Abstract: The WRF-CMAQ model is employed to estimate the atmospheric nitrogen deposition of different nitrogen forms in four major lakes of China in 2018. The nitrogen forms include total nitrogen (TN), oxidized nitrogen (OXN), reduced nitrogen (REDN), nitrate nitrogen (NO^-₃-N), and ammonium nitrogen (NH⁺₄-N). The annual nitrogen deposition fluxes in 2018 for Lake Qinghaihu, Lake Ulansuhai, Lake Donghu, and Lake Taihu were 3.02, 4.38, 64.25, and 21.67 kgN/hm², respectively. Atmospheric nitrogen deposition contributed 0.9%, 22.3%, and 11.3% of the total nitrogen load in Lake Ulansuhai, Lake Donghu, and Lake Taihu, respectively. Lake Donghu and Lake Taihu were significantly more affected by atmospheric nitrogen deposition than Lake Qinghaihu and Lake Ulansuhai, highlighting the need for increased concern regarding atmospheric nitrogen deposition in developed regions. Sensitivity analysis revealed that the deposition velocity of nitrogen pollutants had an insignificant impact on local nitrogen deposition fluxes. However, reducing the source emission rate of nitrogen pollutants significantly decreased the nitrogen deposition fluxes. A 20% reduction in the source emission rate led to a decrease in nitrogen deposition fluxes by 11% to 22% in the four representative lakes. This demonstrates that nitrogen emission sources is the major factor that affects nitrogen deposition compared to deposition velocity. The findings provide a scientific foundation for further understanding the role of atmospheric nitrogen deposition in the total nitrogen load of lakes and developing effective control measures.

Key words: atmospheric nitrogen deposition, atmospheric pollution, numerical modeling, nitrogen pollution, lake pollution