EFFECT OF GEOCHEMICAL CONDITIONS ON FATE OF ORGANIC-COMPOUNDS IN GROUNDWATER

In situ microcosms were successfully used to study the degradation of a range of organic compounds in two pristine aquifers, one aerobic (Ve jen) and one anaerobic (Villa Farm). Degradation and sorption behavior in the laboratory column microcosms packed with Villa Farm sediment w as very similar to that in the in situ microcosms. However, when the c olumns were packed with quartz and equilibrated with aerated Villa Far m groundwater, behavior mirrored that at Vejen, indicating that oxygen rather than sediment or groundwater composition was the critical para meter. The aromatic and polyaromatic compounds (benzene, toluene, o-xy lene, naphthalene) degraded under aerobic conditions only. The organoc hlorine compounds (trichloroethylene, tetrachloroethylene, 1,1,1-trich loroethane, 1,4-dichlorobenzene and 1,2-dichlorobenzene) showed little or no sign of degradation either aerobically or anaerobically. Interp retation of the data was complicated by strong sorption to the Villa F arm sediment but tetrachloromethane, nitrobenzene, and o-nitrophenol a ppeared to degrade under anaerobic conditions only. Phenol degraded ra pidly under both sets of conditions.