Chloroform

CAS RN: 67-66-3

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 34-196(2-3), indicate that chloroform is expected to have high to moderate mobility in soil(SRC). Volatilization of chloroform from moist soil surfaces is expected(SRC) given a Henry's Law constant of 3.67X10-3 atm-cu m/mole(4). Chloroform is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 197 mm Hg(5). In a study of chloroform residence time in soils, chloroform was found to have a half-life of 0.3 days when applied 1 cm deep into soil and 1.4 days when applied 10 cm deep, classifying it as "very short lived", mostly due to volatilization(6). Under aerobic conditions, little or no degradation of chloroform is reported up to 25 wk(7-9). Studies have demonstrated that at low concentrations, chloroform can be anaerobically degraded by methanogenic bacteria in the presence of a primary substrate such as acetic acid(10) and even better under sulfate reducing conditions(11). A 0% of Theoretical BOD using activated sludge in the Japanese MITI test(12) suggests that biodegradation is not an important environmental fate process in soil(SRC).
AQUATIC FATE: Based on a classification scheme(1), Koc values of 34-196(2-3), indicate that chloroform is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 3.67X10-3 atm-cu m/mole(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 3.5 hours and 4.4 days, respectively(SRC). In a field study of chloroform volatilization, it was found that the volatilization half-life from the Rhine River was 1.2 days while in a lake located in the Rhine basin the half-life was 31 days(5). Chloroform is not expected to undergo hydrolysis in the environment base upon estimated hydrolysis half-lives of 3400 and 340 years at pH values of 7 and 8, respectively(6). According to a classification scheme(7), BCFs of 1.4-10.35 measured in various fish(8-10), suggest the bioconcentration in aquatic organisms is low. Chloroform was not degraded aerobically or anaerobically in an aquifer storage and recovery site(11). Chloroform had influent concentrations of 15,250 and <5.0 ug/L and effluent concentrations of <14 and <5.0 ug/L using an activated sludge with a daily mass loading of COD/bacterial mass ratios of 0.3 and 0.6, respectively(12). [
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), chloroform, which has a vapor pressure of 197 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase chloroform 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 156 days(SRC), calculated from its rate constant of 1.03X10-13 cu cm/molecule-sec at 25 deg C(3). The tropospheric half-life for chloroform has been estimated at 3 years(4).
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