The herbicide glyphosate and its metabolite AMPA in the Lavaux vineyard area, western Switzerland: Proof of widespread export to surface waters. Part II: The role of infiltration and surface runoff

Abstract

Two parcels of the Lavaux vineyard area, western Switzerland, were studied to assess to which extent the widely used herbicide, glyphosate, and its metabolite aminomethylphosphonic acid (AMPA) were retained in the soil or exported to surface waters. They were equipped at their bottom with porous ceramic cups and runoff collectors, which allowed retrieving water samples for the growing seasons 2010 and 2011. The role of slope, soil properties and rainfall regime in their export was examined and the surface runoff/throughflows ratio was determined with a mass balance. Our results revealed elevated glyphosate and AMPA concentrations at 60 and 80 cm depth at parcel bottoms, suggesting their infiltration in the upper parts of the parcels and the presence of preferential flows in the studied parcels. Indeed, the succession of rainy days induced the gradual saturation of the soil porosity, leading to rapid infiltration through macropores, as well as surface runoff formation. Furthermore, the presence of more impervious weathered marls at 100 cm depth induced throughflows, the importance of which in the lateral transport of the herbicide molecules was determined by the slope steepness. Mobility of glyphosate and AMPA into the unsaturated zone was thus likely driven by precipitation regime and soil characteristics, such as slope, porosity structure and layer permeability discrepancy. Important rainfall events (>10 mm/day) were clearly exporting molecules from the soil top layer, as indicated by important concentrations in runoff samples. The mass balance showed that total loss (10-20%) mainly occurred through surface runoff (96%) and, to a minor extent, by throughflows in soils (4%), with subsequent exfiltration to surface waters.

Distribution of glyphosate and aminomethylphosphonic acid (AMPA) in agricultural topsoils of the European Union

“…Here GlyBH are usually applied one (cereals and oilseeds) to three times a year (orchard crops and vines), at recommended rates between 0.72 and 2.88 kg glyphosate ha −1 per treatment, and at a maximum annual application rate of 4.32 kg glyphosate ha −1 (EFSA, 2013(EFSA, , 2015. Numerous laboratory and field studies have been performed to investigate glyphosate and/or AMPA behavior in more detail, especially their transport to the aquatic environment (Al-Rajab and Hakami, 2014;Borggaard and Gimsing, 2008;Daouk et al, 2013;Laitinen et al, 2006Laitinen et al, , 2009 indicating some recognition and concern that these substances can move towards surface waters. At the same time, glyphosate and AMPA are only sporadically detected in deep groundwater systems and at low concentrations (Battaglin et al, 2014;Horth, 2012;Poiger et al, 2017) indicating that the leaching of these compounds is generally unlikely and probably negligible.…”

Glyphosate Resistance of Chloris virgata Weed in Australia and Glyphosate Mobility Are Connected Problems

“…Few samples showed exceedingly high concentration levels of glyphosate with this method [12]. Liquid chromatography is another method that can be used for the detection of glyphosate residues in cereal, oilseed, and pulse crops [13].…”

Experiment and analysis on flow rate of improved subsurface drainage with ponded water

“…Situation 1 appears with soil saturated which often happens in farmland with shallow groundwater table. When heavy and intense precipitation happens, water table will reach up to surface within seconds in shallow groundwater areas and surface ponding appears subsequently (Daouk et al, 2013). While for deep groundwater areas, short duration and intense precipitation will generate surface ponding without water table up to surface (Graham and Jan, 2007;Sally, 2011), which was defined as situation 2 in this study.…”