Characterization of peroxyacetyl nitrate (PAN) under different PM2.5 concentration in wintertime at a North China rural site

As a secondary pollutant of photochemical pollution, peroxyacetyl nitrate (PAN) has attracted a close attention. A four-month campaign was conducted at a rural site in North China Plain (NCP) including the measurement of PAN, O-3 , NOx, PM2.5, oxygenated volatile organic compounds (OVOCs), photolysis rate constants of NO2 and O-3 and meteorological parameters to investigate the wintertime characterization of photochemistry from November 2018 to February 2019. The results showed that the maximum and mean values of PAN were 4.38 and 0.93 +/- 0.67 ppbv during the campaign, respectively. The PAN under different PM2.5 concentrations from below 75 mu g/m(3) up to 250 mu g/m(3), showed different diurnal variation and formation rate. In the PM2.5 concentration range of above 250 mu g/m(3), PAN had the largest daily mean value of 0.64 ppbv and the fastest production rate of 0.33 ppbv/hr. From the perspective of PAN's production mechanism, the light intensity and precursors concentrations under different PM2.5 pollution levels indicated that there were sufficient light intensity and high volatile organic compounds (VOCs) and NOx precursors concentration even under severe pollution level to generate a large amount of PAN. Moreover, the bimodal staggering phenomenon of PAN and PM2.5 provided a basis that PAN might aggravate haze through secondary organic aerosols (SOA) formation. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study investigated the wintertime characteristics of photochemistry in a rural area of North China Plain. It found that the concentration of peroxyacetyl nitrate (PAN), a secondary pollutant of photochemical pollution, showed different diurnal variation and formation rate under different PM2.5 concentrations. The results also indicated that even under severe pollution levels, there were sufficient light intensity and precursor concentrations to generate a large amount of PAN, exacerbating haze formation.