SOIL CLEANUP BY IN-SITU AERATION .15. FIELD-SCALE MODEL WITH DISTRIBUTED DIFFUSION

A mathematical model for soil vapor extraction (SVE) is developed whic h models mass transport of volatile organic compounds (VOCs) through a queous boundary layers by means of a distributed diffusion approach. T he well configuration modeled is that of a buried horizontal slotted p ipe. The model yields high off-gas VOC concentrations initially, follo wed by a rapid drop-off to a relatively long plateau, followed in turn by a terminal region of tailing, the length of which is highly variab le and is determined by the range of the distribution of values of the aqueous diffusion layers. The results suggest that it will be difficu lt, if not impossible, to develop models which permit the accurate pre diction of SVE cleanup times from data taken in short-term pilot-scale experiments during which only 5-25% of the VOC present in the domain of influence of the well is removed.