稀土元素在土壤中的释放与迁移研究进展

稀土是全球重要的战略资源,在高科技产业及日常生活中广泛应用。由于稀土资源需求量的日益增加,稀土矿大量开采,加剧了稀土矿区周边环境污染,危害居民健康。因此,探究土壤中稀土元素的释放和迁移机理及影响机制对稀土的污染防治、生态修复及潜在风险评估都具有重要的现实指导意义。文章综述了稀土元素在土壤中释放与迁移机制、形态、及其影响因素方面的研究进展,主要结论为,(1)稀土元素在土壤中的释放与迁移机制主要包括4种类型:铁锰(氢)氧化物的还原溶解、土壤有机质的促进、离子交换作用以及土壤胶体协同。(2)稀土有机络合物、硫酸盐络合物、碳酸盐络合物是稀土元素在土壤中迁移的主要形态,稀土氟、氯、磷酸盐络合物不太可能作为稀土元素在土壤中迁移的载体。(3)稀土元素在土壤中的释放与迁移主要受pH值、氧化还原条件、配体浓度等环境因子影响,pH值与配体浓度与稀土元素的迁移形态高度相关。未来应通过世界各地不同土壤类型、不同环境驱动因子作用下稀土元素释放迁移的研究,探明引起稀土元素在土壤中释放的主导机制;加强稀土元素长距离迁移研究,在土壤环境中稀土元素分馏机制层面揭示稀土元素地球化学循环,为稀土矿区尾矿、废弃地中残留稀土的回收、利用提供理论与技术支持。

The Release and Transport Behavior of Rare Earth Elements in Soil: A Review

Rare earth elements(REEs)are important strategic resource and have been widely used in high-tech industry and our daily lives.The over-exploitation of REEs mines due to the increasing application of REEs absolutely results in the increasing contamination around REEs mines and is harmful to the health of inhabitants.Therefore,understanding the release and transport mechanism as well as the dominant factors of REEs in the soil are significantly important for the pollution control,soil remediation,and risk assessment of REEs.This paper reviews the research progress on the release and transport mechanisms,forms and influence factors of rare earth elements(REEs)in soil.The main conclusions obtained are as follows.Firstly,the release and transport mechanism of REEs in soil mainly including reduction and dissolution of iron manganese(hydrogen)oxides,promotion of soil organic matter,ion exchange,and colloid-facilitating transport.Secondly,the main forms of REEs-organic,-sulfate and-carbonate complexes in soil are discussed.REEs-fluorine,-chlorine and-phosphate complexes are unlikely to be carriers of REEs transport in soil.Thirdly,the release and transport of REEs in soil are mainly affected by pH value,redox conditions,ligand concentration,and other environmental factors.The pH value and ligand concentration are highly correlated with the transport forms of REEs.For further researches,emphases should be laid on the following aspects:(1)the dominant mechanisms of REEs release in different soils and different environmental driving factors around the world should be deeply investigated;And(2)the study of long-distance transport of REEs,and the fractionation mechanism of REEs in soil should be further considered.These information provide theoretical and technical support for recovery and utilization of residual REEs in tailings and wasteland of REEs mining area.