粤西地区土壤-植物系统中稀土元素地球化学特征

在广东省西部不同地区采取土壤、植物样品，并对其中的稀土元素含量采用ICP-MS法测定，研究了稀土元素在土壤、植物叶中的地球化学特征。结果表明：土壤一植物系统的各环节间稀土元素的含量模式基本相似。不同母岩发育的土壤稀土分布有较大的差异，其中以花岗岩发育的土壤稀土含量最高。在土壤的各个剖面层中，心土层和底土层稀土含量高于表土层，轻重稀土发生分异，均有不同程度的Eu亏损，Ce表现为土壤各层位中的正异常。同一采样点的不同种属植物具有相似的稀土分配模式，在不同母岩发育土壤上生存的同一种属植物稀土分配模式不同，其稀土分布均受其所生存土壤的影响和制约，同时具有自身的生物地球化学特性。生物吸收系数表明植物对稀土元素的吸收能力的差异，稀土元素在由土壤向植物体运输迁移中发生了明显的分馏作用，重稀士相对贫乏。

GEOCHEMICAL CHARACTERISTICS OF RARE EARTH ELEMENTS(REEs)IN THE SOIL-PLANT SYSTEM IN WEST GUANGDONG PROVINCE

Concentrations of rare earth elements(REEs)in soil and plant samples collected from different areas,West Guangdong were determined with the ICP-MS method to study geochemical characteristics of these elements.Results show that no big difference was found within a soil-plant system in REEs distribution pattern,but they were detected between soils derived from different parent materials,with the soils derived from granite being the highest in REE concentration.Within a soil profile,REE concentrations were higher in B and C horizons than in A horizon.Differentiation between light REEs and heavy REEs occurred displaying some extent of negative Eu anomaly changes,while Ce showed positive anomaly in all soil layers.Plants different in genera growing in the same sampling site were quite similar in REE distribution pattern,but plant of the same genera growing in soils derived from different parent materials differed in REE distribution pattern.Obviously,REE distribution in plants are influenced by the soils they grow in and also displays their individual biogeochemical characteristics.Biological absorption coefficients indicate that plants vary sharply in REE absorption capacity.REEs are obviously fractionated when they are transported and migrated from soils to plants,revealing that heavy REEs are relatively sparse.