Bacterial degradation of atrazine in redox potential gradients in fixed-film sand columns
2000
Crawford, J.J. | Traina, S.J. | Tuovinen, O.H.
The purpose of this study was to assess the biodegradation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] under different redox conditions in the presence and absence of an electron donor (glucose) and electron acceptors (oxygen, NO3-). Experiments were conducted in sand-column systems saturated with a liquid medium and characterized by the vertical separation of oxic, anoxic, and reduced zones with distinct redox regimes. The columns were inoculated with an atrazine-mineralizing bacterium to establish a fixed film on sand particles. Aerobic and anaerobic zones were created in the column by sparging with air or N2 respectively, and Na2S was added to the deepest zone of the column to establish redox potential gradients ranging from about -400 to 400 mV. Samples were removed from the various depths of the column to determine changes in redox potential and in the concentration of atrazine, NO3- and NO2- with time. Atrazine biodegradation in the sand columns could be described with a first-order rate equation. Concurrent atrazine and NO3- consumption occurred in both de-aerated (N2-purged) and sulfide-poised anaerobic zones of the columns, whereas only atrazine was used under aerobic conditions. Atrazine degradation was not adversely influenced by low redox potential and was enhanced under anaerobic conditions with combined N3- and glucose amendment.
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