Importance of coarse-mode nitrate produced via sea salt as atmospheric input to East Asian oceans

The atmospheric input of anthropogenic total reactive oxygenated nitrogen (NO_y) to ocean regions in East Asia during 2002–2004 was revisited with an updated regional chemical transport model and the latest emissions inventory. The updated model treats both fine- and coarse-mode nitrate (NO₃ ⁻). Coarse-mode NO₃ ⁻ is produced by the reaction of nitric acid (HNO₃) and sea salt particles. The modeling system reproduced the atmospheric concentration and wet deposition amount of NO₃ ⁻ quantitatively compared with observations. The fraction of coarse-mode NO₃ ⁻ was also well captured. NO_y deposition amounts over marginal seas and open oceans were 733 and 730 Gg N/yr, which are increases of 1.6- and 2.2-fold, respectively, by including coarse-mode NO₃ ⁻. Anthropogenic NO_x emissions from China were 5377 Gg N/yr, and 3060 Gg N/yr was exported from China; therefore, the NO_y deposition amount over ocean regions in East Asia (1463 Gg N/yr) corresponded to almost half (48%) of the export amounts.