Redox Biogeochemistry

Research in this area is directed towards characterizing the redox properties and reactivities of major organic and mineral geochemical phases in the environment. We combine mediated electrochemical analyses, a novel electrochemical approach developed in our research group, with spectroscopy measurements to determine the capacities of geochemical phases to accept and donate electrons, the reversibility of electron transfer to and from geochemical phases, the reduction potentials at which electrons are transferred.

Geochemical phases under investigation include natural organic matter, both in dissolved and particulate forms, biochar, iron-bearing clay minerals, and, most recently, iron (oxyhydr)oxides. In addition, we study electron transfer to and from lake sediments which contain different redox active species and phases.

Selected key publications are:

Description of mediated electrochemical analyses

Sander, M., T.B. Hofstetter, C.A. Gorski. Electrochemical analyses of redox-active iron minerals: A review of non-mediated and mediated approaches. Environ Sci Technol, 2015, 49, 5862-5878. DOI: external page 10.1021/acs.est.5b00006

Aeschbacher, M., M. Sander, and R.P. Schwarzenbach. Novel Electrochemical Approach to Assess the Redox Properties of Humic Substances. Environ Sci Technol, 2010, 44, 87–93; DOI: external page 10.1021/es902627p

Natural organic matter

Wallace, G., M. Sander, Y.-P. Chin, and W. A. Arnold. Quantifying the electron donating capacities of sulfide and dissolved organic matter in sediment pore waters of wetlands. Environmental Sciences: Processes & Impacts. 2017, 19, 758-767, DOI: external page 10.1039/C7EM00060J

Walpen, N., M. Schroth, M. Sander. Quantification of phenolic antioxidant moieties in dissolved organic matter by flow-injection analysis with electrochemical detection. Environ Sci Technol, 2016, 50, 6423-6432; DOI: external page 10.1021/acs.est.6b01120

Poggenburg, C., R. Mikutta, M. Sander, A. Schippers, A. Marchanka, R. Dohrmann, G. Guggenberger. Microbial reduction of ferrihydrite-organic matter coprecipitates by Shewanella putrefaciens and Geobacter metallireducens in comparison to mediated electrochemical reduction. Chemical Geology, 2016, 447, 133-147; DOI: external page 10.1016/j.chemgeo.2016.09.031

Wenk, J., M. Aeschbacher, M. Sander, U. von Gunten, and S. Canonica. Photosensitizing and inhibitory effects of ozonated dissolved organic matter on triplet-induced contaminant transformation. Environ Sci Technol, 2015, 49, 8541–8549; DOI: external page 10.1021/acs.est.5b02221

L.C. Bodhipaksha, C. M. Sharpless, Y.-P. Chin, M. Sander, W.K. Langston, and A. A. MacKay. Triplet photochemistry of effluent and natural organic matter in whole water and isolates from effluent-receiving rivers. Environ Sci Technol, 2015, 49, 3453–3463. DOI: external page 10.1021/es505081w

Klüpfel, L., A. Piepenbrock, A. Kappler, and M. Sander. Humic substances as fully regenerable electron acceptors in recurrently anoxic environments. Nature Geoscience, 2014, 7, 195-200. DOI: external page 10.1038/ngeo2069

Page, S.E., G.W. Kling, M. Sander, K.H. Harrold, J.R. Logan, K. McNeill, and R.M. Cory. Dark formation of Hydroxyl radical in Arctic Soils and Surface waters. Environ Sci Technol, 2013, 47, 12860-12867. DOI: external page 10.1021/es4033265

Wenk, J., M. Aeschbacher, E. Salhi, S. Canonica, U. von Gunten, and M. Sander. Chemical oxidation of dissolved organic matter by chlorine dioxide, chlorine, and ozone: Effects on its optical and antioxidant properties. Environ Sci Technol, 2013, 47, 11147-11156. DOI: external page 10.1021/es402516b

Aeschbacher, M., C. Graf, R.P. Schwarzenbach, and M. Sander. Antioxidant properties of humic substances. Environ Sci Technol, 2012, 46, 4916-4925. external page DOI:external page 10.1021/es300039h

Page, S.E., M. Sander, W.A. Arnold, K. McNeill. Hydroxyl radical formation upon oxidation of reduced humic acids by oxygen in the dark. Environ Sci Technol, 2012, 46, 1590-1597. external page DOI:external page 10.1021/es20386f

Aeschbacher, M., D. Vergari, R.P. Schwarzenbach, and M. Sander. Electrochemical Analysis of Proton and Electron Transfer Equilibria of the Reducible Moieties in Humic Acids. Environ Sci Technol, 2011, 45, 8385–8394. external page DOI:external page 10.1021/es201981g

Biochar

Klüpfel, L., M. Keiluweit, M. Kleber, and M. Sander. Redox properties of plant biomass-derived carbon black (biochar). Environ Sci Technol, 2014, 48, 5601-5611. external page DOI: 10.1021/es500906d

Iron (oxyhydr-)oxides

Aeppli, M., A. Voegelin; C. Gorski, T. Hofstetter, and M. Sander. Mediated electrochemical reduction of iron (oxyhydr-)oxides under defined thermodynamic boundary conditions. Environ Sci Technol. 2017. asap, DOI: external page 10.1021/acs.est.7b04483

Hoving, A. L., M. Sander, C. Bruggeman, T. Behrends. Redox properties of clay-rich sediments as assessed by mediated electrochemical analysis: Separating pyrite, siderite and structural Fe in clay minerals. Chemical Geology, 2017, 457, 149-161; external page DOI:10.1016/j.chemgeo.2017.03.022

Gorski, G., R. Edwards, M. Sander, T.B. Hofstetter, and S. M. Stewart. Thermodynamic Characterization of Iron Oxide-Aqueous Fe²⁺ Redox Couples. Environ Sci Technol, 2016, asap; external page DOI:10.1021/acs.est.6b02661

Iron-bearing clay minerals

Gorski, C.A., L. Klüpfel, A. Voegelin, M. Sander, and T.B. Hofstetter. Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties. Environ Sci Technol, 2013, 47, 13477-13485. external page DOI: 10.1021/es403824x

Gorski, C., L. Kluepfel, A. Voegelin, M. Sander, T.B. Hofstetter. Redox properties of structural Fe in clay minerals: 2. Electrochemical and spectroscopic characterization of electron transfer irreversibility in ferruginous smectite, SWa-1. Environ Sci Technol, 2012, 46, 9369-9377. external page DOI: 10.1021/es302014u

Gorski, C., M. Aeschbacher, D. Soltermann, A. Voegelin, B. Baeyens, M. Marques Fernandes, T.B. Hofstetter, M. Sander. Redox properties of structural Fe in clay minerals: 1. Electrochemical quantification of electron donating and accepting capacities of smectites. Environ Sci Technol, 2012, 46, 9360-9368. external page DOI: 10.1021/es3020138

Sediments

Lau, M., M. Sander, J. Gelbrecht, and M. Hupfer. Spatiotemporal redox dynamics in a freshwater lake sediment under alternating oxygen availabilities: combined analyses of dissolved and particulate electron acceptors. Environmental Chemistry, 2016, external page asap

Lau, M., M. Sander, J. Gelbrecht, M. Hupfer. Solid phases as important electron acceptors in freshwater organic sediments. Biogeochemistry, 2015, 123, 49-61. external page DOI: 10.1007/s10533-014-0052-5

Collaborations

Redox properties of iron-bearing clay minerals and iron (oxyhydr)oxides

external page Thomas B. Hofstetter (Eawag, Switzerland), external page Christopher A. Gorski (Penn State University, USA), external page Andreas Vögelin (Eawag, Switzerland), external page Thilo Behrends (Utrecht University, The Netherlands)

Redox properties of Natural Organic Matter

external page Silvio Canonica (Eawag, Switzerland); external page Urs von Gunten (Eawag & EPFL, Switzerland), external page Jannis Wenk (University of Bath, Great Britain), external page Charles Sharpless (University of Mary Washington, USA), external page Andreas Kappler (Eberhard Karls University Tübingen, Germany), external page Kristopher McNeill (ETHZ, Switzerland), external page Rose Cory (University of Michigan, USA)

Redox properties of biochar

external page Marco Keiluweit (University of Massachusetts, USA); external page Markus Kleber (Oregon State University, Switzerland)

Redox properties of Lake Sediments

external page Maximilian Lau, external page Jörg Gelbrecht, external page Michael Hupfer (all IGB Berlin, Germany), external page Beat Müller (Eawag, Switzerland)