Environmental Geochemistry On Arsenic And Antimony In Sediment-Water Interface Of Poyang Lake

Environmental pollution is one of vertical problems faced in 21 century. There are amounts of lakes located in China. Poyang Lake, which is the largest freshwater lake in China is the famous representation. Through the financial supports from The National Natural Science Foundation of China (Grant 20011766), The Excellent Young Teachers Program of MOE, P R China (Grant 40103009) respectively, the environmental geochemistry on trace and ultra-trace elements of As and Sb in the sediment-water interface (SWI) of Poyang Lake was investigated into details.The researched contents are including: (1)a sensitive speciation analysis method was established to measure the trace and ultra-trace elements of arsenic in porewater samples of sediments; (2) vertical profiles on As(III), As(V), As-org, Sb(III), Sb (V), Sb-org and dissolved ions of iron, manganese, S2- and pH value, total organic carbon (TOC) in the series porewater samples in the areas of Kangshan, Ruihong and Hukou, Poyang Lake, China were measured; (3)total arsenic, total antimony (expressed as TAs, TSb) in sediments, arsenic and antimony absorbed onto oxyhydroxides of iron and manganese (expressed as As-oxal, Sb-oxal), associated to organic matters (expressed as AS-H2O2, Sb-H2O₂), and arsenic and antimony existed in the crystallized sulfides (expressed as As-pyrite, Sb-pyrite) in different seasons respectively were extracted by a sequential extracted procedures, and then were analyzed; (4)vertical distributions on TFe, TMn, Fe-oxal, Mn-oxaLFe-H2O2, Mn-H2O2 respectively were also done; (5)total sulfur, acid volatile sulfur, minerals of sulfide and elemental sulfur in sediment samples in the different seasons were extracted and analyzed.Solutions presented in the project can be summarized as follows: it is the first time to discover that the masking agent of 8-hydroxyquinoline was found to be an efficient agent to eliminate interference of transition metals in the determination of arsenic species, especially to eliminate As(V) emission with high selection in the matrix of As(III) and As(V) coexisted solution. A sensitive and interference-free procedure has been successfully established for the arsenic speciation on As(III), As(V), As-org in porewater samples using flowing injection hydride generation atomic fluorescence spectrometry (FI-HG-AFS).We observed that the concentrations of arsenic species in porewaters were relatively high. With the change of the redox in sediments, it is easy to arose the second pollution in overlying waters for their diffusive upward. Arsenic is mainly absorbed onto iron and manganese oxyhydroxides in controlling the behavior of As. The effect factors of the transfer, cycle of arsenic are the redox condition at SWI, disturbance, and microbial action, etc. Arsenic has a directive signification of geochemistry characteristic in SWI because arsenic species are concentrated near the SWI and involved in a dynamic cycle with precipitation - dissolution - diffusion -reprecipitation of iron and manganese oxyhydroxides. Antimony was controlled by several factors and compounds, mainly with the dissolution of sulfide, sulfur complexation and microbials. Although the concentrations of Sb species were relatively much lower than arsenic, the seasonal changes are distinctness. The concentrations of inorganic and organic antimony were fearfully low because it is mainly controlled by sulfides in sediments. Although some new knowledge on geochemical behavior of antimony was achieved on the bases of antimony speciation analysis proposed in this supported projest, some uncertainties are still exised due to the effect factors are very complex located in SWI. The process and mechanism on antimony transfer and transport in SWI need to be further studied.