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Continuous Eh-recordings in sediment columns
Kontinuierliche Messungen des Redoxpotentials in Sedimentsäulen
Helgoländer wissenschaftliche Meeresuntersuchungen volume 27, pages 101–107 (1975)
Kurzfassung
Die Meßergebnisse von Redoxpotentialen in marinen Sedimenten sind oft schwierig zu interpretieren, weil neben vielen Störungen auch Potentialänderungen nach dem Einbringen der Elektrode in das Sediment auftreten. Zur Quantifizierung dieses Problems wurden Sande aus der Nordadria in Plexiglasrohre gefüllt und Laborversuche unter kontrollierten Bedingungen durchgeführt. Nachdem sich das mit Gold- bzw. Platinelektroden gemessene Redoxpotential stabilisiert hatte, die Elektroden herausgezogen und mechanisch gereinigt waren, konnten deutlich andere Potentiale als vor dem Reinigen festgestellt werden, die erst im Verlauf einiger Tage die alten Marken wieder erreichten. Dabei ändert sich das Eh-Profil in den Sandsäulen selber offensichtlich wohl nicht. Es zeigt sich aber, daß die gemessene Form des Redoxprofils von der Stabilisierungszeit abhängig ist. Durch kurzfristige Messungen kann allerdings die Lage der Redox-Potential-Diskontinuität festgestellt werden.
Summary
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1.
Long-term recordings of redox-potential in marine sediments performed under laboratory conditions show that the drift of the measured potential after inserting the electrode cannot be neglected.
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2.
Cleaning and reinserting an electrode considerably changes the measured potential. This change may reach several hundred mV, depending on the position of the electrode and the composition of the sediment.
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3.
It takes several days until the potentials observed before cleaning are obtained again.
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4.
The overall Eh-profile in the sediment column is not changed by successive experiments. An electrode at a certain position in the sediment normally will return to the same potential if enough time is allowed for stabilization.
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5.
Quick measurements of single Eh-values in systems such as marine sediments must be handled with caution.
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6.
The measured shape of the redox-profile strongly depends on the time allowed for stabilization.
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7.
The position of the redox-potential-discontinuity defined as the point of inflection of the curve Eh versus depth seems to be the only meaningful parameter derived from quick measurements.
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Herrn Prof. Dr.R. Riedl zum 50. Geburtstag.
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Schmidt, H.E., Machan, R. Continuous Eh-recordings in sediment columns. Helgolander Wiss. Meeresunters 27, 101–107 (1975). https://doi.org/10.1007/BF01611689
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DOI: https://doi.org/10.1007/BF01611689