Acrylic acid

CAS RN: 79-10-7

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 6-137(2) indicate that acrylic acid is expected to have very high to high mobility in soil(SRC). The pKa of acrylic acid is 4.25(3), indicating that this compound will exist almost entirely in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Volatilization from moist soil is not expected because the acid exists as an anion and anions do not volatilize. Acrylic acid may volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 3.97 mm Hg(5). Utilizing the Japanese MITI test, 67.8% of the theoretical BOD was reached in 2 weeks(6) indicating that biodegradation may be an important environmental fate process in soil(SRC). In a 42 day anaerobic screening study using a sewage seed inoculum, 71% of acrylic acid was mineralized(7).
AQUATIC FATE: Based on a classification scheme(1), Koc values of 6-137(2) indicate that acrylic acid is not expected to adsorb to suspended solids and sediment(SRC). A pKa of 4.25(3) indicates acrylic acid will exist almost entirely in the anion form at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process(4). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow of 0.35(6) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Acrylic acid was determined to be stable to hydrolysis at pH 3, 7, and 11(8). Acrylic acid has experimental aquatic photochemical degradation rates of 2.1X10-4, 5.7X10-4, 4.2X10-4, and 3.9X10-4/sec in distilled water, river water, artificial seawater, and seawater, respectively(9), corresponding to half-lives of 55, 20, and 30 minutes, respectively(SRC). Utilizing the Japanese MITI test, 67.8% of the theoretical BOD was reached in 2 weeks(10) indicating that biodegradation may be an important environmental fate process in water(SRC). In a 42 day anaerobic screening study using a sewage seed inoculum, 71% of acrylic acid was mineralized(11).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), acrylic acid, which has a vapor pressure of 3.97 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase acrylic acid 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 40 hours(SRC), calculated from its rate constant of 1.75X10-11 cu cm/molecule-sec at 25 deg C(3). Vapor-phase acrylic acid is also degraded in the atmosphere by reaction with ozone(SRC); the half-life for this reaction in air is estimated to be 18 days(SRC), calculated from its rate constant of 6.5X10-19 cu cm/molecule-sec at 25 deg C(4). Experimental photodegradation rates in distilled water, river water, artificial seawater, and seawater of 2.1X10-4, 5.7X10-4, 4.2X10-4, and 3.9X10-4/sec(5) corresponding to half-lives of 55, 20, 28, and 30 minutes, respectively(SRC).
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