VENTILATION EFFECTS ON MINERALIZATION AND VOLATILIZATION OF NAPHTHALENE IN A GASOLINE-CONTAMINATED SUBSURFACE SOIL

Soil ventilation is widely used to promote in situ soil bioremediation at leaking underground storage tank sites. Effects of this process on microbial activity, however, are ill-defined. In this study, biodegra dation and volatilization of a model fuel hydrocarbon ([C-14]naphthale ne) in a gasoline-contaminated soil was determined in columns that wer e either intermittently or continuously ventilated at a low air-flow r ate. With continuous ventilation, volatilization was extensive (up to 38.8%) and mineralization relatively minor (10.4%). Intermittent venti lation decreased volatilization ten-fold but also reduced mineralizati on to negligible levels. Compared to the continuously aerated columns, the intermittently vented soil had significant microbial population r eductions, lower CO2 production, and higher residual gasoline. These r esults indicated that the ineffectiveness of intermittent ventilation for stimulating biodegradation could be attributed to its failure to r educe gasoline residues to sub-inhibitory levels. (C) 1996 Elsevier Sc ience Ltd.