南方典型设施蔬菜生产系统镉和汞累积的健康风险

HEALTH RISK OF ACCUMULATION OF CADMIUM AND MERCURY IN GREENHOUSE VEGETABLE PRODUCTION SYSTEMS TYPICAL OF SOUTH CHINA

选取南京市典型设施蔬菜生产系统为研究对象,研究了设施土壤-蔬菜系统中镉和汞的累积特征,评价了不同类型蔬菜中镉和汞的暴露风险,提出了基于健康风险的设施菜地土壤镉和汞的环境质量基准。结果表明:(1)设施菜地表层土壤中镉和汞产生了明显累积,且土壤汞的平均含量超过了温室蔬菜产地环境质量评价标准;(2)叶菜类蔬菜对镉和汞的富集能力最强,部分叶菜中的镉和汞含量超过了食品中污染物限量标准;(3)研究区有约21.2%的蔬菜具有镉的潜在人体摄入风险,蔬菜中汞的风险概率约为1%,不同蔬菜镉和汞的人体摄入风险排序为叶菜>根茎>茄果;(4)不同蔬菜类型土壤镉和汞的环境质量基准值差异较大,因此在今后的标准修订时可考虑针对不同蔬菜类型分别制定设施菜地土壤重金属环境质量基准。

In recent years,greenhouse vegetable production has been growing rapidly,making up a sizeable proportion of the vegetable production in China. Excessive uptake of heavy metals by vegetables may pose potential risks to human health. Therefore,vegetable safety has aroused increasing concerns in the country. To ensure food safety,it is essential to know how heavy metals（ Cd and Hg） accumulate in the greenhouse vegetable production system and pose health risks. The study on this subject may provide some scientific basis for heavy metals health risk assessment of Cd and Hg in the greenhouse vegetable system and decision-making in environmental management. Currently,the standard used for environment of environmental quality of greenhouse vegetable fields fails to take into account vegetable-type-specific bioavailability and human health risk of heavy metals. Hence,it is of critical importance to the management and production of safe greenhouse vegetables to have the standard for environmental quality evaluation of greenhouse vegetable fields established as soon as possible,based on crop-specific bioavailability and human health risks of heavy metals.For that end,a greenhouse vegetable production system typical of the Nanjing area was selected as a case for study on characteristics of Cd and Hg accumulation in the greenhouse soil-vegetable system,and exposure risks of Cd and Hg in vegetables relative to type,and environmental quality criteria were proposed for Cd and Hg in greenhouse vegetable fields based on the standard for vegetable and food hygiene and health risks of vegetable ingestion. Results show：（ 1） Cd and Hg accumulation was apparent in the topsoil of the greenhouse vegetable field,with the average content of Hg exceeding the Environment Quality Evaluation Standard for greenhouse vegetables production fields;（ 2） leafy vegetables were the highest in Cd and Hg enrichment capacity,and followed by root /tuber vegetables and then solanaceous vegetables; and some leafy vegetables were found to contain Cd and Hg higher than the upper limit of the standard for food hygiene; According to sensitivity analysis,the main contribution of different exposure parameters to target hazard quotient for Cd and Hg was concentration of Cd and Hg in vegetables（ Cveg） and daily intake of Cd and Hg through ingestion of greenhouse vegetables（ IRveg）.（ 3） approximately 21.2% of the greenhouse vegetables produced in the studied region were likely to pose potential Cd exposure risk through vegetable ingestion and only 1% in the case of Hg,Cd and Hg exposure risks varied with the type of vegetable,displaying an order of leafy vegetables root /tuber vegetables solanaceous vegetables;and（ 4） As environmental quality criteria of soil Cd and Hg vary sharply with the type of vegetables,it is essential to formulate vegetable-type-specific criteria separately for environmental quality evaluation of heavy metals in greenhouse vegetable fields in amending the standard for environmental quality evaluation of agricultural fields in future.The findings of this study suggest that as vegetables vary sharply in Cd and Hg enrichment capacity with the type,in soils relatively high in Cd and Hg,it is advisable to grow suitable vegetables,like root /tuber or solanaceous vegetables that are relatively lower in heavy metal absorption capacity,so as to lower the risk of Cd and Hg entering the food chain.The environmental quality criteria for Cd and Hg in greenhouse vegetable soils based on the Cd and Hg bioconcentration factors of vegetables and vegetable safety standard would be stricter than that based on vegetable target hazard quotient of Cd and Hg,and more approximate to the current environmental quality evaluation standard for farmland of greenhouse vegetables production in China. The findings of this study will facilitate better understanding of the accumulation characteristics and health risks of heavy metals in greenhouse vegetable production systems. Further study should focus on phyto-availability of Cd and Hg to greenhouse vegetables,and establishment of environmental quality evaluation standard for greenhouse vegetable production fields relative to soil type and vegetable type for better management of the greenhouse vegetables production in different regions of China.