ANNUAL CYCLE OF POLYCHLORINATED-BIPHENYLS AND ORGANOHALOGEN PESTICIDES IN AIR IN SOUTHERN ONTARIO .2. ATMOSPHERIC TRANSPORT AND SOURCES

In the second of a pair of papers describing the measurements of over 90 polychlorinated biphenyl congeners and over 30 organohalogen pesticides, instances of seasonally high concentrations are analyzed in terms of meteorological transport. The seven cases of highest concentrations of the pesticide species all point to long-range transport from the south, especially the southern United States and the Caribbean. The data are also analyzed in terms of the temperature dependence of the air concentration. It is shown that the PCB concentrations, which are only weakly dependent on transport paths, are strongly dependent on temperature through the vapor pressure of the compound. A similar effect is seen in general for the organohalogens with a more strongly apparent influence of air transport path. alpha-Hexachlorocyclohexane (HCH), pentachloroanisole, and heptachlor show no temperature-concentration dependence. The results indicate that modeling predictions of the concentration of PCBs in air can be made by knowing the slope of the log (vapor pressure) vs inverse temperature curve (Antoine equation) as well as expected air concentrations of particulate matter. For other organochlorines, especially those with a more recent or current-use pattern, regional scale and long-range transport from areas with higher concentrations can be expected and further work to obtain samples in those areas is needed.