川中丘陵区铁路旁土壤重金属含量及化学形态研究

对川中丘陵区成昆铁路的三圣段、吴场段和成渝铁路的五凤段3个典型路段铁路沿线土壤重金属Cd、Zn、Cu、Pb含量及其化学形态进行了研究,并运用次生相富集系数法对重金属的潜在生态风险进行评估。结果表明:铁路沿线土壤重金属Cd、Zn、Cu、Pb含量与对照点相比都有不同程度的升高。Cd不仅具有高的含量,且化学形态主要为酸可交换态和可还原态,残渣态含量很低,其有效态比例>75%,具有很强的生物活性和可迁移性。Cu、Pb、Zn的化学形态则主要为残渣态,酸可交换态比例很小,但是Pb和Zn的可还原态和可氧化态比例较高,所以有效态比例也较高,分别为51.1%~54.9%和36.2%~50%。土壤重金属Cu在各典型路段的次生相富集系数为1.4~4.2;Zn在三圣段、吴场段2个典型路段的次生相富集系数超过3.0,均具有较大的潜在生态风险。

Content and speciation of heavy metal in topsoil alongside railway in hills area in sichuan

The total contents and speciations of heavy metals in topsoil were investigated to assessing their bioavailability and mobility alongside three typical sections(Wuchang,Sansheng and Wufeng) of the Chengdu-Kunming and Chengdu-Chongqing railways in hills area of Sichuan province.Potential ecological risk was evaluated using the phase enrichment factor.The results indicated that the contents of Cd,Zn,Cu and Pb have increased in the topsoil close to the tracks.Sequential extractions showed that 61.7-99.7% of Cd existed as acid-extractable and Fe-Mn hydroxide bound fractions,while Cu,Pb and Zn mostly existed as residual fraction.The proportion of available fractions of soil heavy metals followed the sequence of Cd> Pb > Zn> Cu.The average phase enrichment factor of Cu and Zn were 2.7 and 2.5.Considering the total content and fractions distribution,Cd,Cu and Zn have relatively potential effects on local ecosystem.