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I <br /> I <br /> ENDPOINT:CALCULATION OF EFFECTIVE DIFFUSIVITY IN SOIL <br /> page 2 of 3 <br /> EQUATIONS. <br /> f De. = (Da*Pa"3.33)/Pt-2 (Millington-Quirk, 1961) <br /> i <br /> SYMBOLS AND DESCRIPTIONS UNITS VALUE RATIONALE <br /> a, Da = Diffusion Coefficient of Air em2/second see below (EPA, 1990) <br /> Pa = Air-Filled Porosity dimensionless 0.106 (by previous equation) <br /> Pt = Total Soil Porosity dimensionless 0.276 (95% UCL, Alton, 1993) <br /> De = Effective Diffusion Coefficient of Chemical in Soil cm2/second see below (by equation) <br /> Chemical Da Qe <br /> Benzene 8.90E-02 6.55E-04 <br /> i Toluene 8.70E-02 6.40E-04 <br /> ' Ethylbenzene 7.50E-02 5.52E-04 <br /> Xylenes 7.00E-02 5.15E-04 <br /> ENDPOINT:CALCULATION OF CHEMICAL FLUX TO SOIL SURFACE <br /> EQUATIONS: <br /> F = (De*Csg)/L <br /> SYMBOLS AND DESCRIPTIONS UNITS VALUE RATIONALE <br /> ' De = Effective Diffusion Coefficient of Chemical in Soil em2lsecond see below (by previous equation) <br /> Csg = Concentration of Chemical in Soil Gas g1cm3 see below (by previous equation) <br /> L = Depth to Impacted Soil cm see below (95%upper confidence limit) <br /> F = Flux to Ground Level glcm2-second soe below (by equation) <br /> 1 <br /> Chemical De Cis L F <br /> Benzene 6.55E-04 2.05E-05 304 4.42E-I1 <br /> Toluene 6.40E-04 8.42E-06 304 1.77E-11 <br /> Ethyibenzene 5.52E-04 6.20E-05 304 1.13E-10 <br /> Xylenes 5.15E-04 2.4711,05 304 4.18E-1I <br /> ENDPOINT:CALCULATION OF AMBIENT CHEMICAL CONCENTRATION FROM FLUX THROUGH SOIL SURFACE <br /> EQUATIONS: <br /> Co(s) = F*dl* (1/ws)*(I/mh)*efl <br /> IS-EMOLS AND DESCRIPTIONS UMTS VALUE RATIONALE <br /> F = Flux of Chemical to Ground Level g/cm2-second see below (by previous equation) <br /> dl = Downwind Length of Exposed Soil cm 3.06E+03 (estimated length of exposed soil, "100 ft.) <br /> ws = Wind Speed cm/second 4.69E+02 (LARB, 1987) <br /> mh = Mixing Height of Chemical in Air cm 3E+02 (3 meter high doorway) <br /> efl = Conversion Factor (mg/m3)/(g/cm3) 1.00E+09 (by definition) <br /> Co(s) = Concentration of Chemical in Outside Air mg/m3 see below (by equation) <br /> I, Chemical A COW <br /> Be�izane 4.42E_1 t 9.610E-04 <br /> Toluene 1,77E-11 3.86&04 <br /> Ethylbenzene 1.13E-10 2.45E-03 <br /> Xylenes <br /> 4.18 E-11 9.09&04 <br /> IISKCALC4 <br /> tr.> <br />