Ethylene dibromide mineralization in soils under aerobic conditions

Abstract

1,2-Dibromoethane (EDB), which is a groundwater contaminant in areas where it was once used as a soil fumigant, was shown to be degraded aerobically by microorganisms in two types of surface soils from an EDB-contaminated groundwater discharge area. At initial concentrations of 6 to 8 μg/liter, EDB was degraded in a few days to near or below the detection limit of 0.02 μg/liter. At 15 to 18 mg/liter, degradation was slower. Bromide ion release at the higher concentrations was 1.4 ± 0.3 and 2.1 ± 0.2 molar equivalents for the two soils. Experiments with [14C]EDB showed that EDB was converted to approximately equal amounts of CO2 and apparent cellular carbon; only small amounts of added 14C were not attributable to these products or unreacted EDB. These results are encouraging, because they indicate that groundwater bacteria may hasten the removal of EDB from contaminated aerobic groundwater supplies. This report also provides evidence for soil-mediated chemical transformations of EDB.