【作者】 王巧焕；

【导师】 马耀光；

【作者基本信息】 西北农林科技大学 ， 水文学及水资源， 2006， 硕士

【摘要】 在分析和总结国内外有关土壤水盐运移规律研究成果的基础上,针对黄土土壤的特点,利用理论分析和模拟试验方法,对黄土水盐运移基本规律及主要影响因素进行了研究,并根据试验得到的数据推求出灌水条件下一维黄土水盐运移过程的简单数学模型。本文通过野外试验对不同灌水量以及不同施肥量的土壤水盐运移进行了模拟研究,就一维条件下土壤水分运动特性、盐分分布与变化特征、灌水量对土壤水盐运移的影响以及水盐耦合定量关系进行了重点分析。首先,水分分析结果表明:土壤水分在运移的过程中出现了两个明显的水分峰值带,分别位于1.6m～1.8m和7.4m～7.8m处;由于黄土的微孔隙渗流速度非常慢,在整个观测期间变化较小,所以在1.0m～4.0m范围内出现了很宽的湿润带;微孔隙渗流的运移速率随灌水量的增大而增大,且符合良好的指数函数关系;水分通量随灌水量的增大而增大,这两者之间存在着良好的直线关系;湿润峰面运移的深度随灌水量的增加而加深,这两者之间存在良好的对数函数关系。其次,盐分分析结果表明:灌溉水和降水溶解的盐分在盐分低值区被吸附,而在盐分高值区产生淋洗作用,故入渗水流可对土层吸附性离子进行调节;尿素的水解性离子不仅与土壤层中盐分离子发生交换,而且会增加土壤中盐分含量;浅层土壤水分蒸发产生盐分上移,使表层土盐分增加,严重的会引起土壤盐渍化;黄土的细粒微孔隙吸附离子性强会增加土壤中盐分含量;土壤水中的盐分在运移过程中有部分盐分被土壤层吸附,也有部分盐分离子与土壤层中的盐分离子发生交换。其实,土壤盐分运移是在一系列的物理、化学和生物作用下进行的。最后,在分析土壤水盐运移机制的基础上,建立了以达西定律、Richards’方程为基础的一维水分运动模型和以对流弥散作用为基础的土壤盐分运移模型;并利用一维水盐运移试验资料和通过六点差分格式的数值解法对所推求的理论模型进行了验证,检验结果表明所建立的数学模型能反映土壤水盐分布的基本特征。本论文的研究结果将有利于对土壤水盐耦合运移机制的深入认识,有助于推求模拟土壤水盐耦合运移过程简单而适用的数学模型,并对黄土灌区土壤盐渍化的防治有一定的指导意义。更多还原

【Abstract】 The basic laws and primary influence factors of water movement and salt transfer in the loess were studied in allusion to the characteristics of loess through the theoretical analysis and simulation experiments on the basis of analysis and summing-up for research results about laws of water and salt transfer in the soil at home and abroad. At the same time, the simple mathematic model of water and salt transfer in the soil under one-dimension irrigation was ascertained according to experimental data.The water movement and salt transfer in the soil under different irrigation volume and fertilization volume were studied with the simulation model through the field experiments. The characteristics of the infiltration, salt concentration distribution, the influence of irrigation volume on the water and salt transfer processes in the soil and the quantificational relation between characteristics of water and salt coupling transfer were analyzed. Firstly, the results of water analysis indicated that in the process of water movement with time and depth, there are two obvious peak belts of moisture content which are distributed in the 1.6m~1.8m and 7.4m~7.8m respectively. The speed about micropore movement in loess is too slowly, so there is a widly humid zone in 1m~4m and it has little change during whole observation. Water movement rate increases with the increment of irrigation volume and the index function may be used describe the well relationships between them. Water flux increase with the increment of irrigation volume and the linear function may also be used describe the well relationships between them. The depth of humid peak transfer deepens with increment of irrigation volume and the logarithm function may be used describe the well relationships between them.Secondly, the results of salt analysis indicated that salt dissolved by irrigation water and precipitation can be absorbed in the low salinity area, and can be washed out in the high salinity area, so irrigation seepage water can adjust the adsorption ion in soil. The hydrolysis ion of carbamide can produce ion exchange and also increase soil salt. Shallow soil water evaporation can cause salt up-transfer, and increase salt in surface layer and seriously this result can cause soil salinification. The fine grain and micro pores of loess can improve the更多还原