高水位重盐渍化土壤盐分异质性与暗管淋控均质化机制研究

The groundwater depth is very shallow in saline area with high water table.Frequent exchange of saline groundwater and surface soil water not only caused severe soil salinization, but incur strong spatial variability of soil salinity, which increased greatly the difficulty of homogenizing governance. Because of controlling the water table rising and promoting soil salt leaching, subsurface drainage has become a leading technology of governing saline land. Under subsurface drainage and leaching, soil salinity decreased and showed a clear trend of homogenization. Based on the research of spatial heterogeneity property of soil salinity and driving mechanism, we will study on the mechanism and different critical parameters of soil salinity homogenization under subsurface drainage, construct a theoretical model in leaching water conditions with the purpose of homogenazing distribution and determine leaching water conditions from different soil salinity to the same level, providing a theoretical basis for homogenizing governance. The implementation of this project will offer theoretical reference for homogenizing governance and help to provide theoretical and technical support for improving the quality and large-scale application of saline land.

高水位盐碱区地下浅层咸水埋深浅，上层土壤由于受到地下咸水的顶托和频繁交互作用不仅使其成为中重度盐碱地，而且土壤盐分呈空间高异质性的分布特征，极大地增加了重盐碱地均质化治理难度。暗管排水排盐技术通过控制地下水位上升和促进土壤盐分淋排已成为治理高水位盐碱地的领先技术，暗管淋控下土壤盐分呈明显均质化趋势特征。本项目在研究高水位重度盐碱地土壤盐分高空间异质性特征及其驱动机制的基础上，探讨暗管排水排盐技术对土壤盐分均质化过程作用机制与不同临界参数，构建土壤均质化脱盐水分淋洗条件理论模型，确定不同初始盐分条件下均质化淋洗的水分条件，从而为高水位重盐碱地均质化治理提供理论依据。本项目的成功实施可为提高盐碱耕地质量、促进盐碱地规模化应用提供理论与技术支撑。

高水位盐碱区地下浅层咸水埋深浅，上层土壤由于受到地下咸水的顶托和频繁交互作用成为高异质性的中重度盐碱地,极大地增加了治理难度。本项目在对高水位盐渍化土壤盐分异质性特征分析的基础上，探明暗管淋排下土壤均质化过程关键阈值与脱盐特征，并基于此提出土壤盐分均质化措施。主要结果如下：（1）雨季与旱季三个土层深度的土壤盐分空间分布呈显著相关，在进行盐斑精准治理时，应把耕层到地下水的土层部分与地下水作为一个整体系统来综合考虑。（2）通过旱雨两季土壤含盐量相关性与脱盐特征分析得到试验地盐分脱盐下限阈值0.86g/kg与脱盐关键阈值10g/kg。如何保持土壤含盐量≤10g/kg区域的雨季暗管淋洗效果与提高＞10g/kg区域的精准治理效果是实现土壤长期低盐均质化的关键。（3）高强度降水后土壤EC值骤增后缓慢下降，但单次降水淋洗效果具有时间有限性，因此，雨季降水期间，盐斑处（旱季土壤含盐量大于10g/kg）配合高强度灌水淋洗是强化土壤低盐均质化的可行措施。（4）暗管淋控物理模型模拟结果说明暗管埋设间距越小，距离暗管越近，排盐效果越好，因此，在盐斑处加设排水暗管可以有效强化雨季的盐分淋洗效果，加速试验地土壤的低盐均质化进程。