Field- and Lab-Based Potentiometric Titrations of Microbial Mats from the Fairmont Hot Spring, Canada

Potentiometric titrations are an effective tool to constrain the protonation constants and site concentrations for microbial surface ligands. Protonation models developed from these experiments are often coupled with data from metal adsorption experiments to calculate microbial ligand-metal binding...

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Bibliographic Details
Published in:Geomicrobiology journal 2017-11, Vol.34 (10), p.851-863
Main Authors: Warchola, Tyler J., Flynn, Shannon L., Robbins, Leslie J., Liu, Yuxia, Gauger, Tina, Kovalchuk, Olga, Alam, Md. Samrat, Wei, Siwen, Myers, Reed, Bishop, Brendan, Lalonde, Stefan V., Gingras, Murray K., Kappler, Andreas, Alessi, Daniel S., Konhauser, Kurt O.
Format: Article
Language:English
Subjects:
Carbonate
Carbonate minerals
Carbonates
Chemical reactions
Constants
Earth Sciences
Experiments
Field tests
hot spring
Hot springs
Immobilization
in situ
Ligands
Mats
Metals
Microbial mats
Microorganisms
Minerals
Oceanography
Paleontology
pH effects
Potentiometric titration
potentiometric titrations
Protonation
Protons
Reactivity
Sciences of the Universe
Speciation
Spring
surface reactivity
Tectonics
Titration
Volcanology
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Summary:Potentiometric titrations are an effective tool to constrain the protonation constants and site concentrations for microbial surface ligands. Protonation models developed from these experiments are often coupled with data from metal adsorption experiments to calculate microbial ligand-metal binding constants. Ultimately, the resulting surface complexation models can be used to predict metal immobilization behavior across diverse chemical conditions. However, most protonation and metal-ligand thermodynamic constants have been generated in laboratory experiments that use cultured microbes which may differ in their chemical reactivity from environmental samples. In this study, we investigate the use of in situ field potentiometric titrations of microbial mats at a carbonate hot spring located at Fairmont Hot Springs, British Columbia, with the aim to study microbial reactivities in a natural field system. We found that authigenic carbonate minerals complicated the potentiometric titration process due to a "carbonate spike" introduced by the contribution of inorganic carbonate mineral dissolution and subsequent carbonate speciation changes during the transition from low to high pH. This inhibits the determination of microbial surface ligand variety and concentrations. Our preliminary study also highlights the need for developing novel probes to quantify in situ microbial mat reactivity in future field investigations.
ISSN:0149-0451
1521-0529
DOI:10.1080/01490451.2017.1282557