Dissipation of glyphosate and aminomethylphosphonic acid in water and sediment of two Canadian prairie wetlands / Dani Degenhardt, David Humphries, Allan J. Cessna, Paul Messing, Pascal H. Badiou, Renata Raina, Annemieke Farenhorst, and Dan J. Pennock.

Includes bibliographical references (pages 638-639).

Glyphosate [N-(phosphonomethyl)glycine] is the active ingredient of several herbicide products first registered for use in 1974 under
the tradename Roundup. The use of glyphosate-based herbicides has increased dramatically over the last two decades particularly
in association with the adoption of glyphosate-tolerant crops. Glyphosate has been detected in a range of surface waters but this is
the first study to monitor its fate in prairie wetlands situated in agricultural fields. An ephemeral wetland (E) and a semi-permanent
wetland (SP) were each divided into halves using a polyvinyl curtain. One half of each wetland was fortified with glyphosate with
the added mass simulating an accidental direct overspray. Glyphosate dissipated rapidly in the water column of the two prairie
wetlands studied (DT50 values of 1.3 and 4.8 d) which may effectively reduce the impact of exposure of aquatic biota to the herbicide.
Degradation of glyphosate to its major metabolite aminomethylphosphonic acid (AMPA) and sorption of the herbicide to bottom
sediment were more important pathways for the dissipation of glyphosate fromthe water column thanmovement of the herbicide with
infiltrating water. Presently, we are not aware of any Canadian guidelines for glyphosate residues in sediment of aquatic ecosystems.
Since a substantial portion of glyphosate entering prairie wetlands will become associated with bottom sediments, particularly in
ephemeral wetlands, guidelines would need to be developed to assess the protection of organisms that spend all or part of their
lifecycle in sediment.