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Title:	Freeze-thaw processes and soil chemistry
Authors:	Marion, Giles M. (Giles Michael)
Keywords:	Freeze–thaw cycles Soils Frost Frost heave Frost heaving Thawing Frozen soil Frozen ground Permafrost Soil chemistry
Publisher:	Cold Regions Research and Engineering Laboratory (U.S.) Engineer Research and Development Center (U.S.)
Series/Report no.:	Special report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 95-12.
Description:	Special Report Abstract: This review broadly examines the interactions between freeze–thaw processes and soil chemistry, focusing on 1) the effect of solutes on physical properties such as freezing-point depression, unfrozen water and frost heaving, 2) the effect of freeze–thaw cycles and low temperatures on soil chemistry, and 3) modeling of freeze–thaw processes and chemistry. The presence of solutes causes a freezing-point depression, which increases the amount of unfrozen water in soils. Liquid films on soil particles provide the dominant route for the flow of water and associated solutes in frozen soils. In general, salts reduce the hydraulic conductivity and water flow to the freezing front, which reduces frost heaving. Solute exclusion during freezing leads to supersaturated solutions, which promotes the precipitation of secondary minerals in soils. At the watershed level, ionic concentrations in early meltwaters are often 2–9 times higher than snowpack concentrations. Temperature is the dominant factor controlling decomposition rates, with minimal detectable rates occurring at temperatures as low as –10°C; both bacteria and fungi are physiologically active at subzero temperatures. Extracellular enzymes are active in soils at temperatures as low as –20°C; this activity is thought to occur in unfrozen water on surfaces of soil particles. Nitrogen mineralization is reported at temperatures as low as 1°C and is promoted by freeze-thaw cycles. There are strong and complex interactions among soil properties that control solute and water flows along concentration, temperature and hydrostatic gradients in freezing and frozen soils. These complex interactions necessitate the development of computer simulation models that can integrate physical–chemical properties and processes.
Rights:	Approved for public release; distribution is unlimited.
URI:	http://hdl.handle.net/11681/12110
Appears in Collections:	Special Report