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Submicromolar Oxygen Profiles at the Oxic-Anoxic Boundary of Temperate Lakes

Kirf, Mathias ; Dinkel, Christian ; Schubert, Carsten ; Wehrli, Bernhard

In: Aquatic Geochemistry, 2014, vol. 20, no. 1, p. 39-57

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    Titre
    • Submicromolar Oxygen Profiles at the Oxic-Anoxic Boundary of Temperate Lakes
    Auteur
    • Kirf, Mathias. Department of Surface Waters - Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Switzerland
    • Dinkel, Christian. Department of Surface Waters - Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Switzerland
    • Schubert, Carsten. Department of Surface Waters - Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Switzerland
    • Wehrli, Bernhard. Department of Surface Waters - Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Switzerland
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:325885
    Summary
    Elements involved in biogeochemical cycles undergo rapid turnover at the oxic-anoxic interface of stratified lakes. Here, the presence or absence of oxygen governs abiotic and biotic processes and rates. However, achieving a detailed sampling resolution to precisely locate the oxic-anoxic interface is difficult due to a lack of fast, drift-free sensors in the working range of 10 to a few 1,000nmol O2L−1. Here, we demonstrate that conventional amperometric and optical microsensors can be used to resolve submicromolar oxygen concentrations in a continuous profiling mode. The amperometric drift was drastically reduced by anoxic preconditioning. In situ offset correction in the anoxic layer and a high amplification scheme allowed for an excellent detection limit of <10nmolL−1. The optical microsensors also showed a similar performance with a detection limit of <20nmolL−1. Their drift stability allowed for a laboratory calibration in combination with a minor in situ anoxic offset correction. The two different sensor systems showed virtually identical profiles during parallel use in stratified lakes. Both sensors were able to resolve the fine-scale structure at the oxic-anoxic interface and revealed hitherto unnoticed extended zones of submicromolar oxygen concentrations even below a steep oxycline. The zones extended up to several meters and showed substantial vertical variability. These results underline the need of a precise localization of the oxic-anoxic interface on a submicromolar scale in order to constrain the relevant aerobic and anaerobic redox processes.