典型铅锌矿区水田土壤重金属污染特征

采用现场采样及室内分析测试方法,研究了岩溶地区某铅锌矿厂区下游水田表层土壤及典型剖面中Cu、Zn、Pb、Cd的污染特征及其在剖面上的垂向迁移特性。结果表明,厂区下游水田表层土壤Cu、Zn、Pb、Cd的含量范围分别为35-89 mg.kg^-1、1 440-11 100 mg.kg^-1、249-4 610 mg.kg^-1、8.3-61.6 mg.kg^-1。除Cu的污染程度较轻外,Zn、Pb、Cd的污染达到了中度到极重污染的水平,且以Cd的污染最为严重。沿灌溉渠往下,表层土壤受到的污染越来越小,污染指数呈下降趋势。Cu、Zn、Pb、Cd在典型土壤剖面上均呈现出极为明显的向下迁移趋势。在0-20 cm,4种重金属的含量均较大;从20 cm往下至180 cm,其变化趋势基本上是先升高后降低,向下迁移的浓度峰值均出现在60-120 cm,但各元素向下迁移的规律略有差异。Cd向下迁移浓度峰值出现的深度比Cu、Zn、Pb的要深。

Pollution Characteristics of Heavy Metal in Paddy Soil Near a Typical Pb-Zn Mining Area

The pollution characteristics of Cu, Zn, Pb, and Cd in downstream paddy soil near a typical Pb-Zn mining region in the karst area are investigated, and their migration regularity in the soil profiles is also studied. The results show that the contents of Cu, Zn, Pb, and Cd in topsoil（0-20 cm） are 35-89, 1 440-11 100, 249-4 610, and 8.3-61.6 mg·kg^-1 respectively. The topsoil is moderately and seriously polluted by Zn, Pb, and Cd, and excessively by Cd, only slightly by Cu. The contaminated degree in the topsoil decreases gradually along the irrigation channel and the pollution index indicates downward trend. In the representative soil profiles, Cu, Zn, Pb, and Cd transfer obviously from topsoil to subsoil, where their contents are larger than that in the topsoil, and from 20 to 180 cm their contents rise before reaching the peak of 60-120 cm, and then decline. There are some differences in the migration regularity among the four metals. The peak of Cd content appears in much deeper soil than that of the others.