| Effects of anions and cations on soil water retention and shrinkage behavior during dehydration process |
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| DOI：10.7606/j.issn.1000-7601.2018.02.16 |
| Key Words: soil moisture water retention soil shrinkage desiccation cracking salt ion |
| Author Name | Affiliation | | LI Qing-feng | College of Water Resources and Architectural Engineering, Yangling, Shaanxi 712100, China； Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China | | XING Xu-guang | College of Water Resources and Architectural Engineering, Yangling, Shaanxi 712100, China； Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China | | MA Xiao-yi | College of Water Resources and Architectural Engineering, Yangling, Shaanxi 712100, China |
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| Abstract: |
| Soil shrinkage and cracks commonly occur during soil water characteristic curve (SWCC) measurement, and the soil water retention varies with the type of salt ions (i.e., anions and cations) in the soil. A laboratory study was therefore conducted to make further analysis on the effects of four salt cations (K+, Na+, Ca2+, and Mg2+) and anions (Cl-, HCO3-, CO32- and SO42-) with a low concentration of 1 g·L-1 on water retention and soil shrinkage in silty clay loam saturated by salt solutions (1 g·L-1), based on existing findings. The SWCCs were measured by the centrifuge; meanwhile, during dehydration, the heights of soil samples were measured using calipers to estimate the change in soil bulk density and the axial shrinkage. Two indices, crack length and crack area, were directly obtained from the processed binarized images by using MATLAB. The results showed following. (1) The cations, K+, Na+, and four salt anions could improve water retention, and CO32- and K+ increased soil moisture by 35.81% and 3.68%, respectively, relative to the control treatment. (2) Mg2+, SO42-, and CO32- could decrease axial soil shrinkage. The influences of anions and cations on soil shrinkage were ranked in order that HCO3->Cl->SO42->CO32- and Na+>K+>Ca2+>Mg2+, respectively. (3) Na+, Mg2+, and four salt anions could reduce crack length, crack area, crack length density and crack area density. And the performance of CO32- and Na+ was the best. The findings provide theoretical and practical guidance for evaluation of water retention and cognition of the mechanism of desiccation cracking. |
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