Sediment Record and Atmospheric Deposition of Brominated Flame Retardants and Organochlorine Compounds in Lake Thun, Switzerland: Lessons from the Past and Evaluation of the Present

Chronology of brominated fame retardants (BFRs), a class of currently widely used chemicals, was compared to the respective historical profiles of legacy organochlorine compounds in three dated sediment cores from a prealpine lake (Lake Thun, Switzerland). Concentrations of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) started to increase in the 1980s−1990s. In the more recent sediment layers, PBDEs still had steady or increasing concentrations, whereas for HBCDs one sediment core revealed a decreasing trend. In contrast to the contemporary BFRs, concentrations of legacy organochlorines, such as polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and dichlorodiphenyl trichloroethane (DDT), peaked in deeper sediment layers deposited some decades ago. Measurements of atmospheric deposition and evaluation of wastewater discharges point toward deposition on the lake surface as a relevant input pathway and wastewater as a minor source of POPs in Lake Thun. The ef...