常熟市高风险区水稻籽粒重金属污染特征及评价

Heavy metal pollution characteristics and assessment of rice grain from a typical high risk area of Changshu City,Jiangsu Province

为研究长江三角洲经济高速发展区域粮食安全问题,于2005年采集了常熟市10个城镇高风险区农田的155个水稻籽粒样品,分析了稻米和稻壳中Cd、Cr、Cu、Pb、Zn、Ni、Hg和As的含量,并分别评价了样品的污染程度及其安全水平.结果表明,在10个城镇稻米与稻壳样品中,重金属含量顺序基本一致,部分重金属分布特征存在差异.以单因子污染指数法评价,稻米中Pb、Hg、Ni和Cd超标,其中Pb最为严重,超标率达29.7%;其次为Hg,超标率为20.6%.稻壳中As和Pb超标,超标率分别为3.2%和1.3%.稻米样品综合污染指数为0.30～3.50,污染稻米占28.4%,以新港镇稻米重金属综合污染指数平均值1.42为最高,已达轻度污染,其他城镇都没有达到污染水平;稻壳样品综合污染指数范围为0.15～2.46,污染稻壳占3.2%,所有城镇中稻壳综合污染指数均值都为安全级.稻米中重金属对人体暴露风险评价结果表明,该区稻米中Cu和Zn存在潜在食物安全风险,而Pb也有部分城镇出现潜在风险.

In order to concern about safety of food from Yangtze River Delta, one of rapidly developing regions in China, 155 rice grain samples were collected from high risk area in 10 towns of Changshu City in South Jiangsu in 2005. Analysis methods of ICP-AES and HG-AFS were used to determine content of Cd, Cr, Cu, Pb, Zn, Ni, Hg and As in rice flesh and hull samples. According to relative national standards of China and human health risk assessment, pollution and safety of rice flesh and hull in study area were evaluated. There was an identity between the sequence of heavy metals in rice flesh and hull of 10 study towns, and the distribution characteristics of some metals in rice flesh and hull of these towns were different. Some heavy metals in rice flesh were correlated with them in hull, especially Cu, Zn and Ni. Pb, Hg, As and Cd in some rice flesh were above the national standards when evaluated with single factor index method. Pb exceeded the standard seriously by 29.7%, followed with Hg （20.6%）. As and Pb in some hull were above the national standards, they exceeded their standards by 3.2% and 1.3%, respectively. The composite pollution indexes of rice flesh ranged from 0.30 to 3.50, and 28.4% of them were contaminated with metals. The highest arithmetical mean composite pollution index （1.42） was found in Xingang town, which could be categorized as light pollution. However, other towns could be regarded as no pollution from the means of them. The composite pollution indexes of hull ranged from 0.15 to 2.46, and 3.2% of them were polluted. From the means all towns were in security. Results of exposure risk assessment for the rice flesh suggesting that rice grown in Changshu posed Cu and Zn potential risk to food safety and rice from some towns possessed Pb potential risk.