Laserfiche WebLink
flow of wind across the box. Chemical mass enters_ the box through steady-state <br /> emission from the soil, and leaves the box by advection. Based on these assumptions, <br /> the steady-state average concentration in the box is computed as follows: <br /> Cair = Q .103 / (µWI) <--� <br /> where: <br /> C� = chemical concentration in air (mg/m3) —� <br /> Q = average volatile chemical emission rate for the exposure period <br /> (g/s) <br /> µ = mean annual wind speed (m/s). ... �� <br /> W = width of the box perpendicular to the predominant wind direction <br /> (m) .� <br /> H = height of the mixing.zone (m) <br /> 103 = conversion factor g to mg- <br /> The box model should only be used to estimate the average concentration within a <br /> volume of air and does not account for the decrease in concentration with distance or <br /> height from the source. Since the box model does not account for spatial or temporal <br /> variations of concentration, the model is inappropriate for receptors located at large <br /> distances from the source of air emissions. Box models have been found to be the most 4 <br /> applicable for evaluating exposure to receptors working or living in the vicinity of the AL <br /> contaminated area and typically result in very conservative estimates of exposure. <br /> The input requirements used -in 'the box model are listed in Table 4-6. The air <br /> concentrations estimated using the box model°are given in Appendix A, modeling results. �. <br /> 4.4.4 Calculating Inhalation Exposures (Outdoor Air and.Shower Air) <br /> Volatile emissions from volatilization modelingcalculations tons are used to calculate <br /> inhalation exposure. Inhalation intake is computed.as follows: <br /> DI = Ca IR ET BW <br /> S:1LDCXYELLO.Rn May 4,1995 4-13 <br />