High contribution of anthropogenic combustion sources to atmosphericinorganic reactive nitrogen in South China evidenced by isotopes

Due to the intense release of reactive nitrogen (Nr) from anthropogenic activity, the source layout of atmospheric nitrogen aerosol has changed. To comprehensively clarify the level, sources, and environmental fate of NH4+ and NO3- , their concentrations and stable isotopes (d(15)N) in fine particulate matter (PM2.5) were measured in a subtropical megacity of South China. The inorganic nitrogen (NH4+ and NO3-) was an essential part of atmospheric nitrogen aerosol, and the N-NH4+ and N-NO3- contributed 45.8 % and 23.2 % to total nitrogen (TN), respectively. The source contributions of NH4+ and NO3- were estimated by d(15)N, suggesting that the dominant sources were from anthropogenic combustion activities, including coal combustion, biomass burning, and vehicles, contributing 63.2 % and 88.3 % to NH4+ and NO3- , respectively. In particular, biomass burning was the predominant source of NH4+ (27.9 %), whereas coal combustion was the dominant source of NO3- (40.4 %). This study emphasized the substantial impacts of human activities on inorganic Nr. With the rapid development of industry and transportation, nitrogen emissions will be even higher. The promotion of clean energy and efficient use of biomass would help to reduce nitrogen emissions and alleviate air pollution