Spatial Mapping of VOC and NOx Limitation of …€¦ · Web viewThe Smog Production (SP) algorithm1,2,3 was applied to air quality monitoring data from six areas: the northeastern

Spatial Mapping of VOC and NOx Limitation of Ozone Formation in Six AreasPaper no. 215 Session no. AB-2c

Charles L. BlanchardEnvair, 526 Cornell Avenue, Albany CA 94706

ABSTRACTAmbient aerometric data were used to qualitatively predict where ozone formation at specific

times and locations was limited by the availability of volatile organic compounds (VOCs) and

where it was limited by oxides of nitrogen (NOx). The results are of interest for corroborating

the predictions of photochemical air quality simulation models (PAQSMs), or for characterizing

VOC- and NOx limitation for many different days and many different ozone seasons, potentially

corroborating the representativeness of the modeled episodes. The Smog Production (SP)

algorithm1,2,3 was applied to air quality monitoring data from six areas: the northeastern and mid-

Atlantic states (1994-99), the southern Lake Michigan area (1991 and 1994-98), Atlanta (1990

and 1994-99), Texas (1993-1999), central California (1991-98), and southern California (1994-

97). Analyses were carried out for each day and each site within each region. To summarize the

results, maps of the results were prepared using the five highest ozone days at each site during

each year. In addition, tables of summary results were prepared for all sites and hours with

ozone concentrations exceeding either 80 or 120 ppbv. Comparisons with modeling studies and

other types of data analyses were also carried out, but are reported elsewhere.3,4

INTRODUCTIONIncreased attention has been devoted in recent years to the use of ambient aerometric data for

qualitatively predicting whether ozone formation at specific times and locations is limited by the

availability of volatile organic compounds (VOCs) or oxides of nitrogen (NOx)1,5,6,7,8,9.

Procedures for using ambient data are of interest for corroborating the predictions of

photochemical air quality simulation models (PAQSMs) and for characterizing VOC- and NOx

limitation for many different days and many different ozone seasons, potentially corroborating

the representativeness of modeled episodes.

1

The Smog Production (SP) algorithm 1,2,7,9 has previously been applied to data from the 1987

Southern California Air Quality Study1, the 1990 San Joaquin Valley Air Quality Study10, the

1993 Coastal Ozone Assessment for Southeastern Texas (COAST) study and historical data from

the Houston area for the period 1988 through 199211, the 1995 NARSTO-Northeast Study12,

1994-98 data from central California4, and four metropolitan areas of Texas (Houston,

Beaumont-Port Arthur, Dallas-Fort Worth, El Paso) for the time period 1994 through mid-

199913. These previous applications are extended here to cover the time period from 1994

through 1998 or 1999 in each of those study areas, as well as in Atlanta and the southern Lake

Michigan area.

Besides the SP algorithm, other methods have been developed for using ambient measurements

to delineate between VOC and NOx limitation. These methods are the correlation of ozone with

NOy or NOz (defined as NOy - NOx)5, indicator ratios6,14,15,16, radical budgets17, and the

Observation Based Model (OBM)8,18. Limited cross-comparisons of the methods have been

made. Previous work using data from six research sites operated during the 1995 NARSTO-

Northeast Study12 indicated that the results of the SP algorithm were generally consistent with

those derived from a ratio of ozone, corrected for estimated background ozone, to the sum of all

oxidized nitrogen species [NOy, where NOy is defined as the sum of NO, NO2, and the products

of the oxidation of NO2, which include peroxyacetylnitrate (PAN), nitric acid (HNO3), and other

compounds]. The NARSTO tropospheric ozone assessment19 provides further discussion of the

use of methods based upon ambient measurements for corroborating modeling analyses.

METHODSFor the present study, applications of the SP algorithm were obtained from previous studies and

extended for six regions of the country. The regions and time periods covered by the analyses

are:

Central California 1991-98

Texas 1993-99 including 1-year intensive study (1993)

Southern California 1994-97

Atlanta 1994-99 and 1-year intensive study (1990)

2

Northeast and mid-Atlantic 1994-99 including 1-year intensive study (1995)

Southern Lake Michigan area 1994-98 and 1-year intensive study (1991)

The findings are presented in terms of a parameter known as the extent of reaction, which varies

from 0 to 11,2. Values of extent less than 0.6 indicate that ozone formation is locally limited by

the availability of VOCs. Values of extent exceeding 0.9 indicate that ozone formation is locally

limited by the availability of NOx. Intermediate values are transitional or indeterminate.

Analyses were carried out for each day and each site within each region using all daytime hours

during time periods when the highest ozone concentrations are typically reached. These periods

ranged from June through September for the northeastern U.S. and Lake Michigan area sites to

March through October for southern California. Statistical summaries were prepared for hours

with ozone exceeding 80 ppbv and for hours with ozone exceeding 120 ppbv; map displays were

prepared using averages over the five highest ozone days at each site during each year.

Because data-analysis procedures use ambient monitoring data to predict where and when peak

ozone concentrations are limited by the availability of VOCs or NOx, the accuracy of the ambient

measurements strongly affects the accuracy of the predictions. The SP algorithm requires

accurate measurements of ozone, NO, and either NOx or NOy. However, measurements of true

NOx (NO + NO2) or NOy (the sum of NOx and NOx reaction products) are not routinely available

from compliance monitors. The standard NOx monitor measures NOx plus unquantified fractions

of NOx reaction products, such as peroxyacetylnitrate (PAN) and nitric acid (HNO3)20. Such data

are denoted as “NO2” and “NOx” hereafter. These routine “NOx” data were used to provide

upper and lower bounds on the extent of reaction. The lower bound for extent was computed by

using the measurements of “NOx” as if they were true NOx. The upper bound for extent was

computed by using the measurements of “NOx” as if they were true NOy. An example of the

bounding is shown in Figure 1. The two sets of extent values were plotted against their means.

Although the true extent is unknown, the mean of the bounds is likely closer to the true value

than are the bounds themselves. As shown, for VOC-limited cases (less than ~0.6), the bounds

are tight. Thus, the predictions of VOC limitation are robust even when the "NOx”

measurements are biased.3

4

Figure 1. Extent of reaction computed using “NOx” as NOx or as NOy versus the mean of the two calculations at Houston area sites. The data are from all peak hours having ozone mixing ratios greater than 80 ppbv during the period 1994 through 1999. The time periods were March through October of each year except 1999, for which data were available only through July.

5

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Ext

ent

of R

eact

ion

(dim

ensi

onle

ss)

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Mean of Extent Using “NOx” as NOx and as NOy (dimensionless)

“NOx” as NOx“NOx” as NOy

Method for Calculating Extent

The higher-extent values are subject to more uncertainty. When the mean extent is

approximately 1, the bounds are ~0.8 and 1.2. Values exceeding one are overestimates, because

“NOx” underestimates true NOy and uncertainties exist in the deposition rate of NOy. Sensitivity

analyses suggest that both bounds may depart from true extent by roughly 0.1 to 0.2 units when

the true extent is in the range of ~0.8 to 11, so that the mean of the bounds is a reasonable

estimate of the true extent. Here, the criterion for NOx limitation is assumed to be ~0.9 (mean of

the bounds); the bounds themselves are ~0.75 and ~1.05. This criterion appears reasonably

conservative because comparisons with modeling studies indicate that simulated ozone

concentrations generally respond to NOx reductions when extent is greater than ~0.83.

Most current data bases, even for the principal field studies, include measurements of "NOx”

rather than true NOx or NOy. Therefore, the results reported here use the mean of the bounds as a

best estimate of extent of reaction.

RESULTSThe majority of hours exceeding 80 ppbv were VOC limited at monitors throughout the San

Francisco, Los Angeles, San Diego, El Paso, Washington DC, and New York metropolitan areas

(Table 1). At monitors located in other areas, approximately 40 to 60 percent of the hours

exceeding 80 ppbv were transitional, while about 10 to 40 percent were NOx limited. The

Atlanta results illustrate the dependence of the findings on the monitors used: the 1990 data

were obtained from six monitors, three of which were centrally located within the city, and show

a majority of VOC-limited hours. The 1994-99 data included only three downwind monitors, as

other locations did not report "NOx” measurements, and those downwind sites were either

transitional or NOx-limited (Table 1). As with Atlanta, the differences between the 1991 and

1994-98 data from the southern Lake Michigan area reflect differences in the monitoring

locations. In the 1991 study, more nonurban monitoring sites were operated, and a larger

proportion of the hours were NOx limited, whereas the more routine data from 1994-98 are

weighted toward more urban locations, which have more VOC-limited hours.

6

Table 1. Frequency of VOC-limited, transitional, and NOx-limited hours for all monitors during hours when ozone concentrations were greater than 80 ppbv. Domain Years Total

HoursExtent of Reaction (percent of hours)

VOC-limitedExtent < 0.6

Transitional0.6Extent<0.9

NOx-limitedExtent 0.9

Central California

San FranciscoBay Area

1991-98 4269 81.3 18.1 0.6

Sacramento Valley

1994-97 4133 38.4 43.6 18.0

San Joaquin Valley

1994-97 36293 32.4 60.2 7.5

Southern California

South Central Coast

1994-97 11826 42.8 47.8 9.4

South Coast 1994-97 65416 74.4 24.6 1.0

Mojave 1994-97 15991 32.9 56.0 11.1

Salton Sea 1994-97 2844 32.6 54.6 12.8

San Diego 1994-97 6655 80.6 18.9 0.4

Texas

Houston 1994-99* 2979 41.9 43.5 14.6

Beaumont-Port Arthur

1994-99* 509 21.6 56.4 22.0

Dallas-Fort Worth

1994-99* 1777 39.6 48.0 12.4

El Paso 1994-99* 337 74.2 21.1 4.7

Lake Michigan

1991 492 13.8 40.7 45.5

1994-98 2271 38.9 42.3 18.8

Northeast and Mid-Atlantic

Connecticut 1994-99 1482 50.1 40.1 9.7

Washington, DC

1994-99 1692 51.7 38.4 10.0

Delaware 1995-99 416 53.8 40.9 5.3

7

Domain Years Total Hours

Extent of Reaction (percent of hours)




Maine 1995-99 368 8.7 52.2 39.1

Maryland 1994-99 610 37.5 53.3 9.2

Massachusetts 1995-99 1783 30.0 56.1 13.9

New Jersey 1995-99 1551 16.7 56.8 26.5

New York 1995-99 1071 72.5 26.3 1.0

North Carolina 1995-99 3567 39.4 56.0 4.6

Pennsylvania 1995-99 1381 51.4 42.9 5.6

Rhode Island 1995-99 162 25.3 45.1 29.6

Virginia 1994-99 513 52.2 31.0 16.8

Atlanta

1 upwind, 3 central, 2 downwind sites

1990 736 54.1 39.7 6.3

3 downwind site 1994-99 3148 13.3 48.7 38.0* 1999 is a partial year

For hours with ozone exceeding 120 ppbv, only the San Francisco, Los Angeles, and San Diego

metropolitan areas showed a majority of VOC-limited times and locations (Table 2). In other

areas, 50 to 90 percent of the monitoring hours over 120 ppbv were transitional and 10 to 90

percent of the hours were NOx-limited. Through comparison of the summary statistics in Tables

1 and 2, it is evident that important differences occurred among days. In general, higher ozone

concentrations tended to be more associated with NOx-limited conditions. Thus, within each

region, the areas in which ozone formation was VOC or NOx limited varied among days,

depending upon the intensity of the ozone episode. More sites were NOx limited on the highest

ozone days than on moderate ozone days.

8

Table 2. Frequency of VOC-limited, transitional, and NOx-limited hours for all monitors during hours when ozone concentrations were greater than 120 ppbv.






Central California

San FranciscoBay Area

1991-98 184 48.9 45.1 6.0

Sacramento Valley

1994-97 96 3.1 63.5 33.3

San Joaquin Valley

1994-97 1347 1.2 53.2 45.6

Southern California

South Central Coast

1994-97 280 8.6 78.6 12.9

South Coast 1994-97 5878 51.6 46.7 1.7

Mojave 1994-97 705 5.1 71.6 23.3

Salton Sea 1994-97 104 3.8 84.6 11.5

San Diego 1994-97 64 14.1 78.1 7.8

Texas

Houston 1994-99* 364 7.7 58.0 34.3

Beaumont-Port Arthur

1994-99* 16 0 31.3 68.8

Dallas-Fort Worth

1994-99* 55 5.5 56.4 38.2

El Paso 1994-99* 10 60.0 20.0 20.0

Lake Michigan

1991 55 0 40.0 60.0

1994-98 95 3.2 44.2 52.6

Northeast and Mid-Atlantic

Connecticut 1994-99 112 12.5 64.3 23.2

Washington, DC 1994-99 38 2.6 50.0 47.4

Delaware 1995-99 32 0 75.0 25.0

Maine 1995-99 9 0 11.1 88.9

9






Massachusetts 1995-99 36 2.8 77.8 19.4

Maryland 1994-99 54 1.9 64.8 33.3

New Jersey 1995-99 93 0 61.3 38.7

New York 1995-99 38 23.7 76.3 0

North Carolina 1995-99 41 0 82.9 17.1

Pennsylvania 1995-99 39 23.1 69.2 7.7

Rhode Island 1995-99 16 0 12.5 87.5

Virginia 1994-99 0 0 0 0

Atlanta

1 upwind, 3 central, 2 downwind sites

1990 39 5 74 21

3 downwind site 1994-99 243 0.4 24.3 75.3* 1999 is a partial year

The map display for central California, based upon the top five ozone days per site and year for

each year from 1991 through 1998, indicated that ozone formation at sites within the San

Francisco Bay area was VOC limited (Figure 2). On these high-ozone days, the transition

between VOC and NOx limitation typically occurred in the southern Sacramento Valley

(northeast of San Francisco Bay) and the northern San Joaquin Valley (southeast of San

Francisco Bay). However, within inland cities such as Sacramento, Stockton, and Modesto,

fresh emissions provide additional NOx, so that locally ozone formation again becomes VOC (or

radical) limited. Similarly, Fresno and Bakersfield, in the central and southern San Joaquin

Valley, respectively, are locally VOC limited but appear to be surrounded by larger, rural areas

where ozone formation is NOx limited. These analyses of the top five days were supported by

the statistical summaries (Tables 1 and 2), which also indicated that ozone formation was VOC

limited on many days throughout much of the San Francisco Bay area but was more frequently

10

NOx-limited in the Sacramento and San Joaquin valleys.

11

Figure 2. Mean afternoon extent of reaction at sites in central California. The data include the five highest ozone days at each site during each year from 1991 through 1998. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values. Each site had at least two full years of data.

12

3850.0525.0

3900.0

3950.0

4000.0

4050.0

4100.0

4150.0

4200.0

4250.0

4300.0

UTM

N (

km)

575.0 625.0 675.0 725.0 775.0 825.0 875.0UTME (km)

San Jose

San FranciscoLivermore

Sacramento

Fresno

Modesto

Stockton

Bakersfield

Bethel Island

Tracy

Mean Ozone< 120 ppbv120-140ppbv> 140 ppbv

Extent 1991-98 Top 5 Days Per Year

.6 - .7

Greater than .9

.8 - .9

Less than .6

.7 - .8

The analyses of data from the top five days per site and year from 1994 through 1997 indicated

that ozone formation at sites within the western and central South Coast air basin (SoCAB) and

the San Diego area was VOC limited (Figure 3). The large number of monitoring sites, and the

consistency of the predictions, support the robustness of the conclusion. Some sites in the

eastern portion of the SoCAB appear to be transitional between VOC and NOx limitation on

high-ozone days. A transition from VOC to NOx limitation also occurs in moving north from the

basin over the San Gabriel and San Bernardino mountains. Between Atascadero and Ventura,

considerable variability exists among monitoring locations. Sites that are within the cities along

the Highway 101 corridor are locally VOC-limited on high-ozone days. Such sites include

Atascadero, San Luis Obispo, Nipomo, Santa Maria, Gaviota, and Santa Barbara. Sites located

along the coast or inland were NOx limited on many or most high-ozone days.

Data from the 1993 COAST study and routine monitoring data during the period 1994 through

1999 indicated that ozone formation on high-ozone days at sites within central Houston and near

the ship channel was VOC limited (Figure 4). Areas to the north (northern and northwest Harris

County) and southeast (around the mouth of Galveston Bay) were NOx limited. Ozone formation

at sites near Beaumont and Port Arthur was transitional between VOC- and NOx-limitation. The

transitions between VOC and NOx limitation occurred over distances of ~15 to 75 km. However,

the density of monitoring was insufficient to precisely delineate the transition zones.

The numbers of monitoring sites having measurements of both ozone and “NOx” were more

limited in Dallas-Fort Worth and El Paso than in Houston. Ozone formation at the four sites

located within the urban Dallas-Fort Worth area was VOC-limited on most high-ozone days. A

site located about 50 km north of the urban center was NOx-limited on most of the high ozone

days. In El Paso, data from all four monitoring locations strongly indicated that ozone formation

was VOC limited on high-ozone days.

13

Figure 3. Mean afternoon extent of reaction at sites in southern California. The data include the five highest ozone days at each site during each year from 1994 through 1997. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values. Each site had at least three full years of data.

14

3600

3650

3700

3750

3800

3850

3900

3950

4000

150 250 350 450 550 650

UTM East (km)

UTM

Nor

th (

km)

San DiegoOtay Mesa

Alpine

Calexico

29 Palms

Palm Springs

Oceanside

Riverside

San Bernardino

Lake ElsinorCosta Mesa

HesperiaVictorville

Barstow

Phelan

Lancaster

Mojave

Pasadena

LA N. Main

Simi1000 Oaks

El Rio

Ojai

Carpinteria

Los Padres NFGaviota

Pt. Conception

Vandenburg AFB

Lompoc

Santa Barbara

Santa MariaNipomo

Grover City

San Luis Obispo

Atascadero

Trona



.6 - .7

Greater than .9

.8 - .9

Less than .6

.7 - .8

Figure 4. Mean afternoon extent of reaction at sites in southeastern Texas. For each site, the results are based on the five days having the highest peak hourly ozone values each year from 1993 through 1999. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values. Each site had at least two years of data.

15

3150

3200

3250

3300

3350

3400

UTM

Nor

th (

km)

200 225 250 275 300 325 350 375 400 425 450UTM East (km)

Mean Ozone< 120 ppbv

120-140ppbv> 140 ppbv

Extent 1993-99 Top 5 Days Per

Year

.6 - .7

Greater than .9

.8 - .9

Less than .6

.7 - .8

Routinely collected data from 1994-1998 in the Lake Michigan area indicated that ozone

formation was locally VOC-limited within the Chicago and Milwaukee metropolitan areas

(Figure 5). Beyond the metropolitan areas, sites near Lake Michigan were predominantly NOx

limited. More monitoring sites were operated during the 1991 Lake Michigan Ozone Study

(LMOS). The 1991 data followed a pattern similar to the 1994-98 period, with ozone formation

locally VOC-limited within the Chicago metropolitan area. However, three additional sites in

Michigan and two of the three monitors located on boats in Lake Michigan showed high (either

>0.8 or >0.9) extent of reaction, suggesting a transition between VOC and NOx limitation

occurring ~100 to 200 km from Chicago over Lake Michigan. Thus, the urban, VOC-limited

areas appear to be surrounded by a larger region where ozone formation is predominantly NOx

limited.

The data from northeastern and mid-Atlantic states indicated that urban sites within the Boston,

New York, Baltimore, Washington, and Pittsburgh metropolitan areas were VOC-limited (Figure

6). Many sites outside the major urban centers were NOx-limited, including sites located 20 to

30 km from downtown Washington or Baltimore. In general, the spatial coverage of the sites

was too limited to precisely delineate the transition zones between VOC and NOx limitation in

any of the metropolitan regions. However, the data are sufficient to indicate that ozone

formation was locally VOC-limited within the major metropolitan areas, and that these VOC-

limited areas are surrounded by a larger region where ozone formation is predominantly NOx

limited.

During high-ozone days in 1994-99, one of the three downwind sites in the Atlanta area was

NOx-limited and two were transitional (Figure 7). However, the 1990 data indicated that the

central-city sites were VOC-limited on many days. Other studies suggest that urban Atlanta sites

may be locally VOC-limited, but the adoption of anthropogenic emission controls may be less

effective than NOx controls due to the substantial influence of biogenic VOC emissions8,18.

16

Figure 5. Mean afternoon extent of reaction at sites in the southern Lake Michigan area. For each site, the results are based on the five days having the highest peak hourly ozone days each year from 1994 through 1999. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values.

17

4548

4598

4648

4698

4748

4798

4848

4898

4948

4998

UTM

Y

364 414 464 514 564 614UTMX

.9, 2

.9, 1

< .6, 2

< .6, 1

.7 to .8, 2

.7 to .8, 1

.6 to .7, 2

.6 to .7, 1

5020

4902

4784

4666

4548

364 430 496 562 628UTME (km)

UTM

N (k

m) Extent 1994-98

Top 5 Days Per Year

.6 - .7

Greater than .9

.8 - .9

Less than .6

.7 - .8


Figure 6. Mean afternoon extent of reaction at sites in the northeastern and mid-Atlantic states. For each site, the results are based on the five days having the highest peak hourly ozone days each year from 1994 through 1999. Some sites have data only during the 1995 NARSTO-Northeast study. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values.

18

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

UTM

N (

km)

0 200 400 600 800 1000 1200UTME (km)


.8 - .9

Less than .6


.6 - .7

Greater than .9

.7 - .8

Figure 7. Mean afternoon extent of reaction at sites in the Atlanta area. For each site, the results are based on the five days having the highest peak hourly ozone days each year from 1994 through 1999. Symbol sizes indicate the mean peak-hour ozone concentration and symbol types indicate the mean afternoon extent of reaction. For each day, mean afternoon extent was computed from the five hours between 10 a.m. and 7 p.m. having the highest ozone values.

19

Tucker

Dekalb

3700

3710

3720

3730

3740

3750

3760

3770

3780

UTM

Y

700 710 720 730 740 750 760 770 780UTMX

Conyers

3700

3710

3720

3730

3740

3750

3760

3770

3780

UTM

N (

km)

700 710 720 730 740 750 760 770 780UTME (km)


Greater than .9

.8 - .9


CONCLUSIONOverall, the findings indicate that substantial portions of most major metropolitan areas were

VOC-limited on most or all high-ozone days. Differences among regions occurred in the

geographical ranges over which ozone formation was VOC-limited.

At most sites, important differences were observed among days of moderate (> 80 ppbv peak O3)

and higher (> 120 ppbv peak O3) ozone concentrations. Higher ozone concentrations tended to

be more associated with NOx-limited conditions. The majority of hours exceeding 80 ppbv were

VOC limited at monitors throughout the San Francisco, Los Angeles, San Diego, El Paso,

Washington DC, and New York metropolitan areas, and about 40 percent of hours with ozone

concentrations over 80 ppbv were VOC-limited in Houston and Dallas-Fort Worth.

Approximately 40 to 60 percent of the hours exceeding 80 ppbv were transitional between VOC

and NOx limitation in other areas. For hours with ozone exceeding 120 ppbv, only the San

Francisco, Los Angeles, and San Diego metropolitan areas showed a majority of VOC-limited

times and locations; in other areas, 50 to 90 percent of the monitoring hours over 120 ppbv were

transitional between VOC and NOx limitation and 10 to 90 percent of the hours were NOx

limited.

The San Francisco, Los Angeles, and San Diego metropolitan areas showed the greatest

geographical ranges of VOC limitation. In these cities, ozone formation was VOC-limited at all

locations within areas of approximately 100 km on a side. The large number of monitoring sites,

together with the consistency of the results, provides strong evidence that ozone formation was

VOC limited. Ozone formation was NOx-limited at distances exceeding 100 km from the urban

cores on some or all days. Because of their coastal locations, these California cities are unlikely

to experience significant ozone transport from areas where ozone formation is NOx-limited.

Thus, the findings support the application of VOC controls in those cities. However, many sites

within California’s Sacramento and San Joaquin valleys were NOx-limited on most or all high-

ozone days. In those areas, VOC controls alone may not reduce ozone concentrations at all sites

where exceedances now occur.

20

The central Houston and Dallas areas were also VOC-limited. However, the areas in which

ozone formation was VOC-limited were smaller than in the California cites, being about 25 to 50

km on a side. Sites where ozone formation was NOx-limited on some or all days were located

~25 to 50 km from the urban center. The number of monitoring locations was insufficient to

precisely delineate the transition from VOC to NOx limitation. Thus, the findings support the

potential utility of VOC controls within portions of those cities. However, the results also

suggest that VOC controls alone may not reduce ozone concentrations at all sites where

exceedances now occur.

Urban sites within the Chicago, Boston, New York, Baltimore, and Washington metropolitan

areas were VOC limited. Sufficient monitors were operating within the Chicago area to indicate

that the area where ozone formation was VOC limited extended along the Illinois and Indiana

shorelines and inland from ~10 to 40 km. In the other cities, the number of monitoring locations

was insufficient to delineate the transition from VOC to NOx limitation, though this study and

another9 both found that monitors located 20 to 40 km downwind of downtown Baltimore and

Washington were NOx limited. Each of the VOC-limited metropolitan areas is surrounded by

larger regions where ozone formation was predominantly NOx limited. Thus, the findings

support the potential utility of VOC controls within portions of those cities, while also

suggesting that VOC controls alone may not reduce ozone concentrations at all sites where

exceedances now occur.

ACKNOWLEDGMENTSSupport for this project was provided by the American Chemistry Council. I thank S.

Tanenbaum for carrying out calculations and preparing graphics and D. Baker for his review and

oversight. Data were provided by the California Air Resources Board, the U.S. EPA, the

Houston Regional Monitoring program, the NARSTO-Northeast Study, and the Texas Natural

Resource Conservation Commision.

REFERENCES1. C. L. Blanchard, F. W. Lurmann, P. M. Roth, H. E. Jeffries, and M. Korc. The use of

21

ambient data to corroborate analyses of ozone control strategies. Atmos. Environ.. 1999,

33: 369-381.

2. C. L. Blanchard. Ozone process insights from field experiments- Part III: Extent of

reaction and ozone formation. Atmos. Environ. 2000, 34: 2035-2043.

3. C. L. Blanchard and T. Stoeckenius. Ozone response to precursor controls: comparison

of data analysis methods with the predictions of photochemical air quality simulation

models. Atmos. Environ. 2001, In press.

4. C. L. Blanchard and D. Fairley. Spatial mapping of VOC and NOx-limitation of ozone

formation in central California. Atmos. Environ. 2001, In press.

5. M. Trainer, D. D. Parrish, M. P. Buhr, R. B. Norton, F. C. Fehsenfeld, K. G. Anlauf, J.

W. Bottenheim, Y. Z. Tang, H. A. Wiebe, J. M. Roberts, R. L. Tanner, L. Newman, V. C.

Bowersox, J. F. Meagher, K. J. Olszyna, M. O. Rodgers, T. Wang, H. Berresheim, K. L.

Demerjian and U. K. Roychowdhury. Correlation of ozone with NOy in

photochemically aged air. J. Geophys. Res. 1993, 98: 2917-2926.

6. S. Sillman. The use of NOy, H2O2, and HNO3 as indicators for ozone-NOx-hydrocarbon

sensitivity in urban locations. J. Geophys. Res. 1995, 100(D7): 14175-14188.

7. T. Y. Chang and M. J. Suzio. Assessing ozone-precursor relationships based on a smog

production model and ambient data. J. Air Waste Manage. Assoc. 1995, 45: 20-28.

8. C. A. Cardelino and W. L. Chameides. An observation-based model for analyzing ozone

precursor relationships in the urban atmosphere. J. Air Waste Manage. Assoc. 1995, 45:

161-180.

9. T. Y. Chang, D. P. Chock, B. I. Nance, and S. L. Winkler. A photochemical extent

parameter to aid ozone air quality management. Atmos. Environ. 1997, 31: 2787-2794.

10. C. L. Blanchard. Application of the Smog Production (SP) Algorithm to Data Collected

in the 1990 San Joaquin Valley Air Quality Study. San Joaquin Valley Air Pollution

Study Agency (c/o California Air Resources Board, Technical Support Division,

Sacramento CA). 1996.

11. C. L. Blanchard, P. T. Roberts, L. R. Chinkin, and P. M. Roth. Application of smog

production (SP) algorithms to the TNRCC COAST data. 86th Annual Meeting of the Air

and Waste Management Association, San Antonio, Texas. 1995; paper 95_TP15P.04.

12. C. L. Blanchard. Analysis of Data From the 1995 NARSTO-Northeast Air Quality 22

Study: Observation-Driven Methods for Delineating VOC and NOx Limitation.

Coordinating Research Council, Atlanta, GA. March 1998.

13. C. L. Blanchard, S. Tanenbaum, D. Ladner, and P. Roberts. Enhancement of

Measurement-Based Analysis of Preferences in Planned Emission Reductions (Ozone

M.A.P.P.E.R.) and Application to Data From the Beaumont-Port Arthur, Dallas-Fort

Worth, El Paso, and Houston Metropolitan Areas, 1994-1999. Texas Natural Resource

Conservation Commission, Austin TX. 1999.

14. S. Sillman, K. Al-Wali, F. J. Marsik, P. Nowatski, P. J. Samson, M. O. Rodgers, L. J.

Garland, J. E. Martinez, C. Stoneking, R. E. Imhoff, J. H. Lee, J. E. Weinstein-Lloyd, L.

Newman, and V. Aneja. Photochemistry of ozone formation in Atlanta, GA: Models

and measurements. Atmos. Environ. 1995, 29: 3055-3066.

15. S. Sillman, D. He, C. Cardelino, and R. E. Imhoff. The use of photochemical indicators

to evaluate ozone-NOx-hydrocarbon sensitivity: Case studies from Atlanta, New York,

and Los Angeles. J. Air Waste Manage. Assoc. , 1997, 47: 1030-1040.

16. S. Sillman, D. He, M. R. Pippin, P. H. Daum, D. G. Imre, L. I. Kleinman, J. H. Lee, and

J. Weinstein-Lloyd. Model correlations for ozone, reactive nitrogen, and peroxides for

Nashville in comparison with measurements: Implications for O3-NOx-hydrocarbon

chemistry. J. Geophys. Res. , 1998, 103(D17): 22629-22644.

17. L. I. Kleinman. Ozone process insights from field experiments- Part II: Observation

based analysis for ozone production. Atmos. Environ. 2000, 34: 2023-2033.

18. C. A. Cardelino and W. L. Chameides. The application of the observation-based model

to atmospheric measurement datasets. Atmos. Environ. 2000, 34: 2325-2332.

19. W. L. Chameides et al. An Assessment of Tropospheric Ozone Pollution - A North

American Perspective. NARSTO Synthesis Report. Electric Power Research Institute,

www.epri.com. 2000.

20. A. M. Winer, J. W. Peters, J. P. Smith, and J. N. Pitts, Jr. Response of commercial

chemiluminescent NO-NO2 analyzers to other nitrogen-containing compounds. Environ.

Sci. Technol. 1974, 8: 1118-1121.

KEY WORDS

23

ozone, NOx limitation, VOC limitation, control strategy assessment, Smog Production algorithm

24

Documents

Spatial Mapping of VOC and NOx Limitation of …€¦ · Web viewThe Smog Production (SP) algorithm1,2,3 was applied to air quality monitoring data from six areas: the northeastern