茶园土壤重金属空间分异及风险评价

为研究武夷山茶园土壤重金属分布的空间变异性，采集武夷山不同生态区域条件下的茶园土壤样品，检测其Cu、Zn、 Pb、 Cr、 Cd、 As和Hg元素含量，并运用单项污染指数法、综合污染指数法和潜在生态危害指数法对不同区域茶园土壤重金属进行风险评价。结果表明：茶园土壤中不同种类元素的含量差异显著，不同生态条件下同种元素也具有一定的空间分异特征。其中，自然保护区茶园土壤Cd和Hg累积最为显著；生态区茶园土壤的Cu、 Zn、 Pb和Cr有一定累积；景区茶园土壤的Pb、 Cr、 Cd和As含量符合有机茶产地环境条件标准，但Hg略微累积。土壤综合污染指数评价的结果表明，保护区污染最为严重，生态区次之，景区尚无污染。各区域污染物的分担情况也不尽相同，其中各区域中Hg的分担率都较高(>25%)。潜在生态风险指数评价的结果显示， Cu、 Zn、 Pb、 Cr和As在各茶园的风险等级为“低”，属于轻微生态危害； Cd和Hg在保护区的风险等级以“重”为主，在生态区分别以“中”和“较重”为主，在景区则以“低”和“中”为主。各区域综合潜在生态风险危害大小为：保护区>生态区>景区，并应警惕Cd和Hg的潜在生态风险。

Spatial variation and risk assessment of heavy metals in the tea garden soils

To study the spatial variation of heavy metal distribution in the tea garden soil of Wuyishan, the total amount of Cu, Zn, Pb, Cr, Cd, As and Hg elements were analyzed in the soil samples collected from different ecological conditions of Wuyishan tea gardens. And the ecological risk of those heavy metals was evaluated using single pollution index, comprehensive pollution index and potential ecological risk index. The results showed that there were significant differences in the contents between different types of heavy metal elements. The same element also displayed a certain degree of spatial differentiation characteristics under different ecological conditions. The significant accumulation of Cd and Hg was found in the tea garden soils of the nature reserve. The slight accumulation of Cu, Zn, Pb and Cr were found in the ecological zones. The content of Pb, Cr, Cd and As in the scenic areas could meet the environmental condition criteria for organic tea production. But, Hg showed slight accumulation in the scenic areas. Soil pollution index assessment showed that the tea garden soils of the nature reserve had been polluted most seriously, followed by the ecological zones. The scenic areas soils were free of pollution. Pollutants sharing situations were different in various studied areas. But, Hg sharing rates were high ( more than 25% ) and it should be particularly concerned. Potential ecological risk index assessment showed that the risk level of Cu, Zn, Pb, Cr and As was “low” and they had slight ecological harm to the tea garden. But, the risk levels of both Cd and Hg were mainly “heavy” in nature reserve, “medium” or “heavy” in ecological zones, and“low” or “medium” in scenic areas, respectively. Therefore, the order of comprehensive ecological risk harm level was that:nature reserve > ecological zones > scenic areas, and we should pay more attention to the potential ecological risks of Hg and Cd elements in Wuyishan tea garden soil.