Chemcal state of Fe in fine and ultrafine particles in the urban atmosphere

Abstract

The present study has demonstrated the multi-scale investigation of Fe species in urban particulate matter (PM). The PM samples were collected by a cascade impactor and high volume air sampler at Fukuoka, Japan. According to XANES analysis Fe is present mainly as Fe(III). SEM-EDX point analysis has shown that >1 µm particles containing Fe have high concentrations of Si and Al, and <1 µm particles containing high S and low Si concentrations. TEM analysis reveals that Fe-bearing particles <1 µm are spherical maghemite nanocrystallites, which implies the presence of abundant active site for reaction on the surface. A presence of various concentrations of Mn in the maghemite is anticipated to promote oxidizing reaction of co-existing heavy metals such as chromium, resulting in higher toxicity.