Dissipation of Glyphosate and Aminomethylphosphonic Acid in North American Forests

Abstract

Residues of glyphosate (N-phosphonomethylglycine) and its metabolite aminomethylphosphonic acid (AMPA) were followed on three forested sites in Oregon, Michigan, and Georgia. Eight-hectare residual stands of low-quality hardwoods were treated with 4.12 kgha glyphosate ae applied aerially in late summer. Residues were highest in upper crown foliage. Overstory reduced exposure of understory vegetation and streams. Residues in streams were close to the detection limit or undetectable in 3-14 days. Residues in soils were highest where cover was sparse and where litter was removed. No residues were detectable in soil 409 days after treatment; movement below 15 cm was negligible. AMPA appeared at low levels in all degrading matrices, including sediments, soon aRer deposition of glyphosate. In pond sediments, both glyphosate and AMPA remained bound and inactive. Residue concentrations in foliage, water, and soil were below levels known to be biologically active in nontarget fauna.

Effects of pig slurry application on soil physical and chemical properties and glyphosate mobility

“…This demonstrates that glyphosate moved from the surface layer, where it was applied, down to a depth of about 0.80 m, or, alternatively, this level may be a residue from an earlier application, six months before. Glyphosate residues have been found in other studies at depths of 0.15 m (Newton et al, 1994), 0.30 m (Veiga et al, 2001), 0.40 m (Litz et al, 2011) and 1.00 m .…”

“…Fifteen days after application, mean concentration increased again to 0.430 mg L -1 , which is associated with the high rainfall in the 48 h before sampling (47 mm), which contributed to the desorption of glyphosate and its transport through the soil profile. Thirty days after application, glyphosate concentration fell to 0.022 mg L -1 and to 0.013 mg L -1 after 60 days, which may be associated with degradation of the ingredient by microbial action in the period from the time of application, as was also observed by Newton et al (1994).…”

Differential Transport of Atrazine and Glyphosate in Undisturbed Sandy Soil Column

“…Field persistence studies have been performed almost exclusively in forest soils, showing high vertical mobility in the treated soils with the glyphosate to reach quickly high concentrations in the subsoil (Dibyendu et al, 1989;Newton et al, 1994;Veiga et al, 2001). Column tracer experiments, also called miscible displacement or breakthrough curve experiments, are another important approach to obtain sorption and degradation properties of contaminants in soil.…”

Respiração microbiana do solo sob doses de glyphosate e de imazapyr

“…Esse comportamento reflete a facilidade com que a molécula é metabolizada pela microbiota do solo (Torstensson & Aamisepp, 1977;Dick & Quinn, 1995). Embora o glyphosate seja facilmente degradado pelos microrganismos do solo, tem-se observado uma faixa de variação na meia-vida da molécula de poucos dias a anos (Heinonen-Tanski, 1989;Roy et al, 1989;Newton et al, 1994), o que demonstra um estreito relacionamento com os fatores edáficos e climáticos (Torstensson et al, 1989;Souza et al, 1996).…”