Evidence for Atmospheric Transport and Deposition of Polychlorinated Biphenyls to the Lake Tahoe Basin, California−Nevada

PCB congener concentrations in air, water, fish, and snow were determined in the Lake Tahoe basin and in the water and fish of an adjacent but more remote rural comparison lake, Marlette Lake, to examine whether atmospheric transport and deposition are primary sources of contamination to this alpine region of the Sierra Nevada Mountains. Profiles of 97 congeners analyzed by capillary GC−ECD from surface waters of Lake Tahoe and Marlette Lake were closely matched, with total dissolved PCB (t-PCB) concentrations of 0.37 ng/L in Lake Tahoe and 0.67 ng/L in Marlette Lake. Gas-phase t-PCB concentra tions measured in air samples from the Lake Tahoe basin averaged 72 pg/m 3, and t-PCB (dissolved and particulate) concentrations in snow were 4.8−5.1 ng/L. Rainbow trout from Marlette Lake and lake trout from Lake Tahoe had similar distributions of congeners, with t-PCB tissue levels varying from 3 to 14 ng/g wet weight. The finding of PCBs in all sampled compartments, particularly snow and air, and the similar pattern of congeners in surface waters and in fish from Lake Tahoe and Marlette Lake indicate an atmospheric source of contamination.