Measurement of redox species in estuarine sediments using voltammetric micro electrodes (Rehoboth Bay, Delaware USA)

Measurement of redox species in estuarine sediments using voltammetric micro electrodes (Rehoboth Bay, Delaware USA): Part of the annual study of redox cycling in the sediments of Rehoboth Bay

Trouwborst, R.E.

Molengraaff Fonds

1999

This research project is conducted during a three months visit at the Graduate School of Marine Studies, University Delaware. The project is part of the annual study of redox cycling in the sediments of Rehoboth Bay by the research group of Professor Luther III. The main goal is to come to a better understanding considering the behaviour of redox species and phosphate in a shallow water bay. During this project the recently developed solid-state Au-Hg microelectrodes were successfully used to analyse the concentration profiles of oxygen, H2S, FeS, Fe(III), Fe(II) and manganese (II) in the sediment porewater. The profiles provide useful information for the interpretation of the measured porewater and solid phase data. The profiles of the ammonium and phosphate concentration in the porewater indicate the occurrence of an organic rich layer in the upper part of the sediment. This layer of organic matter is likely the result of high productivity during the summer. By degradation of this organic matter, produced nutrients phosphate and ammonium are released to the overlying water in August. The degradation of organic matter seems to directly influence the profiles of the oxidized agents, O2, manganese and iron oxides. The pyrite concentration coincides with the organic matter concentration in both the cores sampled in August and October. Even though a high amorphous iron concentration was measured in the upper part of the sediment, no distinct ratio between the occurrence of amorphous iron oxides and adsorbed phosphate was found. The occurrence of conditions of eutrophocation is most likely to happen in August, because of the observed flux of nutrients during that month. Nutrients are transported to the overlying water and are available for macroalgae.

http://resolver.tudelft.nl/uuid:c8da5ed7-308d-4b56-b8a7-de9d2c6c84eb

Utrecht University

Geoscience Reports

report

(c) R.E. Trouwborst