Microbial Degradation of Pesticides in Aqueous Solutions

The microbial degradation in aqueous solution of the pesticides isopropyl N-(3-chlorophenyl) carbamate (CIPC) and 2,4-dichlorophenoxyacetic acid (2,4-D) was studied by means of radioactive tracer techniques and ultraviolet spectroscopy. 2,4-D was found to be strongly resistant to microbial decomposition in a liquid medium of mineral salts. Less than 40 percent of the acetic acid portion of the molecule disappeared from solution in 6 months, even in the presence of additional sources of organic carbon. CIPC was degraded much more rapidly than 2,4-D. The isopropyl segment of the CIPC molecule was completely metabolized. Metabolism of the carbon atoms in the ring structure ceased after 40 to 60 percent of the atoms had disappeared from solution.