河岸带表土层氮素非饱和入渗运移规律模拟

Simulation of nitrogen infiltration and movement through unsaturated soil in topsoil layer of riparian zone

自制土槽装置,室内模拟氮素在河岸带表土层中非饱和入渗的过程。通过观测土槽中不同点位渗流水体出流时间的先后顺序以及各点水体中TN、NH4+-N浓度随入渗时间的变化,探讨氮素在河岸带表土层中非饱和入渗的运移规律。试验结果表明:在河岸带表土层非饱和入渗过程中,水分水平运移速度小于垂直运移速度,NH4+-N的运移滞后于水分的运移;在土壤"干"-"湿"-"干"过程中,各点TN、NH4+-N浓度值随时间先急剧增加再缓慢减少然后趋于稳定。另外,河岸带表土层对非饱和入渗氮素的截留效果较好,试验11 h时,在1.08m的坡长距离上,距土表面12 cm深度TN、NH4+-N浓度比进水分别下降74.23%和68.02%。

An experimental study was conducted in an indoor soil tank to examine to nitrogen infiltration and movement through unsaturated soil in topsoil layer of riparian zone.The timing of seepage flow from the tank and the seepage sequence at different sampling points were monitored.The variation of nitrogen concentrations（e.g.,total nitrogen TN and ammonia NH＋4-N） was also observed.Results show that the vertical velocity of percolation water is larger than the horizontal one during infiltration into the unsaturated topsoil layer of riparian zone.In the process from dry-to-wet and wet-to-dry,the TN and NH＋4-N concentrations first has a sharp increase and then gradually decrease until reaching a stable state.This is true for every monitoring point.In addition,the nitrogen retention capacity in the topsoil layer of riparian zone is high under unsaturated conditions.Along the 1.08m long slope and 11 hours after the experiment began,the TN and NH＋4-N concentrations at points 12 cm below the surface reduce by 74.23% and 68.02%,respectively.