Influence of glyphosate and aminomethylphosphonic acid on the mobility of trace elements in uncontaminated and contaminated agricultural soils

Glyphosate is one of the most widely used herbicides in the world. In addition to its herbicidal effect, glyphosate is a chelating agent that can form complexes with trace elements. Yet, agricultural soils can be contaminated with both organic and mineral substances, questioning the possible influence of glyphosate application on the trace element mobility. In this context, we specifically studied the extractability of trace elements in uncontaminated and metal-contaminated agricultural soils by adding glyphosate, formulated glyphosate, and aminomethylphosphonic acid (AMPA, a degradation product of glyphosate) in batch experiments from 0 to 100 mg L−1. Results showed that, on average, glyphosate enhanced the extractability of the elements considered (e.g., As, Cd, Cu, Pb, and Zn) at 20 and 100 mg L−1. Surprisingly, the uncontaminated soil highlighted the highest influence of glyphosate compared to the contaminated ones, likely resulting from a higher natural element extractability in the contaminated soils. Although formulated glyphosate presented an overall higher impact than unformulated glyphosate, it was evidenced that AMPA showed lower influence meaning that glyphosate degradation is beneficial to limit deleterious effects.