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

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 (Σ ₁₆ PAHs) in the surface sediments (representing modern times or at least younger than the last decade) ranged from 71 to 5672 ng g ^-1 . Σ ₁₆ PAHs 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 Σ ₁₆ PAH 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.
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