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.

Automated summary

Due to anthropogenic activities, the release of reactive nitrogen (Nr) has significantly changed the sources of atmospheric nitrogen aerosol. This study measured the concentrations and stable isotopes (d(15)N) of NH4+ and NO3- in fine particulate matter (PM2.5) in a subtropical megacity in South China to understand their levels, sources, and environmental fate. The results showed that NH4+ and NO3- were essential components of atmospheric nitrogen aerosol, with N-NH4+ and N-NO3- contributing 45.8% and 23.2% to total nitrogen (TN), respectively. The dominant sources for NH4+ and NO3- were anthropogenic combustion activities, such as coal combustion, biomass burning, and vehicles, contributing 63.2% and 88.3%, respectively. Overall, this study highlights the significant impact of human activities on inorganic Nr and emphasizes the importance of adopting clean energy and efficient biomass use to reduce nitrogen emissions and mitigate air pollution.