Abstract

A. Sebiomo*, V. W. Ogundero and S. A. Bankole

The abilities of twelve bacterial isolates to utilise atrazine and primextra and the degradation dynamics of the two herbicides in soil was determined in this study. Soil treatments were carried out in triplicates using the completely randomized blocked design. Utilisation of atrazine and primextra were determined by monitoring growth rates of the bacteria, actinomyces and streptomyces via viable counts, optical density and pH changes. Chromatographic analysis of soil samples were also done to determine residual concentration of herbicides. The viable count and the optical density values increased significantly (P< 0.001) from the 0 h to the 20th day and latter dropped on the 25th to the 30th day. The pH values dropped significantly (P< 0.001) from the 0 h to the 30th day. Bacillus subtilis recorded the highest viable count values of 8.98 and 9.25 on the 20th day and optical density values of 0.934 and 1.631 respectively on atrazine and primextra on the 20th day during growth on atrazine and primextra thus significantly (P <0.001) utilising atrazine and primextra for growth. Pseudomonas putida had the lowest pH value of 5.84 on atrazine while P. stutzeri recorded the highest pH value of 6.42 during growth on atrazine. Norcadia farcinica had the lowest pH of 5.97 during growth on primextra after the 30th day of growth while Flavobacterium aquantile had the highest pH value of 6.34 after the 30th day of growth on primextra. The area and height of atrazine and primextra detection peaks decreased from the second to the sixth weeks of herbicide treatment. The decrease in atrazine and primextra peak indicated more atrazine and primextra degradation. B. subtillis has shown the best ability to utilise atrazine and primextra respectively. This study has shown that bacterial isolates could be applied to remediate soils polluted with both atrazine and primextra. The progressive biodegradation of atrazine and primextra has also been elucidated in this work.