Dense Nonaqueous Phase Liquids (DNAPLs)

Halogenated Alkanes

Methanes

Trichlorofluoromethane

Trichlorofluoromethane (TCFM, CAS# 75-69-4) has a vapor pressure of 802.8 mm Hg at 25^oC (Howard 1990) and is a noncombustible liquid (NIOSH 2005). The log K_oc of TCFM is about 2.2 (Montgomery and Welkom 1989), the log K_ow is 2.53 (Howard 1990), and the Henry's constant is 9.7 e-2 atm-m³/mole (Howard 1990). The solubility of TCFM is about 1,100 mg/L at 25^oC (HSDB), and its specific gravity is about 1.476 at 25^oC (Montgomery and Welkom 1989).

The relatively low calculated K_oc value for TCFM in soil indicates that the compound is likely to move quickly through soil and sediment (Howard 1990).

Howard (1990) reports that volatilization is the most important removal process for TCFM released to surface waters and that its half life in a typical river is about 4.3 hours. Information in the Hazardous Substances Data Bank (HSDB) file for TCFM suggests a half life of 5 days for the compound in a model lake.

Because of the low K_ow of this chemical, bioaccumulation is expected to be moderate (Howard 1990, HSDB). TCFM is readily degraded by microbial action under anaerobic conditions (Brigmon et al 2000, Sonier et al. 1994, Shana et al. 2010); however; not all anaerobic conditions are favorable, and stalling might occur. Although Plummer and Busenberg (2000) report that TCFM does not degrade directly under aerobic conditions, Blackert and Cibrik (2009) describe a technology for aerobic cometabolic destruction of the compound.

TCFM does not absorb UV radiation greater than 290 nm, nor does it react appreciably with reactive atmospheric species, such as hydroxyl radicals or singlet oxygen atoms. It does not degrade under photochemical smog conditions. Estimates of tropospheric half-lives based on time-series concentration measurements range from 52 to 207 years. The only sink is diffusion to the stratosphere, where photolysis by short wavelength UV radiation occurs. In the stratosphere, TCFM will slowly photolyze to release chlorine atoms, which in turn participate in the catalytic removal of stratospheric ozone (HSDB).

TCFM is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups; however the rate is greatly affected by the presence of metals, such as steel, that act as catalysts (HSDB).

References

Biodegradation of Trichlorofluoromethane by Sediment Associated Anaerobic Bacteria from an Aquifer Contaminated by Landfill Leachate
Brigmon, R.L., D.J. Altman, A.J. Tien, M.M. Franck, and P.C. McKinsey.
WSRC-MS-2000-00311, 4 pp, 2000

Chlorofluorocarbons Background
Plummer, L. and E. Busenberg.
Excerpted from Environmental Tracers in Subsurface Hydrology (P. Cook and A. Herczeg eds.), Chapter 15: Chlorofluorocarbons, p 441-478, Kluwer Acadmic Press, 2000

The authors state that TCFM does not degrade aerobically.

Dechlorination of Trichlorofluoromethane (CFC-11) by Sulfate-Reducing Bacteria from an Aquifer Contaminated with Halogenated Aliphatic Compounds.
Sonier, D., N. Duran, and G. Smith.
Applied and Environmental Microbiology 60(12):4567-4572(1994)
View abstract

In an anaerobic environment, TCFM was degraded to dichlorofluoromethane.

Evaluation of Strategies for Anaerobic Bioremediation of High Concentrations of Halomethanes
Shana, H., H.D. Kurtz Jr., and D.L. Freedman.
Water Research 44(5):1317-1328(2010)
View abstract

Lactate and corn syrup electron donors were effective in reducing TCFM completely.

Fluorotrichloromethane
NIOSH Pocket Guide to Chemical Hazards
National Institute of Occupational Safety and Health, NIOSH Publication Number 2005-149, 2005

Groundwater Chemicals Desk Reference
Montgomery, J. and L. Welkom.
Lewis Publishers, 640 pp, 1989

Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Volume 2: Solvents
Howard, P., ed.
CRC Press, 546 pp, 1990

Trichlorofluoromethane, CASRN: 75-69-4
Pubchem
PubChem, National Center for Biotechnology Information.

For Further Information

Biodegradation of Methane and Halocarbons in Simulated Landfill Biocover Systems Containing Compost Materials
Scheutz, C., G. Pedersen, G. Costa and P. Kjeldsen.
Journal of Environmental Quality 38(4):1363-1371(2009)
View abstract

TCFM was degraded anaerobically to dichlorofluoromethane (DCFM). DCFM is subject to aerobic degradation.

DNAPL Site Evaluation
Cohen, R. and J. Mercer.
EPA 600-R-93-022, 369 pp, 1993

This document contains a broad discussion of DNAPL site evaluation, plus a comprehensive table of physical properties of selected DNAPL chemicals, including TCFM, in Appendix A.