@article {228,
	title = {Sources of n-alkanes in an urbanized estuary: Insights from molecular distributions and compound-specific stable and radiocarbon isotopes},
	journal = {Marine Chemistry},
	volume = {126},
	year = {2011},
	note = {id: 2169},
	pages = {239-249},
	abstract = {Diagnostic molecular ratios and compound-specific 13C and 14C analyses were used to identify n-alkane sources in surface sediments collected along a transect from an urbanized estuary draining a peat-rich catchment (Tyne, UK). The most abundant homologues were generally C29 or C31, and the carbon preference index (CPI; 1.8 to 6.4) and average chain length (ACL; 28.5 to 29.5) of C25{\textendash}C33 n-alkanes became progressively lower in samples closer to the mouth of estuary. δ13C signatures of C19{\textendash}C31 n-alkanes ranged from - 37.1 to - 29.3{\textperthousand} and in general became more depleted with increasing carbon number. Δ14C values for C21 (- 945 to - 738{\textperthousand}) were significantly more depleted compared to C29 (- 591 to - 65{\textperthousand}) and C31 (- 382 to - 96{\textperthousand}), pointing to a much higher component of fossil (i.e., 14C-free) carbon in the shorter homologue. The radiocarbon contents for these three n-alkanes decreased toward the North Sea, which in conjunction with an up to 4{\textperthousand} seaward 13C-enrichment in C29 and C31 and seaward decreases in CPI and ACL pointed to petrogenic hydrocarbon contamination in lower estuarine sediments. Independent 13C and 14C mass balances used to calculate the relative proportions of modern (i.e., plant wax) and fossil (i.e., petrogenic) n-alkanes yielded similar results and demonstrated that mixing with marine-derived organic matter (OM) or microbial degradation during estuarine transport led to a seaward decline in modern, longer-chain homologues, resulting in an increasingly larger fossil carbon contribution toward the mouth of estuary. The ability to clearly distinguish anthropogenic from natural inputs suggests that compound-specific radiocarbon analysis can successfully delineate the age of terrigenous OM delivered to the coastal zone even near historically polluted systems such as the Tyne.},
	issn = {0304-4203},
	doi = {10.1016/j.marchem.2011.06.002},
	author = {Ahad, Jason M. E. and Ganeshram, Raja S. and Bryant, Charlotte L. and Cisneros-Dozal, Luz M. and Ascough, Philippa L. and Fallick, Anthony E. and Slater, Greg F.}
}
@article { ISI:000279304700045,
	title = {Assessing Microbial Uptake of Petroleum Hydrocarbons in Groundwater Systems Using Natural Abundance Radiocarbon},
	journal = {ENVIRONMENTAL SCIENCE \& TECHNOLOGY},
	volume = {44},
	number = {{13}},
	year = {2010},
	month = {JUL 1},
	pages = {5092-5097},
	type = {Article},
	abstract = {Carbon sources utilized by the active microbial communities in shallow groundwater systems underlying three petroleum service stations were characterized using natural abundance radiocarbon ((14)C). Total organic carbon (TOC) Delta(14)C values ranged from -314 to -972 parts per thousand and petroleum-extracted residues (EXT-RES) ranged from -293 to -971 parts per thousand. Phospholipid fatty acids (PLFAs)-biomarkers for active microbial populations-ranged from -405 to -885 parts per thousand and a comparison of these values with potential carbon sources pointed to significant microbial assimilation of (14)C-free fossil carbon. The most (14)C depleted PLFAs 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(14)C values of PLFAs were generally similar to or more enriched than all other carbon in the system indicating microbial utilization of a more (14)C-enriched carbon source and no resolvable evidence for microbial incorporation of petroleum-derived 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).},
	issn = {0013-936X},
	doi = {10.1021/es100080c},
	author = {Ahad, Jason M. E. and Burns, Leanne and Mancini, Silvia and Slater, Greg F.}
}
