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Robert A. Harley - One of the best experts on this subject based on the ideXlab platform.
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Modeling the effect of weekday-weekend differences in Motor Vehicle Emissions on photochemical air pollution in central California.
Environmental science & technology, 2002Co-Authors: Linsey C. Marr, Robert A. HarleyAbstract:Ambient ozone concentrations vary by day of week in some locations, often with higher concentrations observed on weekends in urban and downwind areas. Emissions of ozone precursors appear to be lower on weekends, so the behavior of ozone concentrations on weekends may indicate the outcome of particular ozone control strategies. To examine the influence of day-of-week differences in Motor Vehicle Emissions on ambient ozone concentrations, we combine a fuel-based Motor Vehicle Emission inventory containing weekend-specific activity with an Eulerian photochemical airshed model applied to central California. Emissions of NOx on weekends are approximately 30% lower than on weekdays due to a large drop in heavy-duty diesel truck activity, and Emissions of VOC are only slightly lower on weekends. In rural areas, passenger car traffic and the associated Emissions are highest on Fridays and Sundays. The combination of VOC sensitivity and reduced Emissions of NOx on weekends results in higher ozone concentrations on weekends. Changes in the timing of Emissions also contribute to the weekend ozone effect, but sensitivity tests show that changes in Emissions timing have a minor effect compared to changes in total mass of Emissions on weekends. Even in situations where reductions in NOx Emissions lead to higher ozone concentrations, NOx reductions may still be necessary for control of other air pollutants such as nitrogen dioxide, nitric acid, and aerosol nitrate.
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modeling the effect of weekday weekend differences in Motor Vehicle Emissions on photochemical air pollution in central california
Environmental Science & Technology, 2002Co-Authors: Linsey C. Marr, Robert A. HarleyAbstract:Ambient ozone concentrations vary by day of week in some locations, often with higher concentrations observed on weekends in urban and downwind areas. Emissions of ozone precursors appear to be lower on weekends, so the behavior of ozone concentrations on weekends may indicate the outcome of particular ozone control strategies. To examine the influence of day-of-week differences in Motor Vehicle Emissions on ambient ozone concentrations, we combine a fuel-based Motor Vehicle Emission inventory containing weekend-specific activity with an Eulerian photochemical airshed model applied to central California. Emissions of NOx on weekends are ∼30% lower than on weekdays due to a large drop in heavy-duty diesel truck activity, and Emissions of VOC are only slightly lower on weekends. In rural areas, passenger car traffic and the associated Emissions are highest on Fridays and Sundays. The combination of VOC sensitivity and reduced Emissions of NOx on weekends results in higher ozone concentrations on weekends. C...
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Formation of photochemical air pollution in central California 1. Development of a revised Motor Vehicle Emission inventory
Journal of Geophysical Research: Atmospheres, 2002Co-Authors: Linsey C. Marr, Douglas R. Black, Robert A. HarleyAbstract:[1] Photochemical air pollution problems have proved difficult to understand and control in central California. A major source of uncertainty is the rate of precursor volatile organic compounds and NOx Emissions, especially from Motor Vehicles. We develop alternative Emissions estimates for on-road Motor Vehicles in 1990, using fuel sales data, Emission factors measured in on-road studies, and ambient pollutant ratios, for a region that includes the San Francisco Bay and San Joaquin Valley air basins and Sacramento County. Fuel-based Emissions estimates are compared with predictions of California's most recent Motor Vehicle Emission factor model (EMFAC) and with an inventory that has been used in previous regional-scale photochemical modeling studies. The fuel-based inventory contains 10–50% less CO, 40–100% more nonmethane organic compounds, and 10–20% less NOx than estimated both by EMFAC and the photochemical modeling inventory. We also describe new temporal distributions of Vehicle Emissions by hour and day of week. Diesel trucks, a major source of NOx, have a broad midday peak in Emissions on weekdays, in contrast to passenger Vehicles, which show morning and afternoon commuter peaks. While passenger Vehicle travel is similar on weekdays and weekends, diesel truck activity and Emissions decrease by 70–80% on weekends. Vehicle Emission rates and their temporal patterns are linked to a regional photochemical air pollution episode that spans a weekend in August 1990.
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scaling of infrared remote sensor hydrocarbon measurements for Motor Vehicle Emission inventory calculations
Environmental Science & Technology, 1998Co-Authors: Brett C Singer, Robert A. Harley, David LittlejohnAbstract:Infrared (IR) remote sensors calibrated with propane understate volatile organic compound (VOC) concentrations in Vehicle exhaust by 30−70% when compared to flame ionization detectors (FID). The difference depends on VOC composition and arises because many organic compounds in Vehicle exhaust absorb less IR radiation than propane on a per-carbon basis. This study demonstrates an approach for scaling infrared measurements to reflect more accurately total exhaust VOC Emissions from on-road Motor Vehicle fleets. Infrared versus flame ionization detector response to individual VOC was measured in the laboratory for methyl tert-butyl ether and a range of alkanes, alkenes, and aromatics that are prominent in Vehicle exhaust. Overall IR/FID response to real exhaust mixtures was calculated by summing the response contributions of all individual VOC constituents. Average IR/FID response factors were calculated for typical on-road Vehicle fleets based on VOC speciation profiles measured in several U.S. roadway tunn...
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a fuel based inventory for heavy duty diesel truck Emissions
University of California Transportation Center, 1998Co-Authors: David B Dreher, Robert A. HarleyAbstract:A fuel-based method for estimating heavy-duty diesel truck Emissions is described. In this method, Emission factors are normalized to fuel consumption; Vehicle activity is measured by the amount of diesel fuel consumed. For the San Francisco Bay Area during summer 1996, heavy-duty diesel trucks were estimated to emit 100⋅103 kg/day of NOx and 6.4⋅103 kg/day of exhaust PM. These values were 2.1 and 1.8 times, respectively, the corresponding values predicted by California’s Motor Vehicle Emission inventory model, MVEI 7G. Significant decreases in diesel truck activity and Emissions, 70-80% below typical weekday levels, were observed in the Bay Area on weekends. Reductions in diesel NOx and black carbon (BC) particle Emissions on weekends may contribute to higher ambient ozone concentrations and higher OC/BC ratios observed on weekends. Heavy-duty truck traffic peaks on weekdays during the middle of the day and falls off before the afternoon rush hour. Therefore, the diurnal pattern of heavy-duty truck travel may contribute to increases in ambient OC/BC ratios observed during late afternoon hours.
Cyle Wold - One of the best experts on this subject based on the ideXlab platform.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
Linsey C. Marr - One of the best experts on this subject based on the ideXlab platform.
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modeling the effect of weekday weekend differences in Motor Vehicle Emissions on photochemical air pollution in central california
Environmental Science & Technology, 2002Co-Authors: Linsey C. Marr, Robert A. HarleyAbstract:Ambient ozone concentrations vary by day of week in some locations, often with higher concentrations observed on weekends in urban and downwind areas. Emissions of ozone precursors appear to be lower on weekends, so the behavior of ozone concentrations on weekends may indicate the outcome of particular ozone control strategies. To examine the influence of day-of-week differences in Motor Vehicle Emissions on ambient ozone concentrations, we combine a fuel-based Motor Vehicle Emission inventory containing weekend-specific activity with an Eulerian photochemical airshed model applied to central California. Emissions of NOx on weekends are ∼30% lower than on weekdays due to a large drop in heavy-duty diesel truck activity, and Emissions of VOC are only slightly lower on weekends. In rural areas, passenger car traffic and the associated Emissions are highest on Fridays and Sundays. The combination of VOC sensitivity and reduced Emissions of NOx on weekends results in higher ozone concentrations on weekends. C...
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Modeling the effect of weekday-weekend differences in Motor Vehicle Emissions on photochemical air pollution in central California.
Environmental science & technology, 2002Co-Authors: Linsey C. Marr, Robert A. HarleyAbstract:Ambient ozone concentrations vary by day of week in some locations, often with higher concentrations observed on weekends in urban and downwind areas. Emissions of ozone precursors appear to be lower on weekends, so the behavior of ozone concentrations on weekends may indicate the outcome of particular ozone control strategies. To examine the influence of day-of-week differences in Motor Vehicle Emissions on ambient ozone concentrations, we combine a fuel-based Motor Vehicle Emission inventory containing weekend-specific activity with an Eulerian photochemical airshed model applied to central California. Emissions of NOx on weekends are approximately 30% lower than on weekdays due to a large drop in heavy-duty diesel truck activity, and Emissions of VOC are only slightly lower on weekends. In rural areas, passenger car traffic and the associated Emissions are highest on Fridays and Sundays. The combination of VOC sensitivity and reduced Emissions of NOx on weekends results in higher ozone concentrations on weekends. Changes in the timing of Emissions also contribute to the weekend ozone effect, but sensitivity tests show that changes in Emissions timing have a minor effect compared to changes in total mass of Emissions on weekends. Even in situations where reductions in NOx Emissions lead to higher ozone concentrations, NOx reductions may still be necessary for control of other air pollutants such as nitrogen dioxide, nitric acid, and aerosol nitrate.
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Formation of photochemical air pollution in central California 1. Development of a revised Motor Vehicle Emission inventory
Journal of Geophysical Research: Atmospheres, 2002Co-Authors: Linsey C. Marr, Douglas R. Black, Robert A. HarleyAbstract:[1] Photochemical air pollution problems have proved difficult to understand and control in central California. A major source of uncertainty is the rate of precursor volatile organic compounds and NOx Emissions, especially from Motor Vehicles. We develop alternative Emissions estimates for on-road Motor Vehicles in 1990, using fuel sales data, Emission factors measured in on-road studies, and ambient pollutant ratios, for a region that includes the San Francisco Bay and San Joaquin Valley air basins and Sacramento County. Fuel-based Emissions estimates are compared with predictions of California's most recent Motor Vehicle Emission factor model (EMFAC) and with an inventory that has been used in previous regional-scale photochemical modeling studies. The fuel-based inventory contains 10–50% less CO, 40–100% more nonmethane organic compounds, and 10–20% less NOx than estimated both by EMFAC and the photochemical modeling inventory. We also describe new temporal distributions of Vehicle Emissions by hour and day of week. Diesel trucks, a major source of NOx, have a broad midday peak in Emissions on weekdays, in contrast to passenger Vehicles, which show morning and afternoon commuter peaks. While passenger Vehicle travel is similar on weekdays and weekends, diesel truck activity and Emissions decrease by 70–80% on weekends. Vehicle Emission rates and their temporal patterns are linked to a regional photochemical air pollution episode that spans a weekend in August 1990.
K Lewis - One of the best experts on this subject based on the ideXlab platform.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
W P Arnott - One of the best experts on this subject based on the ideXlab platform.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
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strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument
Journal of Geophysical Research, 2008Co-Authors: K Lewis, W P Arnott, Hans Moosmuller, Cyle WoldAbstract:[1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for Motor Vehicle Emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.