盐渍化灌区土壤水盐时空变异特征分析及地下水埋深对盐分的影响

针对盐渍化灌区土壤盐渍化问题,以河套灌区下游乌拉特灌域为研究区,通过野外实测与室内试验分析结合,采用统计学方法地质统计学原理分析表层土壤(0-20,20-40 cm)及深层土壤(40-100 cm)含水率与盐分(EC值)时空分布和变异规律,以及探求地下水埋深对土壤盐分的影响。结果表明:(1)除6月0-20 cm(9.779%)外,表层土壤含水率变异系数均在12.384%~19.667%,属于中等变异性,深层土壤含水率变异系数较小,在3.513%~9.757%,属于弱变异性;表层土壤盐分(EC值)变异系数在100.845%~129.279%,属于强变异性,深层土壤盐分变异系数均在83.685%~98.853%,属于中等变异性;随着土壤深度的增加,含水率和盐分的变异性都相对减弱。(2)不同时期土壤含水率和盐分在一定范围内具有空间结构特征,均可用高斯模型模拟,各层土壤含水率空间相关度在0.038%~20.408%,各层土壤盐分空间相关度在0.043%~8.374%,均小于25%,说明具有强烈的空间相关性,可以认为主要是受结构性因素的影响,其自相关引起的空间变异性较强。(3)试验区土壤盐分主要集中在北侧盐荒地,由于蒸发强烈,包气带毛细水上升,把深层土壤以及地下水中的可溶性盐类带到土壤表层,致使盐分升高,属于典型的盐分表聚型土壤,需及时防治与治理,同时土壤盐分受地下水埋深的影响较大,随着地下水埋深减小而增大,荒地地下水埋深与土壤盐分满足线性关系,耕地地下水埋深与土壤盐分满足指数关系。荒地0-20 cm土壤盐分含量随地下水埋深变化趋势较大,20-40,40-100 cm土壤盐分含量随地下水埋深变化趋势较小,耕地地下水埋深在1~1.6 m时,土壤盐分含量随着地下水埋深变化趋势较大,当地下水埋深大于1.6 m时,土壤盐分含量随着地下水埋深变化趋势较小。研究结果为河套灌区下游盐渍化土壤的防治与改良提供了重要的理论基础和参考依据。

Temporal and Spatial Variability Analysis of Soil Water and Salt and the Influence of Groundwater Depth on Salt in Saline Irrigation Area

Aiming at the problem of soil salinization in salinized irrigation area, the Urad irrigation area in the lower reaches of Hetao Irrigation District was taken as the research area, the spatial and temporal distribution and variation of water content and salinity (EC value) in surface soil (0-20 and 20-40 cm) and deep soil (40-100 cm) as well as the influence of groundwater depth on soil salinity were analyzed by the method of field measurement combined with laboratory experiment and statistical method of geostatistics. The results showed that:(1) Except for 0-20 cm in June (9.779%), the variation coefficient of surface soil water content was 12.384%~19.667%, which was moderate variability, and the variation coefficient of deep soil water content was small (3.513%~9.757%), which was weak variability. The variation coefficient of EC in surface soil was between 100.845% and 129.279%, which was a strong variability, while that in deep soil was between 83.685% and 98.853%, which was moderate variability. With the increasing of soil depth, the variability of water content and salinity decreased. (2) The soil water content and salinity in different periods had spatial structure characteristics within a certain range, which could be simulated by Gaussian model. The spatial correlation of soil water content in each layer was 0.038%~20.408%, and the spatial correlation of soil salinity in each layer was 0.043%~8.374%, both were less than 25%, indicating a strong spatial correlation, and this could be considered to be mainly caused by structural factors, and the spatial variability caused by autocorrelation was strong. (3) The soil salinity in the research area was mainly concentrated in the north salt wasteland. Due to strong evaporation, the capillary water in the aerated zone raised, and the soluble salts in the deep soil and groundwater were brought to the surface layer of the soil, resulting in the increasing of salinity, which was the typical salt-accumulation type. The immediate control and treatment were needed. At the same time, the soil salinity was greatly affected by the groundwater depth, the soil salinity increased with the decreasing of the groundwater depth. The relationship between the groundwater depth of the wasteland and the soil salinity satisfy was linear, and the relationship between he groundwater depth and soil salinity of the cultivated land was exponential. The soil salinity content in the 0-20 cm soil of the wasteland varied greatly with the depth of groundwater. The change trend of soil salinity with the depth of groundwater was smaller in 20-40 cm and 40-100 cm layers. When the groundwater depth of the cultivated land was 1~1.6 m, the soil salinity content changed greatly with the depth of groundwater. When the groundwater depth was more than 1.6 m, the soil salinity content changed little with the groundwater depth. This study provided an important theoretical basis and reference for the prevention and improvement of salinized soil in the lower reaches of Hetao Irrigation District.