Persistence of triclopyr and glyphosate in a southern Ontario aquatic environment / Donna L. MacKenzie

In situ enclosures were employed to investigate the dissipation of glyphosate and triclopyr in a southern Ontario aquatic environment.Enclosures were treated with Rodeo and Roundup (7.68 kg(ae).ha-1, n=6)and with Garlon 4 and Garlon 3A (12.96 kg(ae).ha-1, n=6) in two experiments. Estimated aqueous DT50s for Roundup and Rodeo treated enclosures ranged from 3.2-13.2 d. No significant difference in dissipation was detected between the two formulations. In all enclosures, glyphosate concentrations in sediments peaked by day 30 and remained detectable throughout the 212 d monitoring period. In all enclosures, less than 0.1% of the total glyphosate was associated with the liner biofilm on any given sampling date. For enclosures treated with Garlon 3A and Garlon 4, estimated aqueous DT50s ranged from 16.4-21.2 d. No significant difference in dissipation was detected between the two triclopyr formulations. Triclopyr residues in sediments reached maxima by day 7 and were non-detectable by da