某铀矿及周边地区土壤放射性水平调查与评价

Investigation and Evaluation of Soil Radioactivity Levels in A Uranium Mine and Surrounding Areas

为查明某铀矿及其周边土壤放射性污染特征,本文对矿区废石场、工业场地和尾矿库周边土壤放射性水平进行现场调查,结果表明,238 U比活度为595.5~2335.1 Bq·kg^(-1),226 Ra比活度为637~16551 Bq·kg^(-1);γ辐射空气吸收剂量率分别为全国、世界平均水平的11.91倍、14.05倍;氡析出率范围为全国范围值的0.34倍~6.62倍,各源项的最大超标点位均位于尾矿库周边。通过对数据进行描述性统计分析发现,226 Ra比活度对放射性源项的拟合度高于238 U。238 U比活度与226 Ra比活度、氡析出率、空气吸收辐射剂量率呈现弱相关性,226 Ra比活度、氡析出率、空气吸收辐射剂量率三者之间达到高度相关,说明226 Ra比活度对氡析出和空气吸收辐射剂量的产生具有重要作用。污染评价结果表明,强潜在生态风险点位占比最大(47.37%),226 Ra对总风险的贡献率较高(最高82.92%);且由226 Ra引发的健康风险值相较于238 U高出1~2个数量级,是主要的健康风险来源,摄入途径是主要暴露途径;研究区空气辐射最大年有效剂量达24.66 mSv,最大集体有效剂量为4476.32人·Sv,最大终生癌症风险为9.53×10^(-2);最大氡年释放量为4.57×10^(12) Bq,影响并辐射周边约36503 m^(2)。研究结果可为矿区退役治理工程提供基础支撑。

To investigate the radioactive contamination characteristics of a uranium mine and its surrounding soil,the radioactivity level of the soil around the waste rock quarry,industrial site,and tailing pond in the mine area was determined.The mass activity of radioactive 238 U and 226 Ra in the soils varied from 595.5 to 2335.1 Bq·kg^(-1) and 637 to 16551 Bq·kg^(-1),respectively.The gamma absorbed dose rate in the air is 11.91 and 14.05 times higher than that of the national and worldwide average values,respectively;the radon precipitation rate ranges from 0.34 to 6.62 times of the national values.The descriptive statistics analysis exhibited that the fitting degree of 226 Ra activity to the source items was higher than that of 238 U.We further noticed,the activity of 238 U was found in a weak correlation with 226 Ra activity,whereas,a significantly high correlation was recognized among 226 Ra mass activity,radon precipitation rate,and air absorbed radiation dose rate,indicating that the activity of 226 Ra plays an important role in radon precipitation and air absorbed radiation.The assessment of pollution showed that most of the sampling sites(47.37%)exhibited high potential ecological risks.The contribution of 226 Ra to the total risk is relatively high(up to 82.92%).The health risk value caused by 226 Ra is 1 to 2 orders of magnitude higher than that of 238 U,which is the main health risk source,and the main exposure route is ingestion.The maximum annual effective dose of air radiation in the study area reaches 24.66 mSv.The maximum collective effective dose,maximum lifetime cancer risk,and maximum annual radon precipitation are 4476.32 man·Sv,9.53×10^(-2),and 4.57×10^(12) Bq,respectively.It is concluded that the affected and radiated area is about 36503 m^(2).Importantly,this research could provide technical support for the mine decommissioning treatment strategies for better management of the environment.