Fluxes of semivolatile organochlorine compounds in Bow Lake, a high-altitude, glacier-fed, subalpine lake in the Canadian Rocky Mountains

The fluxes of several organochlorine compounds (OCs) to and from a high-alt itude lake were calculated to determine the relative contributions of rainf all, snowfall, runoff, gas absorption and volatilization, sedimentation, an d outflow. Runoff inputs, particularly from a glaciated catchment, and gas absorption were major sources of many OCs. Losses by volatilization, outflo w, and sedimentation were also important transport pathways for most OCs. W e observed a net deposition of hexachlorocyclohexanes (HCHs) and DDT to Bow Lake by gas exchange, whereas hexachlorobenzene, chlordanes, and most poly chlorinated biphenyls were seen to volatilize to the air. The insecticide l indane (gamma HCH), widely applied across Canada as a seed dressing in earl y spring, was absorbed by Bow Lake in early summer but gradually equilibrat ed with water as the summer progressed. This was the result of lower concen trations of gamma HCH in air and rising air temperatures in late summer. Re sults indicate that glacially derived tributary inputs are dominant sources of persistent organic pollutants to these glacier-fed mountain lakes and c orroborates recent evidence of OC contamination in glacially derived aquati c systems.