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Table 6: Default Volatilization and Soil-Specific Parameters <br />Parameter Variable Name Units Value Reference <br />Fraction organic carbon in soil FOC g OC/g soil 0.01 ASTM (1996) <br />Thickness of impacted soil d cm 305 ASTM (1996) <br />(10 feet) <br />Wind speed in outdoor air mixing zone Uoir cm/s 225 ASTM (1996) <br />Width of source area parallel to wind, <br />or groundwater flow direction W cm 2500 ASTM (1996) <br />Outdoor air mixing zone height 8., cm 200 ASTM (1996) <br />Volumetric air content in vadose-zone <br />soils el (cm 3 air)/(cm 3 soil) 0.26 ASTM (1996) <br />Total soil porosity OT (cm 3 voids)/(cm 3 soil) 0.38 ASTM (1996) <br />Volumetric water content in vadose- <br />zone soils ew (cm3 water)/(cm 3 soil) 0.12 ASTM (1996) <br />Soil bulk density Pb g/cm3 1.7 ASTM (1996) <br />Averaging time for vapor flux, <br />residential adult <br />tau, s 7.57E8 ASTM (1996) <br />= ED, in sec <br />Averaging time for vapor flux, <br />residential child <br />tau, s 1.89E8 <br />ASTM (1996) <br />= ED, in sec <br />Averaging time for vapor flux, <br />commercial/industrial <br />tauo s 7.88E8 ASTM (1996) <br />= ED0 in sec <br />Averaging time for vapor flux, utility <br />worker tauut s 3.15E7 <br />ASTM (1996) <br />= ED ut in sec <br />Effective diffusion coefficient in soil Deff cm 2 /s Chem. specific calculated <br />Diffusion coefficient in air D„,, cm 2/s Chem. specific See Table 7. <br />Diffusion coefficient in water Dwoter cm 2 /s Chem. specific See Table 7. <br />Organic carbon-water sorption <br />coefficient K.. mL/g Chem. specific See Table 7. <br />Henry's Law coefficient H (cm 3 water)/(cm 3 air) Chem. specific See Table 7. <br />References: <br />ASTM. 1996. Standard Guide to Risk-Based Corrective Action Applied at Petroleum Release Sites, ASTM E1739-95, Philadelphia, PA. <br />19