ANOXIC TREATMENT OF TRIFLURALIN-CONTAMINATED SOIL

Amending anoxic soils with stoichiometric amounts of sodium acetate le d to the complete transformation of trifluralin within the 45 day trea tment period, Under these conditions, a maximum trifluralin transforma tion rate of 4.9 mg kg(-1) of soil per day was estimated, which corres ponded to a chemical half life of 11.9 days. Regression analyses indic ated that the zero order rate model provided the best fit to the exper imental data, suggesting that the trifluralin transformation rate is i ndependent of concentration during acetate addition. Using radiolabele d trifluralin, it was determined that the principal contaminant transf ormation mechanisms were degradation and bound residue formation (i.e. , irreversible adsorption). Volatilization and mineralization of trifl uralin were found to be negligible over the 45 day treatment period. U sing poisoned controls, it was determined that trifluralin transformat ion under acetate-amended conditions was biologically mediated, Amendi ng trifluralin contaminated soils with stoichiometric amounts of iron sulfide resulted in complete trifluralin transformation within 24 hour s of treatment. A maximum trifluralin transformation rate of 380 mg kg (-1) of soil per day was estimated for this system, which corresponded to a chemical half life of 4.4 h. The rates of trifluralin transforma tion followed the first-order kinetic model during iron sulfide additi on. Using radiolabeled trifluralin, it was found that chemical degrada tion was the principal removal mechanism. Neither volatilization nor m ineralization was found to be a significant contaminant removal mechan ism during iron sulfide treatment. Poisoned controls indicated that tr ifluralin transformation was mediated primarily by an abiotic chemical reaction mechanism. Additional study is required to clarify the rate limiting steps so that full scale soil treatment systems may be proper ly designed.