紫色土区土壤初始含水量对坡面径流溶质流失的影响

Effect of the Soil Antecedent Water Content on Soil Solutes Loss on Slope of Purple Soil Region

土壤初始含水量在一定程度上影响着紫色土区的水土流失。通过人工降雨试验,研究了紫色土在5%,10%,15%和20%共4种初始含水量条件下的入渗、产流和径流溶质迁移变化过程。结果表明:径流强度随降雨时间呈对数函数变化;降雨25min后,径流强度趋于稳定值;在单位时间内,紫色土坡面平均径流深度和累积径流量随初始含水量的增大而增大,而坡面平均入渗率则呈相反的变化趋势。径流中PO34-,K+,Br-浓度均呈现相同的变化规律,在开始产流时,径流溶质浓度很高,随后迅速衰减并逐渐趋于稳定。径流溶质的流失量随初始含水量的增加而增加,径流溶质从土壤迁移到径流的过程是从很小值迅速增大到某一峰值,然后逐渐衰减至稳定。指数函数比幂函数更适合描述紫色土丘陵区坡地径流溶质迁移变化过程。

Soil antecedent water content affects soil and water loss in purple soil area to some extent. According to the results of lab simulation rainfall experiments, the process and mechanism of rainfall infiltration, runoff process, release-transport and change of runoff and solutes less than four soil antecedent water content 5%, 10%, 15% and 20% were studied on purple soil region. The results showed that runoff intensity presents a logarithmic function with rainfall time changing, runoff intensity trended to be steady about 25 minutes later when rain occurred. The change of accumulated output runoff presented a linearity relationship with soil antecedent water content in unit time. The soil surface runoff and an average depth increase with the rise of initial the moisture contents, and the average infiltration rates on slope changes in the reverse trend. The concentrations of PO4^3- , K^＋ , Br^- of runoff presented the same law, at the beginning of runoff yields, the runoff concentration was very high, and then it got down quickly, finally, it trended to be steady. The soil solute losses was gaining with the increase of soil antecedent water contents, the process that the solutes transport from soil to runoff increased quickly to a peak value from a very small concentration, then gradually decayed to a stable content. Exponential function model was more siutable to describe the process of runoff solutes release, transport and change on purple soil hilly region compared with power function model.