Chemosphere,Vol.27, No.10, pp 2047-2055, 1993 0045-6535/93 $6.00 + 0.00 Printed in Great Britain Pergamon Press Ltd. ESTIMATION OF PCC LOADINGS FROM THE ATMOSPHERE TO THE GREAT LAKES R. M. Hoff I,* , T. F. Bidleman 2, and S. J. Eisenreich3 I Atmospheric Environment Service, R. R. i, Egbert, ON, Canada L0L IN0 2 Atmospheric Environment Service, 4905 Dufferin St., Downsview, ON Canada M3H 5T4 3 Gray Freshwater Biological Research Institute, U. Minnesota, PO Box I00, Navarre MN 55392 ABSTRACT Recent measurements of the polychlorinated bornanes (camphenes; PCCs) allow the estimation of the dry deposition and wet deposition flux of these chemicals to the Great Lakes. A recent report by Eisenreich and Strachan (1992) estimates the wet flux to be 3.5 - 12.5 kg/yr to each of the five lakes and the dry deposition of particulate bound PCC to be 1.5 - 6.3 kg/yr. This paper estimates the range of fluxes to be expected from gas transfer to Lake Superior. Based on a range of assumptions of the water concentration of PCCs in the lakes, the gas flux will vary from -1.7 to 1.0 ~g m 2 mo "I (positive is a flux into the lakes). The annual loading by gas exchange is more than an order of magnitude higher than the input by wet or dry deposition and indicates that the significant air-water transfer of toxaphene congeners needs further study. INTRODUCTION One goal of the measurement of the concentrations of organic chemicals in the environment is the understanding of the processes and rates of movement of organics from one ecological compartment to another. Annex 15 of the Great Lakes Water Quality Agreement specifically tasks the Governments of Canada and the U. S. with the assessment of the loadings of organic chemicals from the atmosphere to the Great Lakes. A number of estimates of such loadings have been undertaken in the past, the most widely quoted study being one taken under the International Joint Commission auspices by Strachan and Eisenreich (1988). That study provided a scientific assessment of the absolute and relative loadings of ~PCBs, ZDDT, benzo(a)pyrene (BaP) and Pb. One milestone on the Annex 15 timetable as defined in the Implementation Plan (Egar and Adamkus, 1990) for the Integrated Atmospheric Deposition Network (IADN) is the updating on a biannual basis of the loading estimates to the Great Lakes. At the end of January, 1992, a working group on atmospheric deposition of toxic chemicals met in Burlington, Ontario, Canada, under the sponsorship of the Great Lakes Protection Fund (Chicago, Illinois) and the National Water Research Institute (Burlington, Ontario), to update the estimates of loadings based on information which had arisen since 1986. This work has been published 2047