Drivers for the trends of atmospheric inorganic nitrogen deposition in China under the past and future scenarios

Abstract

Atmospheric inorganic nitrogen deposition has changed dramatically across China over the recent decades, exerting profound impacts on regional climate and ecosystem. Here we present an observation- and model-based analysis to disentangle the trends of atmospheric inorganic nitrogen deposition in China, in response to the emission and climate changes, under the past (2013–2022) and future (2020–2050) scenarios. Both observational evidence and model results indicate an obvious declining trend of the national-average inorganic nitrogen deposition across China from 19.31 kg N ha⁻¹ yr⁻¹ to 14.64 kg N ha⁻¹ yr⁻¹ (−24.2 %) between 2013 and 2022, of which wet and dry deposition declines by −15.8 % and −33.4 %, respectively. Using a series of regional climate-chemistry coupled simulations, we find that the declined inorganic nitrogen deposition in 2013–2022 results comparably from the recent emission changes (69.8 % for oxidized nitrogen and 48.1 % for reduced nitrogen) and precipitation decreases. We further predict a significant decrease in inorganic nitrogen deposition under the SSP245 (−39.18 %) and SSP585 (−47.33 %) scenarios in the near-future. Overall, the contribution of emission reductions surpasses that of climatic changes and dominates the projected declining trends in inorganic nitrogen deposition. This paper provides some important insights into the drivers of atmospheric inorganic deposition in China and lays the foundation for assessing the effectiveness of emission control policies on atmospheric nitrogen deposition reduction.