Distribution and mass inventory of mercury in sediment from the Yangtze River estuarine-inner shelf of the East China Sea

Mercury (Hg) was measured in 70 sediment samples from the Yangtze River estuarine-inner shelf of the East China Sea (ECS) to evaluate its occurrence, distribution, and deposition flux. Its concentrations were 10-92 ng/g with a mean of 46±17 ng/g. A decrease of Hg concentration with increasing distance offshore suggested a dominance of riverine input. The high levels of Hg observed at the southern inner shelf were partly due to the sorption affinity of fine-grained sediments. Hg concentration was significantly correlated with total organic carbon content and sediment grain size, implying that the nature of sedimentary organic matter and hydrodynamic forces could influence the Hg occurrence. A moderate correlation between Hg with high-molecular-weight polycyclic aromatic hydrocarbons in the YRE suggested that they shared a similar input pathway. The total deposition flux of Hg was estimated to be ~52 t/y with a deposition rate of 6-120 ng/cm2 y, which indicated that the estuarine-inner shelf of the ECS was a major sink of Hg in the margins off China, and this area could play a significant role in the Hg biogeochemical cycle on a global scale.