Characteristics of soluble Fe in atmospheric particles during winter and summer in an urban mixed-use area in Xi’an

Soluble Fe influenced on the Biogeochemical cycle and the secondary aerosol formation. In this study, diurnal, seasonal variation and size distribution of soluble Fe in atmospheric aerosols were investigated in an urban mixed-use area site in Xi’an. In this paper, we have carried out observational studies of atmospheric particulates with different particle sizes in an urban mixed-use area site of Xi’an in winter and summer. By using an improved liquid waveguide capillary cell (LWCC) to determine the concentration of soluble iron extracted from the acidic medium in the particulates, and to explore its seasonal changes, day and night distribution and particle size distribution characteristics. The results show that the concentration of soluble Fe(Ⅱ) in winter was higher than that in summer, while for summer soluble Fe(Ⅲ) level was higher than that in winter. The mass concentration and solubility of soluble Fe(Ⅱ) and total soluble Fe in PM_2.5 during daytime were found to be greater than those during nighttime. However, Fe(Ⅲ) showed no obvious difference between day and night. The size distribution results showed more active conversion between Fe(Ⅱ) and Fe(Ⅲ) at smaller particle size, which indicated that the conversion rate of Fe(Ⅱ) and Fe(Ⅲ) in PM_2.5was higher than those in PM_2.5-10 and PM₁₀.