Leaching potential of carbamates and their metabolites and comparison with triazines

Abstract This paper reports the results of a laboratory study aimed at defining the leaching potential of the following pesticides and respective metabolites belonging to the families of N -methylcarbamates and triazines: benfuracarb (BF), carbofuran (CF), 3-keto-carbofuran (3KC) and 3-hydroxy-carbofuran (3HC), atrazine (ATR), simazine (SIM), terbuthylazine (TER), deethylatrazine (DEA), deisopropylatrazine (DIA) and desethylterbuthylazine (DET). All tested compounds, but BF, are very mobile in soil. Triazines exhibited a relatively high persistence, especially DEA, with a DT 50 of 72 days. On the contrary, all the tested carbamates resulted easily degradable in soil with a partial exception represented by CF, with a DT 50 of 12 days. The GUS indices show high leaching potentials for all the tested triazines and CF. The GUS index of 3KC lies in the typical area of transient compounds; those of BF and 3HC clearly exhibited a non-leaching behaviour. In the leachate corresponding to the BF column, the parent compound was found at low concentration while its main metabolite, CF, reached much higher values. Also, when applied as parent compound, CF was determined at high values, whereas its metabolites 3KC and 3HC were never detected in the leachates. As to triazines, in the ATR column, the parent compound was found at high levels in the leachate, where DEA exhibited values more than 4 times higher than DIA. In the SIM column DIA reached levels 8-fold higher than those in the ATR column. TER occurred at levels close to that of ATR in the respective leachate; DET was found at high levels whereas DIA was not detectable.