A model for the formation and degradation of bound residues of the herbicide C-14-isoproturon in soil

The humic monomer catechol was reacted with C-14-isoproturon and some of it s metabolites, including C-14-4-isopropylaniline, in aqueous solution under a stream of oxygen. Only in the case of C-14-4-isopropylaniline, incorpora tion in oligomers, in fulvic acid-like polymers, and in humic acid-like pol ymers was observed. The main oligomer was identified by mass spectrometry a s 4,5-bis-(4-isopropylphenylamino)-3,5-cyclohexadiene-1,2-dione. Oligomers and polymers containing bound C-14-4-isopropylaniline were subjected to bio degradation studies in a loamy agricultural soil during 55 days by quantify ing (CO2)-C-14 evolved. In all cases, significant mineralization rates coul d be determined, which, however, were much smaller than those of free C-14- isoproturon and free C-14-4-isopropylaniline in the same soil. (C) 1999 Els evier Science Ltd. All rights reserved.