Characteristics of particles sampled in southern Taiwan during the Asian dust storm periods in 2000 and 2001

Intensive field samplings followed by laboratory measurements were performed to characterize the particles collected at urban and rural sites in southern Taiwan during the Asian dust storm (ADS) periods in 2000 and 2001. These particles were size-resolvedly (cut sizes of eight-and ten-stages) sampled by two side-by-side micro-orifice uniform-deposited impactors (MOUDI). Results show that the concentrations of PM2.5, PM2.5–10 and PM10 increased during the ADS periods and these PM10 concentrations, >150 μg m−3, were roughly 2 to 3 times higher than the average PM10 concentrations measured in non-ADS periods. The concentrations of particle-bearing water-soluble ions including four crust-related species (Ca2+, Mg2+, Na+, and K+), three secondary aerosol-associated species (SO42−, NO3−, and NH4+), and one sea-connected species (Cl−) increased and their size distributions changed during the ADS periods in comparison with those during non-ADS periods, implying that they were partially from foreign sources. This supports the increasing health concerns for ADS. The SO42− had a major mode in fine size range (0.56–1.0 μm) while the Ca2+ obtained a major mode in coarse size (3.2–5.6 μm) at both sites.