Characterization of major water-soluble inorganic ions in size-fractionated particulate matters in Shanghai campus ambient air

The size-fractionated inhalable particles in ambient air were collected at the top of a lab building in a university campus of Shanghai; F-, Cl-, NO3-, SO42-, and NH4+ were extracted to determine the concentration. In every size, the concentration of the five ions followed the order of SO42- > NO3- similar to NH4+ similar to Cl- > F-. Their concentrations in PM1.6 were 5-7, 1-5, 3, 1-3, and similar to0.1 mug/m(3), respectively, and occupied about 8-11%, 2-7%, similar to6%, 2-6%, and similar to0.1% of PM1.6 mass, respectively. In PM8, about 70% of each ion existed in PM1.6, while in PM3.7, 50-80% was in PM1.6. The size distributions of SO42-, NO3-, Cl-, and F- were characterized by bimodal types with fine mode peaking around 0.7 mum and coarse particle mode peaking around 3-5 mum. NH4+ showed a single fine mode peaking at 0.7 mum. Fine mode dominated the size distribution of SO42-, NO3-, and NH4+. SO42-, NO3-, Cl-, and NH4+ had a good correlation in PM1.6 between each other. But SO42- strongly correlated to NO3- at every size stage. Comparison of size-fractionated equivalent ratios between [SO42-] and [NH4+] suggested that the existing forms of SO42-, NO3-, Cl-, and NH4+ were probably (NH4)(2)SO4, NH4NO3, and NH4Cl. [SO42-]/[NO3-] ratio in fine mode was > 1, which revealed that stationary source emission was still the important contributor to fine particles. The main sources of particulate inorganic ions were also discussed. (C) 2003 Elsevier Ltd. All rights reserved.