Rethinking the Ozone Problem in Urban and Regional Air Pollution (1991) / Chapter Skim
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11 VOC Versus NOx Controls
11 VOC Versus NOx Controls
Pages 351-378
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From page 351... ...
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)
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From page 352... ...
The Regional Oxidant Model (ROM) has been applied recently to the northeastern United States and to urban areas in that region.
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From page 353... ...
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.
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From page 355... ...
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From page 356... ...
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From page 357... ...
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 emiss~ons.
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From page 358... ...
Louis, Missouri 9.6 0.58 Washington, D.C. 8.7 0.64 Wilkes Barre, Pennsylvania 14.3 0.44 Average 0.62 an 03/^ VOC7 ratio of percent reduction in ozone concentration to percent reduction in VOC emissions.
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From page 359... ...
(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~.
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From page 360... ...
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
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From page 361... ...
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
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From page 362... ...
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.
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From page 363... ...
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)
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From page 364... ...
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., l991b)
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From page 365... ...
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.
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From page 366... ...
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.)
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From page 367... ...
VOC VERSUS NOX CONTROLS TABLE 11-4 ROM simulations 367 Base case or control strat- Seasonal extra Episode egy Model Purposea polationb Northeastern U.S. Domain Aug.
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From page 368... ...
b/, This simulation was used, along with others, to extrapolate episodic model results to a full season. CTSDF, treatment, storage, and disposal facility.
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From page 369... ...
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.
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From page 370... ...
, 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.
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From page 371... ...
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.
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From page 372... ...
(199lb) 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.
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From page 373... ...
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~.
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From page 374... ...
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From page 375... ...
in ozone abatement varies widely. Most major cities experience ozone concentrations that exceed the National Ambient Air Quality Standard (NAAQS)
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From page 376... ...
CROM, Regional Oxidant Model, and refers to the ROM supplying initial conditions (ICs) , boundary conditions (BCs)
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From page 377... ...
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.
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