宁夏干旱地区工业区对农田土壤重金属累积的影响

随着我国东部沿海地区产业向中西部地区转移,曾经被冠以"净土"的西北干旱地区受到了工业排放污染的威胁.本文以宁夏某县枸杞种植地为研究对象,采用GIS技术,以工业区为中心,结合当地主导风向,沿着黄河进行带状布点采样,分析工业区的建立对农田土壤重金属Zn、Cr、Ni、Mn、Co、Cu、Cd、Pb污染的影响.结果表明,研究区农田土壤重金属累积程度较轻,只有少数样点发生人为Zn和Cd累积;工业区土壤中除了Ni元素以外,其它7种元素都有累积,其中Cd元素浓度达到污染水平的样点占总样点数三分之一.空间分布格局分析结果表明,枸杞地土壤中Cd、Zn、Cu、Mn和Pb等5种元素的分布与工业区位置有较强的相关性.从土壤重金属含量的角度来看,研究区的工业区影响还未造成枸杞地土壤重金属污染,并且由于该区域土壤的pH值普遍较高(平均pH值为8.54),因此,可以认为目前还不存在农田土壤重金属污染问题.但是工业区对农田土壤中重金属累积趋势的影响较为明显.此外,工业区对灌溉水中重金属元素的浓度也有一定影响.

Impacts of Industrial Zone in Arid Area in Ningxia Province on the Accumulation of Heavy Metals in Agricultural Soils

With the transferring of the industry from the east coastal regions of China to the mid and west regions, those places once called "Clean Earth" in the arid north-west region are facing the contamination risks by industrial emission. In order to study the impacts of the industrial zone on the accumulation of heavy metals Zn, Cr, Ni, Mn, Co, Cu, Cd, Pb in agricultural soils, we collected the agricultural soil samples in a county in Ningxia province using GIS technology. Samples were collected in a belt way along the yellow river and expanding from the industrial zone as the center according to the main local wind direction. It was suggested that the accumulation of heavy metals in studied agricultural soils was slight. High accumulation of Zn and Cd only occurred in several sites. However, the accumulation of heavy metals in industrial zone was more apparent. Except for Ni, the rest 7 elements had obvious accumulation. One third of the sites had Cd concentration at contamination level. The spatial analysis revealed that the distributions of Cd, Zn, Cu, Mn, and Pb were closely related to the location of industrial zone. Industrial zone had not caused the contamination of heavy metals in agricultural soils yet. Due to the high pH value (average pH value of 8.54), no soil contamination issue was found at present. However, the impacts of industrial zone on the accumulation of heavy metals in agricultural soils were apparent. The input pathway of heavy metals into agricultural soils was mainly dust deposition. The industrial zone also increased the heavy metal concentrations in irrigation water to some extent.