Fate of glyphosate in soil and the possibility of leaching to ground and surface waters: a review

Abstract

The very wide use of glyphosate to control weeds in agricultural, silvicultural and urban areas throughout the world requires that special attention be paid to its possible transport from terrestrial to aquatic environments. The aim of this review is to present and discuss the state of knowledge on sorption, degradation and leachability of glyphosate in soils. Difficulties of drawing clear and unambiguous conclusions because of strong soil dependency and limited conclusive investigations are pointed out. Nevertheless, the risk of ground and surface water pollution by glyphosate seems limited because of sorption onto variable-charge soil minerals, e.g. aluminium and iron oxides, and because of microbial degradation. Although sorption and degradation are affected by many factors that might be expected to affect glyphosate mobility in soils, glyphosate leaching seems mainly determined by soil structure and rainfall. Limited leaching has been observed in non-structured sandy soils, while subsurface leaching to drainage systems was observed in a structured soil with preferential flow in macropores, but only when high rainfall followed glyphosate application. Glyphosate in drainage water runs into surface waters but not necessarily to groundwater because it may be sorbed and degraded in deeper soil layers before reaching the groundwater. Although the transport of glyphosate from land to water environments seems very limited, knowledge about subsurface leaching and surface runoff of glyphosate as well as the importance of this transport as related to ground and surface water quality is scarce.

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.…”

Controlling Stormwater Quality with Filter Soil—Event and Dry Weather Testing

“…In the second addition, 130 µg/L LAS was added, but nothing was observed in the effluent, which indicates a good retention of LAS in the filter soil. For the pesticides, a good retention of glyphosate, which is known to sorb strongly to soil iron and aluminum oxides [48] was observed with concentrations in the effluent of 0.08 and 0.09 µg/L just below the groundwater quality criterion of 0.1 µg/L. MCPA was not retained at all in the first addition, having an effluent concentration of 0.5 µg/L, whereas in the second addition the effluent concentration could comply with the criterion of 0.1 µg/L.…”

SWV determination of glyphosate in Burkina Faso soils using carbon fiber microelectrode

“…Because glyphosate is strongly adsorbed to the soil surface by particles (Borggaard et al, 2008;Nicholls et al, 1991), we limited the research of glyphosate residues at the depth of 20 cm . According to a well established methodology for soils sampling (Reinaldo et al, 2008), 13 samples were taken in each field and mixed to form a composite sample.…”