苏北地区土壤-水稻系统重金属分布及其食物安全风险评价

2004年在对苏北地区6个县市(丰县、沛县、铜山、睢宁、楚州和东海)采用网格法采样的基础上,随机选择了该区域2种主要土壤类型上98个土样及其上所产水稻籽粒样品,采用原子吸收分光光谱仪和原子荧光光谱仪分别测定了其中的Cu、Zn、Pb、Cd、Cr、Ni、As和Hg 8种重金属的全量.分别以国家绿色食品生产基地标准、无公害农产品生产基地标准以及20世纪80年代的地区背景值为参照依据,分析评价了所研究土壤的重金属污染程度和大米的重金属安全水平,并进一步依据USEPA和WHO推荐的RfD值,结合我国居民平均食物消费结构评估了该地区土壤所产大米对人体的重金属暴露风险.结果显示,该地区的土壤重金属环境质量总体上符合建设绿色食品生产基地的要求,属于总体未明显污染土壤;不过,黄潮土上所产大米中Ni以及砂礓黑土上所产大米中Ni、Pb含量存在超出国家食品卫生安全标准的现象. 依据USEPA的RfD值计算所得结果表明,供试地区所有土壤上所产大米中As、Cr具有明显的食物安全风险,部分地区的大米中Cd存在风险,由于Cd/Zn比值较低,因此基本上仍属安全.为了进一步保障农产品食用安全,一方面需要制订更严格的土壤环境质量标准,控制土壤污染,另一方面可能还需要着力改善大气环境质量.

Distribution of Heavy Metals in the Soil-Rice System and Food Exposure Risk Assessment of North Jiangsu, China

Soil environmental quality and its impact on safety of agro-products has been one of the research targets concerning regional environmental quality and sustainable development in the last decade.Based on a geologic survey and grid sampling of North Jiangsu including six counties and cities,Fengxian,Peixian,Tongshan,Suining,Chuzhou and Donghai,a total of 98 pairs of soil and rice grain samples were taken randomly in areas of two major soil types,Huangchaotu(Motudic Entisols) and Shajiang black soil(Vertisols) for analysis of contents of total Cu,Zn,Pb,Cd,Cr,Ni,As and Hg with an atomic adsorption spectrophotometer and an atomic fluorescence spectrophotometer,separately.Pollution levels of the soil and rice samples were assessed against the standards for green food production bases and hazard-free food production bases, and the background values of the region of the 1980s,and heavy metal exposure risk assessment of the rice produced in the region was conducted with R_fD values recommended by USEPA and/or WHO as benchmark.Results show that the environmental quality of the soils from the studied region basically meets the requirements set for green food production base in terms of heavy metal pollution,and on the whole falls into the category of "No Significant Pollution".Nevertheless,R_fD values calculated based on USEPA indicate that rice grown in all the soils of the region does pose some significant As and Cr exposure risk to food safety and rice from some areas does Cd exposure risk.Fortunately,it still falls into the category of "Safe" due to low Cd/Zn ratio.In order to further guard food safety,it is essential to amend and modify criteria for soil environmental quality,take positive measures to control soil pollution,and endeavor to improve the quality of the atmospheric environment.