闽中某县茶园土壤-茶树-茶汤中镉含量及健康风险评价研究

A Case Study of Cadmium Distribution in Soil-Tea Plant-Tea Soup System in Central Fujian Province and Relative Health Risk Assessment

以闽中某县8个代表性茶园为研究对象,采集茶园土壤和茶树各器官样品,分析镉在茶园土壤-茶树中积累和分布规律,并探讨其受土壤理化性质的影响;同时测定茶汤中镉含量并算出茶叶中镉的溶出率,利用美国国家环保署(USEPA)推荐的健康风险评价模型进行人体致癌健康风险评价。结果表明,茶园土壤全镉含量均值为112.74μg·kg^(-1),是福建省土壤背景值的2.06倍,茶园土壤镉积累明显;茶园土壤有效镉含量均值为26.44μg·kg^(-1),镉活化率均值为24.86%,有效程度较高。土壤pH和有机质是影响土壤镉及其有效性的主要因素,土壤全磷和速效磷是影响镉活化率的主要因子;茶树主根和侧根与土壤全镉、有效镉和有机质呈显著正相关(P<0.05),新叶镉含量与土壤有效镉和全磷呈显著正相关(P<0.05)。茶树各器官镉含量分布规律为:侧根(1 253.89μg·kg^(-1))>主根(382.20μg·kg^(-1))>主茎(167.25μg·kg^(-1))≈侧茎(154.65μg·kg^(-1))>老叶(30.60μg·kg^(-1))≈新叶(27.13μg·kg^(-1)),茶树根部镉富集系数显著大于其他器官(P<0.05),新叶和老叶镉富集系数较低,镉大部分被根和茎固定,向叶的迁移能力较低。茶汤中镉含量均值为192.28 ng·L^(-1),远低于《生活饮用水卫生标准》中镉含量,茶叶中镉溶出率均值为15.29%;茶汤和茶叶中镉致癌健康年风险分别为6.33×10-7和4.42×10-6,比国际辐射防护委员会推荐的化学有害物最大可接受水平(5×10^(-5))低约1~2个数量级,说明可以安全饮用。

Extensive soil and tea tree samples were collected from 8 tea gardens in central Fujian Province to assess the cadmium(Cd)distributions and explore the Cd transportation from tea garden soil,tea leaf to tea soups.Their relations with soil physical and chemical properties were also discussed,and the preliminary health risk assessments of the Cd in tea were conducted using the USEPA health risk assessment model.The results showed that the average total soil Cd content was 112.74μg·kg-1,which was 2.06 times higher than the background value in Fujian.The average available soil Cd content and available rate were 26.44μg·kg-1 and 24.86%.The total and available soil Cd contents had significant but negative correlations with soil organic matter and pH value,and the available soil Cd rate was positively and significantly correlated with total and available soil phosphorus.The Cd contents of the main and secondary roots had a positive and significant correlation with the total and available Cd as well as soil organic matter.The Cd content in new leaves had a positive and significant correlation with soil available Cd and total phosphorus.The Cd distribution in tea plant followed the order as:lateral roots(1 253.89μg·kg-1)>main roots(382.20μg·kg-1)>main stem(167.25μg·kg-1)≈secondary stem(154.65μg·kg-1)>older leaves(30.60μg·kg-1)≈new leaves(27.13μg·kg-1).The enrichment coefficients in roots were significantly higher than other tissues,suggesting the preferential accumulation of Cd in tea roots.The average Cd content in tea soup was 192.28 ng·L-1,which was far below the sanitary standard for drinking water(GB 5749-2006).The dissolution ratio of Cd was 15.29%.Health risk assessment results of the tea soup and dry tea indicated that Cd of personal total annual risk of approximately 6.33×10-7 and 4.42×10-6,which were one or two order of magnitude lower than the threshold recommended by ICRP(1.0×10-5).Thus,these tea would be safe to drink.