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Occurrence and Rates of Terminal Electron‐Accepting Processes and Recharge Processes in Petroleum Hydrocarbon‐Contaminated Subsurface
Author(s) -
Salminen Jani M.,
Hänninen Pekka J.,
Leveinen Jussi,
Lintinen Petri T. J.,
J⊘rgensen Kirsten S.
Publication year - 2006
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0075
Subject(s) - microcosm , methanogenesis , environmental chemistry , chemistry , ferrous , methane , sulfate , denitrification , anaerobic oxidation of methane , hydrocarbon , soil water , electron acceptor , soil contamination , contamination , groundwater , environmental science , ecology , soil science , geology , nitrogen , geotechnical engineering , organic chemistry , photochemistry , biology
The occurrence and rates of terminal electron acceptor processes, and recharge processes in the unsaturated zone of a boreal site contaminated with petroleum hydrocarbons in the range C 10 to C 40 were examined. Soil microcosms were used to determine the rates of denitrification, iron (Fe) reduction, sulfate (SO 4 ) reduction, and methanogenesis in two vertical soil profiles contaminated with oil, and in a noncontaminated reference sample. Furthermore, the abundances of the 16S rRNA genes belonging to Geobacteracaea in the samples were determined by real‐time quantitative polymerase chain reaction (PCR). Analyses of ground water chemistry and soil gas composition were also performed together with continuous in situ monitoring of soil water and ground water chemistry. Several lines of evidence were obtained to demonstrate that both Fe reduction and methanogenesis played significant roles in the vertical profiles: Fe reduction rates up to 3.7 nmol h −1 g −1 were recorded and they correlated with the abundances of the Geobacteracaea 16S rRNA genes (range: 2.3 × 10 5 to 4.9 × 10 7 copies g −1 ). In the ground water, ferrous iron (Fe 2+ ) concentration up to 55 mg L −1 was measured. Methane production rates up to 2.5 nmol h −1 g −1 were obtained together with methane content up to 15% (vol/vol) in the soil gas. The continuous monitoring of soil water and ground water chemistry, microcosm experiments, and soil gas monitoring together demonstrated that the high microbial activity in the unsaturated zone resulted in rapid removal of oxygen from the infiltrating recharge thus leaving the anaerobic microbial processes dominant below 1.5 m depth both in the unsaturated and the saturated zones of the subsurface.