重庆四面山农地土壤前期含水量对优先流及溶质优先运移的影响

发布时间：2018-03-03 16:23

本文选题：农地　切入点：土壤前期含水量　出处：《北京林业大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文针对土壤中的优先流现象对土壤水分的利用率及溶质在土壤中的迁移的问题,以重庆四面山的农地为研究对象,通过设立干燥处理和湿润处理,采用染色示踪法、TDR法和图像处理技术研究了土壤前期含水量对优先流入渗深度和入渗速率的影响；同时,通过人造大孔隙土柱实验研究了土壤前期含水量对溶质优先运移的影响。结果分析表明：(1)土壤前期含水量低的样地,湿润锋的渗透速率随土层深度的增加而增加,湿润锋平均入渗速率为1520mm/h；土壤前期含水量高的样地,湿润锋的渗透速率随土层深度的增加而减小,湿润锋平均入渗速率为515mm/h。说明土壤前期含水量低的样地优先流的入渗速率更快。(2)土壤前期含水量较低的样地垂直剖面的染色示踪物平均最大入渗深度为56.00cm大于前期含水量较高的样地的33.76 cm,说明土壤前期含水量低的样地优先流渗透深度更大。土壤前期含水量较高的样地,优先流主要发生在土壤表土层和心土层的20-30 cm土层深度处,而前期含水量低的样地优先流在表土层、心土层和底土层均有发生。而且土壤前期含水量较低的样地,每层垂直剖面的平均染色面积均大于前期含水量高的样地,说明土壤前期含水量较低的样地优先流现象更明显。(3)土壤前期含水量较低的样地每层深度上染色区与未染色区的稳定出流速率均大于土壤前期含水量较高的样地,水分穿透曲线也是前期含水量较低的样地波动更大、更不稳定。土壤前期含水量较低的样地基本每层土壤染色区与未染色区的各个孔径范围的大孔隙数和孔隙率均大于土壤前期含水量较高的样地,且土壤前期含水量低的样地染色区有效大孔隙的贡献率也较大。(4)土壤前期含水量较低的土柱优先流及溶质优先运移的现象更明显。土壤前期含水量低的土柱非吸附性离子溶质优先运移的作用更明显,初始穿透更早,且回收率较大。不同土壤前期含水量下的土柱,H2PO4-的回收率都在18%以下,绝大部分吸附性离子被土柱颗粒吸收,土壤前期含水量低的土柱初始穿透时间也较早,相对浓度的峰值较大,但溶质优先运移现象不明显。
[Abstract]:In order to solve the problem of soil moisture utilization and solute migration due to preferential flow in soil, the farmland of Simian Mountain in Chongqing was studied by setting up drying and wetting treatment. The effect of soil moisture content on infiltration depth and infiltration rate was studied by means of TDR and image processing. The effect of soil moisture content on the preferential transport of solute was studied by artificial macroporous soil column. The results showed that the infiltration rate of wetting front increased with the increase of soil depth. The average infiltration rate of the wetting front is 1520mm / h, and the infiltration rate of the wetting front decreases with the increase of soil depth. The average infiltration rate of wet front is 515mm / h. It shows that the infiltration rate of preferential flow of sample land with low soil water content is faster. 2) the average maximum infiltration depth of dye tracer in vertical section of sample land with lower soil moisture content is 56.00 cm higher than that before. The results showed that the preferential flow infiltration depth of the sample land with low soil water content was higher than that of the sample land with higher water content in the early stage of soil, and the sample land with higher soil water content in the early stage of the period had a higher infiltration depth. The preferential flow occurred mainly at the depth of 20-30 cm soil layer in the top soil layer and the heart soil layer, while the sample land with low water content in the early stage occurred in the top soil layer, the core soil layer and the bottom soil layer, and the sample land with lower soil moisture content in the early stage. The average dyeing area of each vertical section was larger than that of the sample with high water content in the early stage. The results showed that the preferential flow in the sample plots with lower soil moisture content was more obvious than that in the sample plots with lower soil water content. The steady flow rate in the dyeing and unstained areas was higher than that in the sample plots with higher soil water content. The water penetration curve also shows that the sample with lower water content in the early stage fluctuates more. The large porosity and porosity of each pore size in each layer of soil dyeing area and unstained area were higher than those in the sample land with higher soil water content. And the contribution rate of effective macropores in the dyeing area of the sample land with low water content in the early stage of soil is also larger. 4) the preferential flow of soil column and the preferential transport of solute in the earlier stage of soil water content are more obvious, and the soil column with low water content in the early stage of soil is not absorbent. The preferential transport of para-ion solute is more obvious. The initial penetration was earlier and the recovery rate was larger. The recovery rate of H _ 2PO _ 4- was below 18%, and most of the adsorptive ions were absorbed by soil column particles, and the initial penetration time of soil column with low soil water content was earlier than that of soil column. The peak value of relative concentration is larger, but the preferential transport of solute is not obvious.
【学位授予单位】：北京林业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S152.7

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