武夷山茶园土壤中五种重金属的化学形态和生物有效性

Speciation and bioavailability of five toxic heavy metals in the tea garden soils of Wuyishan

测定了武夷山茶园土壤中5种有毒重金属(汞、镉、铅、铬和砷)的总量和形态分布,运用风险评价编码法(RAC)评价与比较重金属生物有效性,通过次生相与原生相分布比值(RSP)法解析重金属的自然与人为来源,并利用相关系数分析土壤理化性质对重金属形态组分的影响.结果表明:(1)Cd以离子交换态为优势形态;Hg和Pb以残渣态为优势形态;Cr和As元素以残渣态为主.(2)RAC法评价的污染程度大小排序为:Cd>Pb>As>Cr>Hg.其中,Cd以人为来源为主,Hg在很大程度上受农业活动的影响,Pb受人为来源影响不显著,Cr和As以自然来源为主,基本未受人为来源的影响.(3)重金属形态受土壤理化性质的影响与元素属性有关.(4)5种重金属对比得出,武夷茶区土壤Cd富集最显著,生物有效性最高.因此,该茶区应首要关注Cd的污染并采取相应防控措施.

Total contents,chemical speciation and bioavailability of five toxic heavy metals（ Hg,Cd,Pb,Cr and As） in the tea garden soils of Wuyishan were measured. The bioavailability of toxic heavy metal were evaluated by the method of risk assessment code（ RAC）. The natural or anthropogenic sources of toxic heavy metal element were determined by the ratio of secondary phase and primary phase（ RSP）,and the effect of soil physical and chemical properties on heavy metal chemical speciation were investigated by the analysis of correlation coefficient. The results showed that the predominant specie of Cd was the ion exchangeable fraction. The predominant specie of Hg and Pb were residual fractions. And Cr and As were mostly present in the residual state. The contamination levels of RAC assessment decreased in the order of Cd〉 Pb〉 As 〉Cr〉 Hg. Among them,Cd come mostly from anthropogenic sources. Hg was greatly affected by agriculture activities.Human source has no significant influence on Pb. Cr and As mostly come from natural sources. The influence of soil physical and chemical properties on heavy metal element speciation was dependenton the element attribute. The comparison of the accumulation and bioavailability of the five elements indicated that Cd was significantly enriched in the tea garden soil as a result of intensive anthropogenic activities. Therefore,we should pay more attention to Cd and take the corresponding prevention measures to control the toxic heavy metal pollution in the tea garden soils of Wuyishan.