某锌厂周围表层土壤及典型剖面镉污染特征

研究某锌厂周围表层土壤和典型剖面中的镉含量(w(Cd)),采用单项污染指数法评价了表层土壤中镉的污染状况.结果表明:距锌厂较近或在主导风向上的采样点w(Cd)较高,最大值为248.72 mg/kg,最小值出现在距锌厂10 km处的非主导风向上,为0.52 mg/kg.距锌厂1 km处的剖面最上层(0～2 cm)w(Cd)为593.23 mg/kg,下层(60～110 cm)仍达到55.16 mg/kg,距锌厂10 km处的剖面上层w(Cd)为0.3～3.14 mg/kg,下层接近背景值或未检出.根据土壤环境质量标准的二级标准评价,除一个采样点为中度污染外,其余都达到重度污染水平.据分析,污染主要来源于锌厂烟囱的排放、废气废液的不规则排放和未被覆盖的原料堆.表层土壤镉含量分布规律显示,镉的污染程度与距锌厂的距离和当地的风向有关;镉在土壤中能到达的深度与镉在表层土壤中的含量有关,表层土壤含量越大,向下迁移越容易. 

Studies on Cadmium Contamination of Topsoil and Soil Profiles around a Zinc Plant

The distribution of Cd concentration in topsoil(0～20 cm) and soil profiles around a zinc plant were studied,and Cd pollution was evaluated by the method of monomial pollution index.Cd concentrations in topsoil are in the range of 0.52～248.72(mg/kg),and the samples in the prevailing wind direction or near to the zinc plant have higher Cd concentration.In the soil profile,1 km far from the zinc plant,the Cd concentration of topsoil(0～2 cm) reaches 593.23(mg/kg),while that of subsoil(60～110 cm) reaches 55.16(mg/kg).In the other profile,10 km far from the zinc plant,topsoil Cd concentrations are 0.3～3.14(mg/kg),and that of subsoil are close to the background value or not be detected. The topsoil pollution evaluation shows that Cd concentration in all samples exceeds the moderate level,most of which are even over the heavy level.The primary sources of contamination may be from stack emissions,fugitive missions from zinc plant,or wind blown material from uncovered piles of process material.The spatial distribution of Cd concentration is related to the distances from the zinc plant and the prevailing wind.Vertical transport of Cd is influenced by the concentration in surface horizon,and the depth reached by Cd has a tendency to increase with the Cd concentration in surface horizon.