Chlorine levels and species in fine and size resolved atmospheric particles by X-ray absorption near-edge structure spectroscopy analysis in Beijing, China.

An understanding of the species of chlorine is crucial in the metropolis-Beijing, which is suffering serious haze pollution with high frequency. Particulate Matters (PMs) with five different sizes were collected in Beijing from July 2009 to March 2016, and characterized non-destructively by X-ray absorption near edge structure spectroscopy. PM<0.2, PM0.2-0.5 and PM>2.5 contributed for the major PMs mass in spring and summer, PM0.5-1.0 and PM1.0-2.5 contributed for the major PMs mass in autumn and winter. The concentrations of the three chlorine species were in the order of inorganic chlorine (Clinorg) > aliphatic chlorine (Clali) > aromatic chlorine (Claro), indicating that Clinorg constituted the primary chlorine fraction and less toxic Clali constituted the primary total organic chlorine (Clali + Claro, abbreviated as Clorg) in the PMs in Beijing. In addition, these three chlorine species exhibited identical seasonal variation in PM2.5: winter > autumn > spring > summer. Wet precipitation is an important factor to result in the lower mass concentrations of these three chlorine species in summer. The temporal variations of both size resolved PM mass concentrations and chlorine species concentrations suggested that the air pollution prevention and control in Beijing has just won initial success.