双阳河流域土壤—作物—人体系统中重金属元素地球化学特征及健康风险评价

    Geochemical characteristics and health risk assessment of heavy metals in the soil-crop-human system in the Shuangyang River Basin

    • 摘要: 重金属在土壤—作物—人体中的迁移与累积研究,对于评估区域重金属累积程度、潜在生态风险和人体健康具有重要意义。本文基于1∶5万生态地球化学调查数据,评价了双阳河流域土壤—作物—人体中重金属含量特征及健康风险。结果显示:土壤样品中部分重金属已存在局部富集现象,但未超过土壤污染风险筛选值;作物籽实重金属含量均符合食品安全国家标准;女性头发中重金属含量整体高于男性,个别样品Cd、Hg含量高于参考值,呈现相对富集特征,年龄分布上,41 ~ 50岁年龄段重金属含量最高,其他年龄段重金属含量均有不同程度的下降。作物对土壤重金属的生物富集系数(BCF)远小于1,人发对作物重金属的生物富集系数大于1,说明人发对重金属具有较强的浓缩和放大作用,得出重金属在土壤—作物—人体中的迁移与积累呈“V”型模式。单项重金属富集能力及污染程度依次为As>Ni>Cu>Cr>Cd>Pb>Zn>Hg,其中Cd和Hg为单项重金属潜在生态危害主要元素。影响非致癌和致癌的不同途径的暴露量和风险指数为ADDimouth(经口摄入)>ADDidermal(皮肤接触摄入)>ADDibreathe(呼吸吸入),显示口摄入是研究区土壤—作物—人体中重金属产生健康风险的主要途径,在重金属健康风险管理中应重点关注饮食暴露途径的风险。重金属健康风险指数为As>Cr>Pb>Ni>Cu>Zn>Cd>Hg,儿童日均暴露量和非致癌风险指数均高于成人,说明重金属对成人健康不存在明显的非致癌风险,但对儿童存在一定的非致癌风险,这可能与儿童生理特征、暴露期限和饮食摄入量等有关,应引起地方相关机构重视。本次研究结果为地方政府部门精准评估与预警人体健康风险、科学制定食品安全与环境标准提供了科学依据。

       

      Abstract: Investigating the migration and accumulation of heavy metals in the soil-crop-human system is of great significance for assessing the degree of regional heavy metal accumulate, potential ecological risks, and human health impacts. Based on data from 1∶50,000 eco-geochemical surveys, this study examined the heavy metal contents in the soil-crop-human system and associated health risks in the Shuangyang River basin. The results indicate the enrichment of some heavy metals in soil samples, although their contents fell below the risk screening levels of soil contamination. Heavy metal contents in crop seeds all complied with national food safety standards. Heavy metal contents in women's hair were generally higher than those in men's hair. In some samples, the cadmium (Cd) or mercury (Hg) content exceeded the reference range, showing relatively rich characteristics. In terms of age, the highest heavy metal contents were observed in people aged 41~50, while those of other age groups exhibited decreased heavy metal contents to varying degrees. Crops showed bio-concentration factors (BCF) of soil heavy metals far less than 1, while human hair exhibited BCFs of crop-hosted heavy metals exceeding 1, suggesting that human hair can significantly concentrate and amplify heavy metals. These results indicate a V-shaped pattern of heavy metal migration and accumulation in the soil-crop-human system. The enrichment capacity and contamination degree of individual heavy metals decreased in the order of As, Ni, Cu, Cr, Cd, Pb, Zn, and Hg, with Cd and Hg identified as the primary elements posing potential ecological hazards. The exposure levels and risk indices of non-carcinogenic and carcinogenic pathways decreased in the order of ADDimouth (average daily dose via oral intake), ADDidermal (average daily dose via dermal contact), and ADDibreathe (average daily dose via inhalation). This result reveals that oral intake represents the primary pathway of health risks associated with heavy metals in the soil-crop-human system in the study area. Therefore, emphasis should be placed on dietary exposure risks in the health risk management of heavy metals. The health risk indices of various heavy metals decreased in the order of As, Cr, Pb, Ni, Cu, Zn, Cd, and Hg. Additionally, children exhibited higher average daily exposure and non-carcinogenic risk indices than adults. While posing insignificant non-carcinogenic risks to adults, heavy metals carried a certain level of non-carcinogenic risks to children presumably due to their physiological characteristics, exposure duration, and dietary intake. This issue warrants attention from local agencies. The results of this study provide a scientific basis for local government departments to accurately assess and warn of human health risks and to develop scientifically robust standards of food safety and environmental protection.

       

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