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TitleAssessing microbial uptake of petroleum hydrocarbons in groundwater systems using natural abundance radiocarbon
AuthorAhad, J M E; Burns, L; Mancini, S; Slater, G F
SourceEnvironmental Science & Technology (ES & T) vol. 44, 2010 p. 5092-5097,
Alt SeriesEarth Sciences Sector, Contribution Series 20090317
PublisherAmerican Chemical Society (ACS)
Mediapaper; on-line; digital
File formatpdf
Subjectsenvironmental geology; hydrogeology; groundwater; groundwater regimes; groundwater pollution; hydrocarbons; total organic carbon
ProgramEnvironmental Geoscience, Ecosystems Risk Mitigation
AbstractCarbon sources utilized by the active microbial communities in shallow groundwater systems underlying three petroleum service stations were characterized using natural abundance radiocarbon (14C). Total organic carbon (TOC)delta14C values ranged from -314 to -972 permil and petroleum-extracted residues (EXTRES) ranged from -293 to -971 permil. Phospholipid fatty acids (PLFAs)sbiomarkers for active microbial populationssranged from -405 to -885 permil and a comparison of these values with potential carbon sources pointed to significant microbial assimilation of 14C-free fossil carbon.Themost 14C-depletedPLFAs were found in the samples with the highest concentrations of total petroleum hydrocarbons (TPHs). A radiocarbon mass balance indicated up to 43% of the carbon in microbial PLFAs was derived from TPHs, providing direct evidence for biodegradation at two of three sites. At lower levels of TPHs delta 14C values of PLFAs were generally similar to or more enriched than all other carbon in the system indicating microbial utilization of a more 14C-enriched carbon source and no resolvable evidence for microbial incorporation of petroleumderived carbon. Results from this study suggest that it is possible to delineate petroleum biodegradation in groundwater systems using these techniques even in complex situations where there exists a wide range in the ages of natural organic matter (i.e., EXT-RES).