Development, testing, and application of a new Multi-Receptor (MURA) Trajectory Source Apportionment (TSA) method

Trajectory Source Apportionment (TSA) methods are statistical techniques used to identify sources of pollution at a sampling site (receptor). TSA methods have traditionally been applied to a single receptor (Ashbaugh et al., 1985; Seibert et al., 1994; Lui et al., 2003) with some exploration of using more than one receptor (Stohl, 1996; Zeng and Hopke, 1989). A new Multi-Receptor (MURA) method was developed here. It utilizes a two step process to first identify Potential Source Regions (PSRs), and then examine them to see how often they affect each receptor. The MURA method was first tested against the conditional probability method developed by Ashbaugh et al. (1985) to determine each method's ability to detect known sources. Two artificial data sets were used; one containing a single source and one that contained four sources. The MURA method outperformed the conditional probability method. Next, the MURA method was compared to an improved version of the conditional probability method (SIRA). This test utilized three sets of artificial data in the western and eastern U.S. Although the SIRA method was an improvement over the conditional probability method, the MURA method still performed better in the four-source simulation located in the western United States. In the two eastern simulations both the MURA and SIRA methods performed similarly. The third test evaluated the impact of trajectory starting heights from 10m to 500m on the MURA method using the three simulations from the SIRA comparison. In the western simulation, the starting height had little to no impact on the accuracy of the method. In the two eastern simulations, the 10m, 50m, and 250m starting heights performed more consistently over both simulations.;The MURA method was then applied to two groups of IMPROVE receptors to identify sources of sulfate and nitrate. The southwest, the western Great Plains, and the eastern Midwest affect the south central United States group for high sulfate or nitrate. The areas of high sulfate affect the same receptors more consistently than the high nitrate areas across the time period. The Ohio River Valley through the Upper Midwest into the Northeast affects the northeastern group for sulfate and nitrate.