Biodegradation kinetics of bromoxynil as a pollution control technology
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Nonpoint source (NPS) pollution from agriculture is the leading source of impairment to Survey Rivers and lakes. Pesticides are one of the major NPS pollutants that result from agricultural activities. Among those pesticides, is Bromoxynil (BRMX) which is a widely used herbicide. The present study was carried out to determine the capability of selected biological control agents to degrade BRMX at different incubation periods. Microbial degradation of BRMX at the rate of 100 ppm in pure liquid culture media of either seven isolates of bacteria; Azotobacter chroococcum, Azospirillium barasilense, Klebsilense pneumoneae, Pseudomonas cepacia, Pseudomonas fluoresences, Bacillus subtilis, and Bacillus polymyxa or two isolates of fungi; Trichoderma viride and Trichoderma harzianum has been determined at different time intervals using high performance liquid chromatography (HPLC) with UV detection, and solid phase extraction (SPE) technique. A biphasic model was assumed in order to carry out the statistical study of the loss of BRMX from the media enriched with either bacteria or fungi. The results showed that, the percentages of residual amount of BRMX from media enriched with bacteria ranged from 29.51 -71.94, 18.89-43.88, 9.82-35.07, 3.47-31.90 and 1.80-19.24% after 3, 7, 14, 21 and 28 days of incubation, respectively. On the other hand, the residual amount of BRMX from media enriched with fungi ranged from 45.61-60.26, 21.25-30.56, 6.48-20.63, 1.25-10.49 and 0.63-1.56% after 3, 7, 14, 21 and 28 days of incubation, respectively. The data indicate that there was a faster rate of BRMX loss in the first phase than the second one. This is clearly reflected in the t1/2 values. Therefore, it is recommended to use these microorganisms as biological control agents for the integrated pest management (IPM) programs to reduce agricultural non point source (NPS) pollution to prevent pesticides from reaching ground and surface water.