间歇降雨条件下黄土坡面土壤溶质的迁移特征

 【目的】研究间歇降雨条件下黄土坡地水分溶质迁移特征，为减少汛期坡耕地肥料流失率和水土流失量提供理论依据。【方法】以黄土坡地为研究对象，采取表层喷施和拌施两种施肥方式，通过两场间隔24 h的室内模拟降雨试验，从降雨-径流-土壤相互作用角度，研究间歇降雨条件下坡面水土流失和土壤溶质（NO3-、Br-和PO43）的迁移特征。【结果】第二次降雨的稳定产流强度、径流量和侵蚀泥沙量均大于第一次降雨，初始产流时间和产流强度达到稳定的时间也比第一次降雨提前。与第一次降雨平稳阶段NO3-和Br-的浓度相比，第二次降雨开始产流时浓度明显偏大，但其平稳阶段浓度又均小于前者，而吸附性PO43-的第二次降雨浓度高于第一次降雨稳定期浓度。非吸附性NO3-和Br-易随入渗水迁移，导致表层土壤溶质含量显著减少，第二次降雨地表总流失量小于第一次降雨，而PO43-受土壤侵蚀因素影响很大，喷施和拌施条件下PO43-第二次降雨的总流失量分别为第一次降雨的2.93和1.77倍。【结论】对于土体疏松易侵蚀的黄土地区，受降雨间歇期表层土壤溶质含量和土壤抗蚀性变化的影响，第二次降雨的径流溶质浓度过程线不能视作第一次降雨的简单延续，多次降雨会加剧吸附性土壤溶质的地表流失风险。在雨季里，首次降雨应时该采取必备的截流措施，减少非吸附性土壤养分的大量流失;对后期降雨的关注重点则是涵养水土，防范吸附性土壤养分的流失风险。

Release and Transport Characters of Soil Solutes on Loess Slope in interval Rain Events

【Objective】 Transport characters of soil water and solute on slope land in interval rain events are important to reduce soil and water loss and to protect water and soil resources in erosion region. 【Method】 According to the results of indoor simulation experiments of rainfall on loess slope land with spray-applied fertilizer or mixed-applied fertilizer, and the interaction of rainfall, surface runoff and soil, the soil erosion, transport characters of soil NO3-, Br-, and PO43- in two rain events with the interval of 24 hours were investigated. 【Result】 Results showed that the stable rainfall intensity, amount of runoff and sediment in the 2nd rain was usually more than that of the 1st one, and more quick for the surface runoff initiation and the stable period occurrence. Compared with the NO3- and Br- concentration in surface runoff of the stable content period in the 1st rain, the concentration of the surface runoff initiation in the 2nd rain was heigher than the former, while that of the stable content period in the 2nd rain was lower. The soil PO43- concentration in surface runoff in the 2nd rain, however, was usually heigher than that of the stable content period in the 1st rain. There was less surface loss amount of soil NO3- and Br- in the 2nd rain, with the result of its available infiltration and the content decreased in the upper layer. While the PO43- surface loss in the 2nd rain was 2.93 times and 1.77 times greater than that inthe 1st rain, for surface spraying treatment and mixed-applied one, respectively. 【Conclusion】 Therefore, for the vulnerable erosion loess slope, the solute content curve of surface runoff in the 2nd rain is not the extension of that of the former, as the result of the changing solute content and the antierosive ability of the upper soil. Affected by the erosive hazards, there will be more soil solute loss caused by continuous rainfall events. Some flow control measures are suggested for the initial rain event in rainy season to lessen the loss of soil non-adsorbed nutrient. The key to the latter rain is protection of soil and water and prevention of the loss of soil adsorbed nutrient.