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Leaching and degradation of ¹³C₂-¹⁵N-glyphosate in field lysimeters.

ABSTRACT: Glyphosate (GLYP), the globally most important herbicide, may have effects in various compartments of the environment such as soil and water. Although laboratory studies showed fast microbial degradation and a low leaching potential, it is often detected in various environmental compartments, but pathways are unknown. Therefore, the objective was to study GLYP leaching and transformations in a lysimeter field experiment over a study period of one hydrological year using non-radioactive ¹³C₂-¹⁵N-GLYP labelling and maize cultivation. ¹⁵N and ¹³C were selectively measured using isotopic ratio mass spectrometry (IR-MS) in leachates, soil, and plant material. Additionally, HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) was used for quantitation of GLYP and its main degradation product aminomethylphosphonic acid (AMPA) in different environmental compartments (leachates and soil). Results show low recoveries for GLYP (< 3%) and AMPA (< level of detection) in soil after the study period, whereas recoveries of ¹⁵N (11-19%) and ¹³C (23-54%) were higher. Time independent enrichment of ¹⁵N and ¹³C and the absence of GLYP and AMPA in leachates indicated further degradation. ¹⁵N was enriched in all compartments of maize plants (roots, shoots, and cobs). ¹³C was only enriched in roots. Results confirmed rapid degradation to further degradation products, e.g., ¹⁵NH₄⁺, which plausibly was taken up as nutrient by plants. Due to the discrepancy of low GLYP and AMPA concentrations in soil, but higher values for ¹⁵N and ¹³C after the study period, it cannot be excluded that non-extractable residues of GLYP remained and accumulated in soil.

SUBMITTER: Gros P

PROVIDER: S-EPMC6970956 | biostudies-literature |

REPOSITORIES: biostudies-literature

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