拉萨河放射性核素^(238)U和^(232)Th分布特征及健康风险评估

Distribution and Health Risk Assessment of Radionuclides ^(238)U and ^(232)Th in Lhasa River

为了解拉萨河中放射性核素^(238)U和^(232)Th的污染水平及其对人类的致癌风险,利用拉萨河中下游和堆龙曲支流16个采样点水样的^(238)U和^(232)Th含量,采取美国环境保护局(U.S.Environmental Protection Agency,US EPA)推荐的放射性核素健康风险评价方法,评估不同年龄人群因饮水途径摄入核素的致癌风险。结果表明,拉萨河中^(238)U和^(232)Th平均活度浓度分别为(2.62±3.46)×10^(-2) Bq·L^(-1)和(2.3±0.478)×10^(-3) Bq·L^(-1),比我国地表水平均值分别高31%和低61.7%;^(238)U和^(232)Th含量沿程分别呈波动稳定和波动变化的趋势;不同人群平均总致癌风险分别为(4.81±4.61)×10^(-8)(幼儿组)、(2.29±1.81)×10^(-8)(少年组)和(3.08±2.13)×10^(-8) a^(-1)(成年组),均低于1×10^(-6) a^(-1)(US EPA标准)和我国地表水平均致癌风险值,但对幼儿的致癌危害最大;^(238)U和^(232)Th的致癌风险贡献率随年龄的增长分别下降和上升;建议对羊八井镇附近河水进行持续监测,确保地热资源开发不会造成拉萨河放射性核素的污染。本研究不仅可以为拉萨河放射性核素污染的研究提供参考,而且可以为拉萨河未来的环境保护提供科学依据。

In order to understand the pollution level of radionuclides ^(238)U and ^(232)Th and their carcinogenic risks to human beings in Lhasa River,the ^(238)U and ^(232)Th contents of water samples collected from 16 sampling points in the middle and lower reaches and the Doilungqu tributary of Lhasa River were measured.The radionuclide health risk assessment method recommended by the U.S.Environmental Protection Agency(US EPA)was used to assess the carcinogenic risk caused by the intake of radionuclides in drinking water by different age groups.The results showed that the average activity concentrations of ^(238)U and ^(232)Th in Lhasa River were(2.62±3.46)×10^(-2) Bq·L^(-1) and(2.3±0.478)×10^(-3) Bq·L^(-1),respectively.The contents of ^(238)U and ^(232)Th were 31%higher and 61.7%lower than the national average level of surface water,respectively.The content of ^(238)U fluctuated steadily along the way while the content of ^(232)Th fluctuated along the way.The average total risk of cancer in different populations was(4.81±4.61)×10^(-8)(children group),(2.29±1.81)×10^(-8)(juvenile group)and(3.08±2.13)×10^(-8) a^(-1)(adult group),re-spectively,all of which are lower than 1×10^(-6) a^(-1)(US EPA standard)and the national surface water carcinogenic risk average values.The carcinogenic risk of Lhasa River is the highest to children.The contribution rate of carci-nogenic risk of ^(238)U decreases with the increase of age,while that of ^(232)Th increases with the increase of age.It is suggested to monitor the river water near Yangbajing Town continuously to ensure that the development of geother-mal resources will not cause radionuclide pollution in Lhasa River.This study can not only provide a reference for the study of radionuclide pollution in Lhasa River,but also provide a scientific basis for the future environmental protection of Lhasa River.