Comprehensive assessment of fine particulate matter emissions inventories and development of improved allocation profiles

Abstract

Emission inventories of fine particulate matter (PM) were compared to estimates of emissions based on observational data emerging from the EPA Particulate Matter Supersites and other field programs. Six source categories for fine PM emissions were considered: on-road mobile sources, non-road mobile sources, cooking, biomass combustion, fugitive dust and stationary sources. Regional emission inventories of PM in the exhaust from on-road and non-road sources were generally consistent with ambient observations. In contrast, emission inventories of road dust were an order of magnitude larger than ambient observations, and estimated brake wear and tire dust emissions were half as large as ambient observations in urban areas. Although a comprehensive nationwide emission inventory of fine PM from cooking sources and biomass burning is not yet available, observational data in urban areas suggest that cooking sources account for roughly 5-20% of total primary emissions (excluding dust) and the magnitude of biomass burning emissions are highly dependent on the region. Finally, relatively few observational data were available to assess the accuracy of emission estimates for stationary sources. Overall, the uncertainties in primary emissions for fine PM are substantial. Because of these uncertainties, the design of fine PM control strategies should be based on inventories that have been refined by a combination of bottom-up and top-down methods, as demonstrated in this work. This approach was used in the development of a primary PM emissions inventory for air quality modeling. This emissions inventory improved upon previous inventories by updating some source strengths, temporal allocations, and chemical speciation profiles; in addition, size resolution information was incorporated into the inventory.