Temporal and spatial variations of sulfur speciations in the sediments of algae accumulation area in Lake Taihu

The variation of sulfur (S) in the sediment has been proven to be closely related with the break of black and odorous water incidents in various previous studies. However, information on the variations of S speciations in the sediments of algae accumulation area, which is also black and odorous prone area, was still limited. In this study, sediment cores were seasonally sampled from the Zhushan Bay, which is an algae accumulation aera in Lake Taihu. The sediment cores were analyzed for S speciations and distributions using chemical sequential extraction combined with synchrotron radiation X-ray absorption near-edge structure (XANES). The results showed that the distribution of S in the sediments exhibited a significant seasonal difference, with a significant higher content of reduced S in summer rather than that in spring. The extracted S speciations showed that the averaged acid volatile sulfur (AVS) and pyrite-S concentrations in the sediments of algae accumulation area were 12.7 and 4.16 times of those in the non-algae accumulation area, indicating that algae stimulated the formation of reduced S. The S-XANES results also showed that the average percentage of FeS, FeS2, and ES in sediments of algae accumulation area were significantly higher than those in the non-algae accumulation area. Results of the above two methods indicated that the strong reducing sediment environment in the algae accumulation area accelerated the transformation of S to ferrous sulfide, which is conducive to the formation of stable pyrite. The averaged humic sulfur (HS+FS) in sediments of algae accumulation area were 1.53times of that in the non-algae accumulation area, with mercaptans and thioethers to be the main components of organic sulfur. The research showed that the content of reductive and organic sulfur in sediments of algae accumulation area were significantly higher than those in the non-algae accumulation area, which might be one of the main causes of the occurrence of black and odorous water. Therefore, it is necessary to enhance the management of sediments in the algae accumulation area. © 2017, Editorial Board of China Environmental Science. All right reserved.