Abstract
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 ~ 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 water-soluble 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.
Highlights
Dissolved black carbon (DBC) is the largest known slow-cycling organic carbon pool in the world’s oceans
Principal coordinates analysis (PCoA) based on the molecular composition of the solid-phase extraction (SPE)-watersoluble organic carbon (WSOC) clearly separated these groups of aerosol samples, and the results were fully consistent with the origins of the aerosols based on sampling location and backward trajectories (Fig. 1 and Methods)
Considering that the composition of atmospheric WSOC was highly variable, the observed significant correlation between water-soluble black carbon (WSBC) and WSOC in natural aerosol samples was unexpected. This significant correlation suggests that WSBC and WSOC might be released by similar processes[9]
Summary
Dissolved black carbon (DBC) is the largest known slow-cycling organic carbon pool in the world’s oceans. 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. Recent studies have reported condensed aromatic compounds in dissolved organic matter in aerosols[19, 20], hailstones[21], coastal rainwater[22], bulk deposition[23], and snow[24, 25], demonstrating the presence of DBC in atmospheric deposition It is unknown how much of this DBC is eventually deposited in the oceans. Coupled with hotspots of dust and BC emissions in North China, the downwind North Pacific Ocean may receive significant amounts of water-soluble black carbon (WSBC) from atmospheric deposition.
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