National Academies Press: OpenBook

Rethinking the Ozone Problem in Urban and Regional Air Pollution (1991)

Chapter: 11 VOC Versus NOx Controls

« Previous: 10 Ozone Air-Quality Models
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 351

11
Voc Versus Nox Controls

Introduction

Although ozone concentrations in many areas of the United States violate the National Ambient Air Quality Standards (NAAQS), the circumstances of the violations can be quite varied. A few areas, such as Los Angeles, California, are isolated from regional influences, although most are not. Some have relatively high concentrations of VOCs (volatile organic compounds) compared with NOx (the oxides of nitrogen), whereas others do not. One goal of this report is to assess current understanding of the relative effectiveness of VOC versus NOx controls in ozone abatement in the United States. Knowledge of the atmospheric chemistry leading to ozone formation, together with the use of ozone isopleth diagrams (Chapter 6), provides a qualitative understanding of the relationship between ozone concentrations and VOC and NOx emissions. To actually evaluate the effectiveness of potential control strategies requires the use of photochemical air quality models (Chapter 10) that incorporate the best possible information about an area's initial and boundary conditions, emissions, and meteorology. In this chapter, we synthesize and assess much of the information from air quality models about the relative effectiveness of VOC and NOx controls in various regions of the country.

The most widely used method for determining ozone control requirements for urban areas has been the U.S. Environmental Protection Agency's Empirical Kinetic Modeling Approach (EKMA). The limitations of EKMA are discussed in Chapter 6: In practice, only periods of less than one day are simulated, and, as a result, the method cannot capture the multiday nature of

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 352

episodes of high concentrations of ozone. EKMA also simulates ozone formation only along a single trajectory, not providing any regionwide information about the effects of controls.

The number of analyses carried out using grid-based air quality models is limited but growing (see Chapter 10). Urban scale models, such as the urban airshed model (UAM) and the CIT model, have been applied to a number of cities in the United States and elsewhere. The Regional Oxidant Model (ROM) has been applied recently to the northeastern United States and to urban areas in that region.

image

Figure 11-1
Ozone isopleth diagram for three cities (A, B, and C) that have the same peak 1-hour 
ozone concentrations (Cp). The VOC/NOx ratios differ: a low ratio (c), a high ratio (B), 
and a medium ratio (A). Isopleths = lines of constant 1-hour peak ozone.

Ekma-Based Studies

EKMA is used to generate ozone isopleth diagrams for cities, and EPA

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 353

and other agencies have used it to determine the fractional VOC and NOx reductions needed to meet the ozone NAAQS from particular base-year conditions. The ozone isopleth diagram, introduced in Chapter 6, shows the peak 1-hr ozone concentration in terms of the initial VOC and NOx concentrations. Figure 11-1 shows a hypothetical diagram for three cities that have the same peak 1-hr ozone concentration but for which the ambient ratios of VOCs to NOx differ: a low ratio (city C), a high ratio (city B), and a medium ratio (city A). As illustrated in Figure 11-1, at low VOC/NOx (city C), reductions in NOx can have little effect or actually can cause increases in ozone; for city B, reductions in NOx can lead to substantial decreases in ozone. At moderate VOC/NOx (city A), reductions in NOx can lead to small or moderate decreases in ozone, depending on the shape of the isopleth and the amount of NOx reduction. City A is located along what is often called the ridge line. If the molar ratio of carbon to NOx is greater than about 20 ppbC/ppb, NOx control is clearly more effective than VOC control, whereas at a ratio of about 10 or less, VOC control is more effective. At ratios between 10 and 20, control of either VOC or NOx or both might be preferred; specific situations must be carefully evaluated to determine the relative effectiveness of alternative abatement strategies (Blanchard et al., 1991).

Although the VOC/NOx ratio is a useful measure of the overall nature of the VOC-NOx-ozone system, it is at best a qualitative measure of the reactivity of a given city's air because, as noted in Chapter 6, VOC/NOx ratios vary both spatially and diurnally in a given city and from one episode to the next for the same city. Variation among proximate cities is observed as one travels from west to east in the Los Angeles basin; the VOC/NOx ratio in the atmosphere varies from that of city C to that of city A and, as one goes sufficiently far east, to that of city B. In areas where the VOC/NOx ratio is between roughly 10 and 20, control of NOx may reduce the effectiveness of VOC controls. At a fixed level of VOC emissions, NOx control in such cases may cause ozone concentrations to decrease in downwind areas and increase in near-source areas. In some downwind areas, ozone concentrations may decrease less than they would have decreased if VOC emissions alone had been reduced (Blanchard et al., 1991).

Results of sample State Implementation Plans (SIPs) for various cities generated by EKMA are given in Table 11-1. In each case, only VOC control was considered. In general, the higher the original ozone concentration, the greater the VOC control predicted. (Biogenic VOC emissions are not accounted for in the calculations in Table 11-1.)

Chang et al. (1989) used EKMA to study the effect of conventional and methanol-fueled vehicles on air quality in 20 cities. In that study they calculated the effect that removing light-duty VOC emissions (primarily emissions

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 354

TABLE 11-1
Ozone Design Values, VOC Concentrations, VOC/NOx, Mobile Source Emissions, and Estimated VOC control requirementsa,b

Area

Ozone design value, ppb

Median VOC, ppbC

Median VOC/NOx

On-road mobile source percent of emissionse

Required VOC % control to meet standardd

 

VOC

NOx

Akron, Ohio

125

600

12.8

39

e

Atlanta, Georgia

166

600

10.4

52

43

25 - 50

Boston, Massachusetts

165

380

7.6

51

47

35

Charlotte, North Carolina

149

390

10.4

52

25 - 50

Cincinnati, Ohio

157

740

9.1

42

40

> 50

(Table continued on next page)

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 355

(Table continued from previous page)

Area

Ozone design value, ppb

Median VOC, ppbC

Median VOC/NOx

On-road mobile source percent of emissionse

Required VOC % control to meet standardd

 

VOC

NOx

Cleveland, Ohio

145

780

7.5

49

36

25 50

Dallas, Texas

160

730

11.8

52

43

25 50

El Paso, Texas

160

670

11.9

66

25 50

Fort Worth, Texas

160

630

11.8

52

Houston, Texas

200

740

12.9

36

> 50

Indianapolis, Indiana

130

690

10.9

49

Kansas City, Missouri

130

410

8.5

50

Los Angeles, California

360

7.8

46

60

85

Memphis, Tennessee

146

127

13.9

48

25 50

Miami, Florida

130

103

13.3

61

25 50

New York, New York

217

9.6

47

40

Philadelphia, Pennsylvania

180

570

8.0

41

41

25 50

Portland, Maine

140

430

11.6

38

0 15

Richmond, Virginia

125

450

11.2

44

25 50

St. Louis, Missouri

160

570

9.6

43

23

25 50

Washington, D.C.

140

600

8.7

55

56

25 50

(Table continued on next page)

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 356

(Table continued from previous page)

Area

Ozone design value, ppb

Median VOC, ppbC

Median VOC/NOx

On-road mobile source percent of emissionse

Required VOC % control to meet standardd

 

VOC

NOx

Wilkes Barre, Pennsylvania

125

430

14.3

43

Average of nonattainment areas

48

50

aBased on Chang et al. (1989), SCAQMD (1989), OTA (1989), EPA (1983), Systems Applications Incorporated (1990), E.H. Pechan (1990).

b''VOC'' refers to volatile organic compounds excluding methane.

cMobile-source percentage of total NOx emissions primarily derived from EPA (1983) and might not correspond to same period used to derive mobile-source VOC percentage from Chang et al. (1989).

dBased on EKMA. A range indicates uncertainty in the amount of control needed.

e—No data were available or no calculation was made.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 357

from automobiles and pickup trucks) would have on ozone concentrations, and how varying NOx emissions would affect these results. The response—the percentage of ozone reduction achieved in relation to a given percentage VOC reduction—is highly variable. The ratio of those two can be construed as the sensitivity of ozone formation to VOC emissions, and is a measure of the effectiveness of VOC control.

The sensitivity of ozone to VOCs for 20 cities is given in Table 11-2. The sensitivity is seen to correlate with the ambient VOC/NOx ratio in that higher sensitivities are associated with lower ratios. Biogenic emissions were not included in the calculation. At VOC/NOx ratios less than 8, reductions in VOCs were found to be particularly effective, and at higher ratios, the sensitivity slowly declines as the ratio increases. Carter and Atkinson (1989b) obtained similar results for air parcels in urban areas.

Most assessments of control strategies using EKMA have not considered the effects of biogenic VOCs. Chameides et al. (1988) argued that biogenic VOCs must be considered, particularly in southern cities where warm temperatures lead to significant emissions of isoprene. They showed that for Atlanta, anthropogenic VOCs need to be reduced by 30% to meet the NAAQS according to the standard EKMA calculation with no biogenic VOCs. Inclusion of isoprene increases the necessary reduction in anthropogenic VOCs to 70%. With inclusion of other biogenic hydrocarbons, ozone concentrations were predicted to exceed the NAAQS with no anthropogenic VOC emissions. Once isoprene is included, the percent reduction in NOx emissions needed to meet the NAAQS is less than the required reduction in VOC emissions.

Intercomparison of model results indicates that EKMA and other single-and double-layer trajectory models are too limited by their mathematical formulation and lack of physical detail to assess ozone control strategies accurately. A major, shortcoming is that high-ozone episodes are multiday events, and EKMA simulations are generally less than one day long. NOx is removed from the photochemical system faster than the bulk of the VOCs, leading to more NOx-limited conditions on subsequent days of an episode. Grid-based airshed models provide a much stronger foundation on which to build ozone control strategies. Because of EKMA's inherent limitations, our assessment of the relative effectiveness of VOC and NOx controls will focus on applications of grid-based models.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 358

TABLE 11-2
Sensitivity of Ozone Formation to VOC Emissions

Area

Median VOC/NOx

Sensitivity to light-duty vehicle VOC emissions, D O3/DVOCa

Akron, Ohio

12.8

0.44

Atlanta, Georgia

10.4

0.56

Boston, Massachusetts

7.6

1.08

Charlotte, North Carolina

10.4

0.54

Cincinnati, Ohio

9.1

0.52

Cleveland, Ohio

7.5

0.92

Dallas, Texas

11.8

0.53

El Paso, Texas

11.9

0.54

Fort Worth, Texas

11.8

0.51

Houston, Texas

12.9

0.59

Indianapolis, Indiana

10.9

0.51

Kansas City, Missouri

8.5

0.67

Memphis, Tennessee

13.9

0.45

Miami, Florida

13.3

0.55

Philadelphia, Pennsylvania

8.0

1.45

Portland, Maine

11.6

0.43

Richmond, Virginia

11.2

0.49

St. Louis, Missouri

9.6

0.58

Washington, D.C.

8.7

0.64

Wilkes Barre, Pennsylvania

14.3

0.44

Average

 

0.62

aD O3/D VOC, ratio of percent reduction in ozone concentration to percent reduction in VOC emissions.

Source: Chang et al., 1989.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 359

Grid-Based Modeling Studies

Two areas of the United States—the Northeast corridor, which extends from the Washington, D.C. area to beyond Boston, and the Los Angeles basin—have received a large share of attention in the evaluation of ozone abatement strategies. Los Angeles has little influence from upwind sources, whereas each city in the Northeast corridor is affected by transport of ozone and precursors from upwind regions. In essence, the Northeast corridor acts as a system, and the effectiveness of ozone controls in one urban location will depend on controls throughout the region. Limited studies are available for other areas of the country, such as the Southeast and the Midwest.

Los Angeles Basin

The effects of controlling VOC and NOx emissions in the Los Angeles basin have been explored in a variety of studies, for example those of the South Coast Air Quality Management District (1989) and Milford et al. (1989). Basinwide control of VOC emissions was predicted in these reports to reduce ozone concentrations everywhere. Controlling NOx emissions was predicted to lead to increased ozone concentrations in the downtown and midbasin areas but decreased ozone concentrations in the far eastern portion of the region. Since the emissions inventories used in those studies apparently underpredicted VOCs, it is likely that a larger portion of the basin would respond favorably to NOx reduction than was predicted.

Studies of ozone abatement strategies in Los Angeles have used both the urban airshed model (UAM) and the CIT model (see Table 10-1). The UAM was used in developing the air quality management plan for the South Coast air basin (SCAQMD, 1989). The CIT model was used to determine the effects of VOC and NOx controls on ozone, nitric acid (HNO3), nitrogen dioxide (NO2), peroxyacetyl nitrate (PAN), and aerosol nitrate for an episode that occurred Aug. 30-31, 1982 (Russell et al., 1988a,b, 1989; Milford et al., 1989).

Milford et al. (1989) used the CIT Model to develop ozone isopleth diagrams across the Los Angeles Basin, showing how the effectiveness of NOx and VOC controls varies spatially (Figure 11-2). Likewise, they developed the isopleth diagram for peak ozone in the basin (Figure 6-4). In those figures, the base level of emissions corresponds to the upper right hand corner, and increasing levels of VOC and NOx control are plotted along the horizontal and vertical axes, respectively. Milford et al. (1989) found that NOx controls were most effective in the downwind regions, e.g., around San Bernardino.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 360

image

Figure 11-2
Ozone isopleths for locations within the Los Angeles air basin from an airshed 
model for spatially uniform reductions of VOC and NOx. Source: Milford et al., 1989.

These regions also had the highest ozone concentrations. In the central regions, such as downtown Los Angeles and Pasadena, where peak ozone concentrations were lower, VOC controls were most effective, and NOx reduc-

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 361

tions could inhibit ozone reduction. Control of both VOCs and NOx led to basinwide reductions. Correction of the likely underestimation of VOC and CO emissions from motor vehicles would enhance the effectiveness of NOx controls.

The spatial variation in ozone response has been explained by Milford et al. (1989) based on the emission patterns. In Los Angeles and Pasadena, the VOC/NOx ratio is estimated to be between 5 and 10 at 9:00 a.m. Especially in Pasadena, this ratio does not increase dramatically by noon, apparently because of high local NOx emissions compared to downwind locations. Thus the situation corresponds to the region to the left of the ridge line in Figure 11-1, and NOx controls can lead to increased ozone. At the downwind locations, however, there are lower local emissions, and much of the NOx has been lost due to deposition and chemical transformations. The resulting VOC/NOx ratio is much larger image, corresponding to the region to the right of the ridge line in Figure 11-1, where the chemistry is NOx limited, and hence NOx controls are most effective.

As noted in Chapter 6, a significant advantage of using grid-based airshed models to generate ozone isopleths is that these models show the effect of precursor controls on peak concentrations of ozone, regardless of where the peak occurs in the air basin. For example, in the studies of Milford et al. (1989), reducing NOx or VOCs by 25%, or each by 15%, shifts the location of the ozone peak westward from San Bernardino to Chino. Figure 11-3 shows the effect of VOC and NOx controls on peak O3 in the Los Angeles air basin as a whole, i.e. irrespective of the location of peak ozone. A more L-shaped isopleth results. The isopleths in Figure 11-3 show that when the Los Angeles air basin as a whole is considered, up to 80% control of VOCs alone will not result in attainment of the NAAQS.

Tesche and McNally (1990) applied the UAM to the South Central Coast air basin, in the Santa Barbara area of California, for Sept. 5-7, and Sept. 16-17, 1984. They predicted ozone isopleths for this air basin which, like those of Milford et al. (1989) for Los Angeles, are more L-shaped than are the EKMA-type isopleths shown in Figure 11-1. As Milford et al. (1989) and Tesche and McNally (1990) pointed out, although the calculations are specific to the southern California area, the approach and issues involved (e.g. downwind areas) have general validity and applicability.

Nonlinearities in the response of ozone concentrations to emissions changes generally result in smaller ozone reductions than might be expected or desired from reducing emissions. For example, by the year 2000, mobile sources in Los Angeles are expected to account for about 30% of total VOC emissions. Airshed model calculations indicate that removing this fraction of VOCs would decrease peak ozone 16% from 270 to 230 ppb for the particular set of

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 362

image

Figure 11-3a
Maximum predicted ozone concentration (ppb) over the six-day simulation period for 
the model run with anthropogenic emissions only. Source: Roselle and Schere, 1990.

episode conditions studied (Russell et al., 1989). Exposure would decrease by 20%. Chang and Rudy (1989), using a trajectory model, found that eliminating mobile-source VOC emissions would result in a 10-15% reduction in peak ozone concentrations—seldom to below 120 ppb. This has an important ramification: even though mobile sources are the single largest source, their control alone will not solve the smog problem in urban areas.

Northeastern United States

High concentrations of ozone occur in the eastern United States concurrently across urban and rural areas that can span more than 1000 kin. Concentrations often exceed 90 ppb in rural areas, and the greatest concentrations (sometimes exceeding 200 ppb) are found downwind of the largest urban and industrial centers. Episodes of such high concentrations of ozone are associated with the slow-moving high-pressure systems that provide weather conducive to ozone production (see Chapter 4). These episodes occur several times each year, usually between May and September, and ozone concentrations can stay high from late morning into early evening for several consecutive days during

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 363

image

Figure 11-3b
Maximum predicted ozone (ppb) over the six-day simulation period, for the AB run, 
which contains both anthropogenic and BEIS biogenic emissions. Source: Roselle and Schere, 1990.

these episodes (e.g. Logan, 1989).

Pioneering studies by Hov et al. (1978) and Isaksen et al. (1978) showed that ozone can build up to concentrations exceeding 100 ppb in a few days in air subjected to anthropogenic emissions of NOx and VOCs. The ozone can persist for several days, permitting long-range transport. More recently, Liu et al. (1987) examined the relationship between ozone and NOx in detail, focusing on data from Niwot Ridge, Colorado, a remote site affected by urban plumes. They showed that ozone production per unit NOx is greater for NOx <1 ppb than for NOx > 1 ppb, and that the relationship between ozone and NOx is nonlinear in the range of concentrations found in nonurban air, <0.3-10 ppb. The higher production rates at lower concentrations of NOx imply that ozone is generated more efficiently in rural areas than in urban areas, and may explain why rural ozone concentrations are often similar to those in cities (Linnet al., 1988).

Several recent studies have shown that ozone in rural areas of the eastern United States is limited by the availability of NOx rather than hydrocarbons, and that reductions in NOx probably will be necessary to reduce rural ozone values (Trainer et al., 1987; Possiel et al., 1990; Sillman et al., 1990b; McKeen et al., 1991b). Trainer et al. (1987) examined the mechanisms responsible for high concentrations of ozone (110 ppb) observed at a rural site in Pennsylva-

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 364

image

Figure 11-3c
The six-day maximum predicted ozone concentration (ppb) for the run with Biogenic 
Emissions Inventory System (BEIS) biogenic emissions and no anthropogenic VOC 
emissions ("A(NOx)B"). Source: Roselle and Schere, 1990.

nia, where local NOx concentrations were only 1 ppb and isoprene was the dominant VOC. Model simulations showed that oxidation of isoprene in the presence of anthropogenic NOx could result in ozone concentrations of more than 100 ppb. The addition of anthropogenic VOCs to the model made little difference, because the chemical system is in the NOx-limited regime. Trainer et al. argued that reduction of NOx would be needed to reduce rural ozone concentrations. Sillman et al. (1990b) examined the sensitivity of rural ozone to NOx and VOCs for the range of values found in the eastern United States. They found that rural ozone increases as NOx increases, when NOx 2 ppb, but is almost insensitive to anthropogenic VOCs. These conclusions rely only on observations and the chemical mechanisms in the models and are independent of emissions inventories. Sensitivity studies with regional models using the 1980 and 1985 National Acid Precipitation Assessment Program (NAPAP) emissions inventories also demonstrated that NOx reductions will probably be necessary to reduce rural ozone concentrations (Sillman et al., 1990a,b; Possiel et al., 1990; Possiel and Cox, 1990; McKeen et al., 1991b). We focus below on studies using the Regional Oxidant Model (ROM).

ROM is the only regional model available for assessment of control strat-

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 365

egies for urban and rural ozone in the eastern United States. It has the smallest grid size of the regional models discussed in Chapter 10 and has been evaluated in the greatest detail. ROM predicts the occurrence of high ozone concentrations and the spatial distribution of ozone reasonably well, but it systematically underpredicts the highest concentrations of ozone (Schere and Wayland, 1989).

ROM has been used in a variety of regulatory applications, primarily using ROM2.0 with the 1980 NAPAP inventory. These applications are summarized in Tables 11-3 and 11-4, which describe, respectively, the individual emission control strategies and the particular ROM simulations. Many of these simulations are discussed only in unpublished EPA reports. Here we describe the most recent applications to the Northeast, which demonstrate the role of biogenic VOCs in generating high ozone concentrations (Roselle et al., 1991) and the greater efficacy of NOx control compared with VOC control in most of the region (Possiel et al., 1990; Possiel and Cox, 1990). These applications use ROM2.0, discussed in Chapter 10, and ROM2.1. The more recent version of the model includes some changes in the way the wind data are processed, so that more reliance is placed on surface wind data than on upper air data in the lowest layer of the model. This leads to improvement in the westerly bias of the model, which was discussed in Chapter 10 (Schere, pers. comm., NOAA, Research Triangle Park, N.C., 1990).

Roselle et al. (1991) examined the sensitivity of ozone to biogenic emissions for the period July 12-18, 1980 (see Figure 11-3a,b,c). Anthropogenic emissions were taken from the 1980 NAPAP version 5.3 inventory, and biogenic emissions came from the latest inventory developed for EPA (Pierce et al., 1990). Total VOC emissions came about equally from anthropogenic and biogenic sources. Figure 11-4 shows predicted ozone concentrations for the Northeast for three scenarios: A, with anthropogenic VOCs, but without biogenics; AB, with both kinds of VOCs; and A(NOx)B, with only anthropogenic NOx and biogenic VOCs. The charts show the maximum ozone concentrations for the six-day period. The combination of biogenic VOCs and anthropogenic NOx gives rise to ozone concentrations greater than 80 ppb in the entire Northeast corridor, the Ohio Valley, and most of the southern half of the region. There are large areas with ozone in the range of 100 ppb to 120 ppb. Biogenic emissions are generally higher in the south, and large point sources of NOx in the Ohio Valley are predicted to interact with the biogenic VOCs there to produce significant amounts of ozone. These results concur with the earlier analysis by Trainer et al. (1987) of data from rural Pennsylva-nia. The addition of anthropogenic VOCs leads to much higher ozone concentrations (120-180 ppb) downwind of major urban areas such as Detroit, Michigan; Pittsburgh, Pennsylvania; Cleveland, Ohio; and the Northeast corridor cities.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 366

TABLE 11-3
Emission Control Scenarios used with ROM

VOC0 Base emissions projected to 1987 including the effects of existing controls. Largest changes in VOC emissions; some smaller changes to NOx emissions.

VOC1 Base emissions from 1980 reduced to include the effects of existing VOC controls in 1982 SIP. Only VOC emissions are affected.

VOC2 VOC1 plus additional reductions expected by 1995 due to the Federal Motor Vehicle Control Program (FMVCP).

VOC3 VOC2 plus additional reductions in the Northeast corridora, Pittsburgh, Cleveland, and Detroit.

VOC4 VOC3 including a higher level of reductions, up to 90% control in the Northeast corridor.

NOx1 NOx controls on utility boiler emissions from 1980 resulting in a 39% cut in utility emissions (11% cut in regionwide NOx)

NOx2 Utility-industrial boiler plus FMVCP NOx controls only in Detroit (27% resulting cut in NOx emissions) and the Northeast corridor (22% resulting cut). Overall 10% cut in regionwide NOx.

NOx3 Utility-industrial boiler plus FMVCP NOx controls applied regionally. (This resulted in a 22% cut in NOx emissions for the Northeast corridor and a 27% cut in regionwide NOx for the northeastern United States domain.)

NOx4 NOx3 except image cut in point-source NOx emissions in the Northeast corridor.

aNortheast corridor extends from Washington, D.C. to Boston and beyond.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 367

TABLE 11-4
ROM simulations


Episode

Base case or control strategy


Model


Purposea


Seasonal extrapolationb

Northeastern U.S. Domain

Aug. 3-4, 1979

Base case

ROM1.0

R,E

 
 

VOC0

ROM1.0

R

 

April 14-29, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

VOC3 +

ROM2.0

R

image

 
 

Nox3

     

July 12-17, 1980

Without biogenic VOC emissions

ROM2.0

S

 

July 12-26, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

NOx1

ROM2.0

R

 
 

NOx2

ROM2.0

R

 
 

VOC2 +

ROM2.0

R

image

 
 

NOx3

ROM2.0

R

 
 

VOC3 +

ROM2.0

R

 
 

NOx3

ROM2.0

R

 
 

VOC4 +

ROM2.0

R

 
 

NOx3

ROM2.0

R,S

 
 

VOC4 +

     
 

NOx4

     
 

With TSDFc emissions

     

July 12-Aug. 31, 1980

Base case

ROM2.0

E

 

July 22-31, 1980

Base case

ROM1.0

R

 
 

VOC0

ROM1.0

R

 

July 26-28, 1980

Base case with other grid sizes

ROM1.0

S

 
   

ROM1.0

S

 

(Table continued on next page)

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 368

(Table continued from previous page)

Episode

Base case or control strategy

Model

Purposea

Seasonal extrapolationb

August 22-31, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

NOxl

ROM2.0

R

 
 

NOx2

ROM2.0

R

 
 

VOC2 +

ROM2.0

R

 
 

NOx3

ROM2.0

R

image

 
 

VOC3 +

ROM2.0

R,S

 
 

NOx3

     
 

With TSDF emissions

     

Southeastern U.S. Domain:

April 14-29, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

VOC2 +

ROM2.0

R

image

 
 

NOx3

     

June 29-July 14, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

VOC2 +

ROM2.0

R

image

 
 

NOx3

     

August 10-September 1, 1980

Base case

ROM2.0

R

image

 
 

VOC1

ROM2.0

R

image

 
 

VOC2

ROM2.0

R

image

 
 

VOC2 +

ROM2.0

R

image

 
 

NOx3 With TSDF emissions

 

R,S

 

aE, Model evaluation study, S, model sensitivity analysis, R., regulatory analysis.

bimage, This simulation was used, along with others, to extrapolate episodic model results to a full season.

cTSDF, treatment, storage, and disposal facility.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 369

image

Figure 11-4a
Predicted episode maximum ozone concentrations (ppb) for
 the 1985 base case (July 2-17, 1988). Source: Possiel et al., 1990.

Possiel et al. (1990) examined the effects of proposed regional control strategies on ozone in the Northeast for July 2-17, 1988, the most severe episode in this region between 1980 and 1988. The model was run for a base case of 1985. Its emissions data were taken from the 1985 NAPAP inventory, adapted for the above-average temperatures that prevailed during the episode, and from Pierce et al. (1990) for biogenic emissions. The target year was 2005, with projected emissions that accounted for existing federal and state controls. With these controls, anthropogenic VOC emissions were 20% lower than in 1985, carbon monoxide emissions were 43% lower, and total NOx emissions were the same. Several other control scenarios were also applied to the 2005 calculation.

Results for the 1985 base case and for the 2005 case with existing controls are shown in Figure 11-4a,b in terms of maximum ozone concentrations for the episode. Predicted reductions in peak concentrations ranged from 5-10% in and downwind of most major source areas, to as much as 20% in New York City. For both simulations, ozone concentrations exceeded 120 ppb r and downwind of all major source regions. Changes in ozone relative to the 2005 case with existing controls are shown in Figure 11-5 for two scenarios: In one scenario (Figure 11-5a), VOC emissions were reduced throughout the United States, leading to a 45% reduction; other emissions were at levels

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 370

image

Figure 11-4b
Predicted episode maximum ozone concentrations (ppb) for the 2005 case 
with existing controls (July 2-17, 1988). Source: Possiel et al., 1990.

assuming existing controls. In the other scenario (Figure 11-5b), anthropogenic VOCs were reduced by 49% in the Northeast corridor and by 26% elsewhere, with corresponding reductions in NOx of 26% and 34%, respectively. The reduction in VOCs alone produced the greatest effect north of Philadelphia, with reductions in peak ozone of as much as 25-50% in the immediate area of New York City. There was little change elsewhere, including most of New England and the southern part of the corridor. The predictions for the combined NOx-VOC strategy were quite different. Peak ozone was reduced by 10-15% across much of the domain, and the reductions were generally greater than with the VOC-only strategy. In the New York City area, however, the combined controls were less effective in reducing ozone.

The frequency distribution of maximum ozone concentrations was also examined for the two scenarios. The combined strategy was more effective in the Washington-Baltimore area, Philadelphia, and Boston; the VOC-only strategy was more effective in New York City. There was little difference between the two strategies in Connecticut. The combined strategy led to decreased population exposure in all regions of the corridor except the New York City area, but 43% of the corridor's population lives there. Even with the control strategies, ozone concentrations were predicted to exceed 120 ppb

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 371

image

Figure 11-5a
Percentage change in episode maximum ozone concentrations, 2005 base 
case versus a VOC-alone reduction strategy (July 2-17, 1988).

along the Northeast corridor.

Possiel and Cox (1990) examined another set of control scenarios for the period July 2-17, 1988; they showed results for NOx control alone, VOC control alone, and simultaneous NOx and VOC control, all relative to a somewhat different base case for 2005 emissions (see Table 11-4). These scenarios, based on application of ''maximum technology,'' resulted in reduction of NOx by 58% and anthropogenic VOCs by 63% compared with the 2005 base case. Total VOC emissions were reduced by 40% within the Northeast corridor but by only 20% outside the corridor, because of the preponderance of natural emissions there. Control of NOx alone caused large reductions in ozone throughout most of the U.S. portion of the model domain, including the Northeast corridor. The exception was New York City, where ozone increased (see Table 11-5). Outside the Northeast corridor, control of VOCs alone led to ozone concentrations 15-25 ppb higher than did control of NOx alone. However, the VOC-only strategy was more effective in lowering peak ozone in New York City. VOC control resulted in a much larger area with ozone above 120 ppb than did NOx control. Combined control of NOx and VOCs reduced ozone outside the Northeast corridor only slightly more (< 5%) than did NOx control alone. Within the corridor, the combined controls were

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 372

image

Figure 11-5b
Percentage change in episode maximum ozone concentrations, 2005 base case versus a combined NOx-VOC reduction strategy (July 2-17, 1988). Source: Possiel et al., 1990.

more effective than either alone, except in New York City, where VOC-only control was most effective.

McKeen et al. (1991b) also found that control of NOx was more effective than control of VOCs in reducing peak ozone values across most of the eastern United States and that control of NOx alone led to increases in ozone in a few areas of high NOx emissions. Their model had a grid size of 60 km and simulated a different meteorological period. Nevertheless, this model gave results similar to those of ROM for similar scenarios.

The results from ROM for the effect of a NOx-VOC versus VOC-only strategy agree with analyses based on much simpler models (Sillman et al., 1990a,b), as do the studies of the role of biogenic VOCs (Trainer et al., 1987; Chameides et al., 1988; McKeen et al., 1991b). The results from ROM emphasize that a combined NOx-VOC strategy should be more effective than a VOC-only strategy in reducing ozone over a large geographic area in the Northeast. A VOC-only strategy would be more effective in some areas of high population density (New York City) but less beneficial downwind. Although the general nature of these results is likely to be correct, the details of the predictions should be viewed with caution, because of known deficiencies in the base-case emissions inventories (see Chapter 9) and because of the

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 373

possible deficiencies in the model itself, as implied by evaluation studies (Schere and Wayland, 1989).

New York Metropolitan Area

Rao and co-workers (Rao et al., 1989; Rao and Sistla, 1990) have applied the UAM to study the control of ozone in the New York City area. Rao and Sistla (1990) studied imposition of 75% control on NOx, VOCs, or both (Table 11-6). Control of NOx alone decreased ozone concentrations in Connecticut and New Jersey but increased them in New York. Ozone exposure above 120 ppb increased. VOC-only control led to substantial reductions in ozone in all three regions and to a concomitant reduction in exposure, and combined controls were less effective in reducing ozone than were VOC controls alone. These results indicate that VOC controls are necessary to reduce ozone concentrations in the New York area, although downwind areas can benefit from NOx reductions. It also was found that biogenic VOC emissions alone, in concert with emissions of anthropogenic NOx, would lead to ozone concentrations above 120 ppb. The sensitivity of the peak ozone and exposures can be estimated from these results and are given in Table 11-6. The sensitivities to VOCs are for the anthropogenic portion only and are generally less than those found by Chang et al. (1989) for other cities using EKMA. The results of Chang et al. (1989) also showed that the effects of NOx and VOC controls are not additive.

In accordance with the UAM study by Rao and Sistla (1990), peak ozone concentrations as predicted by ROM fell in New York in response to VOC controls but not NOx controls (Possiel and Cox, 1990). Virtually all other cities in the ROM domain responded favorably to control of VOCs or NOx or both. ROM results indicate that eight-hour exposure to ozone would decrease in all cities, including New York, when NOx controls are imposed in addition to VOC controls. This is contradictory to the UAM results discussed above. NOx reductions led to a regionwide decrease in ozone exposure.

A shortcoming of current regional air quality models is that they do not have the spatial resolution required to accurately assess the chemical transformation and transport within urban areas. A solution to this problem is to embed, or "nest" a model with finer spatial resolution. For example, an urban model can be embedded in a regional model. The regional model then prescribes transport into and boundary conditions for the urban domain. A UAM-ROM interface has been developed to serve this purpose (Rao et al., 1989). In this case, the nesting is one way; information flows from ROM to UAM, but not back.

The results of the nested-grid study are interesting in that they compare

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 374

TABLE 11-5
Ozone Response in Northeast to VOC and NOx Controls Found Using ROMab

Area

Basec.d

63% VOC controlc

58% NOx controlc

Combined VOC NOx controlc

Sensitivity of peak ozone to VOC

Sensitivity to NOx

Washington,D.C.

140/87

132/74

122/77

113/74

0.09

0.22

Philadelphia, Pennsylvania

143/92

129/85

116/74

111/73

0.16

0.32

New York, New York

234/107

140/87

257/107

163/83

0.63

-0.17

Rhode Island

138/85

120/78

112/68

105/66

0.20

0.32

Boston, Massachusetts

137/84

121/80

103/67

100/67

0.18

0.43

Pittsburgh, Pennsylvania

136/80

126/77

103/66

101/66

0.12

0.41

Detroit, Michigan

120/76

112/74

104/70

102/69

0.11

0.22

aIn parts per billion.

bFrom Possiel and Cox (1991).

cFirst value is 90th percentile 1-hr ozone, and second value is peak 8-hr average.

dBase case refers to the year 2005.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 375

TABLE 11-6
Effect of Controls on Ozone in New Yorka

Peak Ozone (second day), ppb

Exposure to ozone > 120 ppb (1000 population hours)

 

New York

Connecticut

 

Base Case

167

173

28,127

75% VOC control

144(0.18)b

136(0.28)b

10,418(0.84)

75% NOx control

185(-0.14)b

154(0.14)b

33,120(-0.23)

75% VOC and NOx control

149

138

20,598

aDerived from Rao and Sistla (1990).

bSensitivity of peak ozone and ozone exposure shown in parentheses.

model calculations of a regular (nonnested) simulation with various nesting procedures (Table 11-7). Predicted ozone concentrations vary considerably depending on the kind of nesting employed. Although Rao et al. (1989) did not test how these variations affected estimates of necessary control levels, the scatter in the predictions indicates that the calculated effect of controls would differ greatly depending on which nesting procedure is used.

Summary

Application of grid-based air quality models to various cities and regions in the United States shows that the relative effectiveness of controls of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) in ozone abatement varies widely. Most major cities experience ozone concentrations that exceed the National Ambient Air Quality Standard (NAAQS) one-hour concentration of 120 ppb—a result of the density of precursor emissions in those areas. The predominant sources of emissions are mobile, although other sources contribute significantly. These cities share an ozone problem, but differ widely in the

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 376

TABLE 11-7
Comparison of Nesting Techniques for Peak Ozone Predictionsa, ppb

 

New Jersey

New York

Connecticut

Observed

145

240

303

Regular UAMb

180

199

202

Nested, ROMc ICs, BCs, winds

155

138

148

Nested, ROM ICs, BCs

156

143

167

Nested, ROM BCs

126

259

233

aFrom Rao et al. (1989), for July 21, 1980.

bUAM, urban airshed model, without nesting.

cROM, Regional Oxidant Model, and refers to the ROM supplying initial conditions (ICs), boundary conditions (BCs), wind fields.

magnitude of the problem and in the relative contributions of anthropogenic VOCs and NOx and biogenic emissions. As a result, the optimal set of controls relying on VOCs, NOx, or, most likely, reductions of both, will vary from one place to the next. In cities where the VOC/NOx ratio is high, VOC control provides less ozone reduction per unit of VOC reduction than in cities with a low VOC/NOx ratio. Cities with a high VOC/NOx ratio benefit from NOx control, but less so if the ratio is low. Studies have predicted that in some areas—downtown Los Angeles and New York City, for example—ozone will increase in certain locations (not necessarily those where the peak occurs), if NOx emissions are lowered.

Few urban areas in the United States can be treated as isolated cities unaffected by regional sources of ozone. The regional nature of the ozone problem east of the Mississippi, as demonstrated by ozone observations (see Chapter 4) and model simulations (e.g., Roselle et al., 1990); McKeen et al., 1991a) requires the use of regional models for assessment of control strategies. The Regional Oxidant Model (ROM) has been the major tool used for regulatory studies of areas affected by regional ozone. A significantly greater effort needs to be devoted both to understanding the reason's for the model's failures and to further developing the model itself. The present regional

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

Page 377

models do not have sufficient spatial resolution for detailed studies of major urban areas, and a nested model approach is likely to be necessary. A fully interactive, two-way nested multiscale model is desirable for studying intercity and regional pollutant transport. Ozone air quality is intimately related to other air-quality issues, such as acid deposition and visibility, and a comprehensive modeling system with high spatial resolution is ultimately necessary.

Biogenic VOCs, in combination with anthropogenic NOx, are capable of generating ozone concentrations above 80 ppb in favorable meteorological conditions across much of the eastern United States, with values of more than 100 ppb downwind of a number of major cities. Future assessments of control strategies must include biogenic emissions, given their potential for generating ozone concentrations close to the (NAAQS) concentration.

Many simulations conducted to date have relied on emissions inventories that are suspected of significantly underestimating anthropogenic VOC emissions (see Chapter 9) and that have not included biogenic emissions. The result is an overestimate of the effectiveness of VOC controls and an underestimate of the efficacy of NOx controls (Chameides et al., 1988; McKeen et al., 1991b). Underestimates in the VOC inventories might be partly responsible for the underprediction of ozone concentrations in central urban areas (SCAQMD, 1989; Rao et al., 1989). The consequences of an underestimate in the VOC inventories on predicted concentrations of ozone and its precursors and on control strategies must be investigated.

Even with the limitations of present models and emissions inventories, certain robust conclusions emerge when the modeling studies are synthesized. Production of ozone is limited by the availability of NOx and is much less sensitive to anthropogenic VOCs in most rural environments in the eastern United States, where NOx concentrations are less than ˜2 ppb and the VOC/ NOx ratio is high. Control of NOx is also effective in lowering peak ozone concentrations in many urban areas, although it is predicted to lead to an increase in ozone in some places, such as downtown Los Angeles and New York City. The ozone increases in these urban cores, however, are predicted to be accompanied by decreases in ozone downwind, in the Los Angeles basin and Connecticut, respectively. While control of VOCs never leads to a significant increase in ozone, there are many areas where control of VOCs is either ineffective or does not bring an area into compliance with the NAAQS. Hence NOx control will probably be necessary in addition to or instead of VOC control to alleviate the ozone problem in many cities and regions. The optimal set of controls of NOx, VOCs, or both will vary from one region to another, as discussed above.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×

There was a problem loading page 378.

Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 351
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 352
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 353
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 354
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 355
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 356
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 357
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 358
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 359
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 360
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 361
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 362
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 363
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 364
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 365
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 366
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 367
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 368
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 369
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 370
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 371
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 372
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 373
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 374
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 375
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 376
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 377
Suggested Citation:"11 VOC Versus NOx Controls." National Research Council. 1991. Rethinking the Ozone Problem in Urban and Regional Air Pollution. Washington, DC: The National Academies Press. doi: 10.17226/1889.
×
Page 378
Next: 12 Alternative Fuels »
Rethinking the Ozone Problem in Urban and Regional Air Pollution Get This Book
×
Buy Paperback | $145.00
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Despite more than 20 years of regulatory efforts, concern is widespread that ozone pollution in the lower atmosphere, or troposphere, threatens the health of humans, animals, and vegetation. This book discusses how scientific information can be used to develop more effective regulations to control ozone.

Rethinking the Ozone Problem in Urban and Regional Air Pollution discusses:

  • The latest data and analysis on how tropospheric ozone is formed.
  • How well our measurement techniques are functioning.
  • Deficiencies in efforts to date to control the problem.
  • Approaches to reducing ozone precursor emissions that hold the most promise.
  • What additional research is needed.

With a wealth of technical information, the book discusses atmospheric chemistry, the role of oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in ozone formation, monitoring and modeling the formation and transport processes, and the potential contribution of alternative fuels to solving the tropospheric ozone problem. The committee discusses criteria for designing more effective ozone control efforts.

Because of its direct bearing on decisions to be made under the Clean Air Act, this book should be of great interest to environmental advocates, industry, and the regulatory community as well as scientists, faculty, and students.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!