Cody Millar1, Kim Janzen1, Magali F Nehemy1, Geoff Koehler2, Pedro Hervé-Fernández1,3,4, Jeffrey J McDonnell1,5. 1. Global Institute for Water Security, School of Environment and Sustainability, University of Saskatchewan, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada. 2. NHRC Stable Isotope Laboratory, Environment and Climate Change Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada. 3. Universidad de Magallanes, Instituto de la Patagonia, Departamento de Hidrobiología, Punta Arenas, Chile. 4. Universidad Adolfo Ibañez, Facultad de Ciencias Liberales, Viña del Mar, Chile. 5. School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK.
Abstract
RATIONALE: Hydrogen and oxygen stable isotope ratios (δ2 H, δ17 O, and δ18 O values) are commonly used tracers of water. These ratios can be measured by isotope ratio infrared spectroscopy (IRIS). However, IRIS approaches are prone to errors induced by organic compounds present in plant, soil, and natural water samples. A novel approach using 17 O-excess values has shown promise for flagging spectrally-contaminated plant samples during IRIS analysis. A systematic assessment of this flagging system is needed to prove it useful. METHODS: Errors induced by methanol and ethanol water mixtures on measured IRIS and IRMS results were evaluated. For IRIS analyses both liquid and vapour-mode (via direct vapour equilibration) methods are used. The δ2 H, δ17 O, and δ18 O values were measured and compared with known reference values to determine the errors induced by methanol and ethanol contamination. In addition, the 17 O-excess contamination detection approach was tested. This is a post processing detection tool for both liquid and vapour IRIS triple-isotope analyses, utilizing calculated 17 O-excess values to flag contaminated samples. RESULTS: Organic contamination induced significant errors in IRIS results which were not seen in IRMS results. Methanol caused larger errors than ethanol. Results from vapour-IRIS analyses had larger errors than those from liquid-IRIS analyses. The 17 O-excess approach identified methanol driven error in liquid and vapour-mode IRIS samples at levels where isotope results became unacceptably erroneous. For ethanol contaminated samples a mix of erroneous and correct flagging occurred with the 17 O-excess method. Our results indicate that methanol is the more problematic contaminant for data corruption. The 17 O-excess method was therefore useful for data quality control. CONCLUSION: Organic contamination caused significant errors in IRIS stable isotope results. These errors were larger during vapour analysis than during liquid IRIS analyses, and larger for methanol than ethanol contamination. The 17 O-excess method is highly sensitive for detecting narrowband (methanol) contamination error in vapour and liquid analysis modes on IRIS. This article is protected by copyright. All rights reserved.
RATIONALE: Hydrogen and oxygen stable isotope ratios (δ2 H, δ17 O, and δ18 O values) are commonly used tracers of water. These ratios can be measured by isotope ratio infrared spectroscopy (IRIS). However, IRIS approaches are prone to errors induced by organic compounds present in plant, soil, and natural water samples. A novel approach using 17 O-excess values has shown promise for flagging spectrally-contaminated plant samples during IRIS analysis. A systematic assessment of this flagging system is needed to prove it useful. METHODS: Errors induced by methanol and ethanolwater mixtures on measured IRIS and IRMS results were evaluated. For IRIS analyses both liquid and vapour-mode (via direct vapour equilibration) methods are used. The δ2 H, δ17 O, and δ18 O values were measured and compared with known reference values to determine the errors induced by methanol and ethanol contamination. In addition, the 17 O-excess contamination detection approach was tested. This is a post processing detection tool for both liquid and vapour IRIS triple-isotope analyses, utilizing calculated 17 O-excess values to flag contaminated samples. RESULTS: Organic contamination induced significant errors in IRIS results which were not seen in IRMS results. Methanol caused larger errors than ethanol. Results from vapour-IRIS analyses had larger errors than those from liquid-IRIS analyses. The 17 O-excess approach identified methanol driven error in liquid and vapour-mode IRIS samples at levels where isotope results became unacceptably erroneous. For ethanol contaminated samples a mix of erroneous and correct flagging occurred with the 17 O-excess method. Our results indicate that methanol is the more problematic contaminant for data corruption. The 17 O-excess method was therefore useful for data quality control. CONCLUSION: Organic contamination caused significant errors in IRIS stable isotope results. These errors were larger during vapour analysis than during liquid IRIS analyses, and larger for methanol than ethanol contamination. The 17 O-excess method is highly sensitive for detecting narrowband (methanol) contamination error in vapour and liquid analysis modes on IRIS. This article is protected by copyright. All rights reserved.
Authors: Arthur Gessler; Lukas Bächli; Elham Rouholahnejad Freund; Kerstin Treydte; Marcus Schaub; Matthias Haeni; Markus Weiler; Stefan Seeger; John Marshall; Christian Hug; Roman Zweifel; Frank Hagedorn; Andreas Rigling; Matthias Saurer; Katrin Meusburger Journal: New Phytol Date: 2021-10-15 Impact factor: 10.323