| 内蒙古白云鄂博矿区土壤稀土元素污染特征及评价 |
| 摘要点击 2157 全文点击 768 投稿时间：2020-08-13 修订日期：2020-08-31 |
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| 中文关键词 矿区 稀土元素(REE) 特征参数 污染 生态风险 |
| 英文关键词 mining area rare earth elements (REE) characteristic parameters pollution ecological risk |
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| 中文摘要 |
| 白云鄂博矿床是世界上最大的轻稀土矿床，在长期开采过程中向周围环境中释放了大量的稀土元素.为了制定有效地修复方案，必须对稀土元素的浓度、空间分布、分布模式、污染水平和生态风险进行分析和评价.结果表明，土壤样品总稀土含量平均值为6064.95 mg·kg-1，高于对照点（207.44 mg·kg-1）、内蒙古（150.95 mg·kg-1）和中国（184.72 mg·kg-1）土壤背景值，说明周边土壤出现稀土富集现象.轻稀土元素占到稀土总量的83%~99%，Ce是最主要的轻稀土元素.总稀土的高值区域主要集中于矿源附近，分布极不均匀，受外界干扰较大.各个功能区稀土球粒陨石标准化模式相似，归一化曲线向右倾斜，轻重稀土分馏明显.δCe和δEu的计算显示土壤具有明显的Ce正异常和Eu负异常.La/Yb、La/Sm和Gd/Yb的比值表明，土壤中稀土元素的分布模式是轻稀土元素富集，而且轻稀土元素较重稀土元素具有更为显著的分馏作用.采用4种方法对研究区土壤中稀土元素污染状况和生态风险进行评价.地累积指数计算表明Ce、Nd、Pr和La的均值达到了重污染程度.校正污染程度评价结果显示，不同功能区稀土元素的平均mCd值范围为7.14~31.38，尾矿库属于高污染水平，居民区和工业区属于非常高污染水平，而采矿区和排土场则达到极高污染水平.污染负荷指数评价显示尾矿库属于中度污染水平，其余功能区则达到重度污染水平.白云鄂博矿区土壤中稀土元素的潜在生态风险指数范围为120.99~6376.46，33%的样点呈现出极强生态风险，16%的样点呈现很强的生态风险，12%的样点呈现较强的生态风险，30%的样点呈现中等风险，只有9%的样点呈现较低的生态风险.因此，亟待采取有效地措施来控制白云鄂博矿区土壤中稀土元素的污染和潜在生态风险. |
| 英文摘要 |
| 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-1, which was higher than the background levels of control soils (207.44 mg·kg-1), Inner Mongolia (150.95 mg·kg-1), and China (184.72 mg·kg-1). 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 δCe and δEu 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 (Igeo). The modified degree of contamination method showed that the average mCd 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. |
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