Study On Heavy Metal Pollution In Topsoils Around A Power Plant

In order to research the heavy metal pollution in topsoils around a power plant, a sample collection scheme is made up and soil samples are collected after the field survey, and analytical tests for the issues of soil water content, value of p H, cation exchange capacity, content of eight kinds of heavy metal elements and so on are conducted based on some pertinent soil contest standards.Statistical analysis for the soil data is carried out, and based on Spatial Variation Theory of Geo-statistics, the semi-variance functions are calculated and optimal fitting models are chosen to study the spatial variability of heavy metals in topsoils around the power plant. Based on the Kriging Interpolation Method, a spatial interpolation is taken, the spatial variability of heavy metals is simulated and spatial distribution figures of heavy metals are drawn.The gray incidence degree from the perspective of closeness is introduced and refined to adjust to evaluate the degree of heavy metal pollution in soils. Besides, a quantification index, Gc, is established, which uses the improved grey incidence model from the angle of closeness to evaluate the degree of heavy metal pollution. According the environmental quality standard for soils, with the improved grey incidence model from the angle of closeness applied for evaluating the heavy metal pollution degree of soil, it is found that the heavy metal pollution in foremost area around the power plant is mostly higher than second degree, and heavy metal content in some soils is very high and is evaluated as third pollution degree. Based on comparisons between the improved grey incidence model from the angle of closeness and some other methods, the results show that the improved grey incidence model from the angle of closeness has a relative strict result, the general Gray Incidence Model has a relative loose result, and the Pollution Load Method and the Weighted Average Fuzzy Mathematical Model have a similar comprehensive evaluation results.The potential ecological risk degree of heavy metal in soils is evaluated through the Potential Ecological Risk Index. The Single Factor Potential Ecological Risk Index of Mercury is very high in general, and the ecological risk of Cadmium in 15.6 percent of soil samples manifest as general risk, whereas the six other kinds of heavy metal, including Arsenic, Cuprum, Lead, Chromium, Zinc and Nickel, manifest as no ecological risk. The evaluation results of the Integrated Potential Ecological Risk Index show that the potential ecological risks of most soil samples are general risks or even higher risks, and Mercury plays a dominant role in the calculation of integrated potential ecological risk index.Source identification of heavy metal is carried out adopting the multivariate statistical methods, such as correlation analysis, cluster analysis, principal component analysis, and factor analysis. The impact of the power plant is mainly reflected by Factor 1, called coal combustion factor. The effect of transportation is reflected by factor 2, named traffic factor. The influence of agricultural production and daily life is reflected by factor 3 known as life and agricultural factor. The influence of natural and geological factors is reflected by factor 4, called natural factor.