Wang Zhe, Zhao Ying-Chen, Luo Yi-Fei, Zheng Chun-Li, Bian Yuan, Zhang Guang-Yu
School of Energy and Environment, Inner Mongolia University of Science and Technology, Baotou 014010, China.
School of Environment, Beijing Normal University, Beijing 100875, China.
Huan Jing Ke Xue. 2021 Mar 8;42(3):1503-1513. doi: 10.13227/j.hjkx.202008129.
The Bayan Obo deposit is the largest light rare earth ore deposit in the world, which releases rare earth elements (REEs) to the surrounding environment through long-term mining processes. To inform restoration plans, it is necessary to investigate the concentration, spatial distribution, pollution level, and ecological risk of REEs. Sample analyses showed that the average total concentration of REEs in this area is 6064.95 mg·kg, which was higher than the background levels of control soils (207.44 mg·kg), Inner Mongolia (150.95 mg·kg), and China (184.72 mg·kg). Light REEs (LREEs) accounted for 83%-99% of the detected REE, and Ce was the dominant element. Areas with high REE concentrations were mainly located near the source bed, and the distribution was extremely inhomogeneous, being greatly affected by external interference. Chondrite normalized REE patterns of different functional areas were similar and normalized curves inclined to the right, indicating district fractionation between the LREE and heavy REEs (HREEs). Significant negative Eu anomalies and positive Ce anomalies were observed in the soils based on Ce and Eu values. La/Yb, La/Sm, and Gd/Yb ratios all indicated that the soils were LREE-enriched, whereas the LREEs were more fractionated than the HREE. Four methods were employed to evaluate the pollution and ecological risk of the detected soil REEs. The average values of Ce, Nd, Pr, and La reached heavily contaminated levels based the geo-accumulation index (). The modified degree of contamination method showed that the average m values of REEs in different functional areas ranged from 7.14 to 31.38. The tailings pond had a high level of pollution, residential and industrial areas had a very high pollution level, and the mining area and waste dump showed extremely high levels of pollution. Based on the pollution load index, the tailings pond is moderately polluted while all other functional areas are severely polluted. The potential ecological risk index values ranged from 120.99 to 6376.46, with REEs in soils posing high strong risk, very strong risk, strong risk, moderate risk, and low risk in 33%, 16%, 12%, 30%, and 9% of the sampling sites, respectively. Based on these findings, measures for controlling current pollution and potential ecological risks from REE in the soils of the Bayan Obo mining region are urgently needed.
白云鄂博矿床是世界上最大的轻稀土矿床，长期的开采过程使其向周边环境释放稀土元素（REEs）。为指导修复计划，有必要调查REEs的浓度、空间分布、污染水平和生态风险。样本分析表明，该区域REEs的平均总浓度为6064.95mg·kg，高于对照土壤（207.44mg·kg）、内蒙古（150.95mg·kg）和中国（184.72mg·kg）的背景水平。轻稀土（LREEs）占检测到的REE的83%-99%，Ce为主要元素。REE浓度高的区域主要位于矿源层附近，分布极不均匀，受外界干扰影响很大。不同功能区的球粒陨石标准化REE模式相似，标准化曲线向右倾斜，表明LREE和重稀土（HREEs）之间存在分馏。基于Ce和Eu值，在土壤中观察到显著的负Eu异常和正Ce异常。La/Yb、La/Sm和Gd/Yb比值均表明土壤富含LREE，而LREE比分馏程度高于HREE。采用四种方法评估检测到的土壤REEs的污染和生态风险。基于地累积指数（），Ce、Nd、Pr和La的平均值达到重度污染水平。修正污染程度法表明，不同功能区REEs的平均m值在7.14至31.38之间。尾矿库污染程度高，居民区和工业区污染程度很高，矿区和排土场污染程度极高。基于污染负荷指数，尾矿库为中度污染，而所有其他功能区均为重度污染。潜在生态风险指数值在120.99至6376.46之间，土壤中的REEs在33%、16%、12%、30%和9%的采样点分别构成高、很强、强、中、低风险。基于这些发现，迫切需要采取措施控制白云鄂博矿区土壤中REEs的当前污染和潜在生态风险。
