Metabolism of Dichlobenil by Microorganisms in the Aquatic Environment

The metabolism of [¹⁴C]nitrile-labeled dichlobenil (2,6-dichlorobenzonitrile) by a microbial population in pond water and bottom sediment as well as by a pure culture of a bacterium isolated from the hydrosoil was investigated. More than 75% of dichlobenil added to water and sediment disappeared due primarily to volatilization of the herbicide. Dichlobenil was converted microbiologically to 2,6-dichlorobenzamide and certain unknown metabolites in the water and sediment. The radioactivity remaining in the sediment after methanol and HCl extractions varied from 3 to 5% of the originally applied ¹⁴C. A cell suspension of an Arthrobacter sp. metabolized as much as 71% of dichlobenil to dichlorobenzamide during a 6-day incubation period, but produced very small amounts of other metabolites. When [¹⁴C]amide-labeled dichlorobenzamide was incubated in water and sediment, about 6% of ¹⁴C was converted to ¹⁴CO₂ 39 days after treatment. It appears that in the aquatic environment, dichlobenil can be metabolized to CO₂ via dichlorobenzamide primarily through microbiological action.