Particle size distributions of lead, bromine, and chlorine in urban-industrial aerosols

A high-volume Andersen sampler has been used to measure particle size distributions for atmospheric Pb, Br, and Cl at urban control sites and near secondary lead refineries in Toronto, Canada. Bromine and Cl were measured by instrumental neutron activation analysis, while Pb was determined both by absorption spectrophotometry and by instrumental photon activation analysis. The Pb aerosol near roadsides was predominantly submicrometer in size, whereas elevated Pb concentrations in the vicinity of the refineries were attributed mainly to increases in Pb associated with larger particles which settle more rapidly. The strong correlation between Pb and Br from automobile emissions allowed an indirect estimate of nonautomotive Pb in the atmosphere near the refineries. Chlorine, although also associated with automobile emissions, appears to be derived from several additional sources. The localized contamination of residential areas, which has resulted from refinery emissions, emphasizes the importance of particle size considerations in establishing air quality standards.