【作者】 曹红霞；

【导师】 康绍忠；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2003， 博士

【摘要】 土壤养分运移和土壤次生盐碱化都是土壤溶质运移领域研究的主要内容，而且土壤养分运移研究起源于土壤水盐运动的研究理论。水是溶质运移的载体，水管理（灌水管理和地下水管理）对溶质运移影响很大。目前灌溉制度、地下水位、溶质施加方式对溶质运移影响的研究还很不够。本文通过大量的室内土柱试验，对有、无蒸发条件下不同灌水频率风干土壤中，不同次灌水量、灌水频率、溶质施加方式下各地下水位土壤中水分、溶质（NO₃^-、Br^-）迁移规律进行了较为深入的研究。以期探明次灌水量、灌水频率、地下水位、溶质施加方式等因素对土壤溶质运移的影响，为减缓地下水的NO₃^-—N污染、提高氮肥利用率、防止土壤次生盐碱化、保证作物不受盐害等提供理论依据。并在此基础上建立了溶质运移模型，以便人们随时了解土壤溶质迁移动态，及时采取相应措施，最大程度地控制土壤溶质运移趋势。主要结论如下： 1．蒸发和灌水频率对风干土壤中水分分布的影响表现为：1)有、无蒸发条件下土壤水分差异在灌水初期主要体现在上部土层，此时，灌水频率越低，此区水分差异越大；随灌水次数增多，有、无蒸发条件下上部土层水分差异减少，且灌水频率越高，这种差异减少得越快，而下部土层水分差异增加，主要表现为蒸发条件下湿润锋深度明显小于无蒸发条件下。2)灌水频率可改变土壤水分的空间分布和土壤蓄水量。在相同灌水量下，灌水频率增高，上部土层水分含量在一定范围内增高，且湿润锋深度变浅，上部土层蓄存水量增加；适宜的灌水频率可增加土壤蓄水量。 2．蒸发和灌水频率对风干土壤中溶质迁移的影响表现为：有、无蒸发条件下土壤中NO₃^-浓度峰随灌水频率增加而变陡、变窄，峰值增高，NO₃^-整体向下迁移变慢；在蒸发条件下，还明显表现为随灌水频率增加，NO₃^-浓度峰和浓度锋深度变浅；有效淋洗水量（或灌水频率）影响着溶质峰和溶质锋的深度。 3．灌溉制度和地下水埋深对潜水蒸发影响较大。总体表现为：低灌水频率下，随地下水位升高，潜水蒸发呈增加趋势；在同一水位下，低灌水频率土壤随次灌水量增加潜水蒸发减少，且水位越深，潜水蒸发量减少越多，水位越浅，潜水蒸发量减少越小；在同一水位下，总灌水量相同，灌水频率不同时，随灌水频率增高，潜水蒸发量显著减少。 4．通过对不同地下水位（1.7、1.2、0.8m）土壤在三种灌水处理下表施溶质（Br^-）迁移规律分析研究，结果表明：1)水位对各灌水处理土壤中B^-迁移有较大影响。表现为：水位越浅，Br^-向下迁移越快；水位变深，土表Br^-聚集量增加；随灌水次数增加，土表Br^-含量虽逐渐降低，但降低速度随水位加深而减缓；2)灌水频率， ‘.电.........................................口..^..............口口.........................口...........对不同地下水位土壤中溶质迁移影响表现为:在同一水位下，高灌水频率土壤土表Br一含量降低较快，低灌水频率土壤土表Br一含量降低较慢;水位变浅，高、低灌水频率土壤土表Br一含量降低均加快，但高灌水频率比低灌水频率降低得快:水位越浅，高灌水频率土壤中溶质峰形成得越快，从而高灌水频率土壤中Br^相对较集中地向下迁移;低灌水频率土壤中Br一分布范围较大，除土表SCm土层外，水位越深，Br一分布越均匀、平缓、分散:不同水位或同一水位条件下，高、低灌水频率土壤中溶质锋迁移趋势是变化的，在本试验条件下，1.2m水位可看作高、低灌水频率土壤中溶质迁移快慢的转折点，即水位大于1.2m时，低灌水频率土壤中溶质迁移一直快于高灌水频率，水位小于1.Zm时，在含水量相对较低的上部土层中，低灌水频率土壤中溶质迁移快于高灌水频率，随溶质向下迁移，逐渐转变为慢于高灌水频率，总体而言，水位由深变浅，高灌水频率土壤中Br一迁移由慢于低灌水频率转变为快于低灌水频率;各水位条件下，高、低灌水频率土壤中Br一浓度锋向下迁移的快慢取决于潜水蒸发量和Br一浓度锋处溶质的扩散能力。 5.溶质施加方式对土壤溶质迁移的影响表现为:l)初始风干土壤中，在次灌水量较大的情况下，表施和灌施对溶质迁移有较大影响，灌施溶质将在较大深度内较均匀分布，而表施溶质则在一定深度处集中分布，且土表层分布较少;而当次灌水量很小且灌水非常频繁时（如6Inln/d），表施和灌施土壤中N氏一分布差异不大。2)在地下水位较浅的土壤中，灌施Br一浓度峰较缓、胖，Br一主要分布在近地表土层内，且在近地表一定深度范围内较均匀分布;表施Br一浓度峰较陡、窄，Br一主要分布在一定深度处，非常集中;Br一以表施和灌施方式随等量灌水进入土壤后，形成Br-浓度峰峰形上的差异，在随后迁移过程中一直保持着，灌水频率对表施和灌施Br-峰形无影响，只是影响Br一整体迁移的快慢。 6.次灌水量对地下水位较浅土壤中溶质（Br^）迁移影响表现为:溶质峰迁移距离与灌水量成正相关，与有效淋洗水量成倍比关系;次灌水量对溶质迁移方式有很大影响，当次灌水量等于灌水间隔期耗水量（土表蒸发、根系吸水等）时，土壤溶质主要在扩散作用下进行迁移，表现为溶质峰?更多还原

【Abstract】 Nutrient migration and soil salinisation are the two major concerns in the research of soil solute transport. Such research should provide the theoretical backgrounds for the groundwater pollution control, such as NOs ~ ?N, improvement of nitrogen use efficiency and prevention of soil salinisation in the irrigated land. In this study, the soil water and solute movements in the air-dried soil columns were investigated under different irrigation frequencies, evaporation control and in the soil having groundwater table under different irrigation frequencies, quantities, and solute application. Dynamic models for solute transport at any given time have been presented in this study. The main results are:1. Evaporation influenced the soil water distribution mainly in the upper soil layer at the initial stages of irrigation. Less irrigation frequency would lead to greater uneven water distribution. The increasing total irrigation quantity reduced soil water deficit in the upper layer but enhanced such deficit in the lower layer. Higher the irrigation frequency, the decrease is faster. Irrigation frequency also changed the spatial distribution and storage of soil water. When irrigation frequency increased with the same irrigation quantity, the soil water content and storage in the upper layer would increase but the wet front in soil profile became shallow. Results suggest that a suitable irrigation frequency can increase the soil water storage.2. Evaporation and irrigation frequency influenced the solute transport. When irrigation frequency increased, NOs ~ concentration peak in soil with or without evaporation would become steeper and narrower with higher peak values and slower NC>3 downward movement. Under evaporation, NOs^concentration peak and front would also appeared in the shallower soil layer. The effective leaching water (or irrigation frequency) controlled the solute peak and front depth.3. Irrigation schedule and groundwater table had a great influence on the shallow ground-water evaporation. The evaporation of shallow groundwater increased at lowirrigation frequency when groundwater table was elevated, and decreased at low irrigation frequency under the same groundwater table when the quantity per irrigation increased. Deeper the groundwater table, the less evaporation. The evaporation of shallow groundwater would decrease substantially when irrigation frequency increased at the same groundwater table and same irrigation quantity.4. By analyzing the surface-applied solute transport in soil having different groundwater tables under three irrigation treatments, results showed that: 1) Groundwater table had a great influence on the BR- transport in soil regardless the irrigation treatment. BR-downward movement quickened when water table became shallower. BR- collection in soil surface increased when water table deepened. BR- content in the soil surface reduced gradually when total irrigation quantity increased, but the rate of the reduction slowed when water table deepened. 2) The reduction of Br" content in soil surface was faster in the soil with high irrigation frequency than low irrigation frequency at the same water table. The reduction of BR- content in soil surface quickened in the soil with higher or lower irrigation frequency when water table became shallower, but the reduction was faster in the soil with high irrigation frequency than with low irrigation frequency. The development of solute peak in the soil with high irrigation frequency was quickened when water table became shallower, leading to a more centralized BR-movement. The BR- distribution in the soil profile with low irrigation frequency was wider, and expect for the 5cm layer from the soil surface, and more uniform than with high irrigation frequency. The solute front movement also varied with the irrigation frequency and water table. In this experiment, 1.2m water table appeared as the turning point for quick or slow solute transport. When water table was deeper than 1.2m, solute transport in soil was fast更多还原