n-Pentane

CAS RN: 109-66-0

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 72(SRC), determined from a structure estimation method(2), indicates that n-pentane is expected to have high mobility in soil(SRC). Volatilization of n-pentane from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 1.25 atm-cu m/mole(3). n-Pentane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 514 mm Hg at 25 deg C(4). Screening studies have shown that n-pentane is biodegradable under aerobic conditions(5,6), and these studies suggest that this compound will biodegrade in soil; however, volatilization from soil is expected to be the dominant environmental fate process of n-pentane(SRC).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 72(SRC), determined from a structure estimation method(2), indicates that n-pentane 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 1.25 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 2.5 hrs and 3.4 days, respectively(SRC). According to a classification scheme(5), an estimated BCF of 80(SRC), from its log Kow of 3.39(6) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is moderate(SRC). Screening studies have shown that n-pentane is biodegradable under aerobic conditions(8,9), and these studies suggest that this compound will biodegrade in water; however, volatilization from water surfaces is expected to be the dominant environmental fate process of n-pentane(SRC).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), n-pentane, which has a vapor pressure of 514 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase n-pentane 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 3 days(3), calculated from its rate constant of 3.94X10-12 cu cm/molecule-sec at 25 deg C(4). n-Pentane does not contain chromophores that absorb at wavelengths >290 nm(5) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).
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