1,1-Dichloroethylene

CAS RN:75-35-4

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 64-65(2-3), indicate that 1,1-dichloroethylene is expected to have high mobility in soil(SRC). Volatilization of 1,1-dichloroethylene from moist soil surfaces is expected(SRC) given a Henry's Law constant of 0.0261 atm-cu m/mole(4). 1,1-Dichloroethylene is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 600 mm Hg at 25 deg C(5). 1,1-Dichloroethylene had a biodegradation rate of 0.050 ug/g soil/hr in soil from Skellingsted landfill in Holback, Denmark, incubated with methane(6). Under simulated landfill anaerobic conditions, 1,1-dichloroethylene degraded in 1-3 weeks(7).
AQUATIC FATE: Based on a classification scheme(1), Koc values of 64-65(2-3), indicate that 1,1-dichloroethylene 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 0.0261 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 hours and 4 days, respectively(SRC). A hydrolysis half-life of 6-9 months has been observed for 1,1-dichloroethylene at pH 4.5 to 8.5(6). According to a classification scheme(7), BCFs of <13 measured in carp(8), suggest bioconcentration in aquatic organisms is low. In anaerobic microcosms designed to simulate a groundwater environment, 50% of the 1,1-dichloroethylene disappeared in 5-6 months(9). However, 1,1-dichloroethylene had a biodegradation half-life of 1.25 years in ground water from a former manufacturing facility in New Jersey(10).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,1-dichloroethylene, which has a vapor pressure of 600 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,1-dichloroethylene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl and nitrate radicals, and ozone(SRC); the half-lives for these reactions in air are estimated to be 1.5 days, 27 days and 7.9 years(SRC), calculated from respective rate constants of 1.09X10-11(3), 1.23X10-15(4) and 3.98X10-21(5) cu cm/molecule-sec at 25 deg C. Under photochemical smog situations with nitrogen dioxide present, 1,1-dichloroethylene decomposes rapidly (half-life <2 hr)(6).
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