DEGRADATION OF THE HERBICIDE BROMOXYNIL IN BATCH CULTURES UNDER GROUNDWATER CONDITIONS

The biological degradation of bromoxynil (3,5-dibromo-4-hydroxybenzoni trile) under simulated groundwater conditions was investigated. The in fluence of aerobic and anaerobic conditions on the degradation rate wa s examined in batch cultures at 8 degrees C during 32 days. The cultur es consisted of 400 ml groundwater plus 2000 ml salt basal medium. Fin al bromoxynil concentration was 1 mg/l. Incubation was carried out wit h and without 100 mg/l acetate added as carbon source. Dissolved organ ic carbon (DOG), oxygen, nitrate and sulphate, bacterial number (CFU), enzymatic hydrolysis of fluorescein-di-acetate (FDA), and bromoxynil concentration was estimated along the test. Only anaerobic, nitrate re ducing conditions caused biodegradation of bromoxynil after 17 - 21 da ys. The addition of acetate delayed this process, although the complet e degradation after 32 days in both tests amounted to 99%. In spite of a high bioactivity, no degradation of bromoxynil could be found under aerobic conditions within 32 days.