三峡库区紫色土坡地土壤颗粒流失特征

选取20°长期耕作紫色土坡面径流小区进行模拟降雨试验,分析坡面土壤的颗粒组成及其变异,比较侵蚀泥沙颗粒组成的过程变化及其与坡面土壤颗粒组成的差异。结果表明,紫色土具有较宽变幅的颗粒组成,0.002～0.25mm的颗粒含量最高,坡面土壤存在较大的异质性;降雨初期侵蚀泥沙中<0.05mm的单粒和微团聚体含量都在65%以上,富集率分别为1.30,1.44,整个泥沙中的富集率分别为1.12,1.10,是侵蚀泥沙的主体,这其中又主要是0.002～0.05mm的粉粒和微团聚体;泥沙中<0.01mm的物理性粘粒及>0.25mm的水稳性团聚体富集率分别为1.10,1.16;随着降雨时间延长,单个泥沙样的颗粒组成逐渐接近雨前表土。

Particle Characteristics of Eroded Purple Soil from Slope Land in the Three Gorges Reservoir Region

Simulated rainstorm experiment was carried out on a selected 20° runoff plot filled with purple soil which was long-term under farming practice,grain size composition and its variations of the experimental purple soil were analyzed,comparisons between sediment and soil grain size distributions were conducted as well as the changes of sediment particle composition during the individual event.The results show that:(1)Purple soil contains a broad range of grain sizes,biggish heterogeneity exists in slope surface soil and fine soil particles(0.002~0.25 mm) are of the highest content.(2)Finer primary soil particles and micro-aggregates(<0.05 mm),which are the main body of sediment,occupies more than 65% of the total sediment during the early phase of the event,of which silt and micro-aggregates(0.002~0.05 mm) occupies the most.Mean enrichments of the two types of particles in the individual sediment samples are 1.30,1.44,respectively during the early phase of the event and 1.12,1.10,respectively of the total sediment.(3)Mean enrichments of physical clay(<0.01 mm) and waters-table aggregate(>0.25 mm) of the sediment are 1.10,1.16,respectively.(4)Grain size composition of the individual sediment sample gradually comes close to the matrix soil as the event continued.