’-- FPD^flame

sulfur ^."-^ photometric^.’,.^^Ty-:-^ ,\ .^dete’ctor

Teco SP43(Modifiedin-house)

Me1oy Model 285

1.0 ppb to 5 ppm

0.5 ppb to 1 ppm

Chemi luminescence Monitor Labs(C2H4) Model 8410 A

Ozone 0 to 5 ppm(< 7 ppb)

0 to 5 ppm(" 1 ppb)

NH,., NO, NO., NO ,HNO. Chemi luminescence Modified Monitorx (03) Labs Model 8840

(Continued)

* Al l particle sizes refer to maximum particle dimensions.

-8-



(e) Cl oud and Atmospheric Chemistry (Continued)

HN(L

Totalhydrocarbons**

Nylon filters withteflon pre-fi lterfol lowed by ionchromatographyand/or tungsticacid denuder tubesfol lowed by.chemiluminescentdetection

Gas chromatograph

H?CL (Liquid phase) Chemiluminescentreaction withluminol

Dionex/Monitor Labs

AnalyticalInstruments, Inc.

In-house

Variable

>0.5 ppm

>10 ppbLiquid phase)

(f) Data Processing and Display

Time

Time

Ground communi-cation

Infl ightdata processing

Infl ighf colorgraphics

Recording(digital )

Time code generator

Radio WWV

FM transceiver

Mini-computer

Micro-computer

Micro-computerdi rected cartridgerecorder

Systron DonnerModel 8220

Gertsch RHF 1

Motorola

ComputerAutomationLSI-I II

Apple II

3M

h, min, s(1: 105)

min

200 km

(Continued)

* Al particle sizes refer tomaximum particle dimensions.** Instrument wil not be used in this study.

-9-



(f) Data Processing and Display (Continued)

Recording Floppy disk Calcomp(digital Model 140C

Recording(analog voice Cassette Radio Shacktranscription) recorder Model 3C

Digital Impact printerprintout

Analog 6-channel Hi-speed Brushstrip charts ink recorder Model 260

-10-

GAS ANALYSIS \SYSTEM -A

-HI VOLSAMPLER

ASASP-X

BATCH SAMPLERINTEGRATING NEPHELOMETER

ISOKINETICPROBE

STATICPRESSURETRANSDUCER

SOL HEATEDCHAMBER

FRONT

HYDROCARBONSAMPLE PORT-,

INTEGRATINGNEPMELOMETER-CLOUD WATER

SAMPLER

ItW^ F1LTER

.ÂXIALLYL^ SCATTERING

dTE Fl

^ \

’^^-

\ / SAMPLER- ^^METER-, ^^^: f r S? SPECTROMETERT r T -ÔBE

"iSLTER

: S02NO a

= NOg

I 3

OlFFUStON/^ (-illwla~y/ 71s -^Si^--f-^WAND FOR /IMPACTION Z-ftyw iCAUOI "OTCOSAMPLING AUCM r

^!.- 4

^^SOLSAMPLEBAG

11CCN

SPECTRO-METER

MASS MONITORROYCO Z45BAG SAMPLERCONTROL

DIFFU-SION

BATTERt

LAS 200

CN COUNTER

EAA

^}

xa.(/

?

li0:UJ

&su

a

h7̂

-ISO*

!4SMFAn

<1 //

-t

INLET FORISOKINETICPROBE

^HEATED/ PLENUM

CHAMBER

KINETIC PUMP

^

Fig. 2.1. Aerosol and trace gas instrumentation aboard the University ofWashington s B-23 research ai rcraft. Meteorological navigational and cloudprecipitation instrumentation are not shown.

-11-

The instrument was modified to detect HNOi by adding an additional molyb-

denum converter, preceded by a nylon fi lter, to the NO channel Appropriate

valving enabled the sample stream to either flow through the fi lter/converter or

bypass it. When flowing through the fi lter/converter, HNO, was obtained as the

difference between the signals from the NO and NO channels, since HNO, isX 3

removed by the nylon fi lter. With this arrangement, it was not possible to

monitor al species simultaneously. Thus, depending on the switch position,

data was obtained for either NO/NO,, or NO /HNO-,.X -j

Other modifications included replacing the reaction chambers with larger,

gold-plated chambers, designed to increase the efficiency of photon capture by

the detector. Capi lary flow restrictors were added to reduce the system

pressure and thus reduce adsorption on the wal ls. A pre-reactor was also added

to provide a means of zeroing the instrument in fl ight. The detection l imit of

the modified instrument is -0. 5 ppb for NO, NO? and NO and -I ppb for HNO-. A^ J

schematic flow diagram of the modified instrument is presented in Figure 2.2.

2. 1.3 Sulfur Analyzer

SO? measurements during the Mohave study were made with a Meloy SA 285

sulfur analyzer. This instrument detects photons emitted by excited sulfur in a

strongly reducing hydrogen flame. Particulate sulfur is also detected, but with

poor efficiency. Since SO? is by far the dominant sulfur containing gas, the

output of the instrument is considered to be SO? concentration only. The detec-

tion limit is ~0.5 ppb.

-12-

Oi AIR

i

NO,CONVERTER

ZEFVA^LVE V,

REACTIONCHAMBER

---I C==

1VACUUM

TEFL

REACTIONCHAMBER

P -^-

SAMPLEAIR

ON ^\^Jf f ^-H

\ \

OZONE SOURCE

PRE-REACTOR

-S-(

th

Z:

^(Y

^.

a

LON

NoxCONVERT

? ^’) "^ V^

rER

O/N

ALVE

:RO^LVE

Ox

Figure 2.2. Flow diagram of modified NO analyzer.

-13-

2.1.4 Ozone Analyzer

Ozone was measured with a Monitor Labs 8410A ozone analyzer. This instru-

ment measures ozone by detecting the light emitted from the chemi luminescent

reaction of ozone with ethylene. Detection limit is ~5 ppb.

2.1.5 Teflon Fi lters

Aerosol samples were col lected on Teflon membrane fi lters by vacuum

sampling from a 500 liter polyethylene bag. The bag was fi led by ram ai r in <5

seconds, giving a horizontal resolution of ~300 meters at the normal sampling

airspeed of 65 m s The sample was then drawn through the fi lter at a rate of

-1 L s To col lect enough aerosol for chemical analysis, it was necessary to

3sample "I m of ai r per fi lter, which requi red 3 bag samples. The exception to

this was for plume samples taken relatively close to the stack. In this case

600 liters of ai r (2 bags) was general ly thought to be sufficient. After

col lection, the fi lters were extracted with distil led, deionized water.

The extract was analyzed for SO., N0^ and C1~ by ion chromatography.

2.1.6 Nylon Fi lters

HNO^ was measured by collection on a nylon fi lter mounted di rectly behind

the Teflon filter in the multi-stage, stainless-steel fi lter holder. In this

way the Teflon filter acts as a pre-fi lter, removing the particulate nitrate

from the sample stream. After col lection, the nylon filters were extracted and

analyzed for NOg, fol lowing the same procedure employed for the Teflon fi lters.

-14-

Because of the short sample time (<5 sec) the samples were thought to be homoge-

neous. Shifts in equi librium due to variations in temperature, relative humi-

dity etc. during the course of the sampl ing were not expected to occur. Even

for the case of sampling three consecutive bags on one fi lter, the total amount

of time elapsed during the course of sample collection was <1/2 hour. It is

doubtful that the ai r mass changed significantly during that time period. Tests

by Spicer et at (1982) indicated that degassing of HNO- from the Teflon fi lter

and subsequent col lection on the nylon filter is not a serious problem for short

sampling times such as those we employed. In another plume study, Hegg and

Hobbs (1979) reported the lack of a negative correlation between NO, and SO. on

Teflon fi lters. Assuming the nitrate was present as NH.NO.,, this indicated that

volati lization of NO" due to reaction with H,>SO. was not likely. Cal ibration

and tests of the Teflon/nylon fi lter method of collection and ion chroma-

tographic method of analysis by Goldan et a1 (1983) verified the accuracy of

these procedures. The detection limit was reported to be roughly 0.4 ug. By

summing the values for NO", obtained from a Teflon/nylon fi lter combination, a

good estimate of total nitrate concentration is obtained.

2.2 Design ofjthe Study-

2.2.1 Genera-1v

Measurements’.’ for: the study were made in the plume of the Mohave generating>.’ ;..: .-_.

station, located along the Colorado River in Laughlin, Nevada. This plant is

typical of modern coal -fi red power plants It has two 790 MW generating units.

Combustion gases are removed to the atmosphere via a single 500 ft high stack

-15-

Electrostatic precipitators remove more than 98.6% of the particulate mass

emissions. Low sulfur coal is del ivered by pipel ine in the form of a water

slurry. The coal is dried prior to combustion. Sulfur concentration of the

coal general ly runs ~0.5X.

It was necessary to conduct the plume study during times when the

integrity of the plume was maintained over fairly long distances, thus enabling

changes in the gas and aerosol composition with travel time to be more clearly

detected.

2.2.2 Nitrogen Chemistry

Whi le we have previously examined the nitrogen chemistry of the Mohave

plume (Hegg and Hobbs, 1984), the emphasis has hitherto been on the relationship

of this chemistry to the visual impact of the plume. These studies involved

measurements of NO? in the plume at -various ranges downwind. However, even this

limited aspect of the nitrogen chemistry could not be ful ly evaluated due to

lack of measurements on the presumed major sinks for NO? in the plume, namely,

dry deposition and conversion to nitrate. We have not previously addressed the

issue of dry deposition. With regard to nitrate production, whi le we have pre-

viously taken some-; limited measurements of particulate nitrate and particulate

nitrate production in the Mohave plume, the significance of these data is ambi-

guous due to’a* lack of concurrent measurements of gaseous nitric acid.

Evidence for production of nitric acid (and indeed nitrate in any form)

in power plant plumes is somewhat ambiguous. Davis et a1 (1974) suggested

-16-

the likelihood of hi gh concentrations of HNO^ in power plant plumes. Mi ler

et a1 (1978) presented model ing results indicating increased rates of

HMD., production in plumes relative to ambient ai r. Particulate nitrate for-

mation has been detected in some cases (Meagher et a1 1981) but not in others

(Hegg and Hobbs, 1979, 1983; Forrest et a1 1980; Easter et a1 1980; Richards

et a 1981) Nitric acid has been measured in only a few plume studies. One

study showed plume concentrations not significantly di fferent from ambient

levels (Easter et a1 1980). Another study showed sl ightly elevated con-

centrations of HNO, in the plume, but no evidence for HNO, production with tra-

vel time from the stack (Hegg and Hobbs, 1983) A thi rd study showed plume

concentrations above ambient levels in vi rtual ly every case and significant

HNO., production with travel time (Richards et a1 1981). In the second case,

the production rates of sulfate and nitrate, as wel as nitric acid, were very

low, apparently due to low ambient concentrations of the OH radical In the

thi rd study, HNO., production in the absence of NO" production was attributed to

lack of sufficient NH., to neutralize the HNO~ and to form NH^NO-.

It is thus possible that the lack of nitric acid measurements in the

Mohave plume could compromise any estimate of the sink for plume NO,,.

Certainly, lack of information on nitric acid results in a major uncertainty in

the nitrogen budget;"for the plume. Therefore, in this study we wi focus our

analysis on the concentrations of gaseous nitric acid and particulate nitrate

in the Mohave plume. Particular attention wil be paid to factors that may

affect these concentrations, their ratio under ambient and plume conditions,

and on evidence for the production of nitric acid and nitrate in the Mohave

plume.

-17-

To address these topics, the fol lowing sampling procedure was employed.

Plume measurements began with several passes at different altitudes close to the

stack to locate the plume center. The center was determined as that location

where maximum readings occurred on the continuous SO? and NO monitors andA

nephelometer, and minimum reading on the ozone monitor. Once the plume center

was determined, a grab bag sample was taken at that location. A fi lter sample

was then drawn from the bag whi le the ai rcraft prepared for another pass. This

procedure was repeated at various distances downwind of the stack.

Meteorological and chemical parameters were continuously monitored by the

onboard computer and stored on disc along with the times of the bag samples. In

this way, in post analysis, data from the fi lter analyses could be correlated

with the meteorological and chemical parameters at the precise time the sample

was taken. For the majority of the samples, three bags were collected per

filter. The volumes sampled from the bags were roughly equivalent. In the ana-

lysis of data from a given fi lter, the values of the chemical and meteorological

parameters observed at the time of each bag sample were averaged. These average

values were used to correlate with the filter data. In the case of unequal

volumes sampled, from^the- bags by any one filter, the parameter values were

weighted according to the volumes. Wind velocities requi red for the calculation

of conversion rates ’wepe1 obtained from ai rsonde and piba1 bal loons that were

released at regular intervals from several locations during the course of the

sampling.

During each fl ight, measurements were obtained on the background con-

centrations of various trace gases and aerosols in the ambient ai r. These

-18-

measurements were compared to those obtained in the Mohave plume, as wel as

to provide information on the nitrate chemistry in the background ai r.

The river val ley to the north of the Mohave plant becomes increasingly deep

and narrow. Mountains rising 1200 m above the river form a ridge on both sides.

The effect is less pronounced to the south of the Mohave plant. Southerly wi nds

(which predominated during this study) result in channeling of the plume up the

river val ley. Under these conditions, ambient samples were obtained by flying

over the desert on the other side of the ridge from the river. Grab bag samples

were obtained at two or three different altitudes, comparable to the altitudes

(above ground level at which sampling took place in the plume. As with the

plume sample, meteorological and chemical parameters were continuously moni-

tored. Average values were later correlated with the fi lter data.

2.2.3 Visibi lity

The portion of the 1983 field study devoted to assessment of the visual

impact of the Mohave plume on the surrounding areas revolved around ground-based

scanning telephotometer measurements by the Desert Research Institute. The role

of the B-23 research aircraft in this aspect of the field study was to relay

(via radio) to the telephotometer crew the location of the Mohave plume relative

to the telephotometer site and to provide data on the optical depth of the

plume, average values of b in the plume, and average NO? concentrations

in the plume at the ranges from the stack at which the telephotometer was

operating.

-19-

The sampl ing procedure employed to meet these objectives was straightfor-

ward. The ai rcraft flew down the plume to the range from the stack at which the

telephotometer was sited, and then the ai rcraft crossed the plume transverse to

its mean axis (i .e. di rection of propagation) at various altitudes covering the

vertical extent of the plume. Information on plume thickness and horizontal

extent of the plume were relayed to the ground crew during these traverses.

-20-

SECTION 3

DATA BASE

3.1 Nitrogen Chemistry

3.1.1 Continuous Monitor Data

Relevant data from continuous monitors aboard the B-23 are presented in

Table 3.1. Each value represents an average of the instrument readings at the

times the bag samples were taken. The averages were weighted according to the

volume sampled from each bag. Generally, three bag samples were col lected for

each filter sample.

Offset problems with the NO channel of the Meloy 8840 NO analyzer prevented

determination of NO and NO? concentrations. The NO channel was working pro-A.

perly, thus those values are reported here.

Real time measurements of HNOg with the Meloy 8840 did not correlate with

filter measurements and consequently were not used in this study. It is

believed that poorly matched converters were responsible for this problem. As

HNO^ is determined as the difference between the output of two channels, each

with a converter, it is imperative that the converters be identical Although

the converters are physical ly identical , smal variations in converter effi-

ciency can result in la^ge errors. The problem was more acute in this study

because of the low HNO~ concentrations. Unfortunately, the offset problem on

one channel prevented acquisition of reliable data for HNO,, with this method.

TABLE 3.1 Meteorological and chemical data from B-23 at the time when filter samples were taken.

SO^ N0^Range Barometric Temperature Dew point Ultraviolet Ozone(km) pressure (C) (C) flux (ppb) .3 .3

(mb) /y ^-2 (ppb) (umol m (ppb) (umo1 m

UW Dateflight (Septembernumber 1983)

11161116111611171117111711181118111811191119111911201120112011201121112111211122112211221122112311231123112411241124

2121212121212222222424242727272728282828282828292929303030

9.335

Ambient3.7

15Ambient

1139

Ambient1139

Ambient112237

Ambient1137

Ambient3.7

1039

Ambient9.3

39Ambient

1139

Ambient

968954914942933883935940899929935879934936940883950935886939940908886926935880910923882

23.922.322.127.828.124.525.225.123.219.219.616.117.317.817.715.821.320.818.526.727.224.418.519.320.015.114.415.413.1

-6.1-6.5-3.44.49.12.610.010.29.415.515.614.212.612.112.710.411.59.78.45.96.13.68.411.711.911.012.713.06.1

2.69.518.628.818.525.90.70.40.32.96.322.56.114.0.19.73.20.410.917.829.819.86.917.81.65.44.429.716.44.3

921372320399

152717192989103222313436

3234918296

2635

1405132

50;39’25288199

"+67’3625

1868085153413

"t239’442511523217992416

6.252.31.42.21.71.1

12.98.881.13.01.61.18.33.63.80.671.50.580.4910.72.01.10.492.31.40.764.41.10.71

11929*3010

810280<723617

41211.8

1204218<<

535197<

60<<

15622<

5.311.3

1.30.45

36.212.5

<3.21.62.7618.45.275.361.90.80<<

23.90.850.31<

2.7<<

6.960.98<

+ From SO,/NO correlationNo data

< Less than detection limit

-22-

A few HNO., measurements were also made with tungstic acid coated tubes.

These data showed poor correlation with both fi lter data and real time measure-

ments and were consequently discarded.

Problems were occasionally encountered with the Meloy SA 285 sulfur ana-

lyzer. However, since a strong correlation (r 0.98) existed between [SO,,] and

[NO ] in the plume, when the instrument was not functioning properly the SO,,

concentration was determined from this correlation.

3.1.2 Fi tter Data

Data from fi lter samples are presented in Table 3.2. A blank Teflon and

nylon fi lter were carried on each fl ight. For the Mohave samples, the range of

blank values was unusual ly high, suggesting contamination. To eliminate

possible contamination effects, an average blank value was determined for each

parameter. Any blank values more than one standard deviation from the mean were

thrown out and the remaining values re-averaged. Two of the eight Teflon blanks

and one of the eight nylon blanks were eliminated in this way. These average

blank values were then subtracted from a11 the samples to give the values listed

in Table 3.2. -^"$

3.1.3 Wind Vgloci.ttes’

Wind velocities during plume sampl ing were needed to calculate conversion

rates. These data were obtained from periodic ai rsonde and pibal releases.

Three factors were involved in estimating wind velocities: time of day,

uuflightnumber

11161116111611171117111711181118111811191119111911201120112011201121112111211122112211221122112311231123112411241124

Date(September

1983)

21212121212122i22222424242727272728282828282828292929303030

Range(km)

9.335

AmM ent3.7

15AmbientAmbient

39AmbientAmbient

39AmbientAmbient

2237

Ambient11?37

Ambient3.7

1039

Ambient9.3

39AmbientAmbient

39Ambient

Sulfa

(ug m"3)

0.730.290.261.70.78<0.102.521.11

<0.10<0.13<0.120.200.471.786.00<0.100.352.00.351.310.92<0.11<0.10<0.100.210.181.401.101.20

ite

-3,nmo1 m

7.63.02.718

8.1<1.05.412

<1.0<1.3<1.32.14.918

6.2<1.03.621

3.614

9.6<1.1<1.0<1.02.21.9151112

Nitrate (pi

(vg m’

0.29<0.10<0.090.600.290.100.650.250.100.250.24<0.10<0.120.120.53<0.10<0.120.120.470.820.23<0.11<0.100.10<0.100.100.94<0.11<0.10

irticulate)

(nmo’l m’

4.7<1.6<1.49.74.71.610

4.01.64.03.9<1.6<1.91.98.5<1.6<1.91.97.613

3.7<1.8<1.61.6

<1.6.1.615

<1.8<1.6

Ni

(Ppb)

<0.050.040.030.160.250.110.090.130.070.050.04<0.040.08<0.040.08<0.04<0.04<0.04<0.04<0.06<0.040.12<0.04<0.04<0.04<0.04<0.06<0.04<0.04

itric Acid

(rg m’

<0.150.100.090.450.680.300.26.0.370.200.130.12<0.100.23<0.120.21<0.10<0.12<0.12<0.12<0.16<0.110.32<0.10<0.11<0.10<0.10<0.16<0.11<0.10

(nmol m

<2.41.61.47.111

4.84.15.93.22.11.9

<1.63.6<1.93.3

<1.6<1.9<1.9<1.9<2.5<1.75.1

<1.6<1.7<1.6<1.6<2.5<1.7<1.6

-24-

altitude and geographical location. When a wind velocity measurement was not

avai lable at the level time or location of a plume sample, certain assumptions

had to be made. It was assumed that wind velocity decreased or increased

linearly between the values measured at different levels. Likewise, linearity

was assumed for the difference in velocities at a given altitude and time of day

obtai ned from pibals released at di fferent locations. Final ly, a linear change

was also assumed for the di fference in velocities at a gi ven location and alti-

tude as measured by pibals released at different times of day. The altitude at

which a sample was taken was particularly important, since a fai r amount of wind

shear was general ly present. The wind velocities are presented in Table 3.3.

3.1.4 Water Vapor and Relative Humidity

The mole fraction of water vapor was determined from the barometric pressure

and dewpoint. From the dewpoint, water vapor pressure (P., r>) was determi ned.rlÛ

The mole fraction of water vapor (y,, ) was then found from:

y n \^0 -^-where P^ is the barometric pressure. The relative humidity (RH in %) was then

determined from:H.O

RH 100’-’ ;. ’.. .: sat

where P is the saturation vapor pressure at the temperature at which the

sample was taken. The calculated values for y}\y0 and RH are presented in

Table 3.3.

TABLE 3.3 Supporting and derived data.

UUflightnumber

11161116111611171117111711181118111811191119111911201120112011201121112111211122112211221122112311231123112411241124

Date(September

1983)

2121212121212222222424242727272728282828282828292929303030

Range(km)

9.335

Ambient3.7

15Ambient

1139

Ambient1139

Ambi ent112237

Ambient1137

Ambient2.7

1039

Ambient9.3

39Ambient

1139

Ambient

Win

(m

Not

Not

Not

Not

Not

Not

11.1

Not

Not

d speed Wat

s-1) .ro1{

moles air

10.912.8Applicable4.82.7Applicable4.73.7Applicable6.66.6Applicable5.56.38.2Applicable1.32.0Applicable9.8

9.3Applicable6.85.0Applicable5.05.1N/A

:er vapores H,02

0.00380.00370.00500.00890.01240.00980.01310.01320.01310.01890.01890.01840.01560.01510.01560.01430.01430.01290.01240.00990.01000.00650.00890.01470.01490.01490.01610.01620.0107

Relativehumidityw

13.215.117.321.229.128.337.638.641.579.379.388.571.669.469.870.349.949.251.826.824.225.629.061.359.476.570.685.462.5

Total particlesurface area

2 -3,(urn cm

4.422.471.672.653.211.759.785.042.284.163.953.0313.13.186.262.346.663.542.195.133.051.481.355.413.772.877.905.464.92

Estimated SOp concentration in stack

(ppm)

360360

Not Applicable360360








Not Applicable

-26-

3. 1.6 Estimated SO? Concentrations in Stack

An estimate of the concentration of SO? in the stack was made for each

sampling day to check for differences in source strength from day to day.

SO? emissions and electric power load data from a previous study at Mohave were

correlated for both generating units. These correlations are presented in

Fig. 3.1. Volumetric airflow (Q) is also a function of load. Stack SO?concentrations were determined from these correlations by the fol lowing formula:

[SO?], Q, + [SO?]? Qrsn i 1 1___" z z’-""Z-’stack l + ^2

where [SO?], and Q, are the SO? concentration and volumetric airflow from

Unit 1 and [SO?]? and Q? are the SO? concentration and volumetric airflow from

Unit 2. The estimated values for stack SO? are presented in Table 3.3. It

should be noted that these estimates are very crude and are only used in a

qualitative sense.

3.2 Visibil ity Data

The data base for this aspect of the study consists of calcul ated plume

optical depths taken primarily at the same ranges and during the same time

intervals over which the scanning telephotometer was in operation. Optical

depths for both light absorption by NO? and light scattering by particles were

*calculated. The NO? absorption was calcul ated at 550 nm employing 6 s average

values of NO? concentrations in the plume and absorption coefficients from

Leighton (1961). The light-scattering coefficients due to particles were

* While light absorption by particles was not measured, we have previouslyfound no evidnce of such absorption in the Mohave plume, (see AnnualReport of the University of Washington’s Cloud and Aerosol Research Groupto Southern Cal ifornia Edison, 1983.

100 200 300 400 500 600 700

LOAD (MW)

Correlation between stack SOo concentration and power load for Mohave GeneratingStation Units 1 and 2.

-28-

measured directly by a nephelometer at essential ly the same wavelength as the

absorption (Hegg and Hobbs, 1983)

Values for the absorption and scattering optical depths are shown in Table

3.4, together with the associated average values of b, and NO, concentrationSCdt c.

across the plume. Detailed analysis of these data is beyond the scope of the

present report; however, it is worthwhile to point out that the scattering opti-

cal depths are systematical ly higher than those for NO? absorption, although,

in some instances, NO? absorption wil clearly make a significant contribution

to the total optical depth of the plume.

TABLE 3.4 Optical depths in the Mohave plume for N0^ absorption (r^) and particle light scattering (r ).

UWflightnumber

1116111611171118111811201120112011221122112311241124

Sampletime

0708073615070712090707460831091415151532071909520853

Date,,^Septembei1983)

21212122222727272828293030

Ranger. (nautical

mi 1ies)

51926

216

121925.566

19

AveragN0^(Ppb)

3522188535

26351820

ie Avera

^c.(n-1

0.38x100.24x100.29x100.49x100.42x100.37x100.27x100.25x100.32x100.24x100.27x100.42x100.31x10

ge

t

-4

-4-4-4-4-4-4-4-4-4-4-4

Absorptionopticaldepth, T

a

0.0160.0150.0030.0120.020

0.0100.0010.0040.004

0’.036

Scatteriropticaldepth, T^

0.0480.0210.0110.0680.1280.0730.0420.0270.0090.0100.026o-n?Q

ig Area(m2)

8.06xl043.71X103

1.51xl051.24X10"

N02flux

0

(ppb m s"

1.51xl071.60x10

2.12xl072.89x10’

1)

Windspeed

(m s"1)

3.34.3

9.810.9

-30-

SECTION 4

ANALYSES OF NITRATE DATA

4. 1 Ambient Measurements

The determination of the partitioning of nitrates between the gas and con-

densed phases was a primary goal of this study. A measure of this partitioning

is presented in Table 4. 1. where the molar ratio of gas phase nitrate (HNO-) to*total nitrate has been calculated for the ambient air samples in the vicinity

of the Mohave plant. Unfortunately, the ambient data set is not sufficient for

a comprehensive analysis. Only two flights provided sufficient data to quantify

the ratio [^^/(^ôtaT on three other ^’S"^’ the detection of either

nitric acid or particulate nitrate al lowed for a rough estimate of the par-

titioning. Although the concentration of ambient nitrate was tow throughout the

Mohave study, concentrations were significantly lower during the second half of

the sampl ing period. It is interesting to note that rain showers interrupted

the sampl ing program between UW fl ights 1118 and 1119, and again between UW

fl ights 1119 and 1120. It is conceivable then that the decrease in ambient

levels of nitrate was due to precipitation scavenging processes. However, the

reduction may also have been the result of the frontal passage and subsequent

airmass change.

In Table 4.2 the concentrations of ambient nitrate are compared to ambient

sulfate. On average, the particulate nitrate was present in concentrations at

least as great as sulfate on a mol ar basis. When considering both nitric acid

and particulate nitrate, the dominance of nitrate actual ly decreased, but this

is obviously a sampling anomally, which arises because the particulate nitrate

and total nitrate data sets are not in one-to-one correspondence.

* ^total ^ + ^N(^

-31-

TABLE 4.1 Measurements of [HNOg], [NO;] and [HNO^/tNOg)^^ in ambient air1’in the vicinity of the Mohave power plant.

UWfl ightnumber

1116

1117

1118

1119

1120

1121

1122

1123

1124

[HNO^](nmol m~

1.4

4.8

3.2

<1.6

<1.6

<1.9

<1.6

<1.6

<1.6

[NO;](nmol m~

<1.4

1.6

1.6

<1.6

<1.6

7.6

<1.6

1.6

<1.6

[HNO^](^total

>0.50

0.75

0.67

*

*

<0.20

*

<0.50

*

Average 3. 1 3.1 0.71

+/- standard deviation +/-1.7 +/-3.0 (2 values)

t In both-this arid the fol lowing tables, the ambient-air values weremeasured outside of the Colorado River Valley.

* Not able to determine

-32-

TABLE 4.2 Mol ar ratio of nitrate to sulfate in the ambient air in the vicinity

of the Mohave power plant.

UWflightnumber

1116

1117

1118

1119

1120

1121

1122

1123

1124

Average

+/- Standard

[SC

(nmc

2.

<1.

<1.

2.

<1.

3.

<1.

1.

12

4.

Deviation +/-4.

vI m"3)

7

0

0

1

0

5

0

9

5

3

[NO;

[SO^

<0.

>1.

>1.

<0.

*

2.

*

0.

<0.

1.

(2 values)

>]

5̂2

6

6

76

1

84

13

5

(^total

[SO;;]

0.52

>6.4

>4.8

<0.76

*

2.1

*

0.84

<0. 13

1.2

+/-0.8

* Not ab,1e to determine

-33-

Another goal was to determine if an equi ibrium relationship existed bet-

ween NH~, HNO-, and the condensed phase in the ambient ai r. A thermodynamic

model relating the equi librium constant for Eqn. (1) to temperature and relative

humidity has been developed by Stelson and Seinfeld (1982). At a gi ven tem-

perature below the relative humidity of deliquescence, the equi librium constant

is invariant. An expression for the equi librium constant as a function of tem-

perature can be obtained by integrating the van ’t Hoff equation to yield:

90.990 TIn K^ 84.6 -û- -6.1 In (-^) (4.1)

The relationship is shown graphically as the uppermost curve in Figure 4.1.

Above the relative humidity of deliquescence an expression for the

equi librium constant can be deri ved in a similar fashion to give:

KIn (-^--c--^-} 54.18 ^60- + 11.206 In (^) (4.2)

^H^NOg m

where y.,,, Q is the mean mo1a1 ionic activity coefficient of dissolved0

NH.NO^ and m -is. the mean molality of the NH.NO-. Since m is dependent on

relative humidity. K can be plotted as a function of temperature and relativec

humidity. This has been done in Fig. 4.1.<;-

Given the temperature, relative humidity and HNOg concentration, one can

predict the concentration of NH., at equilibrium with NH.NO^ with this model

The results of these predictions are presented in Table 4.3.

-34-

3.35 3.45 3.55 3.65

1000T

3.75

(K-1)

3.85 3.95

Fig. 4.1. Graphical representation of Eqns. (4.1) and (4.2) The concentration

product of HN03 and NN3 (K(;) in thermodynamic equil ibrium with NN4^3 as a func-

tion of temperature and relative humidity.

-35-

TABLE 4.3 Predicted values for NhL concentrations in ambient air in the

vicinity of the Mohave power plant.

UW ,nnn Relative K HNO- Predicted NH-flight

iuuuHumidity c J (ppb)

number T (%) (ppm (ppb) (from Fig. 4.1)(K"1)

1116 3. 39 17.3 1.3xl0’5 0.03*433

1117 3.36 28.3 2.5xl0"5 0.11 227

1118 3.38 41. 5 1.6xl0"5 0.07 228

* Particulate nttrate not detected

-36-

From the magnitudes of the NH^ concentrations predicted for the ambient air

in the vicinity of the Mohave power plant, it appears that nitric acid and ammo-nia were not in thermodynamic equi librium with pure NH^NO-. Although no

measurements of NH^ were made, the predicted concentrations are several orders

of magnitude greater than expected for a remote, non-agricultural location.

To check whether the particulate nitrate was present as pure NH,NO,, the0

volume concentration of nitrate as NH^NOg was compared to the total aerosol

volume concentration of particles <2 urn in diameter. A value of 1.725 g cm"3was assumed for the density of NH^NOg. These results are presented in Table 4.4

From these data it is apparent that if the measured particulate nitrate was pre-

sent as NH^NO^, its concentration would exceed the concentration of aerosol

<2 pm diameter. This excess would be even greater under conditions of high

relative humidity, where the density of the dissolved NH.NO, would be closer to-31.00 g cm Thus, the particulate nitrate was most likely present in some

form other than NH^NO^. A possible alternative is that nitric acid was adsorbed

onto the surfacs of aerosol particles. If this were the case, a positive corre-

lation should exist between particulate nitrate concentration and particle sur-

face area. Data on particulate nitrate concentrations, particle surface area

for particles >2 urn diameter and total particle surface area are presented in

Table 4.5.^ It can: be seen that there is not a significant positive correlationvbetween particulate nitrate and surface area (coarse particle or total ) Indeed

the coarse particle surface area and particulate nitrate appear to be inversely

-37-

TABLE 4.4 Volume concentrations of nitrate [NH.NO.J and total aerosol less than

and greater than 2 urn diameter.

UW [NO.,] ^No-^ Total aerosol volume Total aerosol volumefli ght as as <2 pm diameter >2 pm diameternumber [NH NO ] [NH..NO,,] 3 -3. 3 -3,

^ 3 4 j (urn m (pm m-3 3 -3(ug m (urn m

1117 0.14 0.083 0.0736 0.212

1118 0.14 0.083 0.0648 0.164

1121 0.68 0.396 0.0793 0.034

1123 0.14 0.083 0.0977 0.543

-38-

TABLE 4.5 Particulate nitrate concentrations, total surface area of particles

>2 urn diameter and total surface area of particles in the ambient ai r in the

vicinity of the Mohave power plant.

Total surface area of Total surface area ofUW ^^ particles >2 urn diameter particlesflight , 2 -3 2 3number (nmol m (pm cm (urn cm"

1117 1.6 0.32 1.75

1118 1.6 0.26 2.28

1121 7.6 0.07 2.19

1123 1.6 0.56 2.87

-A ,?

-39-

related. However, since three out of the four nitrate concentrations are near

the detection limit they have rather large uncertainties associated with them.

4.2 Plume Measurements

[HNO-]/(NO.), correlationsy j___j total________

Correlations of the partition ratio [HN(L]/(NO-) in the Mohave plume

with several other parameters are presented in Table 4.6. Quantification is

difficult, especial ly for samples taken during the latter part of the field

study. An attempt was made to correlate data from all flights with travel time.

This proved unsuccessful most likely due to uncertainties in the wind veloci-

ties used in the calculation of travel time. As can be seen in Table 4.6, on

any si ngle fli ght [HNO~]/(NO~) general ly increased with travel time from the

stack. It is unl kely that the increase was due to shifts in NH.NCL equi librium,J

since temperature and relative humidity were general ly constant during any one

flight. However, since the particle surface area systematical ly decreased with

travel time, a likely explanation for this behavior is adsorption of HNO^ onto

particles. More adsorption would occur early in the plume in the presence of

greater surfaceârea, consequently [HNO~]/(NO.,) would be lower. This may

have been -enhanced in the Mohave plume, since combustion of western coal often

produces a.1ka11ne ftly ash (Downs et a1 .. 1980) The possibi lity of adsorption

was checked by comparing particulate nitrate concentration to total particle

surface area in the plume. From Table 4.7 it is apparent that on most flights

particulate nitrate was correlated with total particle surface area. Thus, it

is likely that HNO., was adsorbed onto aerosol in the plume.

[HNO-]TABLE 4.6 Correlation of i^j in the Mohave plume with various parameters.

3’total

UWflightnumber

\vm cm

11161116111711171118111811191119112011201120112111211122112211221123112311241124

Correlation

CHNO,]

Traveltime(hrs)

0.240.750.211.540.652.930.461.640.550.971.252.355.130.100.251.160.382.120.612.12

Coefficient with:

(NO,),3’total

[

(NOHNO-]

3’total

<0.34>0.500.420.700.290.600.340.33<0.65<0.500.28

<0.50<0.16<0.31>0.74<0.52

<0.14

T(C)

23.922.327.828.125.225.119.219.617.317.817.721.320.826.727.224.419.320.014.415.4

0.67

Surface areaof particles

(A.)c. -j,

4.422.472.653.219.785.944.163.95

13.13.186.266.663.545.133.051.485.413.777.905.46

0.40

RH(1)

’mnl alp’’

13.215.121.229.137.638.679.379.371.669.469.849.949.226.824.225.661.359.470.685.4

0.58

YD"2mol H,02

383789

1241311321891891561511561431299910065148149161162

0.43

P.b

(mb)

969954942933935940929935933936940950935939940908926935910962

0.02

T vy

(K

3^231.27

0^62

0.37

-1 A<y0 "

3cm

1-77

0.760.230.380.370.390.140.610.30

0.640.590.983.090.35

0.23

-1S

urn"2)

T RH"1 A’1

(K cm3 urn’2)

<i no7.923.353.220.811.300.890.931.311.370.67

1.697 11C.

4.077.850.88

0-52

0.65

Slope 0.03 -0.03 -0.004 0.002 0.0007 0.17 0.09

Not able to determine

-41-

TABLE 4.7 Comparison of particulate nitrate concentration [NO"] to total

particle surface area (A ) in the Mohave plume.

UWflightnumber

1116

1117

1118

1119

1120

1121

1122

1123

1124

Range fromstack(km)

9.335

3. 715

1139

1139

112237

1137

3.71039

9.339^.A -\

1139

[N03](ug m" )

0.29<0.10

0.600.29

0.650.25

0.250.24

<0. 120. 120.53

0.120.12

0.820.23

<0.11

0.10<0.10

0.94<0. 11

\(urn cm" )

4.412.47

2.983.13

10.694.75

4.264.08

12.75.166.25

4.684.22

5.142.981.48

5.563.74

7.915.46

-42-

The correlations of the plume [HNOJ/(NO,) with other plume parameters

can be summarized as fol lows. The strongest correlation is with temperature.

Relative humidity (RH) and mole fraction of water vapor (y,, ) are negatively

correlated with [^^^(^ôta’r the re1at1ve """’n’di’ty correlation being the

stronger of the two. Surface area is also negatively correlated with

[HNOgJ^NOg)^^ The parameter T yjj^ A^ . where A^ is particle surface area,

does not correlate wel with [Ô-J/^NO.L In addition, barometric pressure

(P^) shows no correlation at al with [^^/(NOg)^^ Since yjj^ is a function

of P. this may explain why y,, p does not correlate as well as RH with

[HNO^]/(NO^)^^ Indeed, when RH is substituted for y.. Q to form the parameter-1 -1 ^TxRH xA the correlation is greatly improved. Sti a good deal of the

variance in [^^/(M^total remains unexplained. However, in a dynamic environ-

ment like’a power plant plume, one would not expect HNO, necessarily to be in

equi ibrium with condensed phase nitrate, and this appears to be the case for

the Mohave plume.

4.2.2 Formation of nitrate and sulfate in the Mohave plume

To determine. if nitrate or sulfate are produced in the Mohave plume, we

first subtract the ambient concentrations from the plume concentrations. This

is done to avoid errors due to differential entrainment of the various species.. /-:;

as the plume mixes^with the ambient air (which usually contains more sulfate and

nitrate than S(L or NO The resulting plume excess concentrations are pre-

sented in Table 4.8. From these data it is clear, at least qualitatively, that

both HNO, and NO, are produced in the plume along with SO,. If nitrate was

TABLE 4.8 Excess (above ambient) of sulfate and nitrate concentrations 1n the Mohave plume.

UW Travel [SOJ [SO-] [NO 3 [HNO ] [NO-]flight timenumber (hrs)

^^ ^^ ^ ^g ^ ^^ ^ ^^ ^^ ^ ^^ ^ ^ ^^ ^ ^ ^ ^^ ^1116 0.24 108 4.82 0.47 4.9 119 5.31 <0.03 <0.09 <1.4 0.29 4.7

0.75 19 0.85 0.03 0.3 29 1.3 0.01 0.01 0.2 <0.10 <1.6

1117 0.21 25 1.1 1.70 17.7 30 1.3 0.05 0.15 2.4 0.50 8.11.54 14 0.63 0.78 8.1 10 0.45 0.14 0.38 6.0 0.19 3.1

1118 0.65 263 11.7 0.52 5.4 810 36.2 0.02 0.06 0.9 0.65 102.93 174 7.77 1.11 11.6 280 12.5 0.06 0.17 2.7 0.25 4.0

1119 0.46 42 1.9 <0.13 <1.3 55 2.5 0.05 0.13 2.1 0.15 2.41.64 11 0.49 <0.12 <1.2 19 0.85 0.04 0.12 1.9 0.15 2.4

1120 0.55 171 7.63 0.47 4.9 370 16.5 0.08 0.23 3.6 <0.12 <1.90.97 65 2.9 1.78 18.5 76 3.4 <0.04 <0.l2 <1.9 0.12 1.91.25 70 3.1 6.00 62.5 78 3.5 0.08 0.21 3.3 0.53 8.5

1121 2.35 23 1.0 -0- -0- 18 0.80 <0.04 <0.12 <1.9 <0.12 <1.95.13 2 0.09 1.65 17.2 <1 <0.04 <0.04 <0.12 <1.9 0.12 1.9

1122 0.10 228 10.2 1.31 13.6 535 23.9 23.9 <0.06 2.5 0.82 130.25 33 1.47 0.92 9.6 19 0.04 0.85 <0.11 <1.7 0.23 3.71.16 14 0.62 <0.11 <1.1 7 0.12 0.3 0.32 5.1 <0.11 <1.8

1123 0.38 35 1.6 <0.10 <1.0 60 0.04 2.7 <0;11 <1.7 0.10 1.62.12 15 0.67 0.03 0.31 <1 <0.04 <0.04 <0.10 <1.6 <0.10 <1.6

1124 0.61 83 3.7 0.20 2.1 156 <0.06 6.96 <0.16 <2.5 0.94 152.12 8 0.4 -0- -0- 22 <0.04 0.98 <O.U <1.7 <0.11 <1.8

-44-

not being produced in the plume, one would expect the concentration of excess

plume nitrate to decrease with travel time from the stack as the plume was

diluted by mixing with the ambient air. Since travel times were not wel deter-

mined in this study, a conservative plume tracer (NO was used as an indicator

of plume di lution and thus an indirect measure of travel time. Although the

concentrations of NO and SO? in the plume may be slightly depleted due to con-

version to nitrate and sulfate, the conversion rates reported in the l iterature

are on the order of only a few percent per hour (Hegg and Hobbs, 1979, 1983;

Meagher et a1 1981; Richards et at 1981). Thus, the approximation that

SO? and NO are chemical ly conserved is general ly valid. Removal of SO? and

NO by deposition can be neglected, since sampl ing was done at plume center

which was always well clear of the ground. If nitrate was not being produced,

(NO,). should correlate with NO If nitrate was being produced, it should

not be positively correlated with the plume tracer and might even show a nega-

tive correlation. It can be seen from the data in Table 4.8 that nitrate does

not coincide significantly with NO (Fig. 4.2) which is what would be expected

if nitrate was being produced in the plume.

In Table 4.9 the. nitrate concentration is compared to the sulfate con-

centration at different ranges from the stack. On the majority of fl ights, the

ratio (^^ntal^50^ decreased with lâvel time, suggesting that nitrate was

either being formed slower or removed faster than sulfate. Since, as we have

already indicated, the plume was measured under quite stable conditions, deposi-

tional losses were likely to be too smal l to completely account for the effect

shown in Table 4.9. Thus, this suggests that nitrate may have been formed

-45-

0E

X

0

’0 5 10

TOTAL N03 (nmol m’3)

Fig. 4.2. NO versus total NO- in the Mohave plume for the data shown inA 0

Table 4.8. The l ine is a "best-fit" regression.

-46-

TABLE 4.9. Excess (above ambient) values of (NO,) ,/[SO.] in the Mohave plume

versus travel time.

UWflightnumber

1116

1117

1118

1119

1120

1121

1122

1123

1124

Traveltime(hrs)

0.240.75

0.211.54

0.652.93

0.461.64

0.550.971. 25

2.355. 13

0.100.251.16

0.382.12

0.612. 12

(^total

[SO;]

0.950.67

0. 591. 1

2.00.58

>3.5>3.6

0.730. 100.19

0. 11

0.950.38

>4.6

>1.6<5.2

7.1

-47-

more slowly than sulfate. It is suspected that both NO? and SO? are oxidized by

OH" (Heggs and Hobbs, 1983; Richards et a1 1981) Since OH"’reacts with

NO? several times faster than with SO?, nitrate would be formed faster than

sulfate by this mechanism. Hence, the Mohave results indicate then that oxida-

tion by OH" may not have been dominant in the Mohave plume.

A somewhat better measure of the relative reaction rates is the ratio of

C^total^total to ^^total in the P1""^ where ôtal and ôtalrepresent the total nitrogen and sulfur concentrations in the plume. Previous

measurements of this ratio (Hegg and Hobbs, 1983; Richards et a1 1981) indi-

cated a value of 3-4, which is the magnitude to be expected if both SO? and NO?are being oxidized by OH. Calculation of this ratio for the Mohave data is pre-

sented in Table 4.10. The calculated mean value of 0.78+/-0.96 is wel below that

expected for oxidation by OH. The mean value for this ratio is most ikely

higher than 0. 78, since several fl ights had significant (NO,). ,/N. butj rotai cocai

undetectable sulfate, and consequently were not included in the average.

On UM fl ight 1121, a value for [SO^]/S^^ of 190xl0"3 was obtained.

Since this is an order of magnitude higher than the next highest value, it must

be assumed that this value is anomalous; therefore, the mean values of

[SO^]/S^ îs calculated with and without the anomalous value. Omitting

the anomalous value gives a more reasonable value for [SO,]/S.

-48-

TABLE 4.10

UWflightnumber

1116

1117

1118

1119

1120

1121

1122

1123

1124

Mean+/- standard

deviati’oi

<0.68<2.4

<0.620.46

n

Ra

in

tic

the Mohave plume.

A

In

0.59*

I?

5.

of excess values of

[SO;;]ôtal

units of 10"3)

1.00.35

1613

0.461.5

0.646.3

20

*190

1.410

<12

.5+/-41.8

51+/-6.92+

[SOi:ôtal

B

(In

0.880. 15

8.020

0. 300.54

1.85.0

0.220.563.4

<2.4*

0.544.3

17

0.59*

?

to excess values

(^totalôtal

units of 10"

2.1<1.8

.09+/-6.06

of

B/A

0.880.43

0.501.5

0.650.36

<2.6>2. 1

0.340.090. 17

**

0.390.43

>1.4

>0.95*

(""a’totoi"total

3.6*

0. 78+/-0.96

* Not able to determine+ Omitting 190 value

-49-

4.2.3 Conversion rates

Nitrate and sulfate production in a plume can be quantified by calcu-

lating convesion rates. This -can be done by measuring the concentration of pre-

cursors (NO SO?) and the oxidized species (NO,, HNO,, SO,) at two or more

ranges in the plume. By assuming that nitrogen and sulfur are conserved, an

expression for the conversion can be written as:

R RY(t) Tl^-IT- ^’3)

where, R. is the ratio of the concentration of the oxidized species to the con-

centration of the precursor species (e.g. [HNO,]/[NO ]) at the first range and0

R. is the same ratio at the second range. Dividing y(t) by the travel time

between the two sample points and multiplying by 100 gives a conversion rate in

percent per hour. Conversion rates for NO -- (N03)+ota^ ^x ’" ^Sand SO? -> SO, are presented in Table 4. 11.

Examination of Table 4.11 reveals several interesting points. On average,

the SOy conversion rate was greater than the NO conversion rate. However, theC

two rates were of the same order of magnitude, and in some individual cases the

NO? conversion rate exceeded the SO?. As stated before, the data for SO?conversion on flight 1121, which gives an unusually high y value, may be erro-

neous. Therefore, an", average SO? conversion rate is calculated with and without

this value. When not considering the anomalous value, both the N0^ and SO?conversion rates are higher during the afternoon than in the morning, most

ikely due to increased mixing and greater UV flux. It is also apparent that

both nitric acid and particuiate nitrate were produced in the plume.

TABLE 4.11 Conversion rates in the Mohave plume.

UNflightnumber

11161117111811191120112011211122112211231124

AverageAverageOverall

Timeoffl ight

a.m.p.m.a.m.a.m.a.m.a.m.a.m.p.m.p.m.a.m.a.m.

of morning f1of afternoon flightsaverage

Traveltime(hrs)

0.511.332.281.180.420.282.780.150.911.741.51

0. 75+/-0.89 0.32+/-0.46

N0^

^0.000150.02020.000540.00510.000560.0034

0.00430.0170

<0.0036

ights

. (N0^

"i

0.000880.00810.000300.00180.000220.00056

0.000540.00430.000590.0021

0.25+/-0.451.6+/-0.82

^tota1Y(% hr-1)

-0.140.890.0100.280.0811.0*

2.51.4*

<0.10

^0.000150.0130.000220.0022<0.000560.00094

-0-0.017

N0^, -- HNO-A 0

R, Y

<0.00026 <0.00180.0000250.000840.00022<0.00056

-0-<0.0020

0.0590.85

hr"1)

-0.0220.850.00860.11

<0.081>0. 14

**

>1. 7**

(2 value(1 value)

^0.00350.0130.0015

0.00640.0200.200.0065<0.00180.0047

-0-

S)

SOp + S

R, .0.00100.0160.00046

0.000640.0064-0-

0.00130.0065<0.000620.0057

2.1.1.

^hr"

-0.-0.0.

1.4.6.3.

<-0.>-0.-0.

6 (2 values)9+/-2.5

1)

1322046*480455008638

0^2.8 (l. ^. l^(1.3+/-2. 1)

* Not able to determine

t Value in parentheses is when fl ight 1121 is excluded.

-51-

In an effort to understand some of the factors control ing these conversion rates,

several parameters were linearly regressed against the conversion rates. The

results of these correlations are presented in Figures 4.3 to 4. 5.

The most significant correlation is with total particulate surface area (A

(Fig. 4. 3) N0^ conversion in particular shows a very strong inverse linear

relationship with this parameter. If A s considered as a plume tracer, the

correl ation indicates that conversion rate increased with travel time. This, in

turn, suggests that the conversion rate was controlled by some species in the

ambient air (most likely OH) which was mixed into the plume in increasing

amounts as the plume traveled downwind. If this were the explanation for the

strong correlation, one would expect a similar or better correlation with a con-

servative plume tracer such as SO? or NO The correlation with (SO.) is pre-C X t,

sented in Fig. 4.4. In this case Yen correlates better than Yiun To check2 x

whether the Yog correlation is biased by using SO? as the plume tracer,

regressions were also done using NO as the plume tracer. No significant dif-

ference was seen. Correlation coefficients were 0.93 for Yen vs. NO and 0. 72jU? x

for Yô vs N0^.

We conclude.- that S(L conversion in the Mohave plume was most likely

controlled by ah oxidant present in the ambient air. NO conversion, on the

other hand,- appears to,? have been additional ly influenced by particle surface

area. Since y^n correlates better with A than SO? it may be that the surface

area of particles in the plumes had a strong influence on Ynn One explanationA

is that one or both of the reactants in the oxidation of NO was being removedA

by adsorption onto the surface of particles.

-52-

AS (ljm2cm~3)Fig. 4.3. Conversion rates (y) for SO; and NO, a function of tot.) particleClixfaoosurface area (A^) in the Mohave plume.

-53-

SO^ <PPb>

Fig. 4.4. Conversion rates (y) for SO? and NO as a function of

SO? concentration in the Mohave plume.

-54-

Since the above analysis is based on a very limited data set (five values

of Yen and seven values of Yt,n it is prudent to check whether differences

real ly do exist between the correlation coefficients. This can be done by

2 2looking at the R values for the various correlations. The R for Yiun vs.

2 x

A^ is 0.92, whi le Yen vs’ \ has an R of 053. Thus 92% of the variance in

Yn is explained by the correlation with A whi le only 53% of the variance inA

Yen can be expl ained in this way. Similarly, 86% of the variance in Yen is^"9 JUy

explained by the correlation with SO?, while only 52% of the variance in Yin is

2 êxplained by this correlation. These significant differences in R values sup-

port the view that the differences in the correlations of Ynn and Yen MithL

A and SO? are real

It should be noted at this point that neither Yin "or Yen correlated withA

relative humidity; this indicates that oxidation in a liquid fi lm on the plume

aerosol particles was unimportant. In addition, no correlation was apparent

between the conversion rates and ozone concentration, thus, it is unl ikely that

0., was the oxidizing species.

To test whether OH was the oxidizing species, conversion rate can be

correlated with a parameter that gives a measure of OH concentration. Hegg(90-Z)[UV][03][H.O]

and Hobbs derived the’ parameter as a measure of the OH[CO]

concentration, where Z is the solar zenith angle (Hegg and Hobbs, 1980) A

similar parameter, [UV][0,](yn n), was calculated from the Mohave data and

correlated with the conversion rates in the Mohave plume (Fig. 4.5) whi le

-55-

ss

)^

(UV)(03)(yH30> (Wppb m-2)

Fig. 4.5. Conversion rates (y) of S(L and NO as a function of the product of^ ^

ambient UV flux, ozone concentration and mole fraction of water vapor

[(UVKO^Ky^ p)] in the Mohave plume.

-56-

y<, 0 correlates very wel Y..Q exhibits only a marginal correlation. This sup-A

ports the idea that while SO? conversion may have been dependent on the

OH concentration, NO conversion appears to have been dependent on other fac-A

tors as wel One important factor may be particle surface area. Again, the

number of data points avai lable is not adequate for a definitive analysis. The

data only suggests that these processes may have been occurring.

-57-

SECTION 5

SUMMARY OF RESULTS AND RECOMMENDATIONS

5.1 Summary of results

In this study measurements of HNO, and NO, were made in the ambient air and

in the plume from the Mohave coal-fired power plant in the Southwestern United

States. The NH..,-HNO,-NH.NO~ equi ibrium model was tested. Production of

HNO, and N0^, was measured in the plume and compared to sulfate production. SOpand NO conversion rates were then correlated with several parameters in an

effort to elucidate the mechanisms involved in the conversion processes.

Levels of nitric acid and particulate nitrate were found to be very low in

the ambient air over the Southwest desert. Measured HNO, concentrations ranged

from 0.03-0.11 ppb, with an average value of 0.07 ppb. However, on the majority

of samples, HNO, concentrations were below the detection limit (~0.03 ppb)

Nitric acid was not detected after rain showers interrupted the sampling

program.

Nitrate was present in the ambient aerosol in molar concentrations roughly

1-1/2 times greater than sulfate. At least 50% of the ambient nitrate was pre-

sent as -n-itric add. Nitric acid and ammonia did not appear to be in ther-

modynamic equi librium with ammonium nitrate in the airshed of the Mohave plant

(either in or out of plume) The data suggest that the nitrate was not present

as NH.NO. at this location.

On three of the nine Mohave plume flights, significant nitrate and sulfate

production in the plume was measured. Sulfate production was greater than

nitrate production on two of these flights.

-58-

It appears likely that SO? was oxidized by OH in the Mohave plume.

Although NO may also have been oxidized by OH (or at least by a gas-phase

mechanism with a species other than ozone) the conversion rate of NO inA

the plume appeared to be strongly dependent on the particle surface area in the

plume. One possible explanation for this is the adsorption of NO? onto the par-

ticles.

If both SO? and NO? are oxidized by OH, NO conversion should exceed

SO? conversion. On the one day when the NO conversion rate was greater than^ A

the SO? rate, the UV flux was high, the rel ative humidity low and the particle

surface area low (Fl ight 1117 in Tables 3. 1 and 4.8) These conditions would

enhance gas-phase oxidation of NO by OH, particularly if the high particle sur-

face area is indeed inhibiting. Thus, oxidation by OH appears likely in this

case.

Conversely, on the one day when SO? conversion dominated (Fl ight 1120) low

temperature, high relative humidity and high particle surface area were preve-

lant. Thus, it is likely that gas-phase oxidation of NO? by OH was inhibited.

Oxidation of SO? by OH may also have been inhibited under these conditions

The high conversion rate in this case may have been due to another mechanism

(e.g. aqueous-phase oxidation)

NO conversion rates ranged from 0 to 2.5% hr , with an average value of

0.75% hr SO? conversion rates (excluding Fl ight 1121) ranged from 0 to 4.8%

hr~ with an average value of 1.3% hr~ Although the data are limited, it

-59-

appears that NO conversion rates were significantly higher in the afternoon.

The data indicate that SO? conversion was not significantly enhanced during the

afternoon.

Final ly, it appears that some nitric acid formed in the plume and was then

adsorbed onto particles.

-60-

REFERENCES

Davis, D. D. G. Smith and G. Klauber, 1974: Trace gas analysis of a power

plant plume. Science, 186, 733-736.

Downs, W. W. J. Sanders and C. E. Miller, 1980: Control of SO. emissions by

dry scrubbing. Proc. Amer. Power Conf. 42, 262-271.

Easter, R. C. K. M. Busness, J. M. Hales, R. N. Lee, D. A. Arbuthot, D. F.

Mi ler, 6. M. Sverdrup, C. W. Spicer and J. E. Howes, 1980: Plume

conversion rates in the SURE region. EPRI Report EA 1498, Vol 1.

(Available from EPRI, 3412 Hi lview Avenue, Palo A1to. CA, 94304.)

Forrest, J. R. L. Tanner, D. Spandau, T. D’Ottavio and L. Newman, 1980:

Determination of total inorganic nitrate uti lizing col lection of nitric

acid on NaCI impregnated fi lters. Atmos. Envi ron. 14, 137-144.

Goldan, P. D., W. C. Kuster. D. J. Albritton, F. C. Fehnsfeld, P. S. Connell

R. B. Norton and B. J. Huebert, 1983: Cal ibration and tests of the fi lter

col lection method for measuring clean-ai r, ambient levels of nitric acid.

Atmos. Envi ron., 17, 1355-1364.

Hegg, D. A. and P. V. Hobbs, 1979: Some observations of particulate nitrate

concent rations in coal-fi red power plant plumes. Atmos. Environ. 13,

1715-1716.

Hegg, D. A. and^P. V. Hobbs, 1980: Measurements of gas to particle conversion

in the plumes from five coal -fi red power plants. Atmos. Envi ron. 14,

99-116.

-61-

REFERENCES (Continued)

Hegg, D. A. and P. V. Hobbs, 1983: Particles and trace gases in the plume

from a modern coal -fi red power plant in the western United States and

thei r effects on li ght extinction. Atmos. Envi ron., 17, 357-368.

Hegg, D. A. and P. V. Hobbs, 1984: Field studies of the plume from the

Mohave Power Plant. Annual Report for 1983 to Southern Cali fornia Edison

Company for P.O. Number B2618901.

Hegg, D. A. P. V. Hobbs and L. F. Radke, 1976: Reactions of nitrogen

oxides, ozone and sulfur in power plant plumes. EPRI Report EA-270.

(Available from EPRI 3412 Hi llview Avenue, Palo Alto, CA 94304.

Hobbs, P. V. G. S. Glantz, D. A. Hegg and M. w. Eitgroth, 1982: A preliminary

study of the sources of pol lution affecting regional ai r qual ity and visi-

bil ity in the Mojave Desert and the National Parks of the Southwestern

United States. Annual Report to Southern Cal ifornia Edison Company for

P.O. Number B2618901.

Hobbs, P. V. and D. A. Hegg, 1982: Sulfate and nitrate mass distributions

in the near fields of some coal-fi red power plants. Atmos. Envi ron. 16,

2657-2662., :^ ^-*. -l’^’

Hobbs, P. Y,, L. F^’Radke and E. E. Hindman, 1976: An integrated ai rborne

-’ ., " ’&’ "particle^measuring^ facil ity and its preliminary use in atmospheric

aerosol studies. J. Atmos. Sci ]_, 195-211.

Husar, R. B. D. E. Patterson, J. D. Husar, N. V. Gi llani and W. E. Wilson,

1978: Sulfur budget of a power plant plume. Atmos. Envi ron. 12,

549-568.

-62-

REFERENCES (Continued)

Lei ghton, P. A. 1961: Photochemistry of Ai r Pol lution. Academic Press,

New York.

Meagher, J. F. L. Stockburger, R. J. Bonanno, E. M. Bai ley and M. Luria, 1981:

Atmospheric oxidation of flue gases from coal -fi red power plants a

comparison between conventional and scrubbed plumes. Atmos. Envi ron., 15,

749-762.

Mi ler, D. F., A. J. Alkesweeny, J. M. Hales and R. N. Lee, 1978: Ozone

formation related to power plant emissions. Science, 202, 1186-1188.

Poteet, W. R. D. A. Hegg and P. V. Hobbs. 1983: The effects of a coal -fi red

power plant on regional visibi lity. Supplemental Annual Report to

Southern Cali fornia Edison.

Radke, L. ’F. 1983: Preliminary measurements of the size distri bution of cloud

interstitial aerosol In Precipitation Scavenging, Dry Deposition and

Resuspension, Elsevier Science Publishing Co. Inc., New York.

Richards, L. w. J. A. Anderson, D. L. Blumenthal A. A. Brandt, J. A. McDonald,

N. Waters, E. S. Macias and P. S. Bhardwaja, 1981: The chemistry, aerosol

physics and optical properties of a western coal -fired power plant plume.

Atmos. Environ. ^5, 2111-2134.

Spicer, C. W. , J. E. Howes, T. A. Bishop, L. H. Arnold and R. K. Stevens, 1982:

Nitric acid measurement methods: an intercomparison. Atmos. Envi ron. 16,

1437-1500.

Stelson, A. W. and J. H. Seinfeld, 1982: Relative humidity and temperature

dependence of the ammonium nitrate dissociation constant. Atmos.

Envi ron., 16, 983-992.

-63-

APPENOIX A

COMPARISONS OF AMBIENT AEROSOL WITHIN AND OUTSIDE OF THE COLORADO RIVER VALLEY

In a previous study of the Mohave Plume (Poteet et_a1_. 1983) we presented some

data that suggested that "ambient" ai r in the Colorado Ri ver Val ley in the vicinity

of the Mohave generati ng station can be affected, in part, by the Mohave plume. To

explore this possibility further, ambient aerosol samples were obtai ned during the

1983 Mohave field study, both in and out of the Colorado Ri ver Valley.

The mean particle number and particle volume size distribution for the ambient

ai r out of the Valley is shown in Figure A.I. The distributions are the average of

68 samples taken at altitudes above ground and at ranges from the stack comparable

with those for the ambient samples acqui red in the Val ley.

Val ley ambient samples are stratified according to range from the stack and the

di rection of plume propagation. Particle number and volume distributions for the

Valley ambients are shown in Figures A.2 through A.8.

Comparison of the various Val ley ambients with the mean ambient distri bution

out of the Val ley reveals that when the plume propagates to the north (i .e. along the

relatively narrow and confined portion of the Colorado River Valley) the con-

centrations of sub-micron particles in the ambient ai r in the Val ley are systemati

cal ly elevated above those in the ambient ai r out of the Valley. However, when theA’

plume propagates to the south (i .e. into the more open portion of the Ri ver Valley)

the concentrations of sub-micron particles in the ambient ai r in the Val ley at a

range of 12 miles from the stack and beyond, differ little from those in the ambient

ai r outside the Val ley.

These results provide quantitative support for our previous tentative conclu-

sion that the Mohave plume affects the enti re Val ley to the north of the plant when

the plume is propagating in that di rection.

-64-

ifi

o

0

0

S-U\m

Qo

0 ^>.<U0

0

bS

oo

,0 0

00

a o

-1.00 0.00LOG D IUMI

2.00

0B O0!?.

r(R)0

fe.oo

B e>0

""(ÔO

ocPo

LOG 0 (UM)

Fig. A.I. Particle number and volume distributions for ambient air outside of

the Colorado River Valley. The distributions shown are averages of 68 samples.

-65-

0 6 S

a

o1

o ’u"S(0

a

0L3

Dg

OS

oo

o ô a0^

o a-T-----i---oo-i---a-i-eea--i-2.00 -1.00 0.00 1.00 2.00

LOG 0 (UM)-3.00 >.00 -1.00 0.1,0

LOG 0 (UM)

-e-! .:i:->-ii. -i.j 2.00

Fig. A.2. Mean particle number and volume distributions of ambient air in the

Colorado River Valley at a range of 2 miles from the Mohave Power Plant. The

plume was traveling to the north. These measurements were made at the same mean

altitude above ground and at the same range from the Mohave Power Plant as those

shown in Fig. A.I.

-66-.

o

o

0

0

0

(R)

a

s~uN.(D

^J~H00Q

SJS-1!

o

0a

^ ^0

o

0

00

a

(R) o

0

0 0

0 00

^ - 3.90 c

0

-^.00 LOGÛM0) 00 l-00 2-00 Xoo----ia-.00LOG 0 (UM)

o.oo -^-- ,..-.-(^.-^)

Fig. A.3. Mean particle number and volume distribution of ambient air in the

valley at a range of 6 miles from the stack with the plume traveling to the

north.

-67-

o o

o o

0

0

0

.-vOJ(nac-LJ’s(0

e

o

Qt3

Q

."t ^0 0

(D

0

b*b0

0

S o oe,0 o

0

.S (R) 0 0

1 0

^ 00

0----i-----r-----r----a-i---eo --i _-|-----i------i------i----O’- !--CT-i00 -2.00 -1.00 0.00 1.00 2.00 -3.00 -2.00 -1.00 0.00 0:1 3.00

PI (’’ H 111ULOG D (UM) LOG 0 (UM1

Fig. A.4. [Same as A.2 but at 20.21 mile range.]

-68-

a

o

a

o

r^m

(D^-l(-)N.m

’"f

CDL30

^x"CT

0

0 0

-,-<- ---r <3-i--?.r’n -i.oa o. -’r.

LQG 0 (UM.i

e’36CCC -i1. y0 a, IG

(R) 0 0 00

0-r-0- ----P-- :7:;^- --..-ie. v.---?.oo -i .nj r,. -,- i.e.

LQG 1:1 I! M.I

Fig. A.5. [Same as A.2 but at a range of 2 mi les with plume going south.J

-69-

3>

0(D

CO"0

0

s0 <0

0

B

X-

cu

0

o<? S^’’Sro

0 ô3

0 CM0 C=l

L30

^g’s^^^^0 0

00

00 <u

8

0

"oa <D

0

a 0

(R)0

0

00

00 ^Too ~Y.oa 0^00 iToo "2’. on c>-LQG D (UM1 LOG n iUt-’l

0

e

a>

0

B

0 (R)

0

e

co o

0 Oo a

B0 0 o^

0

3.00 -2^ GO -’t..X’i "’.!’;!’ 1.’; "’.:’’’

Fig. A.6. [Same as A.5 but at 5-6 mile range.]

-70-

0

o

o

0 ^.0

2"LJ

(̂T7

rj

QC3e3

^xuQ0

0

aa

’3 0 !’

o c. o’-.^.^,-...^-. ..--(C);(C)--; --e-3S ;j:.ti^?-<.’; --) -). -.-.,.o_Q._^:,-^. .-...^.w. . -i-..M.-2.00 -_ C.3 0.^ i.,,0 ?. .;0 3.C.C -2.00 "Y.-JCJ ,.’. ; > ;?’t

LOG D (Uh.) LFIG D rUM:!

Fig. A.7. [Same as A.5 but at 12 mile range.]

-71-

ui"

00

00

<n"

00

fvT

n

Egu-^- ena o :-" ,? -l0 l? -s-i nOo’,0ZQ

00"Jo

1"

0

(U.

a

(0.

00

d".

o0

0m 0

L .--y- ----|---.-.. <;- <g .-Q09---i-3,00 -2.00 -1.00 0.00 1.00 2.00 0-

LflG n dJMI

r

0a

0

0

01C

0 0

0

0

^"0

00 ^nj

Sg.^^

0 013C3

^gs^.>0a

0

000(0

0 0

0

0 o

sr.0

e

0fU

0 0"

0

0 i’

6

0

03

30 0

00 0 0 0

00

ao0 0

0

0

--i-^ -^ Q.^ -5 cee-,G^ -?.00 -1 ,00 n.’in I.L ,:i ’-.^

LOG D IUM)

Fig. A.8. [Same as A.5 but at 19-21 mile range.]

Documents

THE CHEMISTRY FIELD - carg.atmos.washington.educarg.atmos.washington.edu/sys/research/archive/mohave_plume_85.pdf · AN AIRBORNE STUDY OF THE CHEMISTRY AND VISUAL IMPACT OF THE MOHAVE