AN INVESTIGATION OF SIZE-DEPENDENT CONCENTRATION OF TRACE ELEMENTS IN AEROSOLS EMITTED FROM THE OIL-FIRED HEATING PLANTS

摘要

Aerosols emitted from two oil-fired heating plants were aerodynamically separated into eight size groups and were analyzed using the proton-induced X-ray emission (PIXE) technique. It was found that Zn, Mo, Ag, and Pb, and (to a lesser extent) Cd, have a tendency to concentrate preferentially on the smaller aerosols. All of these elements, in certain chemical forms, are known to be toxic. Zinc and molybdenum, although present in low concentrations in the parent fuels, show the strongest tendencies to be concentrated in finer aerosols. Selenium, previously reported to show a very strong tendency to concentrate in finer fly ash from coal-fired power plants, shows little preference for surface residence. Vanadium, which occurs in significant concentration in the oil fuels for both plants, also shows little preference for surface concentra-tion. Even though the absolute concentrations of the toxic elements involved are well below the safety levels established by the National Institute for Occupational Safety and Health (NIOSH), it would be advisable to raise the heights of the heating-plant exhaust chimneys well above the neighborhood buildings to insure more efficient aerosol dispersal.