1,4-Dioxane

CAS RN: 123-91-1

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), measured Koc values of 29(2) and 17(3) indicate that 1,4-dioxane is expected to have very high mobility in soil(SRC). Volatilization of 1,4-dioxane from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 4.8X10-6 atm-cu m/mole(4). 1,4-Dioxane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 38.1 mm Hg at 25 deg C(5). A 0% of theoretical BOD using activated sludge in the Japanese MITI test(6) suggests that 1,4-dioxane is not readily biodegradable(SRC). Other screening study results indicate that 1,4-dioxane is resistant to biodegradation and slow to biodegrade(7). Using soil microcosms 1,4-dioxane was not biodegraded within 120 days and, therefore, considered recalcitrant(8). 1,4-Dioxane did not biodegrade in most of 20 environmental samples (rivers waters, soils, activated sludge), but it was degradable in soils collected from drainage areas of a chemical factory within 33 days, presumably due to acclimation(9).
AQUATIC FATE: Based on a classification scheme(1), measured Koc values of 29(2) and 17(3) indicate that 1,4-dioxane is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(4) based upon a Henry's Law constant of 4.8X10-6 atm-cu m/mole(5). Using this Henry's Law constant and an estimation method(4), volatilization half-lives for a model river and model lake are 7.3 and 56 days, respectively(SRC). According to a classification scheme(6), a BCF range of 0.2-0.7 measured in carp (Cyprinus carpio)(7) suggests the potential for bioconcentration in aquatic organisms is low(SRC). A 0% of theoretical BOD using activated sludge in the Japanese MITI test(7) suggests that 1,4-dioxane is not readily biodegradable(SRC). Other screening studies have found 1,4-dioxane to be resistant to biodegradation and slow to biodegrade(8) and to be recalcitrant(9). 1,4-Dioxane is considered non-biodegradable under conventional bio-treatment technologies based on results of wastewater treatment monitoring data(10). 1,4-Dioxane is a very weak absorber of UV light(11)and results of aqueous photolysis studies(12) suggest that direct photolyis is not an important environmental fate process(SRC). 1,4-Dioxane is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(4).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,4-dioxane, which has a vapor pressure of 38.1 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,4-dioxane 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 33 hours(SRC), calculated from its rate constant of 1.18X10-11 cu cm/molecule-sec at 25 deg C(3). 1,4-Dioxane is a very weak absorber of UV light(4). Results of aqueous photolysis studies(5) suggest that direct photolysis is not an important environmental fate process(SRC).
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