Ground-based on-line measurements of peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) in the Pearl River Delta, China

Aiming at understanding the regional O-3 problem and the impacts of city to rural areas, ambient peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) were measured by an on-line instrument at a back garden site (BGS), and a receptor site for urban plume from Guangzhou city. The highest mixing ratios for PAN and PPN were 3.9 and 0.7 ppbv, respectively. PAN and PPN had a similar diurnal pattern as that of O-3. As revealed by the slope of the linear regression line between PPN and PAN, anthropogenic volatile organic compounds (AVOCs) dominated photochemical O-3 production most of the time. From the correlation between PAN and O-3, the regional background level of O-3 was derived to be 28 +/- 15 ppbv. Two night-time plumes containing elevated PAN and O-3 were observed, and the backward-trajectory analysis supported the transport of urban plume from Guangzhou city. Based on the temporal variation of PPN/PAN, two day-time episodes were also selected to discuss the influence from Guangzhou.