Abstract: In this study, we measured the content, speciation, and distribution of arsenic in the surface sediments with samples collected from 37 sites in Bohai Sea, China. The ecological risks associated with the sedimentary arsenic were evaluated, and the impacts of aquatic and sedimentary physicochemical parameters on the distribution of arsenic in sediments were explored. The results showed that the total arsenic concentrations in the surface sediments of the Bohai Sea ranged from 9.77 to 20.60 mg·kg^-1, with an average concentration of 13.33 mg·kg^-1. There were significant differences in total arsenic content of the sediments among different sea areas. Generally, the concentration of total arsenic in the surface sediments decreased from the nearshore areas to the middle of the Bohai Sea. Total arsenic burdens in the western areas of the Bohai Sea were usually higher than that from the eastern areas. The highest total arsenic concentrations in the sediments were recorded in Bohai Bay and Laizhou Bay. The results of sequential extractions showed that volatile sulfides, carbonates or amorphous iron and manganese oxides associated arsenic were the main forms of the arsenic in the surface sediments. The arsenic in the sediments of the Bohai Sea had low to moderate ecological risks. Total arsenic content in the surface sediments was significantly correlated with temperature, P concentration, pH, dissolved oxygen content of the overlying seawater, and iron content and organic matter content in the sediments.

Key words: Bohai Sea, arsenic, sediment, ecological risk.