Effects of Meteorology, Emissions, and Regional Transport on Atmospheric Nr Deposition in Lake Taihu, China

Abstract Atmospheric deposition has played an increasingly important role of reactive nitrogen (Nr) loading in Chinese eutrophic lakes, while its major influencing factors and sources remained insufficiently understood. Here, we applied WRF-CMAQ and its source apportionment module to investigate the interannual change and main drivers of atmospheric Nr deposition by species and form over Lake Taihu during 2017–2020. The annual average of Nr deposition was estimated at 6.55 ± 0.18 Gg N yr–1, and reduced nitrogen (RDN) accounted for 70% resulting from abundant NH3 emissions from agricultural activities and continuous NOx controls in the Basin. Meteorological factors played a greater role than emission abatement in driving the interannual variability of Nr deposition for both summer and winter. Long-range transport from outside of the basin became an increasingly important contributor to oxidized nitrogen (OXN) deposition, partly offsetting the benefits of local NOx controls. Upwind cities were identified with greater contributions to Nr deposition in winter, whereas the circulation pattern strongly affected the contributions of cities in summer. This study advances our understanding of Nr inputs from the atmosphere to aquatic ecosystems and provides scientific evidence for the management of external nitrogen to eutrophic lakes.