渭河宝鸡段表层沉积物重金属污染研究

Heavy Metal Pollution in Surface Sediment of Wei River(Baoji),China

采用现场采样及室内分析方法,在对渭河宝鸡段表层沉积物基本理化性质分析的基础上,研究了沉积物中重金属的含量、赋存形态及迁移特征,并进行了污染评价。结果表明,沉积物中Zn、Co、Cd和Hg的平均含量均高于世界、中国和陕西土壤元素背景值,其中Cd（中国和陕西土壤元素背景值的4倍）和Hg（中国和世界土壤元素背景值的7~8倍、陕西土壤元素背景值的16倍）尤为突出。Cr、Ni、Zn、Cu和Co在沉积物中主要以残余态形式存在（50%以上）,Pb主要以可还原态形式存在（近55%）,Mn和Cd主要以乙酸可提取态形式存在（近50%）。重金属迁移顺序为Mn（56.70%）≈Pb（56.65%）〉Cd（53.66%）〉Co（48.82%）〉Cu（43.99%）〉Zn（21.93%）〉N（i15.49%）〉C（r11.43%）,其中Mn、Pb、Cd、Co和Cu的危害较大,有近45%~60%可以发生迁移转化。污染评价结果表明,沉积物主要受到Cd和Hg污染,具有高的潜在生态危害。

The physicochemical properties of surface sediment in Wei River（Baoji） were studied by pH meter,muffle,susceptibility meter,and laser granularity meter.The results showed that the mean values of pH,χLF,χHF,χFD and LOI in surface sediment were 8.64,55.2×10-8 m3·kg-1,54.2×10-8 m3·kg-1,1.96% and 2.47%,respectively.The sediment mainly consisted of 5~50 μm（45.61%） and above 50 μm（41.47%）particles.The heavy metals concentrations in sediment were measured by ICP-MS and AFS.The results showed that the mean concentrations of Cu,Pb,Zn,Mn,Co,Ni,Cr,Cd,As and Hg were 18.43,17.34,90.57,562.94,15.83,21.51,55.20,0.41,9.59 μg·g-1 and 0.47 μg·g-1,respectively.Compared with International,Chinese and Shaanxi Soil Element Background Value,the contents of Zn,Co,Cd and Hg were higher than them,especially for Cd（4 times of Chinese and Shaanxi Soil Element Background Values） and Hg（7~8 times of International Soil Element Background Value;16 times of Shaanxi Soil Element Background Value）.At the same time,the speciation and transfer of heavy metal elements in sediment were investigated by the modified BCR sequential extraction procedure and ICP-MS.The results showed that Cr,Ni,Zn,Cu and Co were dominated by residue（over 50%）,Pb mainly existed in reducible part,Mn and Cd were rich in acetic acid extractable part,and the order of transfer of heavy metal elements was Mn（56.70%）≈ Pb（56.65%）Cd（53.66%）Co（48.82%）Cu（43.99%）Zn（21.93%）Ni（15.49%）Cr（11.43%）,in which of them,Mn,Pb,Cd,Co and Cu had higher harm and stronger transfer（about 45%~60%）.The pollution and ecological risk assessment results of heavy metal elements in surface sediment of Wei River showed that the sediments were mainly contaminated by Cd and Hg,which had higher potential ecologic harm.