Contribution of household herbicide usage to glyphosate and its degradate aminomethylphosphonic acid in surface water drains

BACKGROUND: It is necessary to understand the extent to which different sources of pesticides contribute to surface water contamination in order to focus preventive measures appropriately. The extent to which glyphosate use in the home and garden sector may contribute to surface water contamination has not previously been quantified. The aim of this study was to quantify the widely used herbicide glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in surface water drains (storm drains) that could be attributed to amateur, non-professional usage alone. RESULTS: Maximum glyphosate and AMPA concentrations in surface water drains were 8.99 and 1.15 µg L(-1) respectively after the first rain event following the main application period, but concentrations rapidly declined to <1.5 and <0.5 µg L(-1) . The AMPA:glyphosate ratio was typically 0.35. Less than 1% of the applied glyphosate was recovered in drain water. CONCLUSION: Glyphosate and AMPA losses from urban areas that arise solely from amateur usage have been quantified. In spite of overdosing occurring, glyphosate concentrations in drain flow were lower than concentrations reported elsewhere from professional use in urban areas.