| Coal-fired power plants provide powerful energy for the economic development of our country. However, environmental pollution problems highlighted caused by coal-fired power plants in China, with the continuous development of power industry, coal-burning pollution has brought environment pressure to our country, we should pay more attention to environmental pollution caused by coal-fired power plants. But for the study area of heavy metals and research on natural radioactivenuclide is relatively lacking. This research have important theoretical and practical significance in study of heavy metal and radiation monitoring and protection.Collected soil samples around two coal-fired power plants in Xi’an(Weihe CFPP and Yuxia CFPP), each sample have two layer 0-20cm(A) and 30-50cm(B). A series of physical and chemical properties of soil were measured, using X-Ray fluorescence spectrometer to determine the constants composition and levels of heavy metals in soil in the study area. Using modified BCR continuous extraction method to analyze the occurrence of heavy metals in soil samples form. Application of NaI gamma spectroscopy analysis of natural radionuclides content in the soil around coal-fired power plants. In order to provide reference for power plant impact on the environment, prevent and control pollution, this study mainly conclusion is as follows:(1) The physcio-chemical parameters average value of pH of soil around Weihe CFPP is 8.17, belong to alkaline soil environment. The average value of soil electrical conductivity is 360.58μS/cm, belongs to low salinity levels, sensitive crops have obstacles. The particle size composition shown that the soil composed mainly of 5-50μm/% particles is 63.0%. The standard deviation of a constant element SiO2 and Al2O3, low coefficient of variation are constant elements in soil.The average value of pH of soil around Yuxia CFPP belongs to the neutral environment. The range of soil electrical conductivity is 89.4-317.0μS/cm, average vale is 168.11μS/cm, belong to no salinity range, general and normal crop growth. Low content of calcium carbonate in the mean value of A and B layer were 0.40% and 0.56%, respectively. The particle size composition shown that the soil composed mainly of 5-50μm/%particles is 61.1%. Constant element content in soil of small change, only the content Al2O3 standard deviation is a little higher.(2) The content of Co in soil around Weihe CFPP in 0-20cm and 30-50cm is 2.74 times and 2.58 times than soil background values in shaanxi province, respectively. The content of Cr in 0-20cm and 30-50cm is 1.76 times and 1.86 times than soil background values in shaanxi province, respectively. The content of Cu, Mn, Ni and V are close to or slightly higher than that of soil background values in shaanxi. The content of As and Zn is not exceed the soil background values. The content of Co and Cr overweight multiples is the largest.The content of As in soil around Yuxia CFPP in 0-20cm and 30-50cm is 2.10 times and 1.95 times than soil background values of shaanxi province, respectively. The content of Co in 0-20cm and 30-50cm is 4.55 times and 4.24 times than soil background values of shaanxi province, respectively. The content of Cu is 1.54 times and 1.64 times than soil background values of shaanxi province, respectively. The content of Mn is 1.20 times and 1.25 times than soil background values in shaanxi province, respectively. The content of Ni is 1.36 times and 1.55 times than soil background values in shaanxi province, respectively. The content of Pb is 1.59 times and 1.43 times than soil background values in shaanxi province, respectively. In addition, the rest of the heavy metal content are higher than the background except the content of Zn, and the excessive multiples biggest is Co.(3) The unsteady state from of eight kinds of heavy metal in soil around Weihe CFPP order as follows:pb(83.68%)>Mn(76.27%)>Cd(74.34%)>Ni(57.16%)> Cu(56.88%)>Co(48.65%)>Zn(45.83%)>Cr(32.64%)。The acetic acid extraction state of eight kinds of heavy metal in soil around Yuxia CFPP order as follows:Co>Mn>Cd>Ni>Pb>Zn>Cr>Cu, Heavy metal Co, Mn and Cd extraction of acetic acid is higher, has certain environmental risk. The reducible and the oxidation state size order are Mn>Pb>Cu>Cd>Zn>Ni>Cr>Co and Cd> Zn>Co>Ni>Cu>Cr>Pb>Mn, respectively. Mn is mainly in reducible part and Cd can has the highest percentage of oxidation state.(4) The total potential ecological risk index of heavy metals in the soil around Weihe CFPP is A>B. From longitudinal, two layer are free from contamination-mild pollution, enrichment factor of the largest are Co, followed by Cr. In depth, the comprehensive pollution index average 2.16 and 2.34, respectively, belong to moderate levels, shows that soil plants are polluted by moderate, pollution load index was 1.18 and 1.19, respectively, belong to moderate levels of pollution.The Yuxia CFPP inside the heavy metals may average depth of comprehensive pollution index of 3.51 and 3.35, respectively, belongs to heavy grades, show plants are contaminated soil has been quite serious. The pollution load index is 1.62 and 1.60, respectively belong to moderate levels of pollution.(5) Weihe CFPP soil annual effective dose of coal-fired power plant in the average content of different depth are 0.089 mSv/y and 0.086 mSv/y, respectively. The Yuxia CFPP soil annual effective dose of coal-fired power plant in the average content of different depth are 0.104 mSv/y and 0.103 mSv/y, close to or slightly higher than the Xi’an annual effective dose rate.(6) According to the correlation analysis, factor analysis and clustering analysis, coal-fired power plants around the sources of heavy metals and radionuclides in soil is not the same, can be divided into three categories. The first is the Weihe CFPP is Co-Cr-231Th-226Ra-40K for they are artificial sources, mainly comes from coal-fired power plants, The second part is Cu-Pb-Zn, can be affected by the highway operation. The third part is As-Mn-Ni-V source of both are different from the other elements. How is mainly natural sources. Affected by the nature and influence is under the influence of traffic to them.The Yuxia CFPP soil the first part is Co, Cr,232Th,226Ra and 40K, they are the influence of human activity, mainly comes from coal-fired power plants. The second part is As, Mn, Ni and V, their main source for coal-fired power plants and natural factors mutual influence. The third part is Cu, Pb, Zn, May be affected by the surrounding traffic. |
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