Particle size distribution and anion content at a traffic site in Sha-Lu, Taiwan

Abstract

Ambient air particle concentrations were sampled by two total suspended particle (TSP) samplers, PM 10/PM 2.5 specific sampler and micro-orifice uniform deposit impactor (MOUDI) during July–October 2000 at a traffic sampling site in central Taiwan. The average TSP concentration (194 μg/m 3) was about a factor of two higher than that of the fraction <2.5 μm (93.2 μg/m 3). The mean level of the fraction <10 μm collected by MOUDI (93.2 μg/m 3) was about 1 1 2 times higher than that of the size class <2.5 μm (43.8 μg/m 3). Furthermore, this fraction showed a certain correlation with the TSP concentration. The particle size distribution was bimodal in the ambient air at the traffic site. The major peaks appear at particle diameters between 0.56–1.0 and 3.2–5.6 μm. The percentages of anions contained in TSP were 0.24% F −, 13.7% Cl −, 0.52% Br −, 12.0% NO 3 −, 18.9% NO 2 −, and 54.6% SO 4 2−. The Cl −, NO 2 −, and NO 3 − size distributions were all unimodal and the major peaks appeared at 3.2–5.6 μm. The SO 4 2− size distribution was bimodal, with major peaks at 0.32–0.56 and 3.2–5.6.