PARENT SESSION
15 - Atmospheric Transport and Global Pollution
8:00 AM to 6:30 PM, Monday, 13 May 2002
Exhibition Area

(15-40) Latitudinal trends of legacy POPs and potential new POPs in North America inferred from dated sediment cores and lake waters.

Muir, Derek^*,1, Backus, Sean¹, Douglas, Marianne², Pienitz, Reinhard³, Scott, Brian¹, Spencer, Christine¹, Teixeira, Camilla¹, Vincent, Warwick⁴, Wania, Frank⁵, Yang, Fan¹, ¹ National Water Research Institute, Environment Canada, Burlington, ON, Canada² Dept. of Geology, University of Toronto, Toronto, ON, Canada³ Dépt. de géographie, Université Laval, Québec, PQ, Canada⁴ Dépt. de biologie, Université Laval, Québec, PQ, Canada⁵ Division of Physical Sciences, University of Toronto at Scarborough, Toronto, ON, Canada

ABSTRACT- Sediments cores and lake surface waters were collected over a 40 degree latitude (4400 km) north-south transect from southeastern Ontario and northeastern USA to the northern limit of North America (northern Ellesmere Island), as well as on a longitudinal transect in Canada from northwestern Ontario to Labrador in order to study the current and past deposition of POPs and current use pesticides. The lakes selected were, for the most part, undisturbed, and in many cases uninhabited, so that the major or sole pathway for inputs of contaminants would be from atmospheric deposition to the water surface or the watershed. Analysis of lake water showed significant levels of current use pesticides atrazine, metolachlor, dacthal, lindane, and endosulfan, in the epilimnion reflecting summer time inputs via precipation and gas exchange. Analysis of lake waters for C3-C8-perfluorocarboxylates (e.g. perfluorooctanoic acid) showed low ng/L concentrations in several remote Arctic and temperate lakes indicating widespread dispersal of these persistent compounds or their precursors. Fluxes (ng/m2 yr) of total PCBs and total DDT in sediment cores (concentration, ng/g * sedimentation rate, g/m2 yr corrected for particle focussing) declined significantly with latitude. For PCBs, most of this decline was due to penta- to heptachloro biphenyls. Mono-di and trichlorophenyls showed no latitudinal trend. Decabromo diphenyl ether was detected in sediment cores from isolated temperate lakes and at low levels in three cores from Arctic lakes at 75 - 80 ^oN indicating environmental dispersal, of this very non-volatile compound, from urban source areas.

Key words: POPs, sediments, pesticides, lakes