Dense nonaqueous phase liquids (dnapls)

Halogenated Alkanes

Ethanes

1,1,2,2-Tetrachloroethane

1,1,2,2-Tetrachloroethane (1,1,2,2-TetCA, CAS# 79-34-5) has a solubility in water at 25^oC of about 2,800 mg/L and a specific gravity of 1.6. The vapor pressure is 4.62 mm Hg at 25^oC. The Henry's Law constant (calculated from solubility and vapor pressure) has been reported at 3.67 E-4 atm-m³/mole at 25^oC. The log K_ow is 2.39 (ATSDR 2008). The log K_oc is 2.07 (Cohen and Mercer 1993).

The Agency for Toxic Substances and Disease Registry (ATSDR) has developed a useful summary table of the compound's physical properties in its toxicological profile for 1,1,2,2-TetCA.

Because of 1,1,2,2-TetCA's low K_oc value, it is not expected to adsorb to soil or sediment, nor is it expected to bioconcentrate (ATSDR 2008). It is highly mobile in soil and can leach into ground and surface waters. Given its Henry's constant, the majority of 1,1,2,2-TetCA in surface water is expected to volatilize. Volatilization half life in a model river has been estimated to be 6.9 hours and 6.1 days in a model lake (ATSDR 2008, HSDB). The 1,1,2,2-TetCA that does not volatilize from surface water will degrade through hydrolysis.

In groundwater, the dominant degradation pathways of 1,1,2,2-TetCA are anaerobic biodegradation and chemical hydrolysis. The measured half lives for the chemical hydrolysis of 1,1,2,2-TetCA at neutral pHs range from 29 to 102 days. Chemical hydrolysis depends on the pH and has higher rates in basic to neutral conditions. The hydrolysis product is trichloroethene (TCE). 1,1,2,2-TetCA might degrade under aerobic conditions, but the evidence is mixed (ATSDR 2008).

In the atmosphere, 1,1,2,2-TetCA is removed either by reaction with photochemically generated hydroxyl radicals or precipitation washout. The half life of the hydroxyl reactions is approximately 54 days. 1,1,2,2-TetCA removed through precipitation likely will volatilize back to the atmosphere.

References

1,1,2,2-Tetrachloroethane, CASRN: 79-34-5
PubChem.
PubChem, National Center for Biotechnology Information.

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

Toxicological Profile for 1,1,2,2-Tetrachloroethane
Agency for Toxic Substances and Disease Registry (ATSDR),258 pp, 2008

For Further Information

1,1,2,2-Tetrachloroethane
U.S. EPA, Technology Transfer Network Air Toxics Web Site, 2000

Anaerobic Degradation of 1,1,2,2-Tetrachloroethane and Association with Microbial Communities in a Freshwater Tidal Wetland, Aberdeen Proving Ground, Maryland: Laboratory Experiments and Comparisons to Field Data
Lorah, M.M., M.A. Voytek, J.D. Kirshtein, and E.J. Jones.
U.S. Geological Survey Water-Resources Investigations Report 02-4157, 73 pp, 2003

Atmospheric Chemistry of 1,1,1,2-Tetrachloroethane (CCl₃CH₂Cl): Spectrokinetic Investigation of the CCl₃CClHO₂ Radical, Its Reactions with NO and NO₂, and Atmospheric Fate of the CCl₃CClHO Radical
Mogelberg, T., M. Bilde, J. Sehested, T.J. Wallington, and O.J. Nielsen.
Journal of Physical Chemistry 100(47):18399-18407(1996)
View abstract

Degradation of 1,1,2,2-Tetrachloroethane and Accumulation of Vinyl Chloride in Wetland Sediment Microcosms and In Situ Porewater: Biogeochemical Controls and Associations with Microbial Communities
Lorah, M.M. and M. Voytek.
Journal of Contaminant Hydrology 70(1-2):117-145(2004)
View abstract