Differentiation characteristics and dynamic mechanism of synergistic changes of surface soil water and its salt in different seasons in arid area
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摘要: 【研究目的】围绕西北内陆流域地下水浅埋区不同季节表层土壤水盐协同变化差异特征及其动力机制。【研究方法】基于野外地下水调控试验场内原位多要素高频率监测系统获取的数据，综合对比分析了无降水和灌溉入渗直接影响时段表层土壤含水率、土壤孔隙水电导率、地下水位埋深等要素的变化特征。【研究结果】年内由春末、夏季到秋初，20cm（浅部）和40cm（深部）深度土壤含水率均越来越小，浅部和深部土壤孔隙水电导率（ECp）均越来越大，浅部土壤饱和溶液电导率（ECe）越来越小，深部土壤ECe则越来越大。春末浅部土壤含水率、ECp和ECe日际变化相同，深部土壤含水率、ECp和ECe变化趋势各异。夏季浅部土壤含水率和ECe日际变化趋势相同，与土壤ECp变化不同；深部土壤ECp和ECe变化趋势相同，与土壤含水率变化不同。秋初浅部和深部的土壤含水率、ECp和ECe日际变化趋势均各不相同。【研究结论】灌溉是影响表层土壤水盐季节间差别的主导因素；蒸散发是引发表层土壤水盐季节内变化的直接因素，且气温越高，其影响效应越明显；地下水位埋深是影响表层土壤水盐的重要和可调控因素，夏季增大地下水位埋深，表层土壤含盐量明显降低，研究区夏季农田盐渍化防控的临界地下水位埋深位于1.6 m和1.9 m间。Abstract: [Obiective] The object of the study is focusing on the characteristics and dynamic mechanism of the same variation of surface soil water and its salt in different seasons in groundwater level depth area of the northwest inland basin.[Methods] Based on data obtained from the in situ multi-factor high frequency monitoring system in groundwater regulation field site, changing processes of topsoil moisture content, pore water electronic conductivity (ECp), groundwater level depth and so on without the direct influence of precipitation and irrigation infiltration were comprehensively analyzed and studied.[Results] 20 cm (shallow part)and 40 cm (deep part) depth soil moisture content in later spring, summer and early autumn were all arranged in descending order. However, the shallow and deep part soil ECp were all arranged in increasing order. The shallow part soil electronic conductivity of saturated leach solution (ECe) was arranged in descending order and the deep part soil ECe was arranged in increasing order. In later spring day variation trends of soil moisture content, ECp and ECe were the same in shallow part, which were different in the deep part soil. In summer day variation trends of shallow part soil moisture content and ECe were the same and that of soil ECp was different from them. However, day variation trends of deep part soil ECp and ECe were the same and that of soil moisture content was different from them. In early autumn day variation trends of soil moisture content, ECp and ECe were all different in shallow and deep part.[Conclusions] Irrigation is the leading factor of influencing differences of surface soil moisture content and salt among seasons. Evapotranspiration is the major factor of resulting in changes of surface soil moisture content and salt in each season. Moreover, the higher the temperature, the more obvious the effect of the evapotranspiration. Groundwater level depth is an important and regulatory factor of affecting topsoil moisture content and salt. In summer when the groundwater level depth becomes bigger, topsoil salt content obviously decreases. In the study area the critical groundwater level depth of prevention and control of farmland salinization is between 1.6 m and 1.9 m in summer.
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