广西刁江沿岸土壤As,Pb和Zn污染的分布规律差异

Differentiation of As,Pb and Zn Pollution Distributions in Soils along Diaojiang River,Guangxi Province

分析了刁江流域矿区尾砂和上、中、下游地区土壤剖面重金属的含量.结果表明:刁江流域上、中、下游地区都不同程度受到As,Pb和Zn的污染.上游(距污染源16 km)表层土壤中w(As),w(Pb)和w(Zn)与尾砂相当,分别高达2.4×104,5.6×103和1.2×104mg/kg,下游拉烈和百旺(分别距污染源154和192 km)2个采样点表层土壤中w(As),w(Pb)和w(Zn)的平均值分别是《土壤环境质量标准》(GB15618—1995)三级标准的47.05,1.81和5.48倍.表层土壤中w(As)和w(Pb)随采样点距污染源的距离增加呈幂函数下降,w(Zn)呈线性下降,表明Zn在流域内的迁移能力大于Pb和As.土壤剖面中3种重金属的质量分数均随土层深度的增加呈降低趋势,在土壤剖面的迁移能力表现为Zn>Pb>As.总体上看,刁江流域土壤污染与尾砂中重金属的形态及其迁移特征密切相关,尾砂的排放控制和治理应该是刁江流域污染整治的关键.

Soil profiles of arsenic （As）, lead （Pb） and zinc （Zn） contents were investigated in mine tailings in the upstream, midstream, and downstream areas of the Diaojiang River valley. It was shown that the soils in the upstream, midstream, and downstream areas in the Diaojiang River valley were polluted by As, Pb and Zn to different degrees. The heavy metal concentrations in the surface soils in the upper reaches, 16 km from the mining site, were high up to 2. 4 × 10^4 , 5.6 × 10^3 and 1.2 × 10^4 mg/kg for As, Pb and Zn, respectively, which were close to the heavy metal concentrations in the mine tailings. The average concentrations of As, Ph and Zn in the two samples which were collected in the lower reaches, 154 and 192 km from the mining site, were 47.05, 1.81, and 5.48 times higher than the third grade soil environmental quality standard for soils （GB15618-1995）. The concentrations of As and Pb in the surface soils decreased following power functions with the increase of distance of the sample points from the mining site. Zn concentration decreased slower than Pb and Zn in a linear type, which might indicate that Zn had higher mobility than Pb and As when transported by river flow. Heavy metal concentrations decreased as depth of soil layer increased in soil profile. The mobility of the three heavy metals in the soil profile might follow the sequence Zn 〉 Pb 〉 As. In general, heavy metal pollution in the Diaojiang River valley soils had a very close relation to the speciation and transfer characteristics of heavy metals in the mine railings, so it should be the key to control mine tailing discharge and to clean mine railings from the river and the soils for the environmental remediation of the Diaojiang River.