1,1-Dichloroethane

CAS RN:75-34-3

Environmental Fate

Aquatic and Atmospheric Fate: Chloroethanes are expected to be present in industrial air and water emissions. They volatilize rapidly from surface water and persist in urban atmospheres. Hydrolysis and biodegradation are expected to be slow. /Chloroethanes/

TERRESTRIAL FATE: Based on a classification scheme(1), measured Koc values of 30(2) and 9.2(3) indicate that 1,1-dichloroethane is expected to have very high mobility in soil(SRC). Volatilization of 1,1-dichloroethane from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 5.62X10-3 atm-cu m/mole(4). 1,1-Dichloroethane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 227 mm Hg at 25 deg C(5). The half-life of 1,1-dichloroethane under sulfate-reducing conditions was approximately 115 days using well monitoring data from a landfill with a contamination history(6), indicating that biodegradation is a slow environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), measured Koc values of 30(2) and 9.2(3) indicate that 1,1-dichloroethane is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(4) based upon a Henry's Law constant of 5.62X10-3 atm-cu m/mole(5). Using this Henry's Law constant and an estimation method(4), volatilization half-lives for a model river and model lake are 3 hrs and 4 days, respectively(SRC). According to a classification scheme(6), an estimated BCF of 7(SRC), from its log Kow of 1.79(7) and a regression-derived equation(8), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The half-life of 1,1-dichloroethane under sulfate-reducing conditions was approximately 115 days using well monitoring data from a landfill with a contamination history(9), indicating that biodegradation is a slow environmental fate process in water(SRC). Hydrolysis is not expected to be an important environmental fate process(SRC) given a hydrolysis half-life of 61.3 years at 25 deg C and pH 7(10).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,1-dichloroethane, which has a vapor pressure of 227 mm Hg at 25 deg C(SRC), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,1-dichloroethane is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 59 days(SRC), calculated from its rate constant of 2.74X10-13 cu cm/molecule-sec at 25 deg C(3). 1,1-Dichloroethane does not contain chromophores that absorb at wavelengths >290 nm(4) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

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