Insights into the origin of perylene from isotopic analyses of sediments from Saanich Inlet, British Columbia

Perylene is an abundant and common polycyclic aromatic hydrocarbon in sedimentary settings, yet its origin remains puzzling. We have investigated the relation of perylene to the amount and type of organic matter in the sediments of Saanich Inlet, a coastal marine anoxic basin. Organic matter is predominantly marine in origin, but the proportions of marine and land-derived components have varied. Perylene concentrations generally increase with sediment depth, relative to TOC, which indicates continued formation of this compound by microbially mediated diagenesis. Perylene δ13C values range between −27.7 and −23.6‰, whereas TOC δ13C values vary narrowly from −21.7 to −21.2‰ over the same sediment depth interval. The variation in isotopic difference suggests that perylene originates from more than one precursor material, both aquatic and continental organic matter, different microbial processes, or some combination of these possibilities.