云南沘江沿岸农田土壤磁测分析与重金属污染评价

Magnetic Analysis and Assessment on Heavy Metal Contamination in the Farmland Soil Along Bijiang River in Yunnan Province

沘江上游河段流经全国已知探明储量最大的兰坪铅锌矿区,河流深受矿业活动影响,为典型的重金属污染河流。本文通过对其沿岸农田土壤进行采样测试,研究了土壤磁化率的关系。结果表明,沘江沿岸农田土壤普遍受到重金属Zn、Cd污染,Pb污染主要集中在上游河段,土壤单项污染指数Cd>Zn>Pb,综合污染指数显示,沘江沿岸农田土壤达到重金属重度污染等级;磁化率与重金属Pb、Zn、Cd含量存在一定的正相关,说明磁化率测量在一定程度上可反映沘江沿岸农田土壤重金属污染状况。沘江沿岸农田土壤重金属污染的主要原因与兰坪铅锌矿产资源的开发有关,沘江在污染物的迁移、扩散中起主要作用。

Lanping Lead-zinc Mine is the biggest one in China. The upstream of Bijiang River is originated from the Laping Lead-zinc Mine. Therefore, Bijiang River was affected by mining activities of Lanping Lead-zinc Mine, and had become a typically polluted river by heavy metals. According to the measurement on the magnetic susceptibility and heavy metal pollution in the farmland soil along Bijiang River, the present situation of heavy metal pollution in the farmland soil was delineated, with a simple and effective method to classify the heavy metal pollution in farmland soil around mineral mining sites. The results indicated that： （1） The farmland soil along Bijiang River had all been polluted by Zn and Cd, while the pollution of Pb was mainly on the upstream. （2） For the single contamination index, the severity sequence was Cd〉Zn〉Pb. For the comprehensive contamination index, the soil pollution of heavy metals belonged to the worst grade. （3） A positive correlation between magnetic susceptibility and concentration of heavy metals Pb, Zn, and Cd in farmland soils was found along Bijiang River, which indicated that the magnetic susceptibility can be used to monitor the heavy metal pollution in the farmland soil along Bijiang River. （4） Obviously, it was the mining activities in Lanping County that caused the heavy metal pollution in farmland soils along Bijiang River. Bijiang River was the transferring and dispersing corridor of the heavy metals.The ecological security in the Bijing River catchment need much concern from the local people and government.