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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
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- Environmental Occurrence
- Toxicology
- Detection and Site Characterization
- Treatment Technologies
- Conferences and Seminars
- Additional Resources
Halogenated Alkanes
Methanes
Bromochloromethane
Bromochloromethane (BCM, CAS 74-97-5) has a vapor pressure of 142 mm Hg at 25oC (HSDB) and is a noncombustible liquid (NIOSH 2005). The log Koc of BCM is about 1.43 (Montgomery 1991), the log Kow is 1.41, and the Henry's constant is 1.5 e-3 atm-m3/mole (Howard 1993). The solubility of BCM is about 16,700 mg/L at 25oC, its specific gravity is about 1.93 at 20oC, and its boiling point is about 68oC (HSDB).
The relatively low calculated Koc value for BCM in soil indicates that BCM is likely to move quickly through soil and sediment (Howard 1993, HSDB).
Volatilization is the most important removal process for BCM released to surface waters. The half life in a typical river is estimated at about 4 hours (Howard 1993). Modeling information in the record for BCM in the Hazardous Substances Data Base (HSDB) estimates that the half life of the compound in a model lake is 4.7 days.
Because of the low Kow of BCM, bioaccumulation is expected to be low (Howard 1993, HSDB). The chemical is readily degraded by microbial action under anaerobic conditions (Howard 1993, HSDB) and also will degrade directly under aerobic conditions (HSDB).
Vapor-phase BCM is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals. The half life for this reaction in air is 145 days. Direct photolysis will have only a minor effect on the atmospheric lifetime due to BCM's very low UV absorption in the environmentally significant range >290 nm (HSDB).
Hydrolysis of BCM in environmental waters is not expected to be a significant process as the half-life for this process under environmental conditions at 25oC has been estimated at 44 years (HSDB).
References
Chlorobromomethane, CASRN: 74-97-5
Hazardous Substances Data Bank (HSDB)
TOXNET, National Library of Medicine Web site.
Chlorobromomethane
NIOSH Pocket Guide to Chemical Hazards.
National Institute of Occupational Safety and Health, NIOSH Publication Number 2005-149, 2005
Groundwater Chemicals Desk Reference Volume 2
Montgomery, J.
Lewis Publishers, 944 pp, 1991
Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Volume IV
Howard, P.
Lewis Publishers, 578 pp, 1993
For Further Information
DNAPL Site Evaluation
Cohen, R. and J. Mercer.
EPA 600-R-93-022, 369 pp, 1993
This document has a broad discussion of DNAPL site evaluation and contains a comprehensive table of physical properties of selected DNAPL chemicals, including BCM, in its Appendix A.
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