Heavy Metal Pollution And Evaluation In Farmland Soil:a Case Study In Xintai City

Soil is the material base on which human being rely for existing and developing,it not only had the function of the green plants production but also was the natural place of purification for various pollutions. With the economic development rapidly,the industrial "three wastes" and city rubbish were more and more abandoned into the soil,which made soil received varying degree pollution. Xin Tai City is both an important grain base and an important energy sources ,as well as it is the mineral base of Shandong Province. It is one of priority area environment protection.It had important significance that strengthening investigation and monitoring of pollutants in soil and monitoring of soil environmental quality,which could prevents environment pollution and maintain the quality of soil environment and promote the sustainable use of soil resources. The farmland of Xin Tai City was studied mainly in this thesis. Eight villages and towns were selected from main grain production areas.Through field investigation and samples, 100 samples representatively were collected,the contents of Cu,Zn,Pb,Cd,Cr,Ni,As,Hg were determined.This study adopted the secondary standard of "Soil Environment Quality Standard " (GB15618-1995),used single polluted evaluation, integrative evaluation and fuzzy synthetic evaluation to assess contaminate degree and distribution feature of the heavy mentals in this area soil. According to multiple-factor pollution index,the farmland were classified in this area.Finally,the software ArcView3.2 was used for drawing graphics,and the space distribution picture of eight kinds of heavy metals were obtained. Following conclusion were achieved:Single polluted index show that there had no surpass standard in 100 samples and had accumulation to a certain extent in individual sample,single polluted index of Cu,Pb,Cr,Ni,As,Hg were all less than 1.But single polluted index of Zn and Cd were more than 1 in one and two sample and reached to light pollution,among which single polluted index of Cd in Xiajiayu of Gongli town was even more than 3 and reached to high grade pollution,where pollution of Zn and Cd in soil were very seriously.The average pollution index follow by Gongli>Xizhangzhuang>Tianbao>Zhaizhen>Guli>Yangliu>Loude>Guodu.The average pollution index of Gongli was more than 0.7, reached to alert level, Xizhangzhuang's and Tianboa's approached to 0.7.Apart from Zn and Cd, As and Cr in soil had a certain amount of accumulation,there had no a superscalar sample yet.The other average pollution indexs were all less than 0.7, soil quality grade were security.Through carring on the fuzzy generalized analysis to 100 sample points,the result showed: the quality grade of soil in Xintai were almostly first-level,but subordination degree were 0.5-0.6 in some towns.For example,Xihanzhuang village Xizhangzhuang town and Shanggongyu village Gongli town, etc. The change trend of soil contaminates was already very obviously. The soil quality grade of Yangliu was second-level,it's subordination degree was 0.517,Xiajiayu's was three- level, it's subordination degree was 0.556,it wasn't longer suitable for general agricultural use.The spatial distributions of 8 kind of heavy metals contents were drawn by means of ArcView3.2,The Figure show that : content distribution of Zn and Cd were similar very much,there had high accumulation in the certion area,which were corresponding with single polluted index and average pollution index of Zn and Cd in this area.The distributions of Ni and Cr were vary similarly in a certion samples,it should be Gaojiadian vallage Zhaizhen town, referencing map and single polluted index, average pollution index.But,the distributions of Ni and Cr was different in southwest area.The content of Cr was reduce gradually from the southwest to the eastern. The content of Ni was higher in northeastern part. The spatial distributions of Pb was almost contrary to Cr's. The distributions of Cu was more evener,it indicate that the external source contaminates was less in this area. As had no large areas of contamination,there only had concentration accumulation in individual area. In short, the spatial distributions of eight kind of heavy metals had their own characteristic and distribution regular.In general, according to comparing single polluted evaluation, integrative evaluation and fuzzy synthetic evaluation in soil, drown the conclusion that the pollution of soil was consistent on the whole. That is the pollution of Xiajiayu village was the most serious,next was Yangliu village.The pollution was mainly causes by Cd and Zn. The reason is Xintai is not only important energy mineral production base in central section of Shandong Province but also important industrial base of Taian.It was inevitable that development of economy lead to the reduce of environmental quality. In addition,there have some enterprises of weight pollution and high consumption energy,their pollution was most seriously and caused the degree of soil quality directly.