BIODEGRADATION OF CHLOROTHALONIL IN SOIL AFTER SUPPRESSION OF DEGRADATION

The degradation rate of chlorothalonil (2,4,5,6- tetrachloroisophthalo nitrile) was significantly decreased after repeated application in fie ld experiments. However the degradation rate completely recovered afte r further application of chlorothalonil, Chlorothalonil was also degra ded in a laboratory study, forming a stoichiometric amount of chloride anion, 4-Hydroxy-2,5,6-trichloro-isophthalonitrile (TPN-OH) was also detected as a metabolite in the study, Bacterial which degrade chlorot halonil rapidly were isolated from the soil. The cell suspension of th e bacteria transformed chlorothalonil to TPN-OH and chloride anion, bu t did not utilize chlorothalonil (=cometabolism). it seems thar microb ial acclimation has occurred during repeated application because the b acteria could not be detected in soil which was not treated with chlor othalonil.