Isotopic Fractionation by Transverse Dispersion: Flow-through Microcosms and Reactive Transport Modeling Study

Massimo Rolle, Gabriele Chiogna, Robert Bauer, Christian Griebler, Peter Grathwohl

Research output: Contribution to journalJournal articleResearchpeer-review


Flow-through experiments were carried out to investigate the role of transverse dispersion on the isotopic behavior of an organic compound during conservative and bioreactive transport in a homogeneous porous medium Ethylbenzene was selected as model contaminant and a mixture of labeled (perdeuterated) and light isotopologues was continuously injected in a quasi two-dimensional flow-through system We observed a significant fractionation of ethylbenzene isotopologues during conservative transport at steady state. This effect was particularly pronounced at the plume fringe and contrasted with the common assumption that physical processes only provide a negligible contribution to isotope fractionation Under the experimental steady state conditions, transverse hydrodynamic dispersion was the only process that could have caused the observed fractionation. Therefore, the measured isotope ratios at the outlet ports were interpreted with different parameterizations of the transverse dispersion coefficient. A nonlinear compound-specific parameterization showed the best agreement with the experimental data Successively, bioreactive experiments were performed in two subsequent stages a first oxic phase, involving a single strain of ethylbenzene degraders and a second phase with aerobic and anaerobic (i e, ethylbenzene oxidation coupled to nitrate reduction) degradation. Significant fractionation through biodegradation occurred exclusively due to the metabolic activity of the anaerobic degraders We performed analytical and numerical reactive transport simulations of the different experimental phases which confirmed that both the effects of physical processes (diffusion and dispersion) and microbially mediated reactions have to be considered to match the observed isotopic fractionation behavior.
Original languageEnglish
JournalEnvironmental Science & Technology (Washington)
Issue number16
Pages (from-to)6167-6173
Number of pages7
Publication statusPublished - 2010
Externally publishedYes


  • Chemistry (all)
  • Environmental Chemistry
  • Experimental data
  • Flowthrough
  • Hydrodynamic dispersions
  • Isotope fractionation
  • Isotope ratio
  • Isotopic fractionations
  • Isotopologues
  • Mediated reactions
  • Metabolic activity
  • Model contaminant
  • Nitrate reduction
  • Nonlinear compounds
  • Outlet port
  • Parameterizations
  • Physical process
  • Plume fringes
  • Porous medium
  • Quasi two-dimensional flow
  • Reactive transport
  • Reactive transport modeling
  • Second phase
  • Steady state
  • Steady-state condition
  • Transverse dispersion
  • Biodegradation
  • Degradation
  • Ethylbenzene
  • Isotopes
  • Porous materials
  • Dispersions
  • ethylbenzene
  • isotope
  • nitrate
  • oxygen
  • biodegradation
  • chemical environmental conditions
  • diffusion
  • dispersion
  • hydrodynamics
  • isotopic fractionation
  • isotopic ratio
  • metabolism
  • microcosm
  • nonlinearity
  • numerical model
  • organic compound
  • porous medium
  • reactive transport
  • steady-state equilibrium
  • two-dimensional modeling
  • active transport
  • aromatoleum aromaticum
  • article
  • bacterium
  • diffusion coefficient
  • flow
  • fractionation
  • nonhuman
  • oxygen concentration
  • Pseudomonas putida
  • Aerobiosis
  • Anaerobiosis
  • Chemical Fractionation
  • Diffusion
  • Ecosystem
  • Kinetics
  • Models, Chemical
  • Motion
  • Water Movements
  • conservative transport
  • diffusion process
  • first oxic phase
  • flow-through microcosm
  • homogeneous porous medium
  • plume fringe
  • transverse dispersion coefficient parameterization
  • transverse hydrodynamic dispersion
  • ethylbenzene 100-41-4 oxidation, isotopologue, contaminant
  • isotopes
  • nitrate 14797-55-8 reduction
  • 04500, Mathematical biology and statistical methods
  • 10060, Biochemistry studies - General
  • 10515, Biophysics - Biocybernetics
  • 37015, Public health - Air, water and soil pollution
  • Computational Biology
  • reactive transport model mathematical and computer techniques
  • transverse hydrodynamic dispersion method laboratory techniques
  • Models and Simulations
  • Pollution Assessment Control and Management
  • Experiments


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