铀矿区周边水体典型核素污染特征及风险评价

为研究铀矿区周边水体中典型放射性核素分布特征及其潜在的健康风险，对该地区周边浅层地下水及河水中放射性活度浓度进行分析测定.运用改进内梅罗综合污染指数法和健康风险评价模型对放射性污染及不同年龄段人群健康风险进行评估.结果表明，地下水与河水中放射性核素²³⁸U、²²⁶Ra、²³²Th活度浓度（地下水：0.012~0.102，0.013~0.036，0.002~0.033Bq/L，河水：0.001~0.066，0.013~0.034，0.001~0.013Bq/L）均未超过WHO饮用水水质准则规定的标准限值，但远远高于江西省水体背景值.河水中各核素活度浓度随水流流向呈递减趋势，地下水中各核素空间分布无明显规律性特征.河水中综合污染指数高于地下水，最高值分别为9.21和6.83，属严重污染和中度污染.健康风险评价结果表明，幼儿和少儿致癌风险要高于成人，幼儿终身致癌风险均超过ICRP最大可接受风险值5.0×10^-5，少儿和成年超标率为33.3%和16.7%，即使未超标但也高于USEPA推荐可忽略风险水平10^-6，具有潜在致癌风险.各核素致癌风险水平呈现为²²⁶Ra > ²³²Th > ²³⁸U，因而对于铀矿区周边饮用水中²²⁶Ra和²³²Th要更加重视研究.

Distribution characteristics and risk assessment of typical radionuclides in water around uranium mining area

In order to study the distribution characteristics and potential health risks of typical radionuclides in water around the uranium mining area, the activity concentration of radionuclides in shallow groundwater and river water around the area was analyzed and measured. The improved Nemero comprehensive pollution index method was used to evaluate radioactive pollution level, the cancer risks for people of different ages were assessed by the health risk assessment model. The results showed that activity concentrations of²³⁸U, ²²⁶Ra and ²³²Th in groundwater (0.012~0.102, 0.013~0.036, 0.002~0.033Bq/L)and river water (0.001~0.066, 0.013~0.034, 0.001~0.013Bq/L) did not exceed the standards stipulated by the WHO for drinking-water quality, but far higher than the average values in Jiangxi Province. The nuclides' activity concentration in the river water continuously decreased as water flowed, while no obvious trend was observed for spatial distribution of nuclides. The comprehensive pollution index in river water was higher than that in groundwater:The peak value for river water was 9.21 which was heavy pollution, while the peak value for groundwater was 6.83 which is medium pollution. Results of health risk assessment indicated that the cancer risk for infants and children was higher than that for adults. The lifetime cancer risk for infants exceeded the maximum value of 5.0×10^-5 regulated by ICRP, and meantime the risk values for children and adults were respectively 33.3% and 16.7% higher than standards. Even if the other water samples did not exceed the standard, they were higher than the negligible risk level of 10^-6 recommended by USEPA, and therefore indicating potential cancer risk. The carcinogenic risk level of nuclides decreased in the order of ²²⁶Ra > ²³²Th > ²³⁸U. Therefore, more attention should be focused on the study of ²²⁶Ra and ²³²Th in drinking water around uranium mining area.