| 環境中動態 | TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 97(SRC), determined from a structure estimation method(2), indicates that 1,2-dibromo-1,1-dichloroethane is expected to have high mobility in soil(SRC). Volatilization of 1,2-dibromo-1,1-dichloroethane from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.6X10-4 atm-cu m/mole(SRC), using a fragment constant estimation method(3). 1,2-Dibromo-1,1-dichloroethane is expected to hydrolyze in moist soils based upon an estimated hydrolysis rate constant of 1.5 l/mol sechalf-lives of 5 and 52 days at pH 7 and 8, respectively(4). 1,2-Dibromo-1,1-dichloroethane is expected to volatilize slowly from dry soil surfaces(SRC) based upon a vapor pressure of 0.9 mm Hg(5).AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 97(SRC), determined from a structure estimation method(2), indicates that 1,2-dibromo-1,1-dichloroethane is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 1.6X10-4 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 7.5 hrs and 9 days, respectively(SRC). Under basic conditions, however, hydrolysis of 1,2-dibromo-1,1-dichloroethane will compete with volatilization from surface waters(SRC). A base-catalyzed second-order hydrolysis rate constant of 1.5 L/mole-sec(SRC) was estimated using a structure estimation method(5)this corresponds to half-lives of 52 and 5 days at pH values of 7 and 8, respectively(5). According to a classification scheme(6), an estimated BCF of 50(SRC), from an estimated log Kow of 3(7) and a regression-derived equation(8), suggests the potential for bioconcentration in aquatic organisms is moderate(SRC).ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,2-dibromo-1,1-dichloroethane, which has a vapor pressure of 0.9 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,2-dibromo-1,1-dichloroethane 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 890 days(SRC), calculated from its rate constant of 1.8X10-14 cu cm/molecule-sec at 25 °C(SRC) determined using a structure estimation method(3). |
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