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Halogenated Alkenes
cis 1,2-Dichloroethene
cis 1,2-Dichloroethene (cis-DCE, CAS # 156-59-2) is a highly volatile and flammable chemical. However, it is heavier than air, and therefore its vapors tend to collect in low areas after a spill. Howard (1991) estimates a Koc of 49, a Kow of 1.86 and a Henry's constant of 3.37 x 10-3 atm-m3/mole for cis-DCE. The solubility of cis-DCE is about 3,500 mg/L at 25° C and its specific gravity is 1.28. The Agency for Toxic Substances and Disease Registry has developed a Toxicological Profile for 1,2-Dichloroethene that contains a useful summary table
of the physical properties of cis-DCE.
The low calculated Koc value for cis-DCE in soil indicates that it is likely to move quickly through soil and sediment. It also will be more mobile in aquifer materials than trichloroethene.
The relatively high Henry's constant value indicates a propensity for cis-DCE to volatilize out of water. This property has two implications for environmental remediation. When cis-DCE is in a dissolved-phase ground water plume that discharges into a moving body of water, it is very likely to volatilize relatively quickly. Howard (1991) suggests the half life of cis-DCE in a one-meter deep river to be between three and five hours. The second implication is that cis-DCE may be very susceptible to cleanup using air sparging technology when subsurface conditions permit. When released to the atmosphere, hydroxyl radicals are expected to degrade cis-DCE with an estimated half life of eight days (Howard 1991).
Because of the low Kow value, bioaccumulation is not expected to occur to any significant extent. cis-DCE can be degraded by microbial action under aerobic and anaerobic conditions. While it is more easily degraded under anaerobic conditions, the necessary microbial species may not be present in some aquifers. For more information see the Treatment Technologies section.
For Further Information
Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Volume II Solvents
Howard, P. (ed.)
Lewis Publishers, Chelsea, MI, 1991, 546 pp
This book provides physical and chemical properties and fate and transport information for 82 chemical solvents.
NIOSH Pocket Guide to Hazardous Chemicals
National Institute of Occupational Safety and Health
This guide contains information on the chemical physical properties of 1,2-dichloroethenes and their physical hazards.
Toxicological Profile for 1,2-Dichloroethene
Agency for Toxic Substances and Disease Registry
U.S. Department of Health and Human Services, 1996, 198 pp
This profile covers 1,2-DCE human health effects, chemical and physical properties, manufacturing volume data, potential for human exposure (environmental fate and transport), and analytical methods.
TOXNET
The National Library of Medicine
National Institutes of Health
TOXNET is a comprehensive compendium of information on a variety of chemicals, but it is often dated.
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