【作者】 唐泽军；

【导师】 雷廷武；

【作者基本信息】 中国农业大学 ， 农业生物环境与能源工程， 2002， 博士

【摘要】 中国是世界上水土流失最严重的国家之一，尤以西北干旱半干旱（包括黄土高原）地区最为严重。 造成水土流失一个极其重要的原因是降雨引起的土壤表面结皮，降低了土壤的入渗性能，增加丁土壤表面的径流，加大了土壤侵蚀。本文的目的是研究利用聚丙烯酰胺（PAM）作为土壤改良剂来抑制土壤表面结皮，增加降水入渗，减少土壤表面径流，降低土壤侵蚀；同时采用稀土元素（REE）示踪土壤侵蚀的动态过程，研究土壤侵蚀的动力学机理。 本项研究中，进行了一系列的人工降雨模拟试验。试验土样取自于内蒙古清水河地区耕作表层土，是典型的黄绵土，为淡黄色。土壤颗粒以粉沙为主，粉沙粒占总量的60％左右，粘粒约占15％左右，容重约为1.2g cm^-1，试验前将土样风干并过1×1cm的粗筛。试验由三个雨强(50，100，150mm h^-1)和四个坡度（8.74％，17.63％，36.4％，46.63％）相互交叉的十二个试验构成。每个试验又分两个阶段，在试验的前一阶段的降雨试验完成后，将试验土样静置24h，后一阶段再重复前一阶段的降雨试验过程。 试验过程中，土壤表面采用五个处理，即一个对照、一个秸杆覆盖和覆盖率分别为80％，60％，40％的三个PAM处理。将一个3×8m的土槽分为15个0.2×8m的小槽。每试验小槽采用一个处理，PAM按每m²覆盖土壤表面1g与1kg试验土混合后均匀播撒在地表。同时，REE（Dy、La、Sm、Yb、Ce、Eu、Nd、Tb）经过与土壤混合逐步稀释后，依次填充在每条小槽的表面。试验采用3个重复。 在内蒙古自治区清水河县境内的实验区进行利用PAM增加降雨入渗、提高降雨利用率、增加作物产量的大田实验。在实验区挑选一块坡面相对比较均一、坡度在5～7％的连片玉米田，分别在玉米田的土壤表面采用4个不同的处理：即PAM覆盖率80％、60％、40％和对照，实验采用两个重复。 用电子扫描显微镜（SEM）照片对比了土壤表面结构，分析了土壤的结皮机理，可以认为土壤结皮是由结构结皮和沉积结皮构成，入渗量与时间的历时曲线反映了结皮的四个形成过程。封闭、结皮是土壤表面水土相互作用的结果，能显著减少土壤入渗、降低水资源的利用率，增加地表径流并导致土壤侵蚀。 实验表明经PAM处理后土壤的入渗性能和抗侵蚀的性能都有所提高。PAM具有良好的黏结力，能有效改良土壤的表层结构，维护了土壤孔隙连通性，增加土壤的入渗率。分析建立了降雨入渗率与PAM的覆盖率间的相关关系，确定了PAM的覆盖率对降雨入渗的影响。PAM能明显地黏结土壤表面的颗粒，形成团聚体，阻碍土壤结皮的形成，减少土壤侵蚀。 PAM对土壤的性质有着明显的改进作用，提高土壤的稳定性，减少土壤侵蚀。确定了不同的PAM的使用量及覆盖率与土壤侵蚀量的关系。 田间试验表明，PAM能够有效地减少土壤表面的径流量，增加土壤的降雨入渗，PAM覆盖率越高越有利于降雨的入渗。PAM能够在降雨后一定的时间内保持土壤的含水量，中国农业大学博士论文PAM增加入渗减少土壤侵蚀及稀土元素示踪上壤侵蚀过程的试验研哭 摘要PAM的覆盖率越高，土壤的含水量就越大。PAM能够提高玉米的最终成活率，增进玉米的生长，提高干物质产量。 实验室模拟降雨条件下多种ME示踪土壤侵蚀过程，很好地揭示土壤侵蚀发生和发展的过程，清晰地展示了土壤侵蚀沿坡面的分布规律，及变化过程，客观地反映了土壤表面雨水动力特征随坡面的变化，从土壤表面雨水动力特征沿坡面的变化可以了解土壤侵蚀物理过程。 通过土壤侵蚀沿坡面变化的特征，界定了土壤细沟侵蚀发生的临界距离，并由此得到了土壤细沟侵蚀临界切应力，c参数的计算方法。对不同试验条件下最大细沟侵蚀率与径流剪切力和细流力之间的关系进行了回归分析。土壤表面经PA M处理后，能大大提高土壤的临界剪切力。 雨滴溅蚀和雨滴打击引起的土壤表面结皮是土壤侵蚀的重要影响因素，据REE展示的土壤侵蚀率沿土壤坡面的变化规律，区分了雨滴溅蚀、细沟侵蚀和细沟间侵蚀，并确定了雨滴溅蚀、细沟侵蚀和细沟间侵蚀间的比例构成。分析了雨滴溅蚀与降雨动能和坡度之间的函数关系。 结皮显著地地影响着土壤侵蚀。结皮对土壤侵蚀的影响主要反映在径流造成的土壤侵蚀中，给出了结皮效应率的定义，并据此定量评价了结皮对土壤入渗、土壤侵蚀的影响。更多还原

【Abstract】 China is amongst the countries suffering serious water and soil losses, especially in the arid and semi-arid areas including the Loess Plateaus.In arid and semiarid climate areas, water and soil losses are dominant reasons for poor harvest and degradation of land and ecological environmental systems. Soil crust, a common phenomenon for many soils worldwide, plays an important role in water and soil losses. Soil seals and crusts can significantly reduce soil infiltration rate and subsequently lower the utilization of water resources, increase runoff, and induce heavier soil erosion. The objectives of this study were: i) to understand the mechanism of applying polyacrylamide (PAM) to control crust formation, to increase infiltration and reduce soil erosion; and ii) to quantify the dynamics of soil erosion processes with rare earth elements (REE) tracers.Experiments were conducted with rainfall simulation under laboratory conditions. Experimental soil used in this study was from Inner Mongolia, typical loess sampled from top layer of cultivated soils. The bulk density was 1.2 g cm-1. The soil contents about 60% of silts and about 15% of clays. A slope adjustable flume of 3 by 8 m was subdivided into 15 mini-flumes of 0.2 by 8 m. The experiments involved three different rainfall intensities (50, 100, and 150 mmh-1); four slopes (8.74%, 17.63%, 36.4% and 46.63%), four (%???) soil surface treatments (one control and three PAM coverage rates: 80%, 60%, 40%). And 8 REE elements: Dy, La, Sm, Yb, Ce, Eu, Nd and Tb were applied in sections upon the slope. Each individual experiment run was divided into two consecutive storms. After the first storm, the soil was set for 24 h before the second rainstorm. Three replicates were adopted for each individual experimental treatment.A corn field experiment was conducted at Qingshuihe near Huhehot, Inner Mongolia. The experiment fields, with slope of 5% to 7%, were consisted of eight adjacent rectangle plots sized about 10 by 16 m. The experiment applied four soil surface treatments (one control and three PAM coverage rates: 80%, 60%, 4%). After corn seeds were planted, granular PAM mixed with loess soil was spread to cover the soil surface. Two replicates were adopted in the experiments.Scanning electric microscope (SEM) photographs were used to examine the structure of surface soil experienced a rainstorm, for the purpose of understanding the mechanism of soil crusting. It approved that soil crusting consists of depositional crust and structural crust. The curves of infiltration with time revealed four stages of crust formation. Crust significantly reduces soil infiltration rate and subsequently lowers the utilization of water resources, and increase runoff, which induce heavier soil erosion.PAM treatment can prevent the disintegration of soil aggregates, even improve thestructure of soils and prevent crust formation. PAM, with high viscosity, can significantly increase water infiltration. Analyses were made to relate infiltration rates with PAM coverage and describe impacts of PAM application on infiltration.Experimental results showed that the soils treated with PAM had better and stabile properties. PAM is able to cohere strongly the soil particles at the surface to form bigger aggregates, therefore to significantly increase infiltration and reduce soil erosion. Analyses were made to relate soil erosion with PAM coverage and describe impacts of PAM application on soil erosion.The cornfield experiment showed that PAM could significantly reduce runoff and increase infiltration of rainwater and increase soil water content. Corns planting in the soils treated with PAM were taller and more vigorous, with higher mass produced.The REE tracing of dynamic processes of soil erosion revealed soil erosion mechanism in details. The occurrence and development of soil erosion along slope were showed clearly. From the changes in soil erosion upon the slope, the dynamic processes of runoff and soil erosion along slope was analyzed.With REE to trace the processes of更多还原