2023-03-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/675277稀土元素由15個鑭系元素與鈧、釔所組成，這17個元素的物化性質相近，但自母質釋出經土壤化育過程後會重新排列組合，造成所謂分化現象(fractionation)，因此不同稀土元素比例的變化可做為土壤化學反應之佐證，於是成了一個新穎的特徵化土壤化育作用量化指標。另一方面，稀土元素非植物生長必需元素，其在土壤中的濃度、生物毒性與對人體健康之危害尚不明確，可視為新興污染物質，但稀土元素卻又是高科技產業所需要的技術關鍵元素。因此，稀土元素在土壤科學與農業、環境與資源領域中，是一個值得重視的議題，但其在不同母質土壤剖面中的垂直分布、富集與流失，及其在不同土壤組成分的重新分配等特徵的研究，仍非常欠缺，而臺灣也未曾有過稀土元素在土壤中動態之探討。因此，本三年期計畫擬以相似氣候、地形、植被下的不同母質土壤，即岩性土序，為探討對象，以微形態學、理化性質分析、x-ray繞射鑑定礦物、鐳射剝蝕-感應耦合電漿質譜與電子微探等不同方案，解釋土壤中稀土元素透過洗出/洗入、氧化/還原、溶解/沉澱、螯合作用等作用下的分化。研究主題包括，不同母質土壤稀土元素的含量與分布特徵、岩性土序中稀土元素在土壤化育過程的富集與流失、土壤中稀土元素生物有效性指標的評估，期望能(1)了解稀土元素在臺灣不同類型土壤的含量與範圍，(2)提供土壤性質對稀土元素流布影響的資訊，(3)做為臺灣盤點環境中技術關鍵元素之基準資料庫，(4)了解稀土元素在土壤剖面中的重新群聚或分散現象，(5)利用顯微光譜技術掌握稀土元素在土壤中的空間分布，(6)由稀土元素分布特徵解釋不同岩性母質土壤的風化程度與土壤特性之關係，(7)了解稀土元素在不同土壤的溶解特性，(8)評估適合萃取土壤稀土元素生物有效性的化學速測法，及(9)掌握稀土元素在不同土壤組成分的分配情形。 Rare earth elements (REEs) represent 17 elements including 15 lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), scandium (Sc), and yttrium (Y) which are characterized by the universal occurrence as a group and similar physiochemical properties in the environment stemming from the resemble trivalent chemical affinity. REEs are commonly divided into light rare earth elements (LREEs: La to Gd) and heavy rare earth elements (HREEs: Tb to Lu, Sc and Y) according to their differences in atomic weight, electron configuration, and mineral composition. The LREEs and HREEs from parent materials are therefore partitioned into various soil components by pedogenetic processes. Additionally, REEs are ones of the key materials used for the development of critical technologies including photovoltaic modules, optoelectronics, and computers. REEs become susceptible to soil contamination because of mining activities, wastewater leakage, and disposal of the electronic equipment, and thus they gradually attracted concerns of potential risks to the environmental quality and human health. Hence, study of REEs is an important issue in the fields of on soil science, agriculture, environment, and resource. However, rare studies explored the vertical distribution and fractionation of REEs in soil profiles and soil components along a lithosequence. Moreover, no research has performed on the dynamics of soil REEs in Taiwan. Therefore, this three-year project will elucidate REEs partitioned in the soils of a lithosequence with similar climate and vegetation in eastern Taiwan by combining approaches of micromorphology, physiochemical analysis, x-ray diffraction, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and electron probe micro-analyzer (EPMA). The fractionation of REEs will be demonstrated by the mechanisms of eluviation/illuviation, oxidation/reduction, dissolution/precipitation, and complexation. The main themes of project include: characterization of REEs in soils derived from different parent materials, gain and loss of REEs in a soil lithosequence, and bioavailability evaluation of soil REEs. The aims of project are to: (1) understand the abundance and range of REEs in different types of soils in Taiwan, (2) correlate the relationships between REEs and soil properties, (3) fulfill the database of technology-critical elements in the environment of Taiwan, (4) illustrate the fractionation of REEs in the soil profiles, (5) explore the spatial distribution of REEs by using micro-spectroscopic techniques, (6) trace pedogenic pathways by REEs fractionation and distribution associated with weathering degree and soil characteristics, (7) characterize dissolution dynamics of soil REEs, (8) evaluate the bioavailability of soil REEs by chemical extractions, and (9) depict the partition of REEs in various soil components.土壤分類;岩性土序;化育作用;微量元素;土壤礦物;土壤調查;soil classification; lithosequence; pedogenesis; trace element; soil mineralogy; soil survey