Dissecting the contributions of organic nitrogen aerosols to global atmospheric nitrogen deposition and implications for ecosystems.

Atmospheric deposition of particulate organic nitrogen (ON p ) is a significant process in the global nitrogen cycle and may be pivotally important for N-limited ecosystems. However, past models largely overlooked the spatial and chemical inhomogeneity of atmospheric ON p and were thus deficient in assessing global ON p impacts. We constructed a comprehensive global model of atmospheric gaseous and particulate organic nitrogen (ON), including the latest knowledge on emissions and secondary formations. Using this model, we simulated global atmospheric ON p abundances consistent with observations. Our estimated global atmospheric ON deposition was 26 Tg N yr -1 , predominantly in the form of ON p (23 Tg N yr -1 ) and mostly from wildfires (37%), oceans (22%) and aqueous productions (17%). Globally, ON p contributed as much as 40% to 80% of the total N deposition downwind of biomass-burning regions. Atmospheric ON p deposition thus constituted the dominant external N supply to the N-limited boreal forests, tundras and the Arctic Ocean, and its importance may be amplified in a future warming climate.