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, biodegradation and volatilization of a model fuel hydrocarbon ([14C]naphthalene) in a gasoline contaminated soil was determined in columns that were either intermittently or continuously ventilated at a low air-flow rate. With continuous ventilation, volatilization was extensive (up to 38.8%) and mineralization relatively minor (10.4%). Intermittent ventilation decreased volatilization ten-fold but also reduced mineralization to negligible levels. Compared to the continuously aerated columns, the intermittently vented soil had significant microbial population reductions, lower CO2 production, and higher residual gasoline. These results indicated that the ineffectiveness of intermittent ventilation for stimulating biodegradation could be attributed to its failure to reduce gasoline residues to sub-inhibitory levels.