Research Progress on Stable Nitrogen Isotope Tracing of Atmospheric Nitrate Sources

<p indent="0mm">Nitrate is an important component of atmospheric secondary inorganic aerosols and nitrogen deposition. Atmospheric nitrate pollution and deposition have significant impacts on human health and structures and functions of ecosystems. Therefore, accurately quantifying the contribution of atmospheric nitrate sources is crucial for reducing atmospheric reactive nitrogen emissions and improving air quality. Nitrogen isotope technology is one of the effective tracing methods for the sources and environmental processes of atmospheric nitrogen pollutants. Researchers have preliminarily constructed an isotope quantitative tracing scheme for the contribution of atmospheric nitrate sources, achieving the quantification of atmospheric nitrate source contributions. However, there are still shortcomings in the study of some key parameters in this scheme, which affects the accuracy of the contribution of major nitrogen oxide emission sources. In this paper, we systematically introduce the main research progress on the observation values of nitrate nitrogen isotopes in atmospheric dry and wet deposition at different underlying surfaces, the nitrogen isotope values of major emission sources of nitrogen oxides, and the nitrogen isotope effects of atmospheric nitrate formation processes. Meanwhile, we summarize the shortcomings of the research in the above three aspects and look forward to further work in the future to reduce the uncertainty of the contribution of the major emission sources of atmospheric nitrogen oxides.