金属矿业密集区广西南丹土壤重金属含量特征研究

Evaluation of heavy metal contamination in soils in mining-intensive areas of Nandan,Guangxi

为评估矿业活动对"锡都"南丹耕地土壤重金属含量的影响,并评估其潜在生态风险,分别抽样采集自然土壤、矿区和非矿区耕地土壤、尾砂及河流底泥样品72、172、129、24、6个,测定其As、Pb、Cd、Cu、Zn和Sb含量,并进行空间分布特征分析和风险评估。结果表明:南丹县土壤偏弱酸性,As、Pb、Cd、Cu、Zn和Sb的背景值均值分别为17.74、40.78、0.503、17.94、81.40、3.004 mg·kg-1,Cd背景值明显偏高,比全国土壤背景值高4.16倍;耕地土壤中82.0%的点位存在超标现象,Cd、Sb、As、Zn、Pb和Cu的超标率依次为79.1%、68.3%、56.8%、36.1%、22.8%和9.44%,矿区耕地土样中各重金属含量显著高于非矿区采集的土样;Sb和Cd对南丹县耕地土壤的生态风险贡献率最大,其中大厂镇、车河镇及刁江沿岸存在较高生态风险。南丹县耕地土壤重金属的污染来源主要是大厂和车河镇矿业活动,需要加强管控。

Nandan county is famous for its nonferrous metals in China,especially arsenic and lead.This study was conducted to investigate the concentrations of heavy metals in soil and to assess the ecological risks posed by elevated concentrations of heavy metals. Total 72 background soil, 301 farmland soil, 24 tailing and 6 sediment samples were collected to determine the concentrations of arsenic, lead, copper,cadmium, zinc, and antimony. Results showed that the geometric mean concentrations of As, Pb, Cd, Cu, Zn, and Sb in background soil samples were 17.74, 40.78, 0.503, 17.94, 81.40, and 3.004 mg·kg-1, respectively. Heavy-metal pollution of soil in Nandan County became serious. In 82.0% of the soil samples, more than one of those metals was higher than the Grade Ⅱ of National Soil Environmental Quality Standard（GB 15618—1995）. Specifically, there were 79.1%, 56.8%, 22.8%, 9.44%, 36.1%, and 68.3% of soil samples exceeding the standard for Cd, As, Pb, Cu, Zn, and Sb, respectively. Cadmium and Sb were priority control pollutants in Nandan County. Dachang Town and Chehe Town and the surrounding Diaojiang River coastal area showed high ecological risks. The heavy metal contamination of farmland soils in Nandan County happened in Dachang Town and Chehe Town.