Compound-Specific Radiocarbon Analyses of Phospholipid Fatty Acids and N-Alkanes in Ocean Sediments

Abstract

We report compound-specific radiocarbon analyses of organic matter in ocean sediments from the northeast Pacific Ocean. Chemical extractions and a preparative capillary gas chromatograph (PCGC) were used to isolate phospholipid fatty acids (PLFA) and n-alkanes from 3 cores collected off the coast of California, USA. Mass of samples for accelerator mass spectrometry (AMS) 14C analysis ranged from 13–100 μg C. PLFA extracted from anaerobic sediments in the Santa Barbara Basin (595 m depth) had modern Δ14C values (–20 to +54‰), indicating bacterial utilization of surface-produced, post-bomb organic matter. Lower Δ14C values were obtained for n-alkanes and PLFA from coast (92 m depth) and continental slope (1866 m) sediments, which reflect sources of old organic matter and bioturbation. We present a brief analysis of the blank carbon introduced to samples during chemical processing and PCGC isolation.