Influence of salinity intrusion on the speciation and partitioning of mercury in the Mekong River Delta

摘要: Abstract The lower Mekong and Saigon River Basins are dominated by distinctive monsoon seasons, dry rainy seasons. Most of the is a freshwater region during season, whereas salt water intrudes approximately 70 km inland. To understand role salinity intrusion controlling Hg behavior in Basins, monomethylmercury (MMHg) surface sediment were investigated season. Sediment distribution, ranging from 0.12 to 0.76 nmol g−1, was mainly controlled organic carbon distribution River; however, location point sources more important (0.21–0.65 nmol g−1). MMHg concentrations (0.16–6.1 pmol g−1) (0.70–8.7 pmol g−1) typically showed significant increases estuarine head, with sharp acid volatile sulfide. Unfiltered (4.6–222 pM) filtered (1.2–14 pM) increased zone due enhanced particle loads. Conversely, unfiltered (0.056–0.39 pM) (0.020–0.17 pM) similar between zones, which associated mixing dilution particulate organic- MMHg-depleted resuspended sediment. Partitioning suspended tight correlation partitioning across study sites, while that implied influences chloride: chloride addition matter depletion decreased zone. Primary production an determinant inter-annual variation MMHg. bloom year relatively low C/N ratio, indicating biodilution Hg. In contrast, percentage significantly year, likely greater availability metabolizable fresh matter. overall results emphasize Basin strongly connected local climate, via alterations loads, biological productivity, sulfate,