| Volatilization | The Henry's Law constant for n-octane is estimated as 3.2 atm-cu m/mole(SRC) derived from its vapor pressure, 14.1 mm Hg(1), and water solubility, 0.66 mg/L(2). This Henry's Law constant indicates that n-octane is expected to volatilize rapidly from water surfaces(3). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(3) is estimated as 3 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(3) is estimated as 4.2 days(SRC). Volatilization from water surfaces may be attenuated by adsorption to suspended solids and sediment in the water column(SRC). The estimated volatilization half-life from a model pond is 11 months if adsorption is considered(4). However, in a study using a jet fuel mixture and sterile freshwater controls from the Escambia River (Florida), a 99% loss of n-octane was attributed to evaporation at 25 deg C(5). n-Octane's estimated Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). The disappearance of n-octane was rapid in soil/water mixture (concentration of soil, 25 g/150 mL)(6); an initial concentration of 0.177 ug/mL n-octane disappeared completely in 5 days using a sterile sandy loam soil with an organic matter content of 5.1%(6). The potential for volatilization of n-octane from dry soil surfaces may exist(SRC) based upon its vapor pressure(1).
Literature: (1) Yaws CL; Handbook of Vapor Pressure. Houston, TX: Gulf Pub Co. 3: 78 (1994) (2) Yalkowsky SH, He Y, eds; Handbook of aqueous solubility data. Boca Raton, FL: CRC Press p. 536 (2003) (3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 15-1 to 15-29 (1990) (4) US EPA; EXAMS II Computer Simulation (1987) (5) Spain JC et al; Degrad of Jet Fuel Hydrocarbons by Aquatic Microbial Communities. Tyndall AFB, FL: Air Force Eng Serv Ctr. AFESC/ESL-TR-83-26 (NTIS AD-A139791/8) p 226 (1983) (6) Dean-Ross D; Bull Environ Contam Toxicol 51: 596-99 (1993) |
| Soil Adsorption | The Koc of n-octane is estimated as 3.1X10+4(SRC), using a log Kow of 5.18(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that n-octane is expected to be immobile in soil. Freundlich absorption coefficients of log 4.04 and log 3.49 were measured in Oberlausitz lignite (11.1% moisture content; 53.5 wt% carbon content; 0.6 wt % nitrogen content) and Pahokee peat soil (10.2% moisture content; 46.1 wt% carbon content; 3.3 wt % nitrogen content), respectively(4). Gaseous transport of volatile n-octane in unsaturated porous media was shown to be influenced by air-water interfacial adsorption and water-partitioning(5). Sorption of n-octane from air to snow was measured, resulting in a sorption coefficient of log -4.41 cu m/sq m at -6.8 deg C(6).
Literature: (1) Miller MM et al; Environ Sci Technol 19:522-9 (1985) (2) US EPA; Estimation Program Interface (EPI) Suite. Ver. 4.1. Nov, 2012. Available from, as of Oct 30, 2013: http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm (3) Swann RL et al; Res Rev 85: 17-28 (1983) (4) Endo S et al; Environ Sci Technol 42): 5897-5903 (2008) (5) Kim H et al; Environ Sci Technol 35: 4457-62 (2001) (6) Roth CM et al; Environ Sci Technol 38: 4078-84 (2004) |
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