亚热带地区几种红壤坡面侵蚀泥沙的物质组成特性

COMPOSITION OF SEDIMENTS OF EROSION FROM DIFFERENT RED SOIL SLOPES IN SUBTROPICAL AREA

以三种母质发育的5个红壤为研究对象，在人工降雨条件下，研究不同降雨动能坡面侵蚀泥沙的颗粒分布特征及物质组成状况。结果表明：侵蚀泥沙的颗粒分布受土壤母质和降雨侵蚀力影响差异较大，相同母质红壤产生泥沙的颗粒组成特征相似，纱网覆盖条件下泥沙中细颗粒（〈0.02mm）相对含量普遍高于裸地，泥质页岩发育红壤（HS）和花岗岩发育红壤（TG1和TG2）泥沙（分散后）表现为黏粒和粉粒的富集，富集率为1.15~3.14，第四纪红黏土发育红壤（HQ1和HQ2）泥沙中（分散后）砂粒富集比较明显，富集率最高为3.84；对于HS、TG1和TG2土壤而言，泥沙中有机质（OM）、游离氧化铁铝（Fed和Ald）主要分布在〈0.05mm粒径中，而对于HQ1和HQ2土壤而言，则主要分布在〉0.25mm和〈0.05mm两个粒级的泥沙颗粒中，其中有机质（OM）富集最明显；泥沙中OM、Fed和Ald之间达到极显著相关（r≥0.82），而且它们与土壤中阳离子交换量（CEC）、Fed、Ald、非晶形氧化硅（Sio）、黏粒含量的相关性也达到极显著水平（r≥0.81），说明泥沙中这些物质间相互影响，而且很大程度上取决于供试土壤的自身物质含量。

Particle size distribution and material composition was measured of sediments of erosion from slopes of red soils （five different types of red soils derived from three different kinds of parent materials, i.e, Shale, Quaternary red clay and Granite） as affected by rainfall kinetic energy of artificial rainfall. Rainfall kinetic energy was controlled by either leaving the slopes bare or covering them with mesh. Results show that particle size distribution of the sediments of erosion was influenced significantly by parent material and rainfall erosive force. That is to say, soils derived from the same parent material would generate erosion sediments similar in particle composition and mesh coverage increased the content of fine fractions （non-dispersed） in sediments which was due mainly to the interaction between stability of aggregates and erosive force of rainfall on the slope. The sediments from red soils derived from Shale （HS） and Granite （soil TG1 and TG2） were enriched with silt and clay （dispersed） （1.15 to 3.14 in enrichment rate） while those from soil HQ1 and HQ2 derived from Quaternary red clay enriched with sands with the highest enrichment rate reaching 3.84. In sediments from soil HS, TG1 and TG2, organic matter （OM）, free iron oxide （Fed） and aluminum oxide （Ald） were mostly distributed in fine particles smaller than 0.05 mm （non-dispersed） in size; however, in sediments from HQ1 and HQ2, they were concentrated in two particle size fractions, i.e. 〉0.25 mm and 〈0.05 mm. Among them, OM was the most obvious with enrichment rate varying from 1.05 to 9.88. In the sediments OM, Fed and Ald were extremely significantly related to each other （r≥0.82）. So were they with cation exchange capacity, Fed, Ald, amorphous silica and clay in the original soils, indicating that these substances in the sediments influence each other and depend largely on their content in the original soils.