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)
    
    
    
      
      
	
	    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
    
 
    
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        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
    
 
    
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        Language
        english
    
 
    
        Publication Year
        2021
    
 
    
        Prepublished in Year
        
    
 
    
        HGF-reported in Year
        2021
    
 
    
    
        ISSN (print) / ISBN
        0013-936X
    
 
    
        e-ISSN
        1520-5851
    
 
    
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	    Volume: 55,  
	    Issue: 11,  
	    Pages: 7386-7397 
	    Article Number: ,  
	    Supplement: ,  
	
    
 
    
        
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            ACS
        
 
        
            Publishing Place
            Washington, DC
        
 
	
        
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        Reviewing status
        Peer reviewed
    
 
     
    
        POF-Topic(s)
        20403 - Sustainable Water Management
30202 - Environmental Health
    
 
    
        Research field(s)
        Environmental Sciences
    
 
    
        PSP Element(s)
        G-504390-001
G-504500-001
    
 
    
        Grants
        ERC
    
 
    
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        Erfassungsdatum
        2021-06-23