# Sulfur Development in the Water-Sediment System of the Algae Accumulation Embry Area in Lake Taihu  
[PERSON]  
1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China 111 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese  
of P to phytoplankton increases when the release of P from the sediments increases under anoxic conditions [20; 21]; this usually occurs during algal blooms [22; 23; 24]. The formation of sulfides facilitates the formation of ferrous sulfide (FeS) and the release of P from the sediments [14], aggravating eutrophication and HABs in the water. This process usually takes place in freshwater sediments because of the low sulfate concentration of freshwater [14; 25]. However, in the overlying water, another problem is the formation of volatile sulfur compounds (VSCs) during HABs. Various VSCs, including hydrogen sulfide (H\({}_{2}\)S), methanethiol (MTL), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DITS), have been detected during HABs [26; 27; 28]. MTL, DMS, DMDS, and DMTS are also known as volatile organic sulfur compounds (VOSCs). The high concentration of VSCs causes freshwater sites to become more odorous [29; 30]. In 2007, a crisis occurred in Wuxi City, China, resulting from the accumulation of algae in Lake Taihu, the city's drinking water source, in which the tap water turned black and became odorous [31; 32]. High levels of VSCs were found to be responsible for the crisis [31; 32]. VSCs are difficult to remove from drinking water sources through conventional techniques due to the high cost and the residual of the processes required [33]. Therefore, it is imperative to understand the origin and formation of VSCs in drinking water sources such as lakes and reservoirs.  
Although the formation and migration of sulfides and VSCs have been noted and studied worldwide [28; 34], the development of these compounds in the water and sediment systems still remains unclear, especially in large and shallow eutrophic lakes with serious HABs. The overlying water in shallow lakes mostly maintains oxic conditions because of wind and benthic disturbance [35]. However, during serious HAB seasons, the high accumulation of algae in the water can lead to the depletion of oxygen in the water and sediments [23; 24]. These anoxic conditions lead to a reduction in sulfates and decomposition of algae [36]. The concentrations of sulfides and VSCs might increase accordingly [25; 27], particularly in algae accumulation areas. Nevertheless, some details still remain unclear: 1) The detailed development of these compounds in water-sediment systems during the algal bloom season with a high algae accumulation in shallow and eutrophic lakes; and 2) the detailed mechanisms for the formation and development of these compounds. In this study, a year-long investigation was carried out in an algae accumulation bay area in the hyper- eutrophic Lake Taihu to explore the development of reductive sulfocompounds related to eutrophication and HABs. An algae accumulation experiment was also carried out in the laboratory to further investigate the mechanisms for the development of sulfur in water-sediment systems. Information acquired in this study could be helpful for revealing the sulfur transport and transformation in algae accumulation areas in similar eutrophic shallow lakes and for the management of eutrophication.