蒸发条件下地下水对土壤水盐分布的影响

摘要

土壤水分是盐分运移的载体，蒸发条件下地下水会对土壤盐碱化产生一定影响。本文在白炽灯（275 W）模拟稳定蒸发和土柱模拟50 cm 地下水位的条件下，设置4组重复，试验中水温盐传感器每隔1 h 采集一组数据，测定土柱中5～50 cm 的土壤水、盐含量，观察表层析出盐分。结果表明：蒸发条件下盐分聚集过程中，距地表30 cm 处土壤水、盐含量在蒸发进行3 d 左右出现峰值；距地表30 cm 处含水率的定值略低于距地表50 cm 处含水率定值，而含盐量定值与距地表50 cm 处含水率定值相近。距地表10 cm 处土层水盐含量在蒸发进行第7天左右时间出现峰值，然后水分逐渐降低并趋近一个定值；说明距地表30 cm 以下土体作为一个通道起到盐分的传递作用，土柱蒸发结束后，形成“浅集表聚”的分布特征。K＋、Na ＋和 Mg2＋的含量从纵剖面分析都呈现自下而上50～25 cm 逐渐减小、25～0 cm 逐渐升高的趋势，并且三种离子都在25 cm 埋深即土柱的1／2处产生一个最小值；除去表层由于反盐堆积的离子外，CO32－、SO42－在蒸发过程中无太大波动。蒸发结束后，4种阴离子除 HCO3－含量大于初始值外，其它3种离子均小于初始值。%Soil water was the carry body of salt moving,under the condition of evaporation,the groundwater will be produced certain effect on soil salinization.In this paper using the incandescent lamp (275 W)to simulate the stable e-vaporation and soil column to simulate 50 cm ground water level,set up four repeating groups,in the test the soil salt and temperature sensors will be collected the data by each hour interval,to measure the soil moisture and salt content in the soil column of 5 ~50 cm and observe the precipitated salt in the soil surface layer.The results have shown that:Under the condition of evaporation and salt accumulated process,the soil water and salt content at the 30 cm depth from the sur-face were appeared the peak value in the evaporation process about 3 days.The constant value of soil moisture at the 30 cm was slightly lower the constant value at the 50 cm,but the constant value of salt content was close to constant value of moisture content at 50 cm.The soil moisture and salt content at the 10 cm were occurred the peak values in evapora-tion process about 7 days,and then soil moisture content was gradually reduced to a constant value.It was explained that the soil body below 30 cm was played as a channel function for salt transfer.After the evaporation in the soil column over,has formed the distribution character of “shallow collection and surface accumulation”.The content of K+,Na +and Mg2 + have shown a gradually decrease from down to up by the longitudinal profile analysis of 50 ~25 cm and gradu-ally increasing trend from 25 ~0 cm.Also these three ions total produced minimal values at 25 cm just as 1 /2 of the soil column.Except the accumulated salt ions at the soil surface,the CO32 -,SO42 -have no any big fluctuation in the evap-oration process.After the evaporation over,four kinds of anion,except the HCO3 - content was larger than the initial value,other three ions were less than the initial values.