title: Natural Attenuation of Nonvolatile Contaminants in the Capillary Fringe.
abstract: When anoxic polluted groundwater encounters the overlying vadose zone an oxic/anoxic interface is created, often near the capillary fringe. Biodegradation of volatile contaminants in the capillary fringe can prevent vapor migration. In contrast, the biodegradation of nonvolatile contaminants in the vadose zone has received comparatively little attention. Nonvolatile compounds do not cause vapor intrusion, but they still move with the groundwater and are major contaminants. Aniline (AN) and diphenylamine (DPA) are examples of toxic nonvolatile contaminants found often at dye and munitions manufacturing sites. In this study, we tested the hypothesis that bacteria can aerobically biodegrade AN and DPA in the capillary fringe and decrease the contaminant concentrations in the anoxic plume beneath the vadose zone. Laboratory multiport columns that represented the unsaturated zone were used to evaluate degradation of AN or DPA in contaminated water. The biodegradation fluxes of the contaminants were estimated to be 113 ± 26 mg AN·m(-2)·h(-1) and 76 ± 18 mg DPA·m(-2)·h(-1) in the presence of bacteria known to degrade AN and DPA. Oxygen and contaminant profiles along with enumeration of bacterial populations indicated that most of the biodegradation took place within the lower part of the capillary fringe. The results indicate that bacteria capable of contaminant biodegradation in the capillary fringe can create a sink for nonvolatile contaminants.
authors: School of Civil and Environmental Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0512, United States.|Institute of Scientific Research and High Technology Services , Calle Pullpn, Panamá, Panama.
authors: Zohre
authors: Z
authors: Kurt
authors: DuPont, Corporate Remediation Group, P.O. Box 6101, Glasgow 300, Newark, Delaware 19714-6101, United States.
authors: E Erin
authors: EE
authors: Mack
authors: School of Civil and Environmental Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0512, United States.|Center for Environmental Diagnostics and Bioremediation, University of West Florida , Pensacola, Florida 32514-5751, United States.
authors: Jim C
authors: JC
authors: Spain
mesh_terms: D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D060587:Groundwater / Q000382:microbiology; D014874:Water Pollutants, Chemical
chemical_list: D014874:Water Pollutants, Chemical