U.S. EPA Contaminated Site Cleanup Information (CLU-IN)


U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Chemistry and Behavior

Halogenated Monoaromatics

Chlorobenzene

Chlorobenzene (CAS# 108-90-7) has a vapor pressure of 8.8 mmHg at 20oC (ATSDR 1990) and is a Class IC flammable liquid (NIOSH 2005). The log Koc of chlorobenzene is 2.52, the log Kow is 2.84, and the Henry's constant is 3.58 e-3 atm-m3/mol at 25oC. The solubility of chlorobenzene is about 500 mg/L at 20oC (ATSDR 1990), and its specific gravity is about 1.11 (20oC). The ATSDR toxicological profile for chlorobenzene contains a useful summary tableAdobe PDF Logo of the compound's physical properties.

The relatively low calculated Koc value for chlorobenzene in soil indicates that chlorobenzene is likely to have high to moderate mobility in soil and sediment. Some sorption to suspended sediments can be expected (HSDB).

Based on a Henry's law constant of 3.58 e-3 atm-m3/mol at 25oC, chlorobenzene is expected to volatilize rapidly from water surfaces (ATSDR 1990). Modeling information for this chemical in the Hazardous Substances Data Bank (HSDB) suggests that the half life of chlorobenzene in a model river is about 3.4 hours, and about 4.3 days in a model lake.

Because of the low Kow of chlorobenzene, bioaccumulation is expected to be low, and there should be no biomagnification (HSDB). Microbial degradation of chlorobenzene can occur fairly rapidly under aerobic conditions (ATSDR 1990). Under anaerobic conditions, chlorobenzene degrades to benzene (HSDB).

When released to the atmosphere, hydroxyl radicals are expected to degrade chlorobenzene with a half life of about 21 days. Direct photolysis also can occur (HSDB). Due to its relatively short atmospheric lifetime, chlorobenzene is not expected to be widely dispersed in the atmosphere (ATSDR 1990).

References

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

Chlorobenzene, CASRN: 108-90-7
Hazardous Substances Data Bank (HSDB)
TOXNET, National Library of Medicine Web site.

Toxicological Profile for Chlorobenzene
Agency for Toxic Substances and Disease Registry (ATSDR), 100 pp, 1990

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 chlorobenzene, in its Appendix A.

Reductive Dehalogenation of Dichlorobenzenes and Monochlorobenzene to Benzene in Microcosms
Fung, J.M., B.P. Weisenstein, E.E. Mack, J.E. Vidumsky, T.A. Ei, and S.H. Zinder.
Environmental Science & Technology 43(7):2302-2307(2009)
View abstract