Ambient peroxyacyl nitrate concentration and regional transportation in Beijing

Peroxyacyl nitrates (PANs) are photochemical secondary pollutants that play a key role in the atmospheric chemistry of the troposphere. However, there have been few studies on the long-term variation and inter-regional transport of PANs. In this study, summertime ambient PAN concentrations were monitored at urban and rural sites in Beijing and Hebei, China, between 2006 and 2014. In Beijing, the peak concentrations of PAN and PPN were in the range of 6–17 ppbv and 0.6–2.2 ppbv, respectively, higher than concentrations in other provinces. The nitrogen oxide (NO_x) concentration decreased at a rate of 1.7 ppbv/yr (∼4% yr⁻¹), and the PAN concentration decreased at a rate of 0.03 ppbv/yr (∼3% yr⁻¹), while the ozone (O₃) concentration increased at a rate of 1.5 ppbv/yr (∼4% yr⁻¹). Trajectory clustering analyses showed that high concentrations of PAN were mainly affected by low air masses transported medium/short distances from South Beijing, and the potential source contribution function maps showed that the likely pollution source area was concentrated in the southern region of Beijing. These findings provide a theoretical basis for pollution control in this region.