PARENT SESSION
PW16 - Atmopheric Fate Processes
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P892) Estimating the Contribution of Various Processes to the Global Loss of PCBs.

Wania, Frank¹, Daly, Gillian^*,1, ¹ University of Toronto at Scarborough, Toronto, Ontario, Canada

ABSTRACT- A series of theoretical and semi-empirical approaches, including the zonally averaged global fate and transport model Globo-POP, were used to estimate the rate of loss of selected PCB congeners from the global environment, and the relative contribution of atmospheric degradation and transfer to the deep sea to this loss. The atmospheric fate of PCBs is highly dependent on the OH radical concentration, temperature and the latter^,s influence on the gas/particle partitioning equilibrium. The PCB loss was found to be very congener specific. Atmospheric reaction with the OH radical is the major loss process for the lighter and intermediate PCB congeners, whereas particle-bound transfer to the deep sea dominates the loss of the congeners with a large number of chlorine substituents. As concentrations in air and sea water decline more rapidly than in the terrestrial environment, other loss processes such as degradation in soils are gaining in relative importance with time. Estimated life times of the PCBs in the global environment are on the order of decades, with significant differences between congeners. Research needs are identified that would allow improvements of these estimates.

Key words: polychlorinated biphenyls (PCBs), atmospheric degradation, global loss, deep sea