A preliminary assessment for the use of metabolic inhibitors to evaluate the biodegradation potential of soil

Abstract

The widespread contamination of our nation's groundwater has become a major threat to public health. The magnitude of this threat is escalated by our reliance upon groundwater. Groundwater is the primary drinking water source for over 50% of the U.S. population. Groundwater comprises more than 95% of all available freshwater in the United States.

The objectives of this study were: (1) to make a preliminary assessment of the use of inhibitors to evaluate the biodegradation potential of soil, and (2) to evaluate the significance of each microbial group in the biodegradation process. Static microcosms containing Newport News and Blacksburg soil were used as the experimental environments. Butyrate and propionate were used as substrates. The metabolic inhibitors used were sodium molybdate (Na.7N1o04) and 2-Bromoethane sulfonic acid (BESA), which inhibit sulfate reduction and methanogenesis, respectively. Denitrification was suppressed by the absence Of sodium nitrate (NaNO3) in the microcosm dilution water.

Both Newport News and Blacksburg soils were found to be dominated by denitrfying bacteria. In nitrate-amended Newport News microcosms, 300 mg/L butyrate degraded to .zero concentration in 5.5 days. This microcosm's degradation "rate" was 255% greater than non-nitrate amended microcosms, where sulfate reduction was predominant. Little or no methanogenic activity was observed in both the Newport News or Blacksburg soils.

Advantages of this approach are its simplicity and directness in obtaining approximately the same information as more complicated enumeration procedures. A disadvantage of this approach is its reliance on metabolic inhibitors to suppress the microbial activity of specific microbial groups. Little is known on the effect of Na2MoO4 or BESA on the activities of denitrifiers, fermenters, or acetogens.