High-resolution induced polarization imaging of biogeochemical carbon-turnover hot spots in a peatland

Titelangaben

Katona, Timea ; Gilfedder, Benjamin Silas ; Frei, Sven ; Bücker, Matthias ; Flores-Orozco, Adrian:
High-resolution induced polarization imaging of biogeochemical carbon-turnover hot spots in a peatland.
In: Biogeosciences Discussions. (2021) . - 44 S..
ISSN 1810-6285
DOI: https://doi.org/10.5194/bg-2020-438

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Abstract

Biogeochemical hot spots are defined as areas where biogeochemical processes occur with anomalously high reaction rates relative to their surroundings. Due to their importance in carbon and nutrient cycling, characterization of hot spots is critical to accurately predict carbon budgets in the context of climate change. However, biogeochemical hot spots are difficult to identify in the environment, as sampling resolutions are often too coarse to find these areas in the subsurface. Here, we present imaging results of a geophysical survey using the non-invasive induced polarization (IP) method to identify biogeochemical hot spots of carbon turnover in a minerotrophic wetland. To interpret the field-scale IP signatures, geochemical analyses were performed on freeze-core samples obtained in areas characterized by anomalously high and low IP responses. Our results reveal large variations in the electrical response, with the highest IP phase values (> 20 mrad) corresponding with high concentrations of phosphates (> 4000 μM), an indicator of carbon turnover. Moreover, analysis of the freeze core reveal negligible concentrations of iron sulfides. The extensive geochemical and geophysical data presented in our study demonstrates that IP images can assess changes in the biogeochemical activity in peat, and identify hot spots.