Acetonitrile

CAS RN: 75-05-8

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 2.2(2) indicates that acetonitrile is expected to have very high mobility in soil(SRC). Volatilization of acetonitrile from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 3.45X10-5 atm-cu m/mole(3). Acetonitrile is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 88.8 mm Hg(4). A 65% of theoretical BOD using activated sludge in the Japanese MITI test(5) suggests that biodegradation may be an important environmental fate process in soil(SRC). Available screening studies suggest that acetonitrile is readily biodegradable by adapted microbial populations(6). Biodegradation is generally slower with non-adapted microbes(7,8).
AQUATIC FATE: Based on a classification scheme(1), a Koc value of 2.2(2) indicates that acetonitrile 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 3.45X10-5 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 12 hours and 7.5 days, respectively(SRC). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow of -0.34(6) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). A 65% of theoretical BOD using activated sludge in the Japanese MITI test(8) suggests that biodegradation might be an important environmental fate process in soil(SRC). Available screening studies suggest that acetonitrile is readily biodegradable by adapted microbial populations(9). Biodegradation is generally slower with non-adapted microbes(10,11). The biodegradability of acetonitrile in river water had an observed 12-day ThOD (theoretical oxygen demand) of 40%(12,13). In acclimated river water, 100% removal was observed after 4 days(9). Chemical hydrolysis in water is not expected to be an important fate process(SRC) since the hydrolysis half-life at pH 7 (25 deg C) is reported to be >150,000 years(14).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), acetonitrile, which has a vapor pressure of 88.8 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase acetonitrile 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 610 days(SRC), calculated from its rate constant of 2.63X10-14 cu cm/molecule-sec at 25 deg C(3). Vapor-phase acetonitrile is also degraded in the atmosphere by reaction with ozone(SRC); the half-life for this reaction in air is estimated to be greater than or equal to 76 days(SRC), calculated from its rate constant of less than or equal to 1.5X10-19 cu cm/molecule-sec at 25 deg C(4). Direct photolysis of acetonitrile in the atmosphere is not expected to be an important fate process(4) since acetonitrile absorbs light only in the far UV region(5) with a UV maximum below 160 nm(4). The removal of acetonitrile from the atmosphere by precipitation has been reported to be an important fate process(4).
Find more information on this substance at: PubChem, PubMed