Losses of glyphosate into urban waterways can partly be attributed to uses on urban hard surfaces and transport in urban drainage systems. To quantify and assess such transport and losses from hard surfaces, a field study was performed in a typical Belgian residential area (9.5 ha). The study investigated glyphosate use by local residents, primarily on hard surfaces (e.g. driveways). Monitoring revealed the detection of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) in all analyzed drainflow samples. The overall loss rate was found to be 0.43%. Calculated load and loss rate from rainfall events were used to identify factors controlling losses of glyphosate, mainly the patterns of rainfall and application. Incorporating existing literature and modeling approaches, a conceptual model is developed to characterize the adsorption-desorption and wash-off behaviors of glyphosate and other strongly-adsorbed herbicides on hard surfaces. The conceptual model will be implemented in an existing spatially-distributed hydrological model and tested with the monitoring dataset, where influential factors can be sufficiently accounted for.

Transport and losses of glyphosate and AMPA via a residential storm drainage system

248th National Meeting (2014)

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