稀土元素在红壤、黄棕壤及淋溶黑钙土中赋存形态的研究(英文)

Speciation of Rare Earth Elements in Red Soil,Yellow Brown Soil and Leached Chernozem

本文采用中子活化分析技术对红壤、黄棕壤及淋溶黑钙土等不同类型土壤中的稀土元素含量、分布模式及其赋存形态进行了系统的研究。结果表明,在三类土壤中,稀土总量的分布顺序为黄棕壤>淋溶黑钙土>红壤。黄棕壤及淋溶黑钙土中稀土分布模式为轻稀土富集、铕亏损型,红壤为轻稀土富集、铈亏损型,均与它们相应的母岩一致,三种土壤中均以稳定的残渣态为主,并随着元素原子序数的递增,中稀土残渣态所占比例低于两端的轻、重稀土,稀土非稳定态中所含六种形态百分含量相比较,风化较彻底的红壤中所含水溶态、可交换态及铁锰氧化物态所占比例高于黄棕壤及淋溶黑钙土,而含有机质较多的淋溶黑钙土中所含紧结有机态明显高于红壤及黄棕壤,可能由土壤中所含有机物活性组分不同所致。

Contents, distribution patterns and speciation of rare earth elements(REEs) in three soil samples-red soil (parent material:basalt), yellow brown soil (parent material: loess) and leached chernozem (parent material; Quaternary sediment), were determined with instrumental neutron activation analysis (INAA). Total contents of REEs in the three types of soils follow the order; yellow brown soil>leached chernozem>red soil. The distribution patterns of REEs in the yellow brown soil and leached chernozem are characterized by light REE(LREE) enrichment and Eu-depletion, while the red soil by LREE enrichment and Ce-depletion. These are consistent with the REE features of their parent rocks. In all the three soils, REEs mainly exist in residual form, and with the increase of atomic number, intermediate REEs (MREE) have lower proportions of residual form than light REEs (LREE) and heavy REEs (HREE). For the unstable forms, the red soil , which is most strongly weathered, has higher proportions of water soluble, exchangeable and bound to Fe- Mn oxides forms than the other two types of soil. The leached chernozem, which contains much organic matter, has higher proportions of tightly bound organic matter form than red soil and yellow brown soil. This might be the result of different contents in the active parts of organic matters.