放水冲刷条件下工程边坡产流产沙及氮磷输出特征

为揭示工程堆积体平台汇流造成的水沙及氮磷养分流失特征,以矿区堆土场为研究对象,采用室内放水冲刷试验,研究不同上方来水流量(1.7,2.3,2.9 L/min)和坡度(25°,30°,35°)下地表径流、壤中流及侵蚀泥沙产生过程,分别测定氮磷养分浓度并计算流失量及贡献占比。结果表明:蒙东地区覆土排土场边坡产流方式主要为地表径流,随坡度和冲刷流量的增大,地表径流量增大,壤中流量减小。产沙量随坡度的增大先增大后减小,侵蚀产沙的临界坡度在30°附近。地表径流中铵态氮及磷酸盐流失浓度均大于壤中流,硝态氮浓度在冲刷流量较大(2.9 L/min)时低于壤中流。径流中磷酸盐及侵蚀泥沙中氮磷损失均随坡度的增大先增大后减小。冲刷流量越大,地表径流及侵蚀泥沙中的氮、磷流失量越多。径流中养分流失量表现为硝态氮＞铵态氮＞磷酸盐。侵蚀泥沙是磷酸盐的主要输出途径,占流失总量的59.69%以上;氮素流失量仅在坡度30°时表现为侵蚀泥沙中最大,在25°,35°坡面,地表径流为氮素的主要流失途径,小流量(1.7,2.3 L/min)时壤中流输出的氮素次之。

Characteristics of Runoff, Sediment and Nitrogen and Phosphorus Output of Steep Slope of Abandoned Soil Deposits Under Scouring Flow

In order to reveal the characteristics of runoff and sediment and nutrient loss path of on steep slope caused by platform inflow of engineering soil deposits, a laboratory scouring experiment, designed to have three scouring inflow rates (1.7, 2.3, 2.9 L/min) and three slope gradients (25°, 30°, 35°), was conducted on disposal sites in opencast coal mine to research the processes of surface runoff, interflow and sediment and measure the concentration of nitrogen and phosphorus in these for calculating the nutrient loss and contribution. The results indicated as follows: Surface runoff was the main type of runoff generation in earth-covered engineering slope in eastern Inner Mongolia. With the increase of slope gradient and scouring inflow rates, surface runoff increased but interflow decreased. The sediment yield rose first and then decreased with the increase of slope gradient, and the critical slope gradient was about 30°. The loss concentrations of ammonium nitrogen and phosphate in surface runoff were higher than those in interflow, and the concentrations of nitrate nitrogen were lower when the scouring flow was larger (2.9 L/min). The loss of phosphate in runoff and nitrogen and phosphorus in eroded sediment firstly increased and then decreased with the increase of slope gradient. The loss of nitrogen and phosphorus from surface runoff and sediment increased with the increase of scouring inflow rates. The amount of nutrient loss in runoff was nitrate nitrogen > ammonium nitrogen > phosphate. Erosion sediment was always the main export route of phosphate, accounting for more than 59.69% of the total loss. The maximum nitrogen loss occurred only when the slope gradient was 30°, while on the 25°and 35°slope, surface runoff was the main route of nitrogen loss, at low inflow rates (1.7, 2.3 L/min), the nitrogen output from interflow was the second.