Legacy of legacies: Chlorinated naphthalenes in Lake Trout, Walleye, Herring Gull eggs and sediments from the Laurentian Great Lakes indicate possible resuspension during contaminated sediment remediation

Abstract

Polychlorinated naphthalenes (PCNs) are legacy contaminants, produced primarily as flame retardants and dielectrics until phased-out in Europe and North America in the 1970s. Spatial and temporal trends (1979–2013) of PCN concentrations were studied in whole fish and herring gull eggs throughout the Great Lakes and St. Lawrence River, whereas sediments were analyzed for 2011–2013 only. For both fish and gull eggs, concentrations of PCNs were highest in western Lake Erie (7660 & 3020pg/gww respectively), and declined downstream to St. Lawrence River (range: 34–2370pg/gww). For sediments, concentrations were highest in suspended sediments from the Detroit River (264,000pg/g), and were lower in surficial sediments downstream to the St. Lawrence River (range=440–19,300pg/g). PCNs declined at all sites from ~1980 to 1995, but in Lake Erie concentrations of PCNs increased in gulls fish from 1995 until 2005. The resurgence in PCNs in biota corresponded to the timing of remedial dredging of sediment highly contaminated with PCNs in the Detroit River, whose effects appear to manifest themselves downstream to Lake Ontario. Congener profiles of PCNs differed between Lake Erie and Lake Ontario until post-dredging, where PCN profiles of fish in both lakes became increasingly more similar. PCNs in gull eggs were mostly hepta-PCNs, whereas fish had higher concentrations of lower chlorinated PCNs. Patterns of PCNs in gulls and fish appear to be influenced by differences in not only routes of exposure and differential metabolic ability, but also resuspension of PCN contaminated sediments.