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1 <br /> SECTEONFOUR RKPOSU ®133088men9 <br /> estimates of exposure For this assessment the following default assumptions were used 2 meter <br /> mixing zone height and 5 miles per hour (mph) lateral wind speed The volatilization modeling <br /> was conservative in that no biodegration or loss mechanism in soil is used <br /> Soil particulate emissions were calculated using the GSI software The soil particulate emission <br /> factor is the steady-state ratio of the concentration of organics in particulates in the ambient <br /> breathing zone to the source concentrations of organics in the surface soil The factor <br /> incorporates the release of soil particulates from ground surface and the mixing of these particles <br /> in the ambient air breathing zone directly over the affected surface soil The particulate release <br /> rate used was a conservative default value of 6 9 x 10`14g/cm2-sec (approximately 0 2 <br /> pounds/acre-year) <br /> Values used in the above equations for air emissions are listed in Appendix A Site-specific data were <br /> used wherever possible If site-specific data were not available, conservative ASTM RBCA default <br /> values were used <br /> 4.4.3 Calculation of intake Factors <br /> The intake factor is a value that combines the site-specific and receptor specific assumptions for a given <br /> exposure pathway The intake factor multiplied by the concentration of a chemical of concern results <br /> in an estimate of the chemical intake in mg/kglday for that receptor population and exposure pathway <br /> The generic equation to calculate intake is the following <br /> Intake(mg/kg/day)=Concentration x Intake Factor <br /> Multiplying the intake factor by the concentration of the chemical of concern yields the daily chemical <br /> intake Separate intake factors were calculated for each exposure pathway and receptor The values <br /> and assumptions used to calculate each intake factor are dependent on the exposure pathway and <br /> receptor pathway being evaluated A more detailed description of the values used for intake <br /> rcalculations is presented below <br /> 4.4.3.9 Calculating Inhalation Exposures (Outdoor Air) <br /> Volatile emissions from volatilization modeling calculations are used to calculate inhalation exposure <br />' from soil and groundwater emissions Inhalation intake is computed as follows <br /> DI = Cn IR ET/BW <br /> where <br /> DI = intake of chemical due to inhalation(mg/kg-d) <br /> 9,W0 ® T{1997W3009NA%SPOCKTOMREPORT%SHOREP#1 D0C18-FM-M973009NMSNA 4-11 <br />