在云南某铅锌矿冶炼厂周边农田,采集当地主要绿肥(苕子)与野菜(荠菜)的植株和根部土壤样品,测定重金属(Pb、Zn、Cu和Cd)的全量和DTPA提取的有效态质量比,并进行污染评价。结果表明:1)综合污染指数评价显示,铅锌冶炼厂周边农田土壤以重度和中度重金属污染为主,Cd质量比为GB 15618—1995《土壤环境质量标准》三级标准限值的1.94~8.30倍,污染程度最重,其次为Pb和Zn;2)荠菜植株Pb、Zn和Cd质量比的最大值、平均值均大于苕子;荠菜对Cd的富集系数大于1,对Pb、Zn和Cd的转移系数大于或接近1;3)苕子和荠菜地上部与土壤的Cd、Pb质量比,苕子地下部与土壤的Pb质量比,荠菜地上部与土壤的Zn质量比均呈显著或极显著正相关。研究表明:铅锌冶炼厂周边农田存在严重的重金属污染,Cd是主要污染因子;苕子和荠菜植株重金属质量比高,且荠菜对重金属的富集能力大于苕子。
The paper is attempting to report the study results of its investigation on the heavy-metal pollution features and their effects on the growth of some vegetables around a lead-zinc smelter in Yunnan. The samples we have gained from some wild vegetable( Capsella bursa-pastoris and a green manure( Vicia sativa L.) from the farmlands around the said lead-zinc smelter. We have done carefully planned analysis of the normal and DTPA-extractable contents of such heavy metals as Pb,Zn,Cu and Cd)in the samples. The results of our investigation and analysis indicate that:( 1) The farmlands around the lead-zinc smelter have been moderately or severely polluted by heavy metals. To be sure,Cd is the top element that has heavily polluted the soils of the farmlands,that is,1. 94 to 8. 30 times as much as the standard EQSSC level III( short for the environmental quality standard for soil of China( GB 15618—1995) via the Nemerow integrated index.( 2) The content rate of Pb,Zn and Cd,including that of the maximum and average in Capsella bursa-pastoris( L.) Medik,also proves higher than that in Vicia sativa L. Taking Capsella bursa-pastoris( L.) Medik for example,the content rate of Cd turns out to be greater than 1,whereas its transferring factor for Pb,Zn and Cd is greater than or close to 1.( 3) Noticeable or conspicuous positive correlation with Cd and Pb content rate has been found between the ground-surface plants and the root ones for Vicia sativa L. and Capsella bursa-pastoris( L.) Medik in the aforementioned soils. Thus,it can be concluded that the heavy metal pollution and contamination proves to be serious in the farmlands around the smelter with Cd being the chief pollution maker. The heavy metals content rates in Vicia sativa L. and Capsella bursa-pastoris( L.) Medik turn out rather high,with the content degree of Capsella bursa-pastoris( L.) Medik being heavier than Vicia sativa L.