铁观音茶园土壤-茶树体系中重金属的生物有效性

Bioavailability of heavy metals in soil-tea plant system of Tieguanyin tea garden

茶园土壤中重金属的生物可利用性与其化学形态分布密切相关.本研究采集铁观音主要产区——泉州市安溪县7个茶园14个采样点的表层土壤(0—20 cm)和茶树样品(根、茎、老叶、新叶),采用BCR四步提取法提取土壤样品中6种金属(Cr、Ni、Zn、Cu、Cd、Pb)的4种赋存形态,使用电感耦合等离子质谱仪(ICP-MS)分析土壤样品中金属总量、各赋存形态含量以及茶树样品中金属的含量.使用次生相原生相比值法和风险评价编码法对茶园土壤的生物有效性进行评价,Pearson相关性分析法对土壤的理化性质、金属总量及生物有效性、茶树中金属含量进行分析.结果表明,由于铁观音茶园本身土壤酸化比较严重,Cr、Cu、Cd、Pb以活性态(F1)或者潜在活性态(F2、F3)为主,Ni和Zn残渣态含量较高,但是其他三态含量均不低,因此,使用次生相与原生相比值法(RSP)对铁观音茶园土壤的生物有效性进行评价更加合理;从其评价结果来看,Cd、Pb、Cr具有较强的生物活性,应该特别关注;Pearson相关性分析的结果表明,所有金属的生物活性(RSP)与pH和总有机碳呈负相关关系,金属总量对于金属活性态的影响不显著.因此,控制茶园土壤的酸化、提高茶园土壤的有机质含量,对于降低铁观音茶园土壤中金属的生物活性,降低茶叶的金属富集具有重要作用.

The bioavailability of heavy metals in tea garden soil is closely related to its chemical form distribution.In this study,top soil(0—20 cm)and tea plant samples(roots,stems,old leaves,and new leaves)from 14 sampling sites in 7 tea gardens in Anxi County,Quanzhou City were collected,six metals(Cr,Ni,Zn,Cu,Cd,Pb)in soil samples were extracted by BCR four-step extraction method,analyzed using an inductively coupled plasma mass spectrometer(ICP-MS).The method of ratio of the secondary phase and primary phase(RSP)and risk assessment coding(RAC)were used to evaluate the bioavailability of the soil.The Pearson correlation analysis was used to analyze the physical and chemical properties,the total metal and bioavailability of the soil,and the metal content in the tea plant.The results showed that the soil of Tieguanyin tea garden was severely acidified,and the metal was mainly in active state(F1)or potential active state(F2,F3).Therefore,it was more reasonable that the RSP was used for the evaluation of soil bioavailability.From the evaluation results,Cd,Pb,and Cr had strong biological activity and should be paid special attention.The results of Pearson correlation analysis showed that the biological activity(RSP)of all metals was negative correlation between pH and total organic carbon(TOC),and the total metal had no significant effect on the active state of the metal.Therefore,controlling the acidification of the tea plantation soil and increasing the organic matter content of the tea garden soil had important effects on reducing the biological activity of metals in the soil of Tieguanyin tea garden and reducing the metal enrichment of tea leaves.