RAPID MINERALIZATION OF THE S-TRIAZINE RING OF ATRAZINE IN SOILS IN RELATION TO SOIL-MANAGEMENT

Mineralization of the triazine ring of atrazine was studied in soils w ith similar physicochemical properties, from experimental plots under different crop rotations located in Grignon, France. Rapid mineralizat ion rates were found in plots under continuous maize receiving atrazin e every year. On the contrary, low mineralization rates were measured in plots under continuous wheat or permanent grass that had never rece ived atrazine. The rapid mineralization of the atrazine-ring was obser ved without any previous laboratory microbial enrichment. It was also related to the presence of a chloro-substituent on the ring: rapid min eralization was also observed with simazine, another chloro-s-triazine , but not with terbutryn, a thiomethyltriazine. The characterization o f the extractable metabolites during the incubation experiments did no t allow determination of the degradation pathway. In these soils, two competitive dissipation processes are proposed: (1) rapid dissipation through ring cleavage and mineralization in soil from the plot receivi ng atrazine every year, (2) more progressive dissipation through forma tion of bound residues in the other soils. The rate of mineralization of the atrazine-ring varied during the year and was rather sensitive t o soil storage conditions. Copyright (C) 1996 Elsevier Science Ltd