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>Updated photochemical modeling for California's South Coast Air Basin: Comparison of chemical mechanisms and motor vehicle emission inventories
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Updated photochemical modeling for California's South Coast Air Basin: Comparison of chemical mechanisms and motor vehicle emission inventories
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机译：Updated photochemical modeling for California's South Coast Air Basin: Comparison of chemical mechanisms and motor vehicle emission inventories
Large uncertainties remain in photochemical models used to relate emissions of VOC and NOx to ambient O-3 concentrations. Bias in motor vehicle emission estimates for VOC has been a long-standing concern. An improved Eulerian photochemical model is described and applied to the August 27-28, 1987, period in southern California. The chemical mechanism used in the model is SAPRC93, which predicts peak ozone concentrations 22 higher on average than the LCC mechanism used previously. A revised motor vehicle emission inventory was developed using gasoline sales and infrared remote sensing data for CO and measured ambient NMOC/CO and NOx/CO ratios. On-road vehicle emissions for the South Coast Air Basin in summer 1987 were estimated to be (1800 +/- 400) x 10(3) and (710 +/- 160) x 10(3) kg day(-1) for NMOC and NOx, respectively. These values are 2.4 and 1.0 times, respectively, the corresponding current official inventory estimates (MVEI 7G). Ozone concentrations predicted using the CIT airshed model matched observations more closely when the revised inventory was used in place of official emission estimates. If the vehicle fleet in 1987 were operating with no emission controls, NMOC and NO, emissions would have been 5900 x 10(3) and 1200 x 10(3) kg day(-1) respectively. On average, peak predicted ozone concentrations for the controlled vehicle fleet operating in 1987 were 43 lower than values predicted for the uncontrolled vehicle fleet. The peak predicted ozone concentration with the uncontrolled vehicle fleet was 500 ppb.
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