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Qiu, S. ; Eckert, D.* ; Cirpka, O.A.* ; Hünniger, M. ; Knappett, P.S. ; Maloszewski, P. ; Meckenstock, R.U. ; Griebler, C. ; Elsner, M.

Direct experimental evidence of non-first order degradation kinetics and sorption-induced isotopic fractionation in a mesoscale aquifer: 13C/12C analysis of a transient toluene pulse.

Environ. Sci. Technol. 47, 6892-6899 (2013)
DOI PMC
Open Access Green as soon as Postprint is submitted to ZB.
The injection of a mixed toluene and D2O (conservative tracer) pulse into a pristine mesoscale aquifer enabled a first direct experimental comparison of contaminant-specific isotopic fractionation from sorption versus biodegradation and transverse dispersion on a relevant scale. Water samples were taken from two vertically resolved sampling ports at 4.2 m distance. Analysis of deuterium and toluene concentrations allowed quantifying the extent of sorption (R = 1.25) and biodegradation (37% and 44% of initial toluene at the two sampling ports). Sorption and biodegradation were found to directly affect toluene (13)C/(12)C breakthrough curves. In particular, isotope trends demonstrated that biodegradation underwent Michaelis-Menten kinetics rather than first-order kinetics. Carbon isotope enrichment factors obtained from an optimized reactive transport model (Eckert et al., this issue) including a possible isotope fractionation of transverse dispersion were ε(equ)sorption = -0.31 ‰, ε(kin)transverse-dispersion = -0.82 ‰, and ε(kin)biodegradation = -2.15 ‰. Extrapolation of our results to the scenario of a continuous injection predicted that (i) the bias in isotope fractionation from sorption, but not transverse dispersion, may be avoided when the plume reaches steady-state; and (ii) the relevance from both processes is expected to decrease at longer flow distances when isotope fractionation of degradation increasingly dominates.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Aromatic-hydrocarbons ; Intrinsic Bioremediation ; Organic Contaminants ; Batch Experiments ; Aerobic Aquifer ; Stable Carbon ; In-situ ; Biodegradation ; Variability ; Pollutants
ISSN (print) / ISBN 0013-936X
e-ISSN 1520-5851
Journal Environmental Science & Technology
Quellenangaben Volume: 47, Issue: 13, Pages: 6892-6899 Article Number: , Supplement: ,
Publisher American Chemical Society (ACS)
Publishing Place Washington, DC
Reviewing status Peer reviewed
Institute(s) Institute of Groundwater Ecology (IGOE)