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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 14: Decadal Trend in Emissions of Benzene Relative to Other NMHC's: Evidence from Ambient Atmospheric Measurements
D.D. Parrish, B.J. Howard, P.D. Goldan, W.C, Kuster F.C. Fehsenfeld
Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305
Over the last three decades air pollution control efforts have led to a several fold decrease in the emissions of non-methane hydrocarbons (NMHC's) in the U.S. The 1990 Clean Air Act Amendments (CAAA) required the U.S. EPA to identify and regulate hazardous air pollutants. Benzene is a ubiquitous NMHC that was targeted for particular control efforts under the EPA's Urban Air Toxics Program. We will examine a wide suite of ambient measurements made in the U.S. over the past three decades. In particular we will investigate the temporal change of the ratio of benzene to other related NMHC's that are not targeted under the toxics program. The goal will be to determine to what extent benzene has recently decreased at a faster rate than the NMHC's that were not identified as toxics. This determination from ambient measurements will be compared to the trends suggested by emission inventories. One limit encountered in this evaluation is that the PAMS data are affected by large systematic errors that prevent their utilization in this regard.