Transport of heavy chlorinated hydrocarbons in the atmosphere.

Fluxes of aerosol polychlorinated biphenyl (PCB, 54% chlorine mixture) ranging from 2 X lov9 to 9 X (average: 3 X g m-2 day-l were measured a t La Jolla, Calif., during February and October 1972. A model for mesoscale aerosol transport which treats the plume as a superposition of Gaussian-shaped puffs diffusing isotropically in the plane of the horizon was used with the assumption that deposition occurs irreversibly to compute source strength, aerosol halflife, and isopleths of deposition flux. Hourly wind velocity and daily deposition flux measurements made during a one-month period were used to calibrate the model, and a second month of data provided a check for the predictive capacity of the method. On the basis of flux measurements and model calculations, arguments are presented for most dry deposition of aerosol PCB introduced into the troposphere to occur within 100 km of the source.