| 'Storage of water river'ecosystem is a typical'Mercury-sensitive ecosystems'. Rivers in the world are widely affected by damming the background of large reservoirs on the rivers of mercury biogeochemical cycles of the study, which has been received widespread international attention. Reservoirs formed by damming are the environment which found to be conducive to the activation of mercury, methylation and bioaccumulation place. The sensitivity of mercury transformation and (methyl) mercury pollution in the reservoir, forcing us had to re-examine the ecological risk of mercury pollution of the river water.In this article we studied the 6 reservoirs in different evolution stages of the Wujiang River between the year 2006 and 2009, and we also carried out a systematic observation toward the concentration of different forms of mercury in the river inflows and outflows of the reservoir(January,2006 to June,2007, Guo Yanna; July,2007 to September,2007, Xie Wen; October,2007 to September,2008,Yang Fang; October, 2008 to December,2009, the author).Different reservoirs of mercury in the basic data were provided; we also discussed the construction of reservoirs on the river morphology of mercury. There are three main research topics in this thesis, (1) Characteristics of mercury speciation and distribution inflows and outflows of six reservoirs; (2) the concentration of mercury in precipitation. Based on the detailed researches, the main conclusions we have obtained are as follows:1.The mean annual concentration in four years of total, particulate, dissolved, reactive, total methyl and dissolved methyl mercury in Wujiang River was 5.56±14.0, 0.29±0.32,3.33±12.05,1.70±1.63,0.12±0.11,0.07±0.05ng/L, respectively. Compared to published data from foreign countries, concentrations of THg were significantly lower than values in polluted rivers, and slightly higher than values in unpolluted rivers. Concentrations of DHg, RHg, and TMeHg were slightly lower than those in Hg-impacted rivers, and similar to levels in uncontaminated rivers. Compared to Songhua River, Huangpu River and the remote Brahmaputra, mercury levels were significantly lower.2. From the year 2006 to 2009, the weighted average concentration of total mercury and methylmercury can be drawn the maximum appear in 2008 of the four years. Combined with sampling month and sampling sites comparative analysis, this phenomenon may attribute to the deep-freeze disaster and earthquake in 2008. The average annual change concentration of methylmercury inflows and outflows of the reservoir (except for Hongjiadu reservoir) showed a current decrease year by year from 2006 to 2009. Compared with the weighted average concentration of total mercury inflows and outflows of the reservoir, the total mercury found in reservoirs took on a "clear" function, especially in Puddings and Hongjiadu reservoir in the upstream of Wujiang River.3. Due to the construction of reservoir, concentrations of THg and PHg in outflow rivers decreased, while concentrations of TMeHg and DMeHg increased, and elevated ratio of DHg, RHg, TMeHg to THg also appeared in outflow rivers. Distribution of Hg along the Wujiang River showed that construction of cascade reservoirs influenced the initial biogeochemical cycling of Hg, and concentration of methyl mercury increased at several sites below reservoir. Therefore, it is possible that MeHg would increase with the evolution of reservoir.4. The concentration of THg and TMeHg are 47.54±29.91,0.13±0.11ng/l, respectively. From 2006 to 2009, the total mercury and methylmercury count showed a weighted average concentration decreased year by year, and marked seasonal trend, winter and spring higher than summer and autumn; Analysis of variance spatial distribution of total mercury was significantly higher, and there is no significant difference spatial distribution of methylmercury. The concentration of Methylmercury is roughly equal to the Long Island Sound lake and Superior lake in the United States. |
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