Increases in the formation of water soluble organic nitrogen during Asian dust storm episodes

Abstract

There is increasing interest in understanding the origin of atmospheric sources of water soluble organic nitrogen (WSON) and its impact on anthropogenic nutrient pollution for terrestrial and marine ecosystem. This study aims to investigate the role of Asian dust storm on atmospheric water soluble organic nitrogen. PM2.5 samples were collected simultaneously from April 1 to May 21, 2012 at the urban area of Zhangjiakou, Hebei province and the rural area of Tianjin near the coastal line, respectively. PM2.5 mass and chemical compositions including ions, total metals, WSON, organic carbon and elemental carbon were adopted for source apportionment using receptor modeling. The sources of PM2.5 mass at the two sampling sites were coal combustion, secondary source, industrial source, mobile source, dust source and biomass burning. The Asian dust storm was observed at the two sampling sites from April 25 to 28, 2012. Significant increases in WSON concentration from ~1.6 μg m−3 to 12 μg m−3 were found at the urban site (S1), and from ~1.3 μg m−3 to 18 μg m−3 at the coastal site (S2), respectively. Source apportionment results showed that the contributions to WSON from dust source increased from ~10% during normal days to ~45% during dust storm days, while the contributions from other sources kept relative stable (<5%) within normal days and dust storm days. The largest sources contributing to WSON at the two sampling sites were secondary sources and fuel combustions. Our study highlights the important role of Asian dust storm in the cycles of WSON in urban and coastal environments.