SIZE DISTRIBUTIONS OF TRACE-METALS IN THE LOS-ANGELES ATMOSPHERE

Particle size distributions of Fe, Pb, Mn, Zn, Cu and Ni were measured at two locations in the Los Angeles are during the winter and summer of 1989 using a cascade impactor. Measures were taken to minimize particle bounce and elemental analysis was performed by X-ray fluorescence. Measured Fe size distributions were consistent, with suspended dust being the major source. Pb distributions were observed to be multimodal with modes due to automotive emissions, particle growth and suspended dust. The importance of suspended dust was investigated using Fe as tracer and suspended dust ratios of Fe to Pb and other metals. Mn distributions were observed to be similar to those of Pb with automotive emissions and suspended dust being important sources. Particle size distributions of Zn, Cu and Ni showed significant amounts of these metals to be present in particles less than 1 mum in diameter, indicating anthropogenic sources. Suspended dust was found to be an important source of Zn, but not of Cu or Ni, in particles with diameters greater than 2 mum.