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Electric potential microelectrode for studies of electrobiogeophysics
Author(s) -
Damgaard Lars Riis,
RisgaardPetersen Nils,
Nielsen Lars Peter
Publication year - 2014
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2014jg002665
Subject(s) - microelectrode , sediment , biogeochemical cycle , electric field , diffusion , electric current , electric potential , sediment–water interface , electron , chemistry , analytical chemistry (journal) , materials science , environmental chemistry , geology , electrode , geomorphology , physics , voltage , quantum mechanics , thermodynamics
Spatially separated electron donors and acceptors in sediment can be exploited by the so‐called “cable bacteria.” Electric potential microelectrodes (EPMs) were constructed to measure the electric fields that should appear when cable bacteria conduct electrons over centimeter distances. The EPMs were needle‐shaped, shielded Ag/AgCl half‐cells that were rendered insensitive to redox‐active species in the environment. Tip diameters of 40 to 100 µm and signal resolution of approximately 10 μV were achieved. A test in marine sediments with active cable bacteria showed an electric potential increase by approximately 2 mV from the sediment‐water interface to a depth of approximately 20 mm, in accordance with the location and direction of the electric currents estimated from oxygen, pH, and H 2 S microprofiles. The EPM also captured emergence and decay of electric diffusion potentials in the upper millimeters of artificial sediment in response to changes in ion concentrations in the overlying water. The results suggest that the EPM can be used to track electric current sources and sinks with submillimeter resolution in microbial, biogeochemical, and geophysical studies.