Antimony speciation at the sediment-water interface of the Poyang Lake: response to seasonal variation

In order to identify the effects of seasonal variation on the migration and transformation of antimony species at the sediment-water interface of the Poyang Lake, the largest fresh lake in China, a simulation study was carried out in the laboratory. Antimony species including antimonite Sb(III), antimonate Sb(V) and the fraction of organic forms (Sb-org) in overlying water at different temperatures were regularly measured during the simulation period. Different bound antimony forms in sediments were also determined along with the different antimony species in porewaters after the simulation terminated. The results indicated that temperature change during seasonal alternation plays an important role in the migration and transformation behavior of antimony at the sediment-water interface of the Poyang Lake. Antimony species both in porewaters and overlying water were sensitive to the variation of temperature, especially the Sb-org species. Antimony migrates from porewaters to the overlying water when the temperature decreases, and meanwhile the equilibrium between Sb(III) and Sb(V) in porewaters shifts toward Sb(V) when the temperature increases during seasonal alternation. Although temperature had less influence on the antimony species in sediments than in porewaters or in the overlying water, the average content of each antimony species in sediments increased with the decrease of temperature, suggesting that the decrease of temperature causes enrichment of antimony in the sediment.