Mercury/gold amalgam and bismuth film electrodes (BiFEs) were used to make the first centimeter-scale measurements of redox species in benthic pore waters of prairie pothole wetlands across a hydrologic gradient. Sulfide in pore waters increased across this system from negligible sulfide in hydrologically up-gradient recharge wetlands to thousands of micromolar in down-gradient discharge wetlands. Field measurements of sulfides using the BiFE were tested against an established colorimetric assay. Sulfide measured with the BiFE agreed well with colorimetric measurements but is not subject to analytical artifacts associated with methods needed to extract the pore waters. Use of Hg/Au and BiFE electrodes should allow for rapid in situ detection of redox active species, especially sulfide concentrations of >500 μM, in pore waters over seasonal to decadal time scales. Such measurements are needed to understand important biogeochemical and environmental processes such as carbon cycling and contaminant attenuation tied to sulfur dynamics in these important ecosystems.
Bibliographical noteFunding Information:
This research was funded by Grants EAR 1246594 and EAR 1245135 from the National Science Foundation. The U.S. Geological Survey Northern Prairie Wildlife Research Center provided necessary logistical support in the field, specifically David Mushet and Matthew Solensky. Martin B. Goldhaber, JoAnn Holloway, and Christopher Mills provided useful insight into the local environment that guided our fieldwork. Grant Wallace and Andrew McCabe provided essential assistance in performing analyses. Don Nuzzio provided analytical support. We also thank the three anonymous reviewers for their helpful comments and suggestions that improved the manuscript.
© 2016 American Chemical Society.