污灌条件下农田土壤重金属的空间变异与模拟

Spatial Variation of Heavy Metal Contents in Farmland Soils Under Permanent Irrigation from Polluted River Water

土壤重金属污染影响农田环境质量及食品安全。以天津市武清区北部农产品商品基地(包括10个乡镇)为例,运用地统计学方法和ArcGIS技术,分析了农田土壤中Cu、Zn、Pb、As、Hg5种重金属元素含量的空间变异性和相关性;借助最优空间插值模型模拟它们的空间分布特征。结果表明,Hg元素属于空间弱相关,Cu、Zn、Pb和As元素有中等程度的空间相关性。插值结果进一步表明,在研究区北部5种重金属元素含量均较高;Cu含量以北京排污河为中心,向其两侧递减;Zn和As含量呈岛状区域分布,高值区主要分布在排污河附近;Pb和Hg含量分布表现为北部和东南部较高,与污灌范围和强度有明显关联。其中主要污灌区大沙河乡的土壤重金属污染最为严重。

Heavy metal contents of farmland soils under permanent irrigation from polluted river water affect seriously the quality of farmland environment and food safety. In this paper, with Tianjin urban fringe zone （Wuqing County） as the case study, where the farmland was irrigated permanently using polluted river water, the spatial variation and distribution correlations of five heavy metals in farmland soils, including Cu, Zn, Pb, As and Hg are computed and analyzed based on geostatistics and ArcGIS techniques. The optimal spatial interpolation models of the soil heavy metals are discovered by means of the comparison analysis among the different interpolation methods, such as kriging and other certainty spatial interpolation methods. Then the distributions of the five soil heavy metal contents are mapped by using the optimal spatial interpolation models. The results show that the high values of the five heavy metal contents are located in the northern area of our research region, and Cu content in farmland soils decreases gradually with the irrigation distances along the sides of the Beijing sewage river. The contents of the soil Pb and Hg have high value centers in northern and southeastern area of this region. The high value centers of the soil Zn and As content are distributed just like some island shapes located in this region. Comparing with other towns, the administrative region of Dashahe town is the most serious polluted area in soil heavy metals, and here is the irrigated center using the polluted river water too.