Springtime soluble particles in a suburban area of Taichung in central Taiwan

Abstract

Continuous measurements of concentrations of soluble species between fine and coarse particles were made using a RP 2300 sampler to characterize springtime particulate pollutants in Shalu, a suburban area of Taichung, Taiwan. Particulate matter was closely observed from March 4 to April 2, 2006. The characteristics of ambient particulates were investigated during the winter monsoon period, the weak winter monsoon period and the non-winter monsoon period. The wind speed influenced the ratio of the mass concentration of coarse particles to that of fine particles. The ratio was high during the strong winter monsoon because the coarse particles were re-suspended by high wind speed. In contrast, the low ratio was associated with the accumulation of local anthropogenic particles in a stagnant atmosphere in the non-winter monsoon period. The increases in the concentrations of soluble SO 4 2− and NO 3 − species were associated with the long-range transport of pollutants from the Asian Continent and local urban pollution emissions, respectively. Factor analysis was performed on the measurements to determine the variances of the identified sources among the three atmospheric conditions. The deviations from the seawater Cl −/Na + ratio of 1.16 in the coarse particles indicated the notable deficit of chloride. A large amount of air pollutants was transported by airflow during a dust event: the mass concentrations of fine particles and coarse particles in a dust event were 30% and 160% higher than those in a non-dust event, respectively.