Aerosols as a source of dissolved black carbon to the ocean

Dissolved black carbon (DBC) is the largest known slow-cycling organic carbon pool in the world's oceans. Atmospheric deposition could significantly contribute to the oceanic DBC pool, but respective information is lacking. Here we estimate that, during the dust outbreak season, the atmospheric dry deposition of water-soluble black carbon (WSBC) is similar to 40% of the riverine input to the China coastal seas. The molecular composition of atmospheric WSBC determined by ultrahigh-resolution mass spectrometry, reveals similar soil-derived sources as for riverine discharge. WSBC is significantly positively correlated with watersoluble organic carbon (WSOC) in marine aerosols, and water-soluble black carbon contributes on average 2.8 +/- 0.65% to the total WSOC. Based on this relationship, the global atmospheric deposition of DBC to the ocean is estimated to be 1.8 +/- 0.83 Tg yr(-1). Anticipated future changes in biomass burning and dust mobilization might increase these numbers, with consequences for regional ecosystems and global carbon reservoirs.