Bacterial degradation of atrazine in redox potential gradients in fixed-film sand columns

The purpose of this study was to assess the biodegradation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamio)-s-triazine] under different redox conditions in the presence and absence of an electron donor (glucose) and electron accepters (oxygen, NO(3)(-)). 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 NZ, respectively, and Na(2)S 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, NO(3)(-) and NO(2)(-) with time. Atrazine biodegradation in the sand columns could be described with a first-order rate equation. Concurrent atrazine and NOB consumption occurred in both de-aerated (N(2)-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 NO(3)(-) and glucose amendment.