溶质施放部位对红壤坡面溶质迁移特征的影响

Effect of Solute Application Position on the Solute Transport Characteristics on Red Soil Slope

以非吸附性溴离子为示踪剂,采用室内模拟降雨方法研究间歇降雨和施肥部位对红壤坡面产流、产沙以及溴离子迁移特征的影响。结果表明,降雨特征相同条件下,3次降雨的总径流量无明显差异,但第3次降雨形成的产沙量分别是第1次和第2次的7倍和2.2倍,这表明因前期含水量的提高而降低了土壤抗冲性是红壤侵蚀的主要原因之一;径流溴离子浓度随时间变化均呈幂函数衰减,与施肥部位无关;施肥部位越靠近坡底,径流溴离子初始浓度越高且衰减速度越快;溴离子流失数量与施肥距离呈显著正线性关系。通过估算3次间歇降雨径流中溶质流失数量的来源发现,淋溶到坡面土壤中的溴离子再次参与径流流失的数量,其平均比重从81.61%提高到了93.76%,这表明施加在上坡部位的肥料被淋溶后对后期径流养分流失的贡献十分显著。

According to indoor simulating rainfall experiments, the effects of interval rain events and fertiliza- tion sites on the runoff process, sediment losses and solute transport to runoff on red soil slopes were investi- gated using bromine （Br-） as a tracer to represent a non-adsorbed mobile chemical. Results showed that, the total runoff yields had no significant difference for 3 rainfall events, while the sediment yield in the 3rd rainfall event was 7 times and 2.2 times greater than that in the 1st and the 2nd rainfall event, respectively. The significant decrease in soil antiscouribility with increasing antecedent soil water content was one of the dominant reasons for red soil erosion. The Br- concentrations in runoff were described by a power decay model for 3 rainfall events, independent of the solute application positions. The more close to the bottom of the slope fertilization sites were, the higher initial solute concentration became and the faster Br- concentra- tion decayed. It had a significantly positive linear relationship between the amounts of Br- loss in runoff and the distances from the fertilization position to the top of the slope. Through estimating the source of solute loss for the 3 interval rain events, the average ratio of the amount of Br- loss with runoff, which once leached into soil during the last rainfall event, increased from 81.61% to 93.76%. This result showed that the fertilizer leaching on the upslope significantly affected the ratio of runoff nutrient losses for the successive rainfall events.