PHOTOLYTIC AND MICROBIAL-DEGRADATION OF 3.5.6-TRICHLORO-2-PYRIDINOL

The photolytic and microbial degradation of 3,5,6-trichloro-2-pyridino l (TCP) a metabolite of the insecticide chlorpyrifos and the herbicide triclopyr, has been investigated. TCP (80 mg/L) was decomposed to non detectable levels within 2 h of ultraviolet irradiation. Release of (C O2)-C-14 and chloride ion was observed; however. approximately 60% of the initial radioactivity remained in the solution. Dichlorodihydroxyp yridine isomers and reductive dechlorination products were found as in termediate products of TCP photolysis. It was proposed that both hydro lytic and reductive dechlorination occurred during photodegradation of TCP. Although TCP can be degraded via photolysis, many degradation pr oducts remained in the aqueous medium and only some of them, the reduc tive dechlorination products, can be mineralized by Pseudomonas sp. AT CC 700113. The degradation of he parent compound, TCP, by Pseudomonas sp. ATCC 700113 also appears to involve a reductive dechlorination mec hanism. A consortium of microorganisms may be needed if a treatment pr ofess combining microbial and photolytic activity is to be used ro rem ove TCP in industrial wastewater.