Atmospheric deposition of inorganic nitrogen to the eastern China seas and its implications to marine biogeochemistry

Abstract

Atmospheric deposition of nitrogen to the eastern China seas has been simulated using the MM5/CMAQ model with the 2004 national emission inventory of China. Dry and wet fluxes are 0.05–0.5 and 0.2–0.6 g m−2 yr−1, respectively, with the wet deposition accounting for 79% of the total. The total deposition of inorganic nitrogen species, including NO3−, NH4+, HNO3, NOx, and NH3, to the eastern China seas is 498 GgN yr−1 and accounts for 3.4% of the nitrogen emission by China. Deposition of NO3− and NH4+ dominates. The model results agree well with available in situ measurements. The deposition of NH4+ and NH3 to the East China Sea is up to 166 GgN yr−1, which nearly equals the total input of 184 GgN yr−1 from the mainland, including riverine discharge, industrial wastewater, and domestic wastewater. Deposition of atmospheric ammonium can account for 56% of the external total input, which is 1.1–1.5 times the input from the major rivers to all the eastern China seas. Ammonium deposition to the Yellow Sea accounts for as much as 87% of the total input. The annual total nitrogen deposition can be converted to new primary biological productivity of 100–200 mmol C m−2 yr−1, or 1.1–3.9% of the new productivity in the East China Sea. Our results suggest that atmospheric deposition has important impact on biological productivity in all the eastern China seas.