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

1, 2-Dichlorobenzene

1,2-Dichlorobenzene (1,2-DCB CAS# 95-50-1) has a vapor pressure of 1.36 mmHg at 25oC (ATSDR 2006) and is a Class IIIA Combustible Liquid (NIOSH 2005). The log Koc of 1,2-DCB is 2.51, the log Kow is 3.43, and the Henry's constant is 1.92 e-3 atm-m3/mol at 25oC (ATSDR 2006). The solubility of the compound is about 151 mg/L at 25oC (ATSDR 2006), and its specific gravity is about 1.31 (20oC). The toxicological profile for dichlorobenzenes developed by the Agency for Toxic Substances and Disease Registry contains a useful summary tableAdobe PDF Logo of the physical properties of 1,2-, 1,3-, and 1,4-DCB.

The calculated Koc value for 1,2-DCB in soil indicates that the chemical is likely to have moderate mobility in soil and sediment (ATSDR 2006). Some sorption to suspended sediments can be expected (HSDB).

Based on a Henry's law constant of 1.92 e-3 atm-m3/mol at 25oC, 1,2-DCB is expected to volatilize rapidly from water surfaces (ATSDR 2006). Modeling information for this chemical in the Hazardous Substances Data Bank (HSDB) suggests that the half life of 1,2-DCB in a model river is about 4 hours, and about 120 hours in a model lake.

Because of the relatively high Kow of 1,2-DCB, bioaccumulation is expected (ATSDR 2006), with moderate to high bioaccumulation in aquatic organisms (HSDB). Microbial degradation of 1,2-DCB can occur under anaerobic conditions, although it is slow (HSDB), and it will degrade under aerobic conditions (Lawrence 2006, Werner and Tiehm 1999).

When released to the atmosphere, hydroxyl radicals are expected to degrade this chemical with a half life of about 14 to 31 days (ATSDR 2006). Direct photolysis is not anticipated (HSDB).

References

1,2-Dichlorobenzene, CASRN: 95-50-1
Hazardous Substances Data Base (HSDB)
TOXNET, National Library of Medicine Web site.

Description, Properties, and Degradation of Selected Volatile Organic Compounds Detected in Ground Water: A Review of Selected Literature
Lawrence, S.J.
U.S. Geological Survey Open-File Report 2006-1338, 65 pp, 2006

This report contains a discussion of the biodegradation of chorobenzenes under aerobic and anaerobic conditions and provides degradation routes.

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

Toxicological Profile for Dichlorobenzenes
Agency for Toxic Substances and Disease Registry (ATSDR), 493 pp, 2006

This profile provides information on human health effects, fate and transport, production, and uses of all three dichlorobenzenes: 1,2-, 1,3-, and 1,4-DCB.

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 1,2-DCB, 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