安溪铁观音茶园土壤重金属赋存形态及生态风险评价

用改进的BCR连续提取法提取安溪铁观音茶园土壤中重金属元素(Li、Fe、Zn、Ba、Sr、Ti、Co、Cr、Cd、Mn、Ni、Pb、V、Mg、Cu)的赋存形态,分析其生物有效性并作出生态风险评价。重金属赋存形态研究结果表明,Cd的形态总体分布为弱酸溶态残渣态可还原态可氧化态,Pb的形态总体分布为可还原态可氧化态弱酸溶态残渣态,Cu的形态总体分布为可还原态可氧化态残渣态弱酸溶态,其余重金属皆以残渣态为主。生物有效性分析结果表明,Pb、Cd、Cu、Mn、Ni、Sr等重金属的潜在生物可利用性较高,其所占百分比分别为90.4%、73.0%、36.6%、32.8%、23.8%、22.9%。对茶园土壤中的重金属作生态风险评价,地累积指数法和潜在生态危害指数法结果均表明,大部分土壤样品是清洁安全的,部分土壤受到Cd元素污染,污染程度达到中度污染级别。

Speciation and Ecological Risk Assessment of Heavy Metals in Soil from Anxi Tieguanyin Tea Garden

Modified BCR sequential extraction procedure was applied to extract the speciation of heavy metals(Li, Fe, Zn, Ba, Sr, Ti, Co, Cr, Cd, Mn, Mg, Cu, Ni, Pb, and V) in soil from Anxi Tieguanyin Tea Garden. The bioavailability and ecological risk of heavy metals were evaluated. Results of extraction test show that the speciation of Cd decreases in the order of acid soluble > residual > reducible > oxidizable; the speciation of Pb decreases in the order of reducible > oxidizable > acid soluble > residual; the speciation of Cu decreases in the order of reducible > oxidizable > residual > acid soluble; and the other heavy metals are mainly residual state. Bioavailability analysis results show that the potential bioavailability of Pb, Cd, Cu, Mn, Ni, and Sr is higher, with percentage compositions of 90.4%, 73.0%, 36.6%, 32.8%, 36.6% and 22.9%, respectively. Both the geo-accumulation index and potential ecological risk assessment for heavy metals in garden soil show that majority soil are clean and safe but some garden soil have suffered the pollution of Cd, reaching moderate pollution level.