Characteristics and health risk assessment of heavy metals in soil-rice system in the Ganzhou area, Jiangxi Province
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摘要:
为研究江西省赣州市主要耕作区土壤-水稻系统中重金属的含量及人体健康风险,系统采集了赣州市主要耕作区水稻及根系土样品954组,分析了水稻籽实和根系土中Cd、Cr、Hg和Pb的含量及根系土pH值,利用美国环保署(USEPA)推荐的健康风险评估模型进行健康风险评价。研究表明:随着土壤pH值升高,水稻籽实中各重金属元素超标率逐渐降低,其中Cd是土壤和水稻中最主要的污染元素;在土壤-水稻系统中,Cd的迁移能力和土壤pH值是决定水稻籽实重金属是否超标的主要因素。健康风险评价结果显示,研究区重金属总非致癌风险指数HI < 1,说明几乎不存在由食用水稻得慢性疾病的风险。致癌健康风险值为7.10×10-3,Cd是最主要的致癌风险因子,Cr和Pb致癌风险属于可接受范围。基于行政单元的人体健康风险区划表明,上犹县、兴国县和南康区存在一定的风险,虽然重金属没有出现显著超标,但是有关部门应对水稻及根系土中Cd元素含量予以重视,将Cd元素作为赣州市土壤重金属污染防控工作中优先控制的重金属。
Abstract:Total 954 pairs of rice grain and soil samples were collected to investigate the distribution of heavy metals in the soil-rice system and their human health risk in Ganzhou City.The contents of Cd, Cr, Hg and Pb in rice seeds and root soil and the pH value of root soil were analyzed, and the health risk assessment model derived by USEPA was used to evaluate health risk caused by heavy metals.The results show that exceedance rate of heavy metals in rice decreases with the increase of soil pH; Cd is the most severely contaminated metal; and migration ability of Cd and soil pH value are the main factors that determined whether heavy metals in rice grains exceed the standard.The results of health risk assessment show that the total non-carcinogenic risk index(HI) of heavy metals is less than 1, indicating that there is almost no risk of chronic diseases from ingesting rice.The carcinogenic health risk value is 7.10×10-3; Cd is the most important carcinogenic risk factor; and Cr and Pb carcinogenic risk is within the acceptable range.According to the human health risk zoning, there are risks in Shangyou, Xingguo and Nankang, which is worth paying more attention.Although heavy metals do not exceed the standard significantly, the relevant authorities should take exceedance of Cd seriously, and should take Cd as the priority in the prevention and control of heavy metal pollution in the soil of Ganzhou City.
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致谢: 感谢项目组所有成员对本项目工作的付出,感谢审稿专家提出的宝贵意见。
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表 1 指标的分析方法及检出限
Table 1 The analysis method and detection limit of the index
类型 元素 分析方法 检出限 类型 元素 分析方法 检出限 Cd ICP-MS 0.03 Cd ICP-MS 0.03 Hg AFS 0.0005 Hg AFS 0.005 土壤 Cr ICP-MS 5 水稻籽实 Cr ICP-MS 0.5 Pb XRF 2 Pb XRF 0.1 pH ISE 0.1** 注:“ ** ”为无量纲,其他元素单位为mg/kg;AFS—原子荧光光谱法;ICP-MS—等离子体质谱法;XRF—X射线荧光光谱法;ISE—离子选择性电极法 表 2 土壤中重金属元素含量特征
Table 2 Descriptive basic statistics of metal concentrations in paddy soil
元素 算术平均值 最小值 最大值 标准偏差 CV/% 中国土壤背景值[21] 评价标准③ pH≤5 5.5<pH≤6.5 6.5<pH≤7.5 pH>7.5 Cd 0.194 0.004 4.040 0.21 106.47 0.097 0.3 0.4 0.6 0.5 Cr 53.20 7.92 269.00 25.10 47.18 61 250 250 300 350 Hg 0.12 0.01 1.19 0.08 66.94 0.065 0.5 0.5 0.6 1 Pb 44.36 8.10 335.50 25.22 56.86 26 80 100 140 240 pH 5.32 4.30 7.95 0.49 9.13 6.7 表 3 水稻籽实中各重金属元素含量
Table 3 Statistics of metal concentrations in rice grains
mg/kg 元素 Cd Cr Hg Pb 平均值 0.079 0.297 0.006 0.058 最小值 0.002 0.080 0.0002 0.005 最大值 1.660 3.470 0.316 0.860 标准偏差 0.12 0.33 0.01 0.06 CV/% 155.33 112.43 228.25 98.20 最高允许界限值④ 0.2 1.0 0.02 0.2 表 4 土壤重金属对人体的日摄入量、非致癌风险和致癌健康风险
Table 4 Daily intake, non-carcinogenic risk and carcinogenic health risk of soil heavy metals
非致癌风险指数 致癌风险指数 元素 范围 平均值 元素 范围 平均值 HQ-Cd 0.010623~ 8.817490 0.420475 RISK-Cd 0.16×10-3~ 1.32×10-1 6.31×10-3 HQ-Cr 0.000283~ 0.012289 0.00105 RISK-Cr 2.12×10-4~ 9.22×10-3 7.89×10-4 HQ-Hg 0.003541~ 5.595034 0.109075 RISK-Hg - - HQ-Pb 0.006082~ 1.142024 0.076431 RISK-Pb 2.07×10-7~ 3.88×10-6 2.60×10-6 HI 0.056648~ 8.938562 0.060703 TRISK 4.75×10-4~ 1.34×10-1 7.10×10-3 -
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