Deposition and evaporation of polychlorobiphenyl congeners to and from Siskiwit Lake, Isle Royale, Lake Superior

Abstract

The relative importance of polychlorobiphenyl (PCB) transport into and out of lakes was studied by constructing a mass balance of PCB congeners in Siskiwit Lake, a remote lake in the Isle Royale National Park in Lake Superior. Measurements of winter and summer air, rain, snow, water, and sediments were obtained over several months and used to determine PCB fluxes to and from the lake, assuming steady-state conditions over 1 years. By solving the mass balance equation under selected conditions, we estimated the deposition velocity and the overall liquid water-to-air mass transfer coefficient for PCBs to be 0.16 cm/s and 0.1 m/day, respectively. Wet deposition was generally 3 times as great as dry deposition and was dominated by particle washout. Rain was a more important removal process than snow. Removal from the lake by volatilization was more important than sedimentation for most congeners.