中国5种典型土壤的侵蚀泥沙粒径分布特征

Size Distribution Characteristics of Sediments Eroded from Five Typical Soils in China

通过天然降雨试验,研究我国5种典型土壤的侵蚀泥沙团粒和单粒粒径分布以及泥沙各级团粒的机械组成特征。2013—2014年汛期(6—9月),监测红壤、紫色土、黄绵土、褐土和黑土径流小区的降雨产流事件,收集侵蚀泥沙样品,利用湿筛法和吸管法测定其团粒和单粒粒径分布;同时,筛选出泥沙各级团粒样品,进一步测定其单粒粒径组成。结果表明:(1)侵蚀泥沙粒径分布是土壤质地和降雨强度综合作用的结果,团粒粒径分布更适合作为表征泥沙输移的指标;(2)5种土壤的侵蚀泥沙皆表现出粉团(0.002~0.05mm)和黏团(<0.002mm)的明显富集;(3)在泥沙单粒粒径分布方面,除红壤的粉粒(0.002~0.05mm)和黏粒(<0.002mm)有轻微富集外,其余4种土壤的各级单粒均无明显富集;(4)红壤侵蚀泥沙粉团(0.002~0.05mm)中的黏粒含量最多,其余4种土壤侵蚀泥沙机械组成和各级团粒的机械组成均与原土接近。

This study investigated the size distributions of aggregates and primary particles in the sediments eroded from five typical soils in China under natural rainfalls.The experiment was conducted on five runoff plots packed with the Red Soil,Purple Soil,Loess,Cinnamon Soil and Black Soil.Sediment samples in four runoff events of these plots under natural rainfall were collected during June to September in 2013 and 2014.Using the pipette method and wet sieving technique,the compositions and size distributions of primary particles and aggregates were measured.Moreover,the sediment aggregates with different sizes were sieved and determined for the size distribution of primary particles.The results showed that：（1）The sediment size distribution was affected by both soil texture and rainfall intensity.The aggregate size distribution was more suitable as a better indicator for sediment transport.（2）Larger portions of silt-sized（0.002-0.05 mm）and clay-sized（〈0.002 mm）aggregates were obtained in the sediments of five types of soils.（3）However,no obvious enrichment of primary particles was observed in the eroded sediments of any soil but the Red Soil,which possessed slightly elevated percentages of silt and clay in the corresponding sediments.（4）When further analyzing the primary particle-size composition of sediment aggregates with different size,the highest percentage of clay particles was determined in the silt-sized aggregates of the Red Soil.For the rest four types of soils,the mechanical composition of eroded sediment and the mechanical composition of the aggregates at all sizes were all similar to the source soil.