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Author: Leinweber, Peter × Version: publishedVersion ×

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    AMPA-15N - Synthesis and application as standard compound in traceable degradation studies of glyphosate
    (Amsterdam : Elsevier, 2021) Wirth, Marisa A.; Longwitz, Lars; Kanwischer, Marion; Gros, Peter; Leinweber, Peter; Werner, Thomas
    Stable isotope labeling of pollutants is a valuable tool to investigate their environmental transport and degradation. For the globally most frequently used herbicide glyphosate, such studies have, so far, been hampered by the absence of an analytical standard for its labeled metabolite AMPA-15N, which is formed during the degradation of all commercially available glyphosate isotopologues. Without such a standard, detection and quantitation of AMPA-15N, e.g. with LC-MS/MS, is not possible. Therefore, a synthetic pathway to AMPA-15N from benzamide-15N via the hemiaminal was developed. AMPA-15N was obtained in sufficient yield and purity to be used as a standard compound for LC-MS/MS analysis. Suitable MS-detection settings as well as a calibration using the internal standard (IS) approach were established for Fmoc-derivatized AMPA-15N. The use of different AMPA isotopologues as IS was complicated by the parallel formation of [M+H]+ and [M]+• AMPA-Fmoc precursor ions in ESI-positive mode, causing signal interferences between analyte and IS. We recommend the use of either AMPA-13C-15N, AMPA-13C-15N-D2 or a glyphosate isotopologue as IS, as they do not affect the linearity of the calibration curve. As a proof of concept, the developed analysis procedure for AMPA-15N was used to refine the results from a field lysimeter experiment investigating leaching and degradation of glyphosate-2-13C-15N. The newly enabled quantitation of AMPA-15N in soil extracts showed that similar amounts (0.05 - 0.22 mg·kg-1) of the parent herbicide glyphosate and its primary metabolite AMPA persisted in the topsoil over the study period of one year, while vertical transport through the soil column did not occur for either of the compounds. The herein developed analysis concepts will facilitate future design and execution of experiments on the environmental fate of the herbicide glyphosate.
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    Phosphorus speciation in long-term drained and rewetted peatlands of northern germany
    (Basel : MDPI, 2020) Negassa, Wakene; Michalik, Dirk; Klysubun, Wantana; Leinweber, Peter
    Previous studies, conducted at the inception of rewetting degraded peatlands, reported that rewetting increased phosphorus (P) mobilization but long-term effects of rewetting on the soil P status are unknown. The objectives of this study were to (i) characterize P in the surface and subsurface horizons of long-term drained and rewetted percolation mires, forest, and coastal peatlands and (ii) examine the influence of drainage and rewetting on P speciation and distributions using wet-chemical and advanced spectroscopic analyses. The total P was significantly (p < 0.05) different at the surface horizons. The total concentration of P ranged from 1022 to 2320 mg kg−1 in the surface horizons and decreased by a factor of two to five to the deepest horizons. Results of the chemical, solution 31P nuclear magnetic resonance (NMR), and P K-edge X-ray absorption near-edge structure (XANES) indicated that the major proportions of total P were organic P (Po). In the same peatland types, the relative proportions of Po and stable P fractions were lower in the drained than in the rewetted peatland. The results indicate that long-term rewetting not only locks P in organic matter but also transforms labile P to stable P fractions at the surface horizons of the different peatland types. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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    Degradation of glyphosate in water by the application of surface corona discharges
    (Bristol : IWA Publishing, 2021) Zocher, Katja; Gros, Peter; Werneburg, Matthias; Brüser, Volker; Kolb, Juergen F.; Leinweber, Peter
    Glyphosate (GLP) is one of the most widely applied herbicides, and is found ubiquitously in the environment. The removal of glyphosate from waste water and soil is challenging and can be achieved with chemical or biological methods, which, nevertheless, suffer from different disadvantages. The application of a physical plasma for the removal of GLP in water was examined by the application of surface corona discharges in a wire-to-cylinder setup filled with argon. The plasma was ignited at the liquid surface without any additives. By applying a photometric method, GLP was detected after derivatisation with fluorenyl methoxycarbonyl chloride, whereas phosphate was determined with ammonium molybdate. A GLP degradation rate of 90.8% could be achieved within a treatment time of 30 minutes with an estimated energy efficiency of 0.32 g/kWh.