韶关工矿区水稻土和稻米中重金属污染状况及风险评价

为探明韶关市工矿业活动对矿区周边农业生产的影响,选取韶关市凡口铅锌矿(FK)、大宝山多金属矿(DBS)、曲江发电厂(QJ)三个典型工矿区为研究对象,采集周边村庄的54个稻田土壤及对应的54个稻米样品,分析了重金属含量特征,并采用潜在生态风险评价法和人体健康风险评价法对土壤-稻米中重金属进行生态风险及人体健康风险评价。研究表明,三个典型工矿区周边水稻土中重金属严重超标,Cd、Pb、Cu、Zn含量的超标率分别为100%、30%、50%、74%;水稻土均具有很高或高潜在生态风险,风险大小依序为QJFKDBS;其中Cd为最主要的风险元素因子。稻米中Cd、Pb、Cu、Zn含量超标率分别为94%、85%、2%和4%,Cd和Pb是稻米中最主要的健康风险因子。土壤重金属的人体健康风险评价结果表明,工矿区周边水稻土中重金属的非致癌健康指数均小于1,不会对周围居民造成明显的非致癌健康影响,其中Pb是最主要的非致癌风险元素因子;水稻土中的Cd致癌风险度基本在可接受风险水平,但仍不可忽视其对矿区儿童的潜在致癌风险;经口摄入是最主要的土壤重金属非致癌和致癌风险暴露途径。稻米中重金属的健康风险远高于土壤,对周围村民存在明显的非致癌风险,甚至慢性致毒效应;其中Cd和Pb是研究区域稻米中最主要的非致癌风险元素因子;稻米中Cd的致癌风险度在10~(-3)~10~(-2)范围,远远超过了可接受风险水平(10~(-6))。研究结果为当地如何采取有针对性的措施以防治土壤重金属污染、保障矿区居民健康提供了更全面的依据。

Status and risk assessment of heavy metal pollution in paddy soil and rice grains from the industrial and mining area of Shaoguan, Guangdong Province

To obtain a better overview of the impact of industrial and mining activities on the agricultural production around the mining areas in Shaoguan, Guangdong Province, heavy metal contents in 54 paddy soils and corresponding 54 rice grain samples were investigated. The samples were collected from the villages surrounding three typical industrial and mining areas, i.e. Fankou Lead-Zinc Mine(FK), Dabaoshan Polymetallic Mine(DBS) and Qujiang Power Plant(QJ). The potential ecological risk and human health risk were also assessed for the heavy metals in both soil and rice. The results showed that the paddy soils around the three industrial and mining areas were seriously contaminated, and the Cd, Pb, Cu and Zn contents in soils exceed the national standard values by 100%, 30%, 50% and 74%, respectively. These metals posed very high or high potential ecological risk, with the degree of risk followed the sequence of QJ > FK > DBS. Among the metals, Cd was the most important risk factor. In rice grains, the contents of Cd, Pb, Cu and Zn exceed the national standard values by 94%, 85%, 2% and 4%, respectively. Cd and Pb were the most important health risk factors in rice. The results of human health risk assessment showed that the non-carcinogenic health index of heavy metals in paddy soils in the studied areas was lower than 1, which would not cause obvious non-carcinogenic health effects to surrounding residents, and Pb was the most important non-carcinogenic risk factor. The carcinogenic risk level of Cd in paddy soils was generally acceptable, but attention should still be paid to its potential carcinogenic risk to children in the mining areas. Oral ingestion was the most important exposure pathway for non-carcinogenic and carcinogenic risk of heavy metals in paddy soils. The health risk of heavy metals in rice was much higher than that in soils. The obvious non-carcinogenic risk and even chronic toxic effects on local residents were imposed by heavy metals in rice. Among the four metals, Cd and Pb were the most important non-carcinogenic risk factors in rice in the studied area. The carcinogenic risk of Cd in rice was at the level of 10^-3~10^-2, far exceeding the acceptable level(10^-6) that USEPA recommended. Our results can provide a more comprehensive basis for the control of heavy metal pollution in the local soil, in order to guarantee the health of residents in the surroundings of industrial and mining area.