Field examination of ground water quality as an indicator of microbiological activity at gasoline contaminated sites

Various portable electrodes and an on-line colorimetric test kit were used in the field to examine ground water quality as an indicator of natural bioremediation across two sites in Connecticut having subsurface gasoline contamination. The parameters examined included dissolved oxygen, dissolved carbon dioxide, direct redox potential (Eh), nitrate, ammonia and pH. These parameters permitted delineating regions of aerobic and anaerobic microbiological activity. Variations in these parameters over an eighteen month period along with gas chromatographic analyses of certain gasoline components in the ground water indicated that in-situ bioremediation was effective at containing the petroleum contamination at both sites. It was found that a new on-line colorimetric test kit for the determination of oxygen was more accurate than a commonly used dissolved oxygen electrode.