- 期刊
稀土元素在土壤中之含量、分化現象及其於環境議題之應用
Rare Earth Elements Concentrations, Fractionation in Soils and Applications in Environmental Issues
摘要
稀土元素（rare earth elements, REEs）為15個鑭系元素、鈧和釔的總稱，由於其電子組態相近而具有相似物化性質，在環境中常以「群」的特徵出現。REEs除了來自土壤母質的風化，在高科技產業與綠電設備等工業製程中，是個技術關鍵元素，使用量逐年上升，但可能會伴隨增加洩漏在環境中的風險。此外，REEs對生物及人體的潛在毒性不明確，而REEs中的某些元素濃度低不易檢測，因此是個需要重視的新興污染物。REEs之離子半徑隨原子序增加遞減，使其和土壤固相物質（例如，有機質、黏粒和氧化鐵）結合後，存在著輕REEs（鑭～釓）與重REEs（鋱～鎦、鈧和釔）於土壤中重新分布之分化現象（fractionation）。REEs的組成及元素分化具有來源專一性，且可以反映土壤性質變化。因此，瞭解土壤中REEs之含量和地球化學行為，除了可釐清其自然背景基線及進入土壤環境後的分化機制，並根據其分化特徵作為土壤與地下水污染溯源之環境法醫工具，同時增加土壤、底泥及地下水污染預防、評估與整治技術參考的方法學。
並列摘要
Rare earth elements (REEs) include 15 lanthanides, scandium, and yttrium. These elements exhibit great resemblance in physiochemical properties due to their similar trivalent chemical affinity and are hence generally found as a group in the environment. As one of the technology-critical elements in high-tech and green power industries, the globally burgeoning demand for REEs is accompanied by rising environmental impacts. Furthermore, considering the possible pathways for entering the ecosystem and eventually presenting unacceptable threats to human health, REEs are regarded as potential agents of soil contamination. On the other hand, owing to the gradual decrease in the ionic radius along with the increased atomic weight, a differential distribution, that is, fractionation, occurs between light REEs (Z = 57-64) and heavy REEs (Z = 21, 39, and 65-71) in soils after the association with soil solid phases such as organic matter, clay, and iron oxides. The elemental composition and fractionation tendency of REEs have source specificity and can indicate alterations in soil properties. The understanding of REEs concentrations in soils and their geochemical behaviors provides insights into background concentrations of REEs and elucidates their fractionation mechanism in soils for monitoring and management of soil, sediment, and groundwater pollution in the future. This study sets up a scientific foundation for applying REEs as environmental forensics tools for tracing soil contaminants.