摘要
土壤斥水性广泛存在于各类土壤,是影响植物生长、土壤水分运动以及土壤侵蚀等水土过程的重要因素。该文阐述了土壤斥水性的基本概念,介绍了几种常用的斥水性强度测定方法及适用范围。在此基础上,论文对土壤斥水性如何影响土壤水力性质以及水分运动特征等研究现状作了全面评述,重点讨论了近年来该领域的研究热点,如土壤斥水性影响下的指流观测和理论模拟以及斥水性土壤蒸发过程等。最后,提出了相关研究中亟待解决的若干关键科学问题,主要包括确定土壤斥水性影响指流现象和蒸发过程的物理机制的揭示;考虑土壤斥水性参数的土壤水分运动数学模型的构建;以及对新模型的求解及对数值解的理论分析。由于土壤斥水性对土壤水分运动有重要的关联效应,相关问题的深入研究对进一步认识土壤水分运动的内在物理机制具有重要理论意义,也将为掌握和有效利用土壤斥水性提供实践指导。
Soil water repellency(SWR)is a normal property with major repercussions for plant growth,surface and subsurface hydrology,and for soil erosion.Important advances have been made since the late1960s in identifying the range of environments affected by SWR,its characteristics and its hydro-geomorphological impacts.In this review,we outlined the concept of SWR,summarized the commonly used methods of soil water content(SWC)measurement and classification criterion,but focused particularly on recent advances in identifying the impacts of SWR on water movements,and indicated the existing research gaps.Significant advances relating to the impacts of SWR on the hydraulic properties as well as the dynamics of water infiltration and evaporation in these unique systems were discussed.SWR affected the matric potential through the contact angle,and shifts the water entry values.The wetting branch of water retention curves is strongly affected by the contact angle,in contrast,effects for the drying branch are minimal,SWR can resist or retard surface water infiltration.Besides the retardation or resistance of surface water infiltration,water repellent soils have been associated with fingered flow.Fingers are known to have a distinctive nonmonotonic saturation profile,with water accumulation behind the wetting front(tip)and lower saturation above it(tail).This nonmonotonic saturation profile is known as saturation overshoot.Saturation overshoot is associated with capillary pressure overshoot and has been confirmed to be the cause for gravity driven fingering.However,the saturation overshoot cannot be described by the Richards equation,the primary unsaturated flow equation.Richards'equation in its basic form,along with the standard(monotonic)pressure-saturation relations is incompatible with the saturation overshoot for fingered flow.Modifications of Richards'equation and other approaches have been proposed to account for and describe the nonmonotonicity of the saturation field.In comparison with numerous work on infiltration,studies on evaporation are relatively less but show uniform results,namely SWR suppresses soil evaporation.Percolation-based morphological pore network modeling of evaporation confirms the results.Experimental and modeling results suggest that water repellency affects liquid phase continuity in partially wettable porous media and reduces the evaporation characteristic length relative to capillarity effects.Major research gaps,however,remain in(a)identifying the exact role of,and the interactions between the variables controlling the development and effectiveness of flow pathways through repellent soils;(b)establishing and improving the models with new mechanisms with consideration of the effects of SWR in controlling fingers,and proposing the relevant analytical and numerical methods for solving these new models.Improved understanding of effects of SWR will enable its overall roles in surface and subsurface hydrological and erosion processes to become more clearly defined.
作者
王秋玲
施凡欣
刘志鹏
熊云武
Wang Qiuling;Shi Fanxin;Liu Zhipeng;Xiong Yunwu(School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236037, China;Colloge of Resources and Environmental Sciences, Nanjing Agriculture University, Nanjing 210095, China;Colloge of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2017年第24期96-103,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(41701254
41771258)
安徽省国际科技合作项目(1403062027)
阜阳市政府-阜阳师范学院横向合作项目(XDHX2016008)
关键词
土壤
水分
蒸发
土壤斥水性
土壤水力性质
指流
soils
moisture
evaporation
water repellency
soil hydraulic properties
finger flow
