Interaction And Environment Effect Of Selenium And Mercury Interaction In Freshwater Aquiculture Zone Of Tianjin

As to the toxic heavy metal elements, mercury (Hg) can be enriched and transported through food chain,and eventually cause serious threats on organisms and human being.While, selenium (Se) has obvious antagonism and suppression effect on the toxicity and methylation processes of mercury. Therefore, selenium and mercury in aquiculture area of Xiqing District, Tianjin, China were chose in this thesis, which were carried out through a series of studies on the migration and transformation of different selenium and mercury species in the microsystem among fish, water and sediment in aquiculture area and the interactions between different species of selenium and mercury by liquid chromatography coupled hydride generation atomic fluorescence spectrometry (LC-HG-AFS), fourier transform infrared spectrometry (FT-IR) and microcalorimeter. These results obtained in this study can be contributed to guide the environment pollution problems of prevention and abatement of mercury. Main conclusions in this work were summarized as following:(1) The simultaneous analytical method for Se(Ⅳ), Se(Ⅵ), SeMet, SeCys and Hg(Ⅱ),MeHg, EtHg was studied by the LC-HG-AFS technique. The results showed that neither single nor multidimensional liquid chromatography can achieve effective and simultaneous separation between different selenium and mercury species. Therefore, the determination for selenium species or mercury species in aqueous samples can be analyzed separately only based on sigle elemental speciation analysis method of LC-HG-AFS.(2) The interaction between different selenium and mercury species in aqueous solution at 25.0℃ was investigated by BT 2.15 microcalorimeter, and the samples were also analyzed before and after mixing by FT-IR and LC-HG-AFS. The results showed that there is obvious interaction between different selenium and mercury species, and all these processes are in exothermic processes. It was found that the characteristic peaks of Hg(Ⅱ)and Se(Ⅵ) disappeares from the FT-IR spectrogram after the interaction, while new vibrational frequencies at 870.37 cm-1 and 1090.27 cm-1 are presented. The reaction heat between Hg(Ⅱ) and Se(Ⅵ) is 14.017 kJ/mol, while it is only 1.488 kJ/mol for that between Hg(Ⅱ) and Se(Ⅳ), meanwhile no new functional groups are presented in the FT-IR spectrogram. The reaction mechanism between Se(Ⅳ) and MeHg is similar to that between Se(Ⅵ) and MeHg, and there are new vibrational frequencies in the FT-IR spectrograms for both solutions.(3) The species and content of selenium and mercury in the microsystme of water,sediments and fish collected from wild and aquiculture fishponds of Xiqing District in Tianjin were determined. The results revealed that the total selenium (TSe) and total mercury (THg) concentrations in each component of wild area are higher than those of aquaculture area, and that selenium concentration is obviously higher than mercury concentration in water of both ponds. The residual chemical fraction of a sequential extraction treatment is the main occurrence form for selenium in sediments of both ponds,whereas the oxidizable form is the dominant species for mercury, suggesting that the release of mercury is easier than that of selenium from sediments to water with the environmental conditions change. But the molar ratios of TSe:THg are much larger than 1 in water and sediments, which demonstrates that selenium can effectively prevent toxicity and methylation of mercury.