For more information on the DNAPL Website, please contact:
Linda FiedlerTechnology Assessment Branch
PH: (703) 603-7194 | Email: fiedler.linda@epa.gov
Dense Nonaqueous Phase Liquids (DNAPLs)
Chemistry and Behavior
- Overview
- Policy and Guidance
- Chemistry and Behavior
- Environmental Occurrence
- Toxicology
- Detection and Site Characterization
- Treatment Technologies
- Conferences and Seminars
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Halogenated Alkanes
Methanes
Methylene Chloride
Methylene Chloride (MC, CAS # 75-09-2) has a vapor pressure of 349 mm Hg at 20oC (ATSDR 2000) and is a combustible liquid (NIOSH 2005). The log Koc of MC is 1.4, the log Kow is 1.3, and the Henry's constant is 2.03 e-3 atm-m3/mol at 25oC. The solubility of MC is about 20,000 mg/L at 20oC (ATSDR 2000), and its specific gravity is about 1.32 (25oC). The Agency for Toxic Substances and Disease Registry has developed a toxicological profile for MC that contains a useful summary table
of the physical properties of MC.
The relatively low calculated Koc value for MC in soil indicates that MC is likely to move quickly through soil and sediment (ATSDR 2000).
Based on a Henry's law constant of 2.03 e-3 atm-m3/mol at 20oC, MC is expected to volatilize rapidly from water surfaces (ATSDR 2000). Modeling information in the Hazardous Substances Data Bank (HSDB) suggests that the half life of MC (as dichloromethane) in a model river is about one hour, and in a model lake, about four days.
Because of the low Kow of MC, bioaccumulation is expected to be low, and biomagnification is not likely to occur. Microbial degradation of MC can occur under aerobic or anaerobic conditions. The rate of biodegradation was found to be dependent on soil type, substrate concentration, and redox state of the soil (ATSDR 2000).
When released to the atmosphere, hydroxyl radicals are expected to degrade MC with a half life of about 130 days. Direct photolysis is not expected to occur. Due to its relatively long atmospheric lifetime, MC can be widely dispersed, but it is not expected to accumulate in the atmosphere (ATSDR 2000).
References
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 MC, in Appendix A.
Dichloromethane, CASRN: 75-09-2
Hazardous Substances Data Bank (HSDB)
TOXNET, National Library of Medicine Web site.
Methylene Chloride
NIOSH Pocket Guide to Chemical Hazards.
National Institute of Occupational Safety and Health, NIOSH Publication Number 2005-149, 2005
Toxicological Profile for Methylene Chloride
Agency for Toxic Substances and Disease Registry (ATSDR), 313 pp, 2000
Proceed to "Ethers (for future development) > Chloroform"
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