滇西沘江流域水体中重金属元素的地球化学特征

Geochemical characteristics of heavy metals in water bodies and sediments of the Bijiang River drainage area,western Yunnan,China

通过测定流经兰坪金顶铅锌矿区的沘江水体中Pb、Zn、Cd、As的含量和底泥中重金属元素的化学形态的含量,分析了重金属元素的分布和化学形态的变化。结果表明,沘江水遭到了Cd污染,底泥已经成为重金属元素的蓄积库,以国家土壤环境质量标准(Ⅲ级)衡量,Pb、Zn、Cd和As分别超标3.4倍、15.8倍、106倍和2.6倍。沘江水中重金属元素含量的峰值在矿山附近的下游,而底泥中重金属元素的峰值在矿山下游30～50km的地方,矿业活动、水流变缓、pH等水体环境条件的变化都能影响水和底泥中重金属元素的含量。底泥中的Pb以碳酸盐结合态为主,Zn和Cd以铁锰氧化物结合态为主,而As以残渣态为主。Pb、Cd、Zn三种元素的环境有效态含量比较高,对沘江流域生态环境具有潜在的巨大的危害。

The contents of Pb, Zn, Cd and As in the water of the Bijiang River and the speciation fractions of heavy metals m bed mud were determined and the distribution of heavy metals and speciation changes were analyzed. Results show that the water has been contaminated by Cd, while heavy metals have been highly enriched in bed mud. According to grade Ill of the national environmental quality standards for soils, the contents of Pb, Zn, Cd and As are separately 3.4, 15.8, 106 and 2.6 times higher than the standards. The distributions of contaminants show that the peak of heavy metal contents in water lies in the lower reaches near the mine, while the peak of heavy metal contents in bed mud is located 30-50 km downstream of the mine. The mining activities, terrain, warming of water flow, pH and other water body environmental changes all can affect the contents of heavy metals in water and bed mud. In the bed mud, Pb mainly occurs as the carbonate binding state and Zn and Cd as the Fe-Mn oxide binding state, while As mainly occurs as the residual state. The contents of environmental available states of Pb, Cd and Zn are relatively high in the Lanping area, which has great potential danger to the eco-environment of the Bijiang River drainage area.