Lake-wide distribution and depositional history of current- and past-use persistent organic pollutants in Lake Simcoe, Ontario, Canada

The surface sediment concentrations of past-use persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated napthalenes (PCNs), and organochlorine pesticides (OCPs), and current-use chemicals such as the polybrominated diphenylethers (PBDEs) and perfluorinated chemicals (PFCs), were determined in sediments from 22 sites across Lake Simcoe. PFCs were also measured in surface waters. Maximum concentrations of historical POPs, which included PAHs (5400 ng/g), PCBs (36 ng/g) and PCNs (800 pg/g), occurred in Kempenfelt Bay, indicative of past inputs from sources in the Barrie area. This contrasted with the PFCs which had maximum sediment concentrations (2.0 ng/g perfluorooctane sulfonate (PFOS) and 1.4 ng/g perfluorooctanoic acid (PFOA)) in the Main Basin of Lake Simcoe. The distributions of many of the chemicals included in the study were relatively uniform across Lake Simcoe outside of Kempenfelt Bay, indicating contributions by atmospheric pathways from regional air masses that cover large urban and industrial areas. This is further supported by the similarity of sediment concentrations of PBDEs and PAHs and water concentrations of PFCs between Lake Simcoe and the lower Great Lakes, Lake Erie and Lake Ontario. PBDE concentrations were more variable within basins than the other compounds, and contributions from the urban Barrie area were apparent. A sediment core collected from Kempenfelt Bay showed increasing concentrations to current times for PBDEs and PFCs, while historical inputs of PCBs, PAHs, polychlorinated dibenzo-p-dioxins, and PCNs peaked in the 1950s (PAHs) and late 1960s (chlorinated contaminants), generally consistent with usage and emissions history.

Research highlights
► Lake Simcoe sediments contain past- and current-use POPs.
► Relatively uniform distributions indicate influence of atmospheric pathways.
► Current-use POPs (PBDEs and PFCs) continue to increase in sediment cores.