High contribution of anthropogenic combustion sources to atmospheric inorganic 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 NHinline-formula $M1inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimg9e82b08d319a1c899f60c89d4a61df91 acp-23-6395-2023-ie00001.svg8pt15ptacp-23-6395-2023-ie00001.png and NOinline-formula $M2inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-}$ 9pt16ptsvg-formulamathimg53e1f98be2cdf70dbe180d95894fc6b5 acp-23-6395-2023-ie00002.svg9pt16ptacp-23-6395-2023-ie00002.png , their concentrations and stable isotopes (inline-formulaδ¹⁵N) in fine particulate matter (PMinline-formula_2.5) were measured in a subtropical megacity of South China. The inorganic nitrogen (NHinline-formula $M5inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimgaa378b71f34a6c23384fc0eb7c6e7621 acp-23-6395-2023-ie00003.svg8pt15ptacp-23-6395-2023-ie00003.png and NOinline-formula $M6inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-})$ 12pt16ptsvg-formulamathimge729ab1aeb604d70003d67ee45e4a0b8 acp-23-6395-2023-ie00004.svg12pt16ptacp-23-6395-2023-ie00004.png was an essential part of atmospheric nitrogen aerosol, and the N-NHinline-formula $M7inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimga896672a5a2c6d19cc4695ffc843bfde acp-23-6395-2023-ie00005.svg8pt15ptacp-23-6395-2023-ie00005.png and N-NOinline-formula $M8inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-}$ 9pt16ptsvg-formulamathimg7de8959157e6c258409d4c11688ca166 acp-23-6395-2023-ie00006.svg9pt16ptacp-23-6395-2023-ie00006.png contributed 45.8 % and 23.2 % to total nitrogen (TN), respectively. The source contributions of NHinline-formula $M9inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimge480ef7ec07e999cc23d83cf2e7b4868 acp-23-6395-2023-ie00007.svg8pt15ptacp-23-6395-2023-ie00007.png and NOinline-formula $M10inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-}$ 9pt16ptsvg-formulamathimg78ed0f7e81615226176402cdd6a1afd5 acp-23-6395-2023-ie00008.svg9pt16ptacp-23-6395-2023-ie00008.png were estimated by inline-formulaδ¹⁵N, suggesting that the dominant sources were from anthropogenic combustion activities, including coal combustion, biomass burning, and vehicles, contributing 63.2 % and 88.3 % to NHinline-formula $M12inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimg9ae7496f73369cba691a3bcfb358d1a5 acp-23-6395-2023-ie00009.svg8pt15ptacp-23-6395-2023-ie00009.png and NOinline-formula $M13inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-}$ 9pt16ptsvg-formulamathimga192f22c747584054322d55d69a940ca acp-23-6395-2023-ie00010.svg9pt16ptacp-23-6395-2023-ie00010.png , respectively. In particular, biomass burning was the predominant source of NHinline-formula $M14inlinescrollmathml{}_{\mathrm{normal\; 4}}^{+}$ 8pt15ptsvg-formulamathimgd0f05de3ef9fdb7d2948354df3a21cd8 acp-23-6395-2023-ie00011.svg8pt15ptacp-23-6395-2023-ie00011.png (27.9 %), whereas coal combustion was the dominant source of NOinline-formula $M15inlinescrollmathml{}_{\mathrm{normal\; 3}}^{-}$ 9pt16ptsvg-formulamathimg9f81e901bf06635e082f559a787da68a acp-23-6395-2023-ie00012.svg9pt16ptacp-23-6395-2023-ie00012.png (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.