Alkane and PAH depositional history, sources and fluxes in sediments from the Fraser River Basin and Strait of Georgia, Canada

Hydrocarbon data for dated sediment cores from Fraser Basin lakes and the Strait of Georgia in Canada reveal a pristine pre-industrial background that remains unaltered in modern sediments far from human activities. These pristine sediments contain polycyclic aromatic hydrocarbons (PAHs) from combustion (natural forest and prairie fires), and alkanes and PAHs from weathering of soils containing vascular plant remains and natural petroleum hydrocarbons, and algal production. At other locations examined, however, these natural loadings have been augmented over the past century by hydrocarbons from petroleum, the combustion of liquid (oil, gasoline) and solid (coal, wood) fuels and from processing of wood either directly from disturbed land and slash burning or indirectly through pulp mill effluent. Although contamination is clearest where there are nearby human activities, alkane profiles, PAH distributions and alkane unresolved complex mixtures suggest a widespread contamination from petroleum. Combustion products from human activities can also be identified, although with less source specificity than with the petroleum products. Regional emissions from anthropogenic combustion processes appear to support modern PAH increases within the Fraser River Basin and there is little evidence of inputs from global emissions. Principal components analysis using the new centred log ratio normalisation procedure to normalise data discriminates well between PAHs entering lakes from runoff or the atmosphere and PAH formed diagenetically within lake sediments, as well as between combustion and petroleum PAHs. (C) 2003 Elsevier Ltd. All rights reserved.