基于Monte-Carlo模拟方法的内蒙古大兴安岭南端矿区周边农田土壤重金属风险概率评估

Health Risk Probabilistic Assessment of Heavy Metals in Farmland Soil around Mining Areas at the South of Da Hinggan Mountains in Inner Mongolia Based on Monte Carlo

  • 摘要:
    目的 为考察内蒙古大兴安岭南端矿区周边农田土壤的重金属污染状况及对人体的健康风险。
    方法 从内蒙古某县5个镇的矿区周边农田获得了1120份耕层土样,测定了铬(Cr)、镉(Cd)、砷(As)、铅(Pb)、汞(Hg)的含量,分析了5个镇土壤重金属含量超标情况。利用潜在生态危害指数法评价了土壤重金属的潜在生态风险,运用基于Monte-Carlo模拟方法的人体健康风险评价模型评估了5个镇矿区周边农田土壤对人体健康风险的概率。
    结果 各镇农田土壤中Cr和Hg含量均未超过《土壤环境质量 农用地土壤污染风险管控标准》(GB 15618—2018)中相应pH下的土壤风险筛选值,A镇农田土壤Cd、As点位超标率分别是1.67%和19.86%,B镇农田土壤Cd、As点位超标率分别是22.22%和9.88%,C镇农田土壤Pb、Cd点位超标率分别是6.06%和24.24%,D镇农田土壤无重金属超标,E镇农田土壤只有Cd超标,点位超标率为3.03%。该县中部处于中等生态风险水平,县南部和北部则处于低生态风险水平。A、B、C、D和E镇农田土壤对儿童非致癌风险的概率分别是0.75%、1.67%、1.00%、0.66%和0.78%,对成人致癌风险的概率分别是3.11%、7.81%、24.57%、0.89%和2.56%;儿童非致癌风险累计概率的平均值高于成人,成人致癌风险累计概率的平均值高于儿童,基于确定性风险的评估会低估致癌风险。对人体健康风险贡献较大的因子是经口暴露途径和体重,Cd浓度、As浓度对人体健康风险也有一定的影响,经口暴露途径是优先控制途径,Cd、As是优先控制元素。
    结论 该县农田土壤中Cd污染较重,中部农田土壤重金属污染重于南部和北部,处于中等生态风险水平;农田土壤重金属对成人致癌风险的概率较大,呈现中部>北部>南部的空间分布趋势;矿区源头要控制Cd、As的排放。

     

    Abstract:
    Objective The aims were to investigate the heavy metal pollution and health risk in farmland soil around the southern mining area of Daxing'an Mountains in Inner Mongolia.
    Method The topsoil samples (1120) were obtained from the farmland around the mining area in five towns of a certain county. The contents of chromium (Cr), cadmium (Cd), arsenic (As), lead (Pb) and mercury (Hg) were determined in the soils of five towns, and the potential ecological risks of heavy metals in soil were evaluated by potential ecological hazard index. A probability risk assessment model based on Monte-Carlo was introduced to evaluate the health risk of five towns.
    Result The results showed that the contents of Cr and Hg of every town was lower than the screening value from soil environment quality risk control standard for soil contamination of agriculture land (GB15618-2018) . The over standard rates of Cd and As were 1.67% and 19.86% in town A, and were 22.22% and 9.88% in town B. The over standard rates of Pb and Cd in town C were 6.06% and 24.24%. There was no over standard of heavy metals in town D, and only 3.03% in town E. Town B and C were at medium ecological risk, while other towns were at low ecological risk. The probability of non-carcinogenic risks to children in towns of A, B, C, D and E were 0.75%, 1.67%, 1.00%, 0.66% and 0.78%, respectively. And that of carcinogenic risks to adults were 3.11%, 7.81%, 24.57%, 0.89% and 2.56%, respectively. The average value of cumulative probability of non-carcinogenic risk in children was higher than that in adults, and that of carcinogenic risk in adults was higher than that in children. Assessment based on deterministic risk would underestimate carcinogenic risk. The main contributing factors to the health risk sensitivity of crowd were oral exposure and body weight. Body weight had negative on children's health, followed by oral exposure. The concentration of Cd and As also had a certain impact on human health risk sensitivity. Oral exposure was the priority control way, and Cd and As were the priority control pollutants.
    Conclusion The Cd pollution in the farmland soil of the county was relatively heavy, and the pollution of central town was higher than that of the south and north, showing a moderate ecological risk. The probability of adult cancer risk in the soil was relatively high, presenting a pattern of central>northern>southern. The emission of Cd and As should be controlled at the source of the mining area.

     

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