非稳态土壤中热传输及水分蒸发机理

Non-rigid soils are common in natural and agricultural systems. These soils are characterized by their strong temporal variations in structure, morphology, and physical properties. Traditional soil physics theories, however, are established based on the assumption that soil is a rigid porous medium, thus are unable to describe the properties and processes accurately in non-rigid soils. The objective of this project is to investigate the characteristics of pores, thermal properties, and coupled heat and water transfer of non-rigid soils under repeated wetting-drying processes. Pedo-transfer functions will be developed for soil porosity and pore diameter based on thermal property and water infiltration measurements, which will be applied for improving soil thermal property models. Finally soil heat flux and water evaporation rate will be estimated using the Fourier equation and sensible heat balance approach, respectively. The results are useful in understanding the spatial and temporal features of the pore system and thermal properties of non-rigid soils, and can be applied for studying water movement, solute transport, and gas diffusion in nonrigid soils.

非稳态土壤在自然和农田生态系统中非常普遍。受各种自然因素和人类管理措施的影响，这类土壤的结构、形态和物理性状呈现高度时间变异特征。因此，基于 “土壤是刚性多孔介质” 的传统土壤物理学理论难以准确描述非稳态土壤的性状和过程。本项目拟开展干湿循环过程中非稳态土壤孔隙、热特性和水热耦合传输的时间变异研究，在定位监测土壤热特性、 入渗过程和水分特征曲线的基础上，明确土壤结构变化过程中孔隙度和孔径的变异规律，建立包含孔隙特性的土壤热特性模型，并结合傅立叶定律和感热平衡原理模拟热传输和水分蒸发过程，发展非稳态土壤中热量传输和水分蒸发的理论和方法。研究结果不仅有助于深入认识非稳态土壤结构和物理特性的时间变异特征，而且对探讨非稳态条件下土壤水分运动、溶质运移和气体扩散具有重要的理论意义和应用价值。

在各种自然因素和人类管理措施的影响下，土壤的结构、形态和物理性状呈现高度时间变异特征。传统土壤物理学理论基于刚体多孔介质的假设，难以准确描述非稳态土壤的物理性状和过程。本项目通过理论分析、模拟研究和室内外实验，开展了不同质地土壤非稳态水热传输性状和过程定的定量化研究。主要研究成果包括：明确了土壤结构变化过程中孔隙度和孔径的动态特征；建立了包含孔隙度因子的土壤热惯量和热扩散率模型；通过非稳态土壤热传输、水分蒸发和农田蒸散的定位实验研究，完善了非稳态土壤温度预测、含水量反演、水热及冻融过程监测的方法和技术，发展了非稳态结构土壤水热耦合传输研究的理论和方法。研究结果不仅有助于深入认识非稳态土壤结构和物理特性的时空变异特征，而且对探讨非稳态土壤水分运动、溶质运移和气体扩散具有重要的理论意义和应用价值。