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NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
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Poster 6: A Conceptual Model to Adjust Fugitive Dust Emissions to Account for Near Source Particle Removal in Grid Model Applications
Thompson G. Pace
US EPA
For a number of years air quality analysts have recognized that fugitive dust emission inventories, when coupled with air quality models, substantially overestimate PM2.5 ambient crustal material when compared to the crustal material found in ambient samples. Fugitive dust categories of interest include unpaved and paved road dust, dust from highway, commercial and residential construction, agricultural tilling, windblown dust from agricultural and other exposed land, quarrying and other earthmoving. In the mid 1990´s, the U.S. Environmental Protection Agency´s (EPA) Office of Air Quality Planning and Standards (OAQPS) began to use, as an interim measure, a “divide-by-four”factor to “adjust” the fugitive dust emission estimates in grid modeling analyses to obtain better agreement between the regional model results and ambient data. Since then, the EPA has been actively working to understand the reasons for the ambient-emissions differences. Work by the U.S. EPA, Desert Research Institute, Western Regional Air Partnership, Midwest Research Institute and University of Utah have concluded that much of these emissions are removed near the source by interaction of the plume with the ground, nearby vegetation and structures. This paper reviews these efforts, proposes a conceptual model of fugitive dust removal processes near the source and compares this model with recent field studies that measure near source removal. This conceptual model is intended as an improvement to the “divide-by-four” approach that may be useful for adjusting fugitive dust emission inventories when used in grid models.