Beware of effects on isotopes of dissolved oxygen during storage of natural iron-rich water samples: A technical note

Köhler I, Piatka D, Barth J, Martinez RE (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Rapid Communications in Mass Spectrometry Wiley

Book Volume: 35

Article Number: e9024

Journal Issue: 6

DOI: 10.1002/rcm.9024

Abstract

Rationale: Investigations of the isotope ratios of dissolved oxygen (δ18ODO) provide valuable information about the oxygen cycle in aquatic systems. However, oxidation of Fe(II) may change pristine δ18ODO values during storage and can lead to a misinterpretation. We sampled an Fe(II)-rich spring system and measured δ18ODO values at various time intervals in order to determine influences of Fe-oxidation. Methods: Water samples were collected from an Fe-rich spring and related stream and the δ18ODO values were measured in fresh, 4- and 13-day-old samples with an isotope ratio mass spectrometer. Three replicates were measured for each sample with a 1σ of ± 0.2‰. On-site parameters and Fe(II) contents were also measured over the course of the spring system by multi-parameter probes and spectrophotometry. Results: The δ18ODO values over the course of the spring system in fresh, 4- and 13-day-old samples revealed differences of up to 8‰. We explain this increase by the consumption of DO by Fe(II)-oxidation. After a flow length of 85 m the differences in δ18ODO values between fresh and older samples decreased because most of the Fe(II) was consumed. Conclusions: False interpretations of δ18ODO values are possible if Fe-rich water samples are measured after too long storage, and we recommend measurement immediately after sampling.

Authors with CRIS profile

Inga Köhler Lehrstuhl für Angewandte Geologie David Piatka Lehrstuhl für Angewandte Geologie Johannes Barth Lehrstuhl für Angewandte Geologie

Involved external institutions

Max-Planck-Institut für Biogeochemie / Max Planck Institute for Biogeochemistry DE Germany (DE)

How to cite

APA:

Köhler, I., Piatka, D., Barth, J., & Martinez, R.E. (2021). Beware of effects on isotopes of dissolved oxygen during storage of natural iron-rich water samples: A technical note. Rapid Communications in Mass Spectrometry, 35(6). https://doi.org/10.1002/rcm.9024

MLA:

Köhler, Inga, et al. "Beware of effects on isotopes of dissolved oxygen during storage of natural iron-rich water samples: A technical note." Rapid Communications in Mass Spectrometry 35.6 (2021).

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