Spatio-temporal distribution and environmental risk of arsenic in sediments of the East China Sea

To understand the spatial and temporal distributions, environmental risks and sources of As, 38 surface sediments and three sediment cores were collected in the East China Sea (ECS). As concentrations in sediments ranged from 1.70 to 22.1 μg/g with an average of 11.5 μg/g. As concentration had positive correlations with clay + silt and total organic carbon (TOC) content with higher As values near the Changjiang Estuary and Hangzhou Bay mouth, indicating fine-grained sediments and riverine inputs as the main factors controlling As distribution. Chemical fraction analysis, sediment quality guidelines, together with geoaccumulation index, suggested that As in sediments of the ECS was at low risk, low adverse effect and moderately polluted level. Vertical profiles of As concentrations and burial fluxes, combined with 210Pb dating, reflected the As pollution history in the ECS within the last one hundred years. It showed a stable trend before one hundred years ago, a slight increase from the 1900s to 1990s, with peak values in the 1980s and 1990s, and a declining trend after the 1990s to 2009 with a relatively low value in 1998. These trends were closely associated with both natural and anthropogenic activities.