Comparison of sample preparation methods for stable isotope analysis of dissolved sulphate in forested watersheds |
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Authors: | Phil-Goo Kang Bernhard Mayer Myron J Mitchell |
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Institution: | 1. Department of Environmental and Forest Biology , College of Environmental Science and Forestry, State University of New York , NY , USA;2. National Institute of Environmental Research , Incheon , South Korea philgkang@gmail.com pkang01@syr.edu;4. Department of Geoscience , University of Calgary , Calgary , Alberta , Canada;5. Department of Environmental and Forest Biology , College of Environmental Science and Forestry, State University of New York , NY , USA |
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Abstract: | Pretreatment methods for measuring stable sulphur (δ34S) and oxygen (δ18O) isotope ratios of dissolved sulphate from watersheds have evolved throughout the last few decades. The current study evaluated if there are differences in the measured stable S and O isotope values of dissolved sulphate from forested watersheds when pretreated using three different methods: Method 1 (M1): adsorb sulphate on anion exchange resins and send directly to isotope facility; Method 2 (M2): adsorb sulphate on anion exchange resins, extract sulphate from anion exchange resins, and send the produced BaSO4 to the isotope facility; and Method 3 (M3): directly precipitate BaSO4 without anion exchange resins with the precipitates being sent to the isotope facility. We found an excellent agreement of the δ34Ssulphate values among all the three methods. However, some differences were observed in the δ18Osulphate values (M1 versus M2:?1.5 ‰; M1 versus M3:?1.2 ‰) associated with possible O contamination before isotope measurement. Several approaches are recommended to improve the pretreatment procedures for δ18Osulphate analysis. |
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Keywords: | isotope measurements methods and equipment isotope ratio mass spectrometry natural abundances oxygen-18 sample preparation methods sulphate sulphur-34 watersheds |
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