Atmospheric wet deposition of dissolved organic carbon to a typical anthropogenic-influenced semi-enclosed bay in the western Yellow Sea, China: Flux, sources and potential ecological environmental effects

Dissolved Organic Carbon (DOC) is a key organic compound in wet precipitation, but few data are available in China marginal seas. To probe the concentration, deposition flux, seasonality, source and potential ecological environmental effects of precipitation DOC, in this study, one-year precipitation samples were collected at Jiaozhou Bay (JZB), a typical anthropogenic-influenced semi-enclosed bay in the western Yellow Sea for the first time from June 2015 to May 2016. The concentrations of DOC in precipitation were highly variable with a volume-weighted mean (VWM) concentration of 3.63 mg C L-1, which was mostly higher than those in other areas. DOC concentrations were lower in wet season than that in dry season due to the dilution from more amount of rainfall. The wet deposition flux of DOC was calculated to be 3.15 g C m(-2) yr(-1) with 68.7% of which occurred in wet season mainly owing to the promoting of more rainfall amount. Besides, local emissions together with the long-range transport of pollutants were other factors controlling precipitation DOC. Fossil fuel combustion particularly coal burning was considered to be the leading source of precipitation DOC based on correlation analysis with some generally accepted indicators. Wet deposition dominates the external input of DOC at JZB by comparison with riverine input with a percentage of 54%. Heavy storm may exert enrichment effect on DOC levels in the surface water of JZB, and then promote the secondary productivity. This study emphasizes that wet deposition is an important process that should be seriously considered in the models of global/regional carbon biogeochemical cycling.