| The reservoir is a typical "mercury sensitive ecosystem", it causes environmental mercury pollution problem, and has become a hot topic in related disciplines. Three Gorges Reservoir is a large artificial control reservoir, it’s normal water level elevation175m, level of flood control is145m, then this reservoir regulation makes the reservoir to form a vertical height of30m, an area of400km2water-level-fluctuating zone(WLFZ). on the other hand, WLFZ soil periodically stayed in the long-term wet-dry cycles, and soil properties such as pH, CEC, organic matter, microorganisms will change. Soil and water environment transformation will affect the migration and transformation of mercury, especially the methylation, further affecting the quality of the reservoir ecosystems. It is also an important issue worth exploring.Therefore, in this study, the hinterland of the Three Gorges Reservoir area of Fuling, Zhongxian and Kaixian has selected4representative sampling points, respectively, Fuling District Zhenxi Town Shuikou village (S1), Zhongxian Tujing village Ping Shan (S2), Zhongxian Shibao Zhai Xinzheng village (S3) and Kaixian Hanfeng Lake (S4), of which, S1and S3point is located in the Yangtze River, S2and S4were located in the reservoir tributaries Ruxi River and the East river. Samples were collected in2011September to2012June, at sampling time, according to different contours and soil utilization types of hierarchical collection of one samples (sediments), were collected519soil (sediment) samples. Analysis of total mercury, methylmercury content and the physicochemical properties, discussed the Three Gorges Reservoir water-level-fluctuating zone soils (sediments) dynamic characteristics and influencing factors of total mercury and methylmercury, it aims to provide a reference for understanding the environmental geochemical processes and ecological risk of mercury. The results are as follows:In this study, the Three Gorges Reservoir soil (sediment) the mean MeHg content were distributed between0.195and0.779μg/kg, the mean total Hg content were distributed between33.074and55.427μg/kg. MeHg and total Hg mean content were respectively0.455μg/kg,51.704μg/kg.it is all lower than in most parts of the world. MeHg and total Hg showed the highest value in June. The formation of this summer to methylmercury.In four samples of this study, the sequence of soils (sediments) mean THg contents is S1(70.384μg/kg)>S3(64.679μg/kg)>S4(57.651μg/kg)>S2(14.102μg/kg),it explained Three Gorges Reservoir Area soils (sediments) THg contents greater than tributaries’. The sequence of MeHg is S4(0.540μg/kg)>S3(0.470μg/kg)>S2(0.406μg/kg)>S1(0.405μg/kg). THg and MeHg content space distribution law is inconsistent. On the vertical direction, except of S4, the other three plots, the soil (sediment) MeHg content were concentrated between0and1.000μg/kg, the larger value is typically appears in the surface layer of0to5cm or5～10cm, minimum in20cm.Different locations surface soil (sediment) of MeHg in different level elevation showed significant difference,with the flooded time increasing, the surface soil (sediment) MeHg content does not keep increasing or decreasing trend. It showed no obvious correlation that the surface soil (sediment) MeHg content with elevation or submerged time.Paddy soil (sediment) total mercury content was43.004μg/kg, significantly higher than the vegetable’s, the eucalyptus forest soil (7.761μg/kg) showed minimum. Vegetable soil(sediment) MeHg content were0.493μg/kg, much higher than that of the two others, eucalyptus forest soil (sediment) MeHg content were0.170μg/kg showed a minimum.MeHg content and soil (sediment) texture of soil (sediment) showed significantly or very significantly correlation in different land use patterns. The paddy soil of pH and MeHg showed a highly significant correlation. Methylation rate and CEC showed a significant correlation in the paddy soil and eucalyptus forest soil, while the texture of eucalyptus forest soil (sediment) also showed highly significant correlation.This study will provide scientific basis to explore the activation effect of mercury and its arising ecological and environmental problems after the Three Gorges Reservoir impoundment, and it has the potential theoretical significance. |
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