几种典型红壤模拟降雨条件下的泥沙特征研究

ESTIMATING SEDIMENT CHARACTERS OF SEVERAL TYPICAL RED SOILS BY SIMULATED RAINFALL

泥沙是土壤侵蚀过程的产物,直接反映了土壤的侵蚀特征。本文利用人工模拟降雨,研究了南方几种典型母质发育红壤侵蚀泥沙的颗粒分布特征、不同粒级中胶结物质的种类和含量。研究结果表明,径流优先选择携带0.002~0.02 mm颗粒,该级别颗粒占泥沙总量的26.68%~60.33%。粘粒含量高的第四纪粘土红壤,泥沙中粗颗粒含量较高,且多为较稳定的团聚体;沙粒和粉粒含量较高的页岩红壤和花岗岩红壤侵蚀泥沙中单粒含量较高,且泥沙分散后粉粒和粘粒的含量高于原土壤。花岗岩红壤侵蚀泥沙中Fe_d,Al_d,Al_o和Si_o含量随泥沙粒径的增大而降低,而泥质页岩红壤和第四纪粘土红壤中,Fe_d,Al_d,Al_o含量随粒径增大而增加,因此其粗粒径泥沙具有较强的稳定性。侵蚀泥沙对有机质有富集作用,泥质页岩红壤和第四纪粘土红壤的粗颗粒对有机质的富集作用强于细颗粒。

Sediment is the product of soil erosion, so it can reflect the characters of erosion process. In this study, six red soil samples, derived from three parent materials（Quaternary red clay, Shale and Granite） were selected and subjected to simulated rainfall experiment. The particle size distribution and cementing material of sediments were tested. From the compare of the physic-chemical properties of different sizes sediment, the main results as followed： Compared to the particle size distribution of test soils, there were more 0.002–0.02 mm particles in sediments, which occupied26.68%–60.33% in sediments. It means that the runoff was preferred to transit particles between 0.002 mm to 0.02 mm.The proportion of 0.02–0.002 mm and 0.002 mm particles were far greater than that in test soil from Shale and Granite while the proportion was lower than test soil from Quaternary red clay. After chemical dispersion treatment, the particle size distribution of sediment were different from the test soil, and there were more 〈0.02 mm particles in sediments than test soils. The large particles（〉0.25 mm） in sediment from high-clay soils（derived from Quaternary red clay） is abundant,and most of which were stable aggregates. After chemical dispersion, there were more primary particles in sediments from high-sand soils（derived from Granite） and high-silt soils（derived from Shale） than in high-clay soils, and more clay and silt than test soils. The content of Fed, Ald, Alo and Sio decreased with the increase of particles size in sediments derived from Granite, while Fed, Ald and Alo increased with the increase of particle size in sediments from Shale and Quaternary red clay. As a result, the large particles of sediments from Shale and Quaternary red clay were more stable than that from Granite. However, no obvious distribution regularities of Sio were found in different size particles in three sediments.The content of organic matter also increased with the increase of particles size of sediment from shale and Quaternary red clay.However, the enrichment was not obvious for sediments from Granite, the content of organic matter of which was higher in0.25–0.05 mm particles than in other sizes particles. The ration of MWD（mean weight diameter） before dispersion and after dispersion was positively correlated with the contents of oxide except Sio, which was negatively correlated with the ration. It indicated that iron-aluminum oxides（Fed, Ald and Alo） are important stable factors of red soil aggregates.