| Abstract: | The potential for degradation of atrazine or isoproturon in the unsaturated zone of two boreholes was studied under laboratory conditions. Intact and uncontaminated samples were obtained from regular depths of 0–16.45 m and 0–9 m using a percussion coring technique. The results showed that the deep unsaturated zone contained micro-organisms capable of degrading atrazine or isoproturon. The rate of degradation was much faster in surface soil than in most unsaturated materials of both boreholes. The amount of atrazine remaining six months after incubation also varied between the two boreholes. A relatively small amount of atrazine was lost from sterilised samples, suggesting a significant role for microbial degradation. The addition of nutrient and energy sources into materials of low degradation capacity did not enhance the degradation of atrazine. Degradation rate was more related to the presence of a competent microbial population rather than to the presence of indigenous organic matter. However, the competent micro-organisms are more likely to be present when the organic matter content is high. The type and activity of these micro-organisms and their physical environment may have considerable influence on atrazine degradation and are likely to be responsible for much of the variation in the rate of degradation observed at different depths. © 1999 Society of Chemical Industry |
