湘潭市郊响水乡稻田土壤重金属污染评价及空间分析

Assessment and Spatial Variability of Heavy Metal Pollution in Paddy Soils in Suburban Xiangshui Township of Xiangtan City

城市郊区农田重金属污染已成为人们关注的焦点,研究以湘潭市郊响水乡稻田土壤为研究对象,对其重金属污染程度进行评价,并利用地统计学中的半方差函数模型分析其空间分布特性。结果表明:湘潭市郊响水乡稻田中,土壤Hg的理论模型为指数模型,土壤As、Cd、Pb的理论模型为高斯模型,土壤Cr的理论模型为球状模型;土壤Hg、Pb和Cr含量的基底效应分别为1.2%、9.7%和22.4%,表现出强烈的空间相关性;土壤Cd含量的基底效应为32.4%,具有中等的空间相关性;土壤As含量的基底效应分别为87.4%,表现出较弱的空间相关性;采用单项污染指数评价法发现响水乡土壤重金属的污染程度依次为Cd>As>Hg,Cr和Pb无污染;采用内梅罗综合污染评价法发现研究区西南部污染较高,西北和东部次高,中心部、北部和西部污染较低。

Heavy metal contamination in agricultural fields has been serious in suburban regions. Geographical information system combined with geostatistics was applied to reveal the evaluation and spatial variability of heavy metal pollution in suburban paddy soils in Xiangshui township of Xiangtan city. The results indicate that theoretical semivariogram models of soil Hg were best described with exponential model; whereas soil As, Cd and Pb, with gaussian model; and soil Cr, with spherical model. The ratios of nugget to sill of the soil Hg, Pb and Cr were 1.2%, 9.7% and 22.4%, respectively, with strong spatial correlation. The ratios of nugget to sill of the soil Cd were 32.4%, with a moderate spatial correlation. The ratios of nugget to sill of soil As were 87.4%, with weak spatial correlation. According to the assessment result with single factor pollution index, the pollution degree for three kinds of heavy metal means： Cd〉As〉Hg, and there are not pollution of Cr and Pb in soil. According to the assessment result with Nemerow index, the area of high soil compound pollution lies in the southwest, the area of moderate soil compound pollution in the northwest and east, and the area of low soil compound pollution in the center, north and west.