矿区农田土壤重金属分布特征与污染风险研究

对渭北旱原矿区130个农田土壤样品的Cd、Cr、Cu、Pb、Zn含量进行了测定,结果显示,Cd、Cu、Pb平均含量均高于陕西省土壤背景值,而Cr和Zn含量低于背景值。利用地统计方法得到的土壤重金属含量分布图显示,土壤各重金属含量由西向东呈下降趋势,水泥厂周边土壤重金属含量最高。相关性分析和主成分分析结果表明,5种重金属之间呈极显著正相关,说明其存在较高的同源性或复合关系。第1主成分主要由Cd构成,且主要反映了人为活动的影响,而第2主成分中的Cr所占负荷最高,体现了成土母质的作用,Cu、Pb和Zn含量受人为活动和成土母质共同影响。分别利用污染负荷指数(PLI)法和潜在生态危害指数(PER)法对研究区域土壤污染风险进行了评价,评价结果为煤矿区呈无污染或轻微到中度污染,水泥厂区土壤呈中度污染水平,单一元素污染程度由高到低依次为Cd、Pb、Cu、Cr、Zn。

Distribution of Farmland Heavy Metals and Pollution Assessment in Mining Area

Shallow brackish water is widely distributed throughout north and northwest China and could be rational used. To evaluate the spatial distribution and variability of cotton field salinity under mulched drip irrigation with brackish and fresh water in southern Xinjiang, electromagnetic induction EM38-MK2 was applied to measure the apparent soil electrical conductivity. Statistical characteristics of soil salinity from the interpretation models of soil salinity showed that the scenario of brackish water irrigation had the higher salinity level and the lower variation coefficient than the fresh water irrigation. The optimal semi-variance models of brackish water and fresh water irrigation were exponential and Gaussian models respectively. Both models were characterized by strong spatial correlation. Compared with fresh water irrigation, the scenario of brackish water irrigation with the higher salinity level had the lager range variation and increased the spatial dependency of soil salinity. The spatial distribution of field salinity interpolated by Kriging method showed that both scenarios of brackish and fresh water irrigation had some filed parts with high salinity level, which would affect cotton emergence. EM38-MK2 would be suggested to investigate the field salinity distribution. According to soil salinity levels of different parts, amount of fresh water of flood irrigation for leaching salinity could be defined to save water and ensure the agriculture production.