Molecular characterization and carbon isotope ratio analysis of marine hydrocarbons in sediments from Trinity Bay, Newfoundland

摘要

To better understand the cycling of carbon in a cold ocean coastal environment, molecular distributions and stable carbon isotopic compositions of various aliphatic and poly cyclic aromatic hydrocarbons (PAH) have been determined for marine sediments of Trinity Bay, Newfoundland. Sediments were collected in the form of grab and core samples from the Northwest and Southwest Arms, extending into Trinity Bay. High levels of sulfur in the sediments required an exhaustive procedure for the complete removal sulfur interferences in chromatography. Separation of aliphatic hydrocarbons from PAH was accomplished through alumina/silica column chromatography. The combination of molecular characterization by gas chromatography mass spectrometry (GCMS) and isotopic fingerprinting through gas chromatography combustionisotope ratio mass spectrometry (GC/CIRMS) enabled the distinction between marine, terrestrial. and anthropogenic sources of some of the hydrocarbons. -- Aliphatic hydrocarbon results indicate large biogenic influences from marine sources, with particular evidence being the abundance of C25 highly branched isoprenoid alkenes. It is believed that these compounds are produced by certain diatoms immediately preceding the spring diatom bloom. The molecular distributions and carbon isotopic compositions of /z-alkanes can be attributed to contributions from mari The concentration levels of PAH in most sediment samples are extremely low, revealing that the marine environment in this area is relatively pristine. The distribution patterns and isotopic results of PAH present indicate source inputs from combustion, most likely due to wood-burning, with minor contributions from petroleum sources.ne and terrestrial sources with slight mixing of anthropogenic petroleum sources.