CAS RN:76-06-2

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 81(2) indicates that chloropicrin is expected to have high mobility in soil(SRC). Volatilization of chloropicrin from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 2.05X10-3 atm-cu m/mole(2). Chloropicrin is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 23.8 mm Hg(3). Half-lives in soil ranging from 0.2 to 4.5 days at 20 deg C(4) suggests that biodegradation is an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), a Koc value of 81(SRC), determined from a structure estimation method(2), indicates that chloropicrin 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 2.05X10-3 atm-cu m/mole(2). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 4 hours and 5 days, respectively(SRC). According to a classification scheme(4), an estimated BCF of 8(SRC), from its log Kow of 2.09(5) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Chloropicrin photohydrolyzes rapidly in water when exposed to light below 300 nm producing CO2, chloride and nitrate in the presence of air; its half-life in sunlight is about 3 days(7). However, under ambient room light chloropicrin is stable to photodegradation(7). The photooxidation of vapor-phase chloropicrin to form phosgene has also been observed in the field(8). A half-life of 0.5 days in activated sludge(9) suggests that biodegradation may be an important environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), chloropicrin, which has a vapor pressure of 24 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase chloropicrin 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 120 days(SRC), calculated from its rate constant of 1.3X10-13 cu cm/molecule-sec at 25 deg C(SRC), that was derived using a structure estimation method(3). Chloropicrin absorbs UV light in the 280 to 390 nm range(4) and therefore may be susceptible to direct photolysis(SRC).

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