贵州开阳磷矿开采对洋水河放射性核素的影响评价

程馨+张成江+施泽明+倪师军

基金项目：国家自然科学基金项目(41272100)

摘要：为探究磷矿资源采选对矿区周围水体天然放射性核素的影响，以贵州开阳磷矿洋水矿区洋水河为研究对象，测试和分析了河水及表层沉积物中铀和钍的质量浓度、质量分数和分布特征，并运用潜在生态危害指数法对沉积物中的铀进行生态风险评价。结果表明：受磷矿资源采选活动影响，洋水河河水中铀的平均质量浓度(0958 44 ng·mL-1)明显高于中国部分河水中铀的平均质量浓度，钍在河水中的质量浓度极低，接近于0，钍不易富集在河水中而铀易于富集；矿井冷却水中铀的质量浓度为2.87 ng·mL-1，是河水中铀平均质量浓度的2.99倍，表层沉积物中铀平均质量分数为4.95×10-6，是中国水系沉积物背景平均值的2.24倍，钍的平均质量分数为5.43×10-6，低于中国水系沉积物元素背景平均值，钍和铀在沉积物中均有富集且富集程度相当；沉积物中铀的平均污染指数和潜在生态危害指数分别为1.06和530，总体上属于中等污染水平，其潜在生态风险程度为中等。

关键词：放射性核素；影响评价；潜在生态危害指数法；河水；开阳磷矿；贵州

中图分类号：P641.3；X522文献标志码：A

Impact Assessment of the Exploitation of Kaiyang Phosphate Deposit

on the Radionuclide of Yangshui River in Guizhou

CHENG Xin, ZHANG Chengjiang, SHI Zeming, NI Shijun

(Sichuan Province Key Laboratory of Geological Nuclear Technology, Chengdu University of Technology, Chengdu 610059， Sichuan, China)

Abstract: In order to find the effect of phosphorite resource exploitation on the natural radionuclide of water around the mining area, taking Yangshui River of Kaiyang phosphate deposit in Guizhou as the research target, the mass concentrations, mass fractions and distribution characteristics of uranium and thorium from water and surface sediment were measured and analyzed, and the ecological risk of uranium in the sediment was assessed by potential ecological risk index method. The results show that because of phosphorite resource exploitation, average mass concentration of uranium (0958 44 ng·mL-1) from water in Yangshui River is obviously higher than that in part rivers of China, and the mass concentration of thorium is extremely low (approximately zero), and the uranium is rich in river water but thorium is not; mass concentration of uranium (2.87 ng·mL-1) from cooling water in mine is 2.99 times more than that from river water; mass fraction of uranium (4.95×10-6) is 2.24 times more than the average background value of stream sediment in China, and mass fraction of thorium (5.43×10-6) is lower than the average background value of stream sediment in China, and uranium and thorium are equivalently rich in the sediment; average pollution index and potential ecological risk index of uranium in the sediment are 1.06 and 5.30, so that the pollution level is medium, and the potential ecological risk is moderate.

Key words: radionuclide; impact assessment; potential ecological risk index method; river water; Kaiyang phosphate deposit; Guizhou

0引言

磷矿石常与天然放射性核素铀、钍共生或伴生，磷矿石中铀的品位一般为0.005%～0.030%，沉积型磷块岩要高些［1］，个别超过0050%。近年来，随着中国人口的快速增长和科学技术的高速发展，2003～2007年中国磷矿石产量增长了82.54%，磷矿资源的开采量逐年攀升，加之磷矿资源开采过程中存在诸多不利于环境的因素，伴生或共生于其中的天然放射性核素随着矿山“三废”进入矿区周围水体，给水体和生态环境带来深远影响［2］。……