Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 54, Issue 7, Pages 3988-3995Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.9b06092
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- Ministry of Science and Technology (Taiwan, R.O.C.) [MOST 104-2611-M-002-017-MY3, 107-2611-M-002-004, 107-2918-I-002-006]
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Distinct spatiotemporal distributions of sea surface dissolved elemental mercury (DEM) and its air-sea exchange flux were observed in the river-dominated and monsoon-influenced East China Sea (ECS). Spatially, DEM concentrations were higher in the nearshore Changjiang diluted water (90 +/- 20 to 260 +/- 40 fM) than in the offshore Kuroshio water (60 +/- 10 to 160 +/- 40 fM) and correlated with salinity and total Hg concentrations, suggesting that the total Hg discharged from the Changjiang river is a controlling factor. In summer, monsoon-driven coastal upwelling formed a transient nearshore water mass with very elevated DEM concentrations (290 +/- 20 to 320 +/- 70 fM). Seasonally, DEM concentrations in all water masses were the highest in summer (120 +/- 30 to 320 +/- 70 fM). Estimated rate coefficients for DEM production varied seasonally and strongly correlated with sea surface temperature (SST). Hg-0 evasion fluxes also peaked in summer (670 +/- 380 pmol m(-2) day(-1)), while in winter, DEM was close to equilibrium with gaseous elemental mercury in the atmosphere. Based on the air-sea Hg fluxes for all four seasons from this study and regional atmospheric deposition fluxes from others, we conclude that the ECS is a net sink of Hg annually, but it is a source of Hg to the atmosphere in summer. Moreover, the contribution of the ECS to Hg evasion may increase as a result of flood-associated high Changjiang discharge and rising SST.
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