Spatially and chemically resolved source apportionment study of high particulate matter event

This article presents the results of a detailed source apportionment study of the high particulate matter (PM) event in the Seoul Metropolitan Area (SMA), South Korea, during late February 2014. Using the Comprehensive Air Quality Model with Extensions with its Particulate Source Apportionment Technology (CAMx-PSAT), we defined 10 source regions, including five in China, for spatially and chemically resolved analyses. During the event, the spatially averaged PM10 concentration at all PM10 monitors in the SMA was 129 mu g/m(3), while the PM10 and PM2.5 concentrations at the BulGwang Supersite were 143 mu g/m(3) and 123 mu g/m(3), respectively. CAMx-PSAT showed reasonably good PM model performance in both China and the SMA. For February 23-27, CAMx-PSAT estimated that Chinese contributions to the SMA PM10 and PM2.5 were 84.3 mu g/m(3) and 80.0 mu g/m(3), respectively, or 64% and 70% of the respective totals, while South Korea's respective domestic contributions were 36.5 mu g/m(3) and 23.3 mu g/m(3). We observed that the spatiotemporal pattern of PM constituent concentrations and contributions did not necessarily follow that of total PM10 and PM2.5 concentrations. For example, Beijing-Tianjin-Hebei produced high nitrate concentrations, but the two most-contributing regions to PM in the SMA were the Near Beijing area and South Korea. In addition, we noticed that the relative contributions from each region changed over time. We found that most ammonium mass that neutralized Chinese sulfate mass in the SMA came from South Korean sources, indicating that secondary inorganic aerosol in the SMA, especially ammonium sulfates, during this event resulted from different major precursors originating from different regions. (C) 2017 The Authors. Published by Elsevier Ltd.