淹水条件下土壤中元素迁移的地球化学特征

GEOCHEMICAL CHARACTERISTICS OF ELEMENTAL MIGRATION IN SOILS UNDER SUBMERGED CONDITION

本文研究了淹水条件下水稻土的两种主要母土的元素活化迁移规律及其地球化学特征。结果表明,淹水条件下淋溶迁移元素来源于不同的母体;铁、锰、钙、镁等元素的活化作用加强,迁移能力增加,元素的迁移序列中锰的迁移能力已接近钙、镁等活泼元素;两种土壤中元素的迁移序列不同。性质相似的元素在迁移过程中具有相似的行为,相互之间有很好的相关性,因而在统计区分中位置靠近。引起元素在土壤中活化迁移的过程包括还原、重碳酸化、水化、络合、置换等。按照土壤地球化学类型,红壤中元素的迁移类型属于盐基不饱和型,而普通潮土则介于碳酸盐型和盐基饱和型之间。相平衡分析表明,在淹水且不断移去渗漏液的前提下,两种土壤其矿物风化产物均落在高岭石稳定区内。

Activation and migration and their geochemical characteristics of elements under simulated submerged condition were studied, with red soils and fluvo-aquic soils as substrates. The results showed that leached elements came from different soil parts. The activities of Fe, Mn, Ca and Mg were strengthened, and their migrating abilities increased. Migration coefficient of Mn was nearly as large as that of Ca and Mg. The orders of elements migration in the two soils were different, in the red soil, being the order of Ca>Mn>Fe>Mg, Na>K>Si, P>Al, but Ca>Mg>n>Na>K, Fe>P>Si>Al in the fluvo-aquic soils.Elements which have similar geochemical properties had similar behaviors during migrating processes, thus there existed close correlations among them and they took the near locations each other in the diagrams derived from principal component analysis. There were several distinctive groups of leached elements:Ⅰ. Mg, Ca, Sr, Ba. (ⅡA Family)Ⅱ. Fe, Mn, Co. (Ferrous elements)Ⅲ. K, Na, Si, Al. (Lithophile elements)Soil processes causing the activation and migration of elements included reduction, bio-carbonization, complexation and hydration. Element leaching type of red soil was a dystric geochemical one, while Meadow soil between the eutric and car bonated geochemical leaching types. Phase equilibrium analysis showed that under the condition of submergence and continuous removal of percolation solution, the stable product of chemical weathering of minerals the in the two soils was kaolinite.Key words Submerged soils, Element migration, Pedogeochemical features Mineral transformation