[Transport Characteristics of PAN and O 3 in the Lower Atmosphere of the Boundary Layer in Tianjin in Summer].

The volume concentration of peroxyacetyl nitrate (PAN) and O ₃ in the atmosphere were measured at the Tianjin Meteorological Tower in summer 2017 by using the online instrument with meteorological parameters and back trajectory analysis to analyze the delivery characteristics of PAN and O ₃ . The average volume concentrations of PAN and O ₃ during the observational period are (0.73±0.56)×10 ^-9 and (53±25)×10 ^-9 , respectively. The hourly maximum concentrations of PAN and O ₃ are 3.49×10 ^-9 and 137×10 ^-9 . The volume concentrations of PAN and O ₃ show pronounced diurnal profiles, which are both characterized by much higher values at daytime than at nighttime. In addition, the correlation coefficient between PAN and O ₃ at daytime ( R ² =0.52) is notably higher than that at nighttime ( R ² =0.21). The air masses originating from the south show the highest volume concentration of PAN and O ₃ , with the lowest volume concentration originating from the east. The wind rose plot and cluster analysis of the back trajectories show that the highest concentration of pollutants mainly originates in the southwest. The air massess originating from the east and circulating through the Bohai Sea and coastal areas of the Hebei and Liaoning provinces show the lowest volume concentrations of PAN and O ₃ . The transportation within the boundary layer plays an important role in the concentration distribution of PAN and O ₃ .