Different clean-up methods to determine isotopic composition of n-alkanes were tested. Sources of organic matter in Guanabara Bay were re-examined through the δ13C of individual n-alkanes in surface sediment samples. The n-alkanes were efficiently isolated without significant losses of the compounds of interest. The δ13C of n-alkanes (n-C17 to n-C35) ranged between –34.0 and –26.4. More depleted δ13C values associated to higher carbon preference index (CPI > 4) suggest prevalence of biogenic n-alkanes from terrestrial origin in the inner stations influenced by inputs from mangrove areas. Small isotopic differences between odd and even-numbered chains and 13C-enrichment in long-chain homologues indicate a petrogenic hydrocarbons contribution. Higher concentrations of short-chain compounds associated to a more 13C-enriched total organic carbon (TOC) were found near the most intense sewage discharges. Results show that δ13C of n-alkanes can be applied to a highly degraded system as the Guanabara Bay and help improve the characterization of the organic matter.
CITATION STYLE
Ceccopieri, M., Scofield, A. L., Almeida, L., & Wagener, A. L. R. (2018). Compound-specific δ13C of N-Alkanes: Clean-up methods appraisal and application to recent sediments of a highly contaminated bay. Journal of the Brazilian Chemical Society, 29(11), 2363–2377. https://doi.org/10.21577/0103-5053.20180114
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