KINETICS OF ALACHLOR TRANSFORMATION AND IDENTIFICATION OF METABOLITESUNDER ANAEROBIC CONDITIONS

Alachlor is one of the two most commonly used herbicides in the United States. In the environment, little mineralization of this compound ha s been found to occur, and metabolites of alachlor may be formed and c ould accumulate. The objectives of this study were to determine the ra te of alachlor biotransformation and to identify the transformation in termediates formed under aqueous denitrifying, methanogenic, and sulfa te-reducing conditions. Second-order biotrasnformation coefficients fo r alachlor were determined to be 7.6x10(-5) (+/-4.0x10(-5)), 2.9x10(-3 ) (+/-1.6x10(-3)), and 1.5 x 10(-2) (+/-1.4 x 10(-2)) 1 mg VSS-1 day(- 1) under denitrifying, methanogenic, and sulfate-reducing conditions, respectively. Acetyl alachlor and diethyl aniline were positively iden tified as transformation products of alachlor under all conditions. In denitrifying reactors aniline was identified as a product of alachlor . When acetyl alachlor was fed as the parent compound, aniline was als o identified as a transformation product under methanogenic conditions . This research showed that although alachlor is degraded under denitr ifying, methanogenic, and sulfate-reducing conditions, significant con centrations of several metabolites are formed and are only slowly degr aded. (C) 1997 Elsevier Science Ltd.