残膜对土壤水分水平运动的阻滞作用

为探明不同残膜量对土壤水分水平运动过程的影响规律,设置6个残膜量水平,分别为0,80,160,320,640,1 280kg/hm~2,采用室内水平土柱吸渗法,分析残膜对水平湿润锋运移、累积入渗量、Boltzmann系数和土壤水分扩散率的影响。结果表明:水平湿润锋运移速率、土壤含水率和累积入渗量均随残膜量增加而减小,残膜量≥160kg/hm~2时,水平湿润锋运移速率和累积入渗量大幅降低;残膜对土壤水分水平运动的阻滞系数与残膜量呈正相关关系,残膜阻滞系数的最大增长率出现在80~160kg/hm~2残膜量区间,高达251.15%;随残膜量的增加,阻滞作用较强区域距离入渗点的距离增大,Boltzmann系数和水分扩散率则逐渐减小,土壤基质势对水分水平运动的驱动作用和土壤持水能力逐渐减弱;混有残膜的土壤水分水平运动过程,仍符合土壤水分扩散率单一参数模型和Kostiakov入渗模型。残膜是一种难降解持续性污染物,会降低水平湿润锋运移速率、累积入渗量和土壤水分扩散率,对土壤水分水平运动的阻滞作用随残膜增多而增强。

Ability of Retarding Water Horizontal movement for Residual Plastic Film Mixed in Soil

In this study, we aimed to investigate the effect of different amounts of residual plastic film on soil water horizontal diffusion process. By using the horizontal soil column simulation investigation, Six kinds of residual plastic film(0,80,160,320,640 and 1280kg/hm2) were designed with triplicate. The water wetting front transport distance, the accumulative infiltration amount and soil water content were determined, then we could calculate the Boltzmann coefficient and water diffusivity by using iterative method. The results showed that the migration rate of horizontal wetting front, the accumulative infiltration amount and volumetric soil water content gradually declined with the increase of residual plastic film amount. When residual plastic film amount was more than 160 kg/hm2, the migration rate of horizontal wetting front and the accumulative infiltration amount would dramatically reduce. There were extremely significant positive correlation relationship between the amount of residual plastic film and retardation coefficient. When the amount of residual plastic film ranges from 80 kg/hm2to160kg/hm2, increase rate of retardation coefficient reached up to 251.15%. The distance from stronger retardation region to infiltration point was enlarged with increase of residual plastic film. However, Boltzmann coefficient and water diffusivity were gradually declined, driving force of soil matric potential on soil water diffusion and soil water holding ability wore off. The horizontal diffusion process of soil mixed with residual plastic film still conforms to single parameter model of soil water diffusivity. Our results suggest that the residual plastic film as soil pollutant would reduce migration rate of horizontal wetting front, accumulative infiltration amount and soil water diffusivity, the retardation effect of residual film on soil water diffusion will enhance with residual plastic film amount increasing.