Pre- and post-industrial levels of polycyclic aromatic hydrocarbons in sediments from the Estuary and Gulf of St. Lawrence (eastern Canada)

Abstract

The concentrations of 23 polycyclic aromatic hydrocarbons (PAHs; 16 parent PAHs and 7 alkyl-PAHs) were determined in 45 surface sediment and 7 basal sediment box core samples retrieved from the Estuary and Gulf of St. Lawrence in eastern Canada. The concentration sums of 16 priority PAHs (Σ₁₆PAHs) in the surface sediments (representing modern times or at least younger than the last decade) ranged from 71 to 5672 ng g^-1. Σ₁₆PAHs in the basal sediments ranged from 93 to 172 ng g^-1 among the pre-industrial samples (pre-1900 common era or CE) and from 1216 to 1621 ng g^-1 among the early post-industrial samples (~1930s and ~1940s CE). The highest Σ₁₆PAH values occurred in samples retrieved from the Baie-Comeau-Matane area, an area affected by intense industrial anthropogenic activities. Source-diagnostic PAH ratios suggest a predominance of pyrogenic sources via atmospheric deposition, with a minor contribution of petrogenic seabed pockmark sources. The PAH concentrations in the sediments from the study areas reveal low ecological risks to benthic or other organisms living near the water-sediment interface.

Keywords: Baseline; Polycyclic aromatic hydrocarbons; Risk assessment; Sediments; Spatial distribution; St. Lawrence estuary.