基于环境同位素的黄土高原白草塬土壤水分特征及其影响因素研究

发布时间：2018-03-19 18:06

本文选题：土壤水分　切入点：土地利用变化　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：黄土高原严重的土壤侵蚀对人们赖以生存的生态环境造成严重的破坏,进而制约着区域经济发展。为此,国家开展了退耕还林还草等大量水土保持工作,导致黄土塬区的土地利用方式近年来发生了巨大的变化,进而影响水循环机制。因此,土地利用变化引起的水文效应备受关注。在此背景下,具体分析水循环中间环节的土壤水分特征与土地利用的关系,将为水资源管理和生态建设提供重要的参考依据。本研究以黄土高原白草塬为研究区域,测定塬区降水和土壤水分的同位素和水化学组成,研究了白草塬土壤水分特征,并分析了其影响因素。通过对大气降水氢氧稳定同位素组成和降水水汽气团后向回溯轨迹分析,探讨塬区不同月份的水汽来源及变化特征,进而为研究区域水文效应提供依据;分析不同土地利用方式土壤水分及其同位素特征,探讨土壤水分运动情况;分析土地利用变化产生的水文效应,并利用CMB法量化土壤水分深层渗漏,揭示土地利用变化对土壤水分的影响。本研究主要有如下结论:1、阐明了白草塬区降水的氢氧同位素特征及水汽来源。降水氢氧稳定同位素特征在全年范围内变化幅度较小,δD和δ18O除大降雨事件外基本不存在温度效应和降雨量效应。对大气降水线、氘盈余和水汽气团后向回溯轨迹综合分析,塬区夏秋季有多种水汽来源,主要为西风带环流、东南亚季风和大陆内循环等输送的水汽,而春冬季主要为西风带环流输送的水汽。2、探讨了不同利用方式土壤水分及其同位素特征。土壤水分氢氧稳定同位素组成主要位于塬区大气降水线右下侧,降水在浅土壤层与老水发生混合作用,并受蒸腾蒸发作用而富集。对比降水和土壤水同位素组成特征,土壤水分主要受夏秋季降水补给。不同利用方式土壤水分的δD和δ18O剖面分布特征及其Cl-浓度具有差异性,土地利用变化对土壤水分运动具有重要影响。3、揭示了土地利用变化对土壤水分的影响。不同利用方式对土壤水分的影响程度和深度不同,6种土地利用方式0~10 m平均含水量表现为:农地荒草地苜蓿地杏林地杏林柠条间作地杏林苜蓿间作地,苜蓿地与荒草地的影响集中在0~5 m,而包含杏树类利用方式对土壤水分的影响向深层推进甚至贯穿整个剖面。土地利用变化造成土壤水分储水量减少和干燥化现象严重,形成了深厚的土壤干层。农地转变为其他利用方式后深层土壤水分入渗速率变化幅度不大,但塬区降雨量少、土壤水分下渗缓慢以及土壤干层严重削弱了土壤水分入渗到深土壤层以及地下水的可能性。
[Abstract]:The serious soil erosion on the Loess Plateau has caused serious damage to the ecological environment on which people depend for their survival, thus restricting the development of regional economy. For this reason, the state has carried out a great deal of soil and water conservation work, such as returning farmland to forests and grassland, etc. In recent years, great changes have taken place in the land use mode in the loess plateau, thus affecting the mechanism of water circulation. Therefore, the hydrological effects caused by the land use change have attracted much attention. The analysis of the relationship between soil moisture characteristics and land use in the intermediate link of water cycle will provide an important reference for water resources management and ecological construction. The isotopic and hydrochemical compositions of precipitation and soil water were measured, the characteristics of soil water in Baicaoyuan were studied, and the influencing factors were analyzed. The hydrogen and oxygen stable isotopic composition of precipitation and the backtracking trace of precipitation vapor and air mass were analyzed. The source and variation characteristics of water vapor in different months were discussed in order to provide the basis for the study of regional hydrological effects, and the characteristics of soil moisture and their isotopes in different land use patterns were analyzed, and the soil moisture movement was discussed. The hydrological effect of land use change was analyzed, and the CMB method was used to quantify the deep leakage of soil water. The main conclusions of this study are as follows: 1. The hydrogen and oxygen isotopic characteristics and water vapor sources of precipitation in Baicaoyuan region are expounded. The stable isotopic characteristics of hydrogen and oxygen in precipitation vary throughout the year. The amplitude is small, 未 D and 未 18O have no temperature effect and rainfall effect except for heavy rainfall events. The comprehensive analysis of deuterium surplus and water vapor backward trace shows that there are many kinds of water vapor sources in the tableland in summer and autumn, mainly from the circulation of the westerly zone, the Southeast Asian monsoon and the continental circulation, etc. In spring and winter, the water vapor transported by westerly circulation is mainly. 2. The characteristics of soil moisture and its isotopes in different utilization patterns are discussed. The stable isotopic compositions of soil water hydrogen and oxygen are mainly located at the lower right side of the precipitation line in the plateau. Precipitation is mixed with old water in shallow soil layer and enriched by transpiration and evaporation. Soil moisture is mainly recharged by precipitation in summer and autumn. The distribution characteristics of 未 D and 未 18O profiles and the Cl-concentration of soil moisture in different uses are different. Land use change has an important effect on soil moisture movement, which reveals the influence of land use change on soil moisture. The average water content was: alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, The effects of alfalfa land and wasteland were concentrated at 0 ~ 5 m, and the effects of apricot use patterns on soil moisture were pushed forward to the deep layer, even through the whole section. The soil water storage and desiccation phenomenon was serious due to the change of land use, which resulted in the decrease of soil water storage and the desiccation of alfalfa land. A deep dry layer of soil was formed. The infiltration rate of deep soil water changed little after the conversion of farmland to other forms of utilization, but the rainfall in the plateau region was less. Slow infiltration of soil water and soil dry layer seriously weaken the possibility of infiltration of soil water to deep soil layer and groundwater.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S152.7

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