Mass Budget of Perfluorooctane Surfactants in Lake Ontario

Perfluorooctane surfactants have been reported in biota, water, and air samples worldwide. Despite these reports, the main environmental sources of these compounds remain undefined. To address this gap in knowledge, an annual lake-wide mass budget of eight perfluorooctane surfactants was developed for Lake Ontario. To determine the atmospheric contribution to the mass budget, over-the-lake gas-phase air concentrations for N-EtFOSE and N-EtFOSA and particulate-phase air concentrations for PFOS in any air sample are reported for the first time, with mean concentrations when present of 0.5 ± 0.32 (N-EtFOSE gas-phase), 1.1 ± 0.9 (N-EtFOSA gas-phase), and 6.4 ± 3.3 (PFOS particulate-phase) pg/m³. The mass budget finds inflow from Lake Erie (14 361 ± 4489 kg Σperfluorooctane surfactants) and wastewater discharge (1762 ± 2697 kg Σperfluorooctane surfactants) to be the major sources, while outflow through the St. Lawrence River is the dominant loss mechanism (22 727 ± 7060 kg/year Σperfluorooctane surfactants). Using the mass budget data, the steady state and measured mean concentrations in the lake water are the same at the 95% confidence level.