Measurements of acidic sulfates and trace metals in fine and ultrafine ambient particulate matter: Size distribution, number concentration and source region.

摘要

Epidemiological studies have demonstrated a coherent association between ambient particulate matter (PM) and adverse health effects. Exposure studies strongly suggested that the fine fraction of ambient PM and its associated acidic sulfates and trace metals are closely correlated with the adverse health effects observed. In addition, evidence is accumulating that the number concentration of acidic particles is also a significant factor affecting lung toxicity.; The goals of this research were: (1) measure the size distribution of acid and trace metals within the fine fraction of the ambient aerosol in air masses originating from different source regions; (2) measure the number concentration of acidic particles within the ultrafine fraction of the ambient aerosol; and (3) examine the effect of the source region on the aerosol composition.; Results from 30 sampling sessions demonstrated that the midpoint diameter of the largest mass fractions of sulfate, acid and ammonium was 0.38 μm. Higher concentrations of these ions were observed during warm months than during cold months of the year. Although most of the acid and sulfate mass was measured in the 0.38 μm midpoint diameter, particles with diameters 0.09 μm are more acidic.; Results from iron film detectors show that during warm months 13.5% of the total number of ultrafine particles are acidic whereas only 6.1% are acidic during the cold months.; The maximum concentration of metals that are associated with high temperature combustion sources was measured at the 0.4 μm midpoint diameter. The particle size distribution profiles of these metals are about the same as sulfate, hydrogen, and ammonium. The concentration profiles of the remaining metals were different and unique to the individual elements.; No apparent source region effect was noticed in terms of the size distribution profile of the ions. However, samples collected from air masses that originated from, or passed over, high sulfur dioxide emission areas demonstrated higher concentrations of the different ions.