Denitrification‐Driven Transcription and Enzyme Production at the River‐Groundwater Interface: Insights From Reactive‐Transport Modeling

Störiko, Anna; Pagel, Holger; Mellage, Adrian; Cappellen, Philippe Van; Cirpka, Olaf A.

doi:10.1029/2021wr031584

Cited by 7 publications

(1 citation statement)

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“…Traditional methods for the quantification of microbial abundance, activity and community composition have to rely on destructively‐sampled sediment because 80% to >99.9% of the bacteria in groundwater are located at the surfaces of the solid matrix rather than in the mobile water phase (Griebler & Lueders, 2009; Mellage et al., 2015). This is a severe limitation in bench‐scale experiments in which sacrificial sampling based on preliminary knowledge can, but not necessarily will capture reaction dynamics (Störiko et al., 2022). Thus, finding easy‐to‐measure proxies for microbial activity is key for improved monitoring of microbially mediated reactions in porous media.…”

Section: Introductionmentioning

confidence: 99%

Spectral Induced Polarization (SIP) of Denitrification‐Driven Microbial Activity in Column Experiments Packed With Calcareous Aquifer Sediments

et al. 2023

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Microbially mediated reactions facilitate the in situ degradation of many contaminants in groundwater thus contributing substantially to the water-purification capabilities of the subsurface (Griebler & Avramov, 2015). The ability to understand and predict contaminant removal through microbially mediated reactions in aquifers hinges on our ability to monitor and quantify reaction rates (Pinay et al., 2015) and microbial activity in the subsurface (Leckie et al., 2004). Microbially mediated reactions are subject to spatial variability and temporal dynamics (Li et al., 2021). In general, that spatial variability depends on the co-occurrence of reactants and Abstract Spectral Induced Polarization (SIP) has been suggested as a non-invasive monitoring proxy for microbial processes. Under natural conditions, however, multiple and often coupled polarization processes co-occur, impeding the interpretation of SIP signals. In this study, we analyze the sensitivity of SIP to microbially-driven reactions under quasi-natural conditions. We conducted flow-through experiments in columns equipped with SIP electrodes and filled with natural calcareous, organic-carbon-rich aquifer sediment, in which heterotrophic denitrification was bio-stimulated. Our results show that, even in the presence of parallel polarization processes in a natural sediment under field-relevant geochemical conditions, SIP is sufficiently sensitive to microbially-driven changes in electrical charge storage. Denitrification yielded an increase in imaginary conductivity of up to 3.1 𝐴𝐴 μS cm −1 (+140%) and the formation of a distinct peak between 1 and 10 Hz, that matched the timing of expected microbial activity predicted by a reactive transport model fitted to solute concentrations. A Cole-Cole decomposition allowed separating the polarization contribution of microbial activity from that of cation exchange, thereby helping to locate microbial hotspots without the need for (bio) geochemical data to constrain the Cole-Cole parameters. Our approach opens new avenues for the application of SIP as a rapid method to monitor a system's reactivity in situ. While in preceding studies the SIP signals of microbial activity in natural sediments were influenced by mineral precipitation/dissolution reactions, the imaginary conductivity changes measured in the biostimulation experiments presented here were dominated by changes in the polarization of the bacterial cells rather than a reaction-induced alteration of the abiotic matrix. Plain Language SummaryTo better predict the contribution of microbes to groundwater clean-up it is important to locate microbes in the ground that are actively removing contaminants and measure how fast they are doing so. Our ability to do so, however, is limited by the difficulty in visualizing underground processes. Electrical methods such as spectral induced polarization (SIP) have been applied to monitor microbes and provide an alternative to visualize them underground. SIP, however, has so far only been shown to work in controlled environm...

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Section: Introductionmentioning

confidence: 99%