title: Enhanced biodegradation by hydraulic heterogeneities in petroleum hydrocarbon plumes.
abstract: In case of dissolved electron donors and acceptors, natural attenuation of organic contaminant plumes in aquifers is governed by hydrodynamic mixing and microbial activity. Main objectives of this work were (i) to determine whether aerobic and anaerobic biodegradation in porous sediments is controlled by transverse dispersion, (ii) to elucidate the effect of sediment heterogeneity on mixing and biodegradation, and (iii) to search for degradation-limiting factors. Comparative experiments were conducted in two-dimensional sediment microcosms. Aerobic toluene and later ethylbenzene degradation by Pseudomonas putida strain F1 was initially followed in a plume developing from oxic to anoxic conditions and later under steady-state mixing-controlled conditions. Competitive anaerobic degradation was then initiated by introduction of the denitrifying strain Aromatoleum aromaticum EbN1. In homogeneous sand, aerobic toluene degradation was clearly controlled by dispersive mixing. Similarly, under denitrifying conditions, microbial activity was located at the plume's fringes. Sediment heterogeneity caused flow focusing and improved the mixing of reactants. Independent from the electron accepting process, net biodegradation was always higher in the heterogeneous setting with a calculated efficiency plus of 23-100% as compared to the homogeneous setup. Flow and reactive transport model simulations were performed in order to interpret and evaluate the experimental results.
authors.affiliation: Helmholtz Zentrum Muenchen - German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Bauer
authors.forename: Massimo
authors.initials: M
authors.lastname: Rolle
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bauer
authors.forename: Christina
authors.initials: C
authors.lastname: Eberhardt
authors.forename: Peter
authors.initials: P
authors.lastname: Grathwohl
authors.forename: Olaf
authors.initials: O
authors.lastname: Kolditz
authors.forename: Rainer U
authors.initials: RU
authors.lastname: Meckenstock
authors.forename: Christian
authors.initials: C
authors.lastname: Griebler
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D003198:Computer Simulation; D004583:Electrons; D006838:Hydrocarbons / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010578:Petroleum / Q000032:analysis* / Q000378:metabolism*; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D006838:Hydrocarbons; D010578:Petroleum; D012989:Soil Pollutants; D010100:Oxygen