The deposition of trace metal-containing particles in the Los Angeles Area

Measurements were made of deposition from the free atmosphere of lead, zinc and cadmium on flat teflon plates. To determine the mechanisms of deposition, simultaneous measurements were made of the airborne size distributions of these metals by isokinetic sampling with a cascade impactor. Measurements of the airborne mass of lead, zinc and cadmium indicated 17%, 32% and 37% in the size range greater than 10 μm (aerodynamic diameter) respectively. Calculations based on these data showed about 70% of the total mass deposition for each metal was due to sedimentation of these large particles. The bulk of the airborne mass of these metals, in particles much smaller than 10 μm, played only a minor role in the deposition process.