本文選題：農(nóng)地　切入點：土壤前期含水量　出處：《北京林業(yè)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：本文針對土壤中的優(yōu)先流現(xiàn)象對土壤水分的利用率及溶質(zhì)在土壤中的遷移的問題,以重慶四面山的農(nóng)地為研究對象,通過設(shè)立干燥處理和濕潤處理,采用染色示蹤法、TDR法和圖像處理技術(shù)研究了土壤前期含水量對優(yōu)先流入滲深度和入滲速率的影響；同時,通過人造大孔隙土柱實驗研究了土壤前期含水量對溶質(zhì)優(yōu)先運移的影響。結(jié)果分析表明：(1)土壤前期含水量低的樣地,濕潤鋒的滲透速率隨土層深度的增加而增加,濕潤鋒平均入滲速率為1520mm/h；土壤前期含水量高的樣地,濕潤鋒的滲透速率隨土層深度的增加而減小,濕潤鋒平均入滲速率為515mm/h。說明土壤前期含水量低的樣地優(yōu)先流的入滲速率更快。(2)土壤前期含水量較低的樣地垂直剖面的染色示蹤物平均最大入滲深度為56.00cm大于前期含水量較高的樣地的33.76 cm,說明土壤前期含水量低的樣地優(yōu)先流滲透深度更大。土壤前期含水量較高的樣地,優(yōu)先流主要發(fā)生在土壤表土層和心土層的20-30 cm土層深度處,而前期含水量低的樣地優(yōu)先流在表土層、心土層和底土層均有發(fā)生。而且土壤前期含水量較低的樣地,每層垂直剖面的平均染色面積均大于前期含水量高的樣地,說明土壤前期含水量較低的樣地優(yōu)先流現(xiàn)象更明顯。(3)土壤前期含水量較低的樣地每層深度上染色區(qū)與未染色區(qū)的穩(wěn)定出流速率均大于土壤前期含水量較高的樣地,水分穿透曲線也是前期含水量較低的樣地波動更大、更不穩(wěn)定。土壤前期含水量較低的樣地基本每層土壤染色區(qū)與未染色區(qū)的各個孔徑范圍的大孔隙數(shù)和孔隙率均大于土壤前期含水量較高的樣地,且土壤前期含水量低的樣地染色區(qū)有效大孔隙的貢獻率也較大。(4)土壤前期含水量較低的土柱優(yōu)先流及溶質(zhì)優(yōu)先運移的現(xiàn)象更明顯。土壤前期含水量低的土柱非吸附性離子溶質(zhì)優(yōu)先運移的作用更明顯,初始穿透更早,且回收率較大。不同土壤前期含水量下的土柱,H2PO4-的回收率都在18%以下,絕大部分吸附性離子被土柱顆粒吸收,土壤前期含水量低的土柱初始穿透時間也較早,相對濃度的峰值較大,但溶質(zhì)優(yōu)先運移現(xiàn)象不明顯。
[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.
【學(xué)位授予單位】：北京林業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：S152.7

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