Trifluoromethane

CAS RN:75-46-7

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 32(SRC), determined from a structure estimation method(2), indicates that trifluoromethane is expected to have very high mobility in soil(SRC). Volatilization of trifluoromethane from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 0.0952 atm-cu m/mole(3). Trifluoromethane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 35,300 mm Hg at 25 deg C(4). Biodegradation in soil is not expected based on aerobic pure culture studies(5).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 32(SRC), determined from a structure estimation method(2), indicates that trifluoromethane is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 0.0952 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 2.5 hours and 3.3 days, respectively(SRC). Estimated hydrolysis half-lives of 5.1 years and 190 days at pH values of 7 and 8, respectively(2), suggest that hydrolysis is not expected to be an important process(SRC). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow of 0.64(6) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation in water is not expected based on aerobic pure culture studies(7).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), trifluoromethane, which has a vapor pressure of 35,300 mm Hg at 25 deg C(2), is expected to exist solely as a gas in the ambient atmosphere. Gas-phase trifluoromethane 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 140-160 years(SRC), calculated from rate constants of 2.7X10-16 to 2.8X10-16 cu cm/molecule-sec at 25 deg C(3-5). Trifluoromethane does not contain chromophores that absorb at wavelengths >290 nm(6) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC). This relatively slow half-life in the lower atmosphere suggests that some trifluoromethane may gradually diffuse into the stratosphere(SRC). The diffusion half-life for transport from the troposphere to the stratosphere is on the order of 20 years(7). Trifluoromethane has Global Warming Potentials of 8200-15,486 (20 Yr), 9200-19,691 (100 Yr) and 9900-15,547 (500 Yr(4, 8-11). The atmospheric life-time for trifluoromethane has been calculated to be 234-295 years(4, 8-11).
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