重庆土壤铅含量污染评价及其影响因素分析

对重庆市8个区县160个表层土壤样品进行铅（Pb）含量分析，探讨土壤Pb含量特点及其影响因素，并运用地积累指数法对各区县表层土壤Pb污染作出评价。结果表明：全部供试土壤样品的Pb浓度几何平均值为37．30mg／kg，显著高于重庆市土壤Pb背景值（22．20mg／kg），表现出一定的积累趋势。pH值是影响土壤全Pb含量的重要因素，当pH≤6．5和pH≥7．5时，随着pH值的增大，土壤全Pb含量增加；而6．5〈pH〈7．5时，随着pH值的增大，土壤全Pb含量减少。在供试样品有机质含量范围内，随着有机质含量的增加，土壤全Pb含量呈线性增加。总体上看，重庆市8个区县表层土壤Pb污染为轻度至中度，其中秀山县Pb污染最严重，达到中度污染水平。

An assessment of lead content in soils and the factors influencing its accumulation in Chongqing

In the present study, lead content of 160 surface soil samples taken from 8 districts （counties） in Chongqing were analyzed to determine the total Pb content in soil and to study its influence on the surface soil by geo-aecumulation index method. The results showed that the average total lab content in soils collected from different districts of Chongqing was 37.3 mg/kg, which was significantly above the Pb background value in soil of Chongqing （22.2 mg/kg）. The pH of the soil was found to be the important factor affecting the Pb accumulation in soil. The total Pb content in soil was found to be increased at pH ≥ 6.5 and pH ≤7.5. Furthermore, it was also found that total Pb content increased linearly with the increase in organic matter in soil. The data revealed that the Pb pollution in soils collected from Chongqing was from light to moderate, while it was severe in soils collected from Xiushan County.