Measurement report: Nitrogen Isotope (δ¹⁵N) Signatures of Ammonia Emissions from Livestock Farming: Implications for Source Apportionment of Haze Pollution

Abstract. Ammonia emissions from agriculture are the primary source of atmospheric reactive nitrogen, significantly impacting air pollution, soil acidification, eutrophication of water bodies, and human health. Accurate quantification of ammonia from different sources is crucial for effective mitigation. In this study, the air extraction method was employed to collect gases from livestock farms, and the δ¹⁵N values of volatilized ammonia (NH₃) from the animal husbandry industry in the southern Huang - Huai - Hai Plain of China were analyzed using stable nitrogen isotopes. The results show that isotopic signatures differ significantly among livestock types: dairy cows (-20.6 ‰ ± 0.8 ‰), laying hens (-27.4 ‰ ± 1.0 ‰), and pigs (-38.4 ‰ ± 1.7 ‰). These livestock-derived signatures are distinct from those associated with combustion sources (-7.0 ‰ ± 2.1 ‰) and traffic emissions (6.6 ‰ ± 2.1 ‰), and they exhibit considerably lower variability than fertilizer-derived signatures. Overall, this work provides high-precision isotopic source signatures for livestock operations, offering essential parameters for regional atmospheric ammonia source apportionment and highlighting the need for locally tailored mitigation strategies.