Form Approved
REPORT DOCUMENTATION PAGE
OMB No. 0704-0188
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1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE
3. REPORT TYPE AND DATES COVERED
March 1995
4. TITLE AND SUBTITLE
5. FUNDING NUMBERS
FreezeThaw Processes and Soil Chemistry
PR: 4A161102AT24
TA: EC and SC
WU: AT25-EC-B03
6. AUTHORS
Giles M. Marion
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION
REPORT NUMBER
U.S. Army Cold Regions Research and Engineering Laboratory
72 Lyme Road
Special Report 95-12
Hanover, New Hampshire 03755-1290
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
Office of the Chief of Engineers
Washington, D.C. 20314-1000
11. SUPPLEMENTARY NOTES
12a. DISTRIBUTION/AVAILABILITY STATEMENT
12b. DISTRIBUTION CODE
Approved for public release; distribution is unlimited.
Available from NTIS, Springfield, Virginia 22161.
13. ABSTRACT (Maximum 200 words)
This review broadly examines the interactions between freezethaw 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 freezethaw cycles and low temperatures on soil chemistry, and 3) modeling of freezethaw pro-
cesses 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 associ-
ated 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 pro-
motes the precipitation of secondary minerals in soils. At the watershed level, ionic concentrations in early melt-
waters are often 29 times higher than snowpack concentrations. Temperature is the dominant factor controlling
decomposition rates, with minimal detectable rates occurring at temperatures as low as 10C; both bacteria and
fungi are physiologically active at subzero temperatures. Extracellular enzymes are active in soils at temperatures
as low as 20C; this activity is thought to occur in unfrozen water on surfaces of soil particles. Nitrogen mineral-
ization is reported at temperatures as low as 1C and is promoted by freezethaw 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 physicalchemical properties and processes.
14. SUBJECT TERMS
15. NUMBER OF PAGES
28
Freezethaw cycles
Soils
16. PRICE CODE
Frozen soil
Soil chemistry
17. SECURITY CLASSIFICATION
18. SECURITY CLASSIFICATION
19. SECURITY CLASSIFICATION
20. LIMITATION OF ABSTRACT
OF REPORT
OF THIS PAGE
OF ABSTRACT
UNCLASSIFIED
UNCLASSIFIED
UNCLASSIFIED
Standard Form 298 (Rev. 2-89)
NSN 7540-01-280-5500
Prescribed by ANSI Std. Z39-18
298-102
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