Degradation of glyphosate in a Colombian soil is influenced by temperature, total organic carbon content and pH. (April 2020)

• Record Type: Journal Article
• Authors: Muskus, Angelica M.; Krauss, Martin; Miltner, Anja; Hamer, Ute; Nowak, Karolina M.
• Is Part Of: Environmental pollution. Volume 259(2020)
• Publication Date: 2020-04
• Subjects: Glyphosate -- 13C and 15N mass balance -- Degradation pathway -- Biogenic NER -- Tropical soil; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2019.113767
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Glyphosate is one of the most used herbicides in the world. The fate of glyphosate in tropical soils may be different from that in soils from temperate regions. In particular, the amounts and types of non-extractable residues (NER) may differ considerably, resulting in different relative contributions of xenoNER (sorbed and sequestered parent compound) and bioNER (biomass residues of degraders). In addition, environmental conditions and agricultural practices leading to total organic carbon (TOC) or pH variation can alter the degradation of glyphosate. The aim of this study is thus to investigate how the glyphosate degradation and turnover are influenced by varying temperature, pH and TOC of sandy loam soil from Colombia. The pH or TOC of a Colombian soil was modified to yield five treatments: control (pH 7.0, TOC 3%), 4% TOC, 5% TOC, pH 6.5, and pH 5.5. Each treatment received 50 mg kg −1 of 13 C3 15 N-glyphosate and was incubated at 10 °C, 20 °C and 30 °C for 40 days. Rising temperature increased the mineralization of 13 C3 15 N-glyphosate from 13 to 20% (10 °C) to 32–39% (20 °C) and 41–51% (30 °C) and decreased the amounts of extractable 13 C3 15 N-glyphosate after 40 days of incubation from 13 to 26% (10 °C) to 4.6–12% (20 °C) and 1.2–3.2% (30 °C). Extractable 13 C3 15 N-glyphosate increased with higher TOC and higher pH. Total 13 C-NER were similar in all treatments and at all temperatures (47%–60%), indicating that none of the factors studied affected the amount of total 13 C-NER. However, 13 C-bioNER dominated within the 13 C-NER pool in the control and the 4% TOC treatment (76–88% of total 13 C-NER at 20 °C and 30 °C), whereas in soil with 5% TOC and pH 6.5 or 5.5 13 C-bioNER were lower (47–61% at 20 °C and 30 °C). In contrast, the 15 N-bioNER pool was small (between 14 and 39% of the 15 N-NER). Thus, more than 60% of 15 N-NER is potentially hazardous xenobiotic NER which need careful attention in the future. Graphical abstract: Image 1 Highlights: Temperature controls mineralization and extractable glyphosate. More extractable glyphosate in soil with elevated TOC and with higher pH. No effect of temperature, TOC or pH on total non-extractable residue (NER) contents. 13 C-biogenic NER highest in control soil and 4% TOC and lowest in pH 6.5 and 5.5 High formation of potentially hazardous xenobiotic 15 N-NER was observed. Abstract : Temperature controlled mineralization and extractable glyphosate, whereas total organic carbon and pH influenced formation of xenobiotic and biogenic non-extractable residues.