The Study On Mercury Pollution Features In The Surface Waters Of Huainan City

In this paper, according to the case that the atmosphere, soil and other environmental factors are to some extent been polluted by mercury in Huainan, which is a large-scale coal bases and a typical city of energy, we select some typical areas of natural surface waters(Gaotanghu and Hudajian in Datong region , Laolongyan reservoir in Tianjiaan region, Shijianhu in Xiejiaji region, Nihe in Panji region )to be the study object. By using the AMA254 mercury analyzer and AI3300 HG-atomic fluorescence spectrometer to determine the mercury contents in the sample of water and sediment, we studied the temporal and spatial distribution characteristics and endanger degree of mercury pollution of each water body. The results are as follows:1. The mercury concentrations in water during the two different seasons of wet period(August) and dry period(December)have some differences. The total mercury concentrations are summerwinter and the dissolved mercury are summer Shijianhu > Nihe > Laolongyan reservoir>Gaotanghu. The highest concentration of mercury is in Hudajian, with an average content of 138.5 ng/L, which exceed class III of the surface water environmental quality standard,indicating that Hudajian has been polluted to a certain extent. The mercury concentration of water in the remaining waters are within the class III of the surface water environmental quality standard.3. The total mercury contents in sediment during the two different seasons of wet and dry period have little differences. The contents of total mercury range from 0.0534mg/kg to 0.1346mg/kg. The average content of total mercury is in the following order: Hudajian > Laolongyan reservoir > Shijianhu > Nihe > Gaotanghu. Besides Hudajian close to the first class standard of soil environment quality (0.15mg/kg), others are greatly lower than it. Comparing with the Huainan soil background value, the mercury in sediment of each water body has a certain extent of accumulation and enrichment. The enrichment coefficients of Gaotanghu, Hudajian, Laolongyan reservoir, Shijianhu and Nihe are 2.33,5.73,3.0,2.56 and 2.43 respectively. Hudajian is most affected by mercury pollution, and this is relative to the coal-fired power plant, which is the nearest one to Hudajian.4. The speciation analysis of mercury content in sediment shows that: the residual state is the main form of mercury in sediment of each water body, the percentage of residual state ranges from 56.62% to 95.09%, and the average percentage is about 72%. The non-residual state accounts for less percentage, and mainly are sulphide - organic matter bound, which can only pose a risk through release in the strong oxidized conditions.5. The level of mercury pollution in water was evaluated by the standard index method, and the size order of the pollution index is: Hudajian > Shijianhu > Nihe > Laolongyan reservoir>Gaotanghu. The mercury pollution index of Hudajian is greater than 1, exceeding class III of the surface water environmental quality standard, which indicates that Hudajian has been contaminated by mercury. The pollution indexes of mercury in the remaining waters are smaller than 1, which is at security level, but all exceed 0.6, showing that the mercury in the water has become a potentially hazardous element, and attention needs to be sustained to prevent it from reaching the extent of pollution.The level of mercury pollution in sediments and the potential ecological risk grade were assessed by Hakanson assessment, and the size order of ecological risk coefficient is: Hudajian > Laolongyan reservoir > Shijianhu > Nihe > Gaotanghu. When using the highest background value of heavy metal of sediment before global industrialization as ratio to evaluate, the result is that the potential ecological harm levels of sediment are minor and at the security level, but while using the Huainan soil background value as ratio, the potential ecological harm levels of sediment reach to the strong grade, among them Hudajian reaches to the very strong grade. This show that in terms of Huainan soil background value, the mercury pollution of sediment in each water body has been in existence for a very strong enrichment phenomenon, and with the cumulative of time, the degree of risk will gradually increase, so the status of mercury pollution in sediment should be concerned continuously.