RATE CONSTANTS FOR REACTIONS OF OZONE AND HYDROXYL RADICALS WITH SEVERAL PHENYL-UREAS AND ACETAMIDES

Second-order rate constants for the reactions of molecular ozone and o f hydroxyl radicals with some nitrogenous herbicides (phenyl-ureas and acetamides) have been measured in water at 20 degrees C using absolut e and relative rate methods. Molecular ozone oxidation was carried out at acidic pH and in the presence of hydroxyl radical scavenger (tert- butanol). Hydroxyl radicals were generated from the aqueous decomposit ion of ozone by hydroxyde ions or by hydrogen peroxide. The order of k inetic rate constants for molecular ozone with the herbicides was foun d to be as follows : Isoproturon >> Chlortoluron > Diuron > Linuron ap proximate to Metolachlor approximate to Alachlor > Propachlor. Rate co nstants for the reactions of hydroxyl radicals with these herbicides w ere in the range of 4.3 10(9) - 5.2 10(9) l mol(-1) s(-1.)