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Sun, F. ; Mellage, A.* ; Gharasoo, M. ; Melsbach, A. ; Cao, X. ; Zimmermann, R. ; Griebler, C.* ; Thullner, M.* ; Cirpka, O.A.* ; Elsner, M.

Mass-transfer-limited biodegradation at low concentrations-evidence from reactive transport modeling of isotope profiles in a bench-scale aquifer.

Environ. Sci. Technol. 55, 7386-7397 (2021)

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Organic contaminant degradation by suspended bacteria in chemostats has shown that isotope fractionation decreases dramatically when pollutant concentrations fall below the (half-saturation) Monod constant. This masked isotope fractionation implies that membrane transfer is slow relative to the enzyme turnover at μg L^-1 substrate levels. Analogous evidence of mass transfer as a bottleneck for biodegradation in aquifer settings, where microbes are attached to the sediment, is lacking. A quasi-two-dimensional flow-through sediment microcosm/tank system enabled us to study the aerobic degradation of 2,6-dichlorobenzamide (BAM), while collecting sufficient samples at the outlet for compound-specific isotope analysis. By feeding an anoxic BAM solution through the center inlet port and dissolved oxygen (DO) above and below, strong transverse concentration cross-gradients of BAM and DO yielded zones of low (μg L^-1) steady-state concentrations. We were able to simulate the profiles of concentrations and isotope ratios of the contaminant plume using a reactive transport model that accounted for a mass-transfer limitation into bacterial cells, where apparent isotope enrichment factors *ε decreased strongly below concentrations around 600 μg/L BAM. For the biodegradation of organic micropollutants, mass transfer into the cell emerges as a bottleneck, specifically at low (μg L^-1) concentrations. Neglecting this effect when interpreting isotope ratios at field sites may lead to a significant underestimation of biodegradation.

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Publication type Article: Journal article

Document type Scientific Article

Corresponding Author

Keywords 2,6-dichlorobenzamide ; Csia ; Gc-irms ; Bioavailability ; Flow-through System ; Reactive-transport Model; Pollutant 2,6-dichlorobenzamide Bam; Bacterial Sulfate Reduction; Metabolite 2,6-dichlorobenzamide; Stable Carbon; Bioavailability Restrictions; Anaerobic Biodegradation; Chlorinated Hydrocarbons; Fractionation Analysis; Bioreactive Transport; Herbicide Dichlobenil

ISSN (print) / ISBN 0013-936X

e-ISSN 1520-5851

Journal Environmental Science & Technology

Quellenangaben Volume: 55, Issue: 11, Pages: 7386-7397

Publisher ACS

Publishing Place Washington, DC

Non-patent literature Publications

Reviewing status Peer reviewed

Institute(s) Institute of Groundwater Ecology (IGOE)
Cooperation Group Comprehensive Molecular Analytics (CMA)

Grants ERC