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Sampling of herbicides in streams during flood events
Jens Petersen1, Ruth Grant, Søren E Larsen
1Department of Bioscience, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark. jens.petersen@agrojur.dk
Journal of Environmental Monitoring : JEM
|November 16, 2012
Summary
Stream water herbicide concentrations surge during flood events, not just from recent applications but also from past use. Intensive sampling reveals unpredictable pulses, highlighting limitations of standard methods for assessing environmental impact.
Area of Science:
- Environmental Chemistry
- Hydrology
- Agricultural Science
Background:
- Xenobiotics, particularly herbicides, enter streams primarily through pulsed events linked to precipitation, surface runoff, and tile drainage.
- Understanding the dynamic behavior of these contaminants during flood events is crucial for assessing ecological risks and water resource management.
Purpose of the Study:
- To investigate herbicide concentrations and occurrence patterns in stream water during flood events.
- To compare the effectiveness of intensive sampling during floods versus grab sampling under non-flood conditions.
- To evaluate the predictability of herbicide and transformation product occurrence in stream systems.
Main Methods:
- Intensive water sampling at 30-minute intervals for 7 hours during flood events in small agricultural catchments.
- Monitoring of herbicide concentrations and their transformation products (e.g., glyphosate, AMPA, terbuthylazine, desethylterbuthylazine).
- Comparison with data from grab sampling under non-flood conditions.
Main Results:
- Elevated herbicide concentrations were consistently recorded during flood events, contrasting with non-flood conditions.
- Observed herbicide pulses varied significantly in timing, duration, and concentration, including contributions from both recent and older applications.
- Asynchronous occurrence of parent compounds and transformation products was noted, complicating prediction.
- Grab sampling under non-flood conditions proved insufficient for capturing the dynamic nature of herbicide presence.
Conclusions:
- Intensive, event-based sampling is essential for accurately characterizing herbicide dynamics in stream water.
- Current sampling strategies relying on non-flood conditions underestimate herbicide exposure and associated risks.
- Sampling design must account for the unpredictable, pulsed nature of herbicide contamination during hydrological events.
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