The Correlation Between Ozone Production Efficiency (OPE) And VOCs At Shangdianzi Atmospheric Background Monitoring Station

Ozone (O3) is one of the important trace components in Earth's atmosphere. The increase of the O3 level in the troposphere has added to global warming and caused increasingly serious regional photochemical pollution. To facilitate the understanding of the complex nonlinear relationship between O3 and its precursors, some observation-based indicators have been developed; with ozone production efficiency (OPE) being one of the common indicators. In this thesis, observational studies of OPE and volatile organic compounds (VOCs) are conducted at the Shangdianzi Background Station, relationships between VOCs and OPE are discussed,and differences in pollutants concentrations and OPE values among different air parcel backward trajactories are studied.Concentrations of reactive gases were observed at Shangdianzi station in the April-September 2008 period and the corresponding OPE values were calculated. Air samples were collected at the station using stainless steel canisters and analyzed in the laboratory for VOCs. The comprehensive two-dimensional gas chromatography (GC×GC)technique was applied to the analysis of VOCs and oxygenated volatile organic compounds (OVOCs) in the carbon range of C4-C16, while the dual-capillary gas chromatography was used to analyzed VOCs in the carbon range of C2-C10. During the observation and analysis QA/QC measures were taken to ensure the data quality.The observation-based OPE results show that overall average OPE at Shangdianzi was 4.9±3.6 for the period from April to September 2008, with the values in April and July being slightly higher than those in other months. The dependence of OPE on the NOx concentration can be described using an empirical parabolic function. If the concentration of NOx is lower than 14.2 ppb, OPE increases with NOx; while if the concentration of NOx is higher than 14.2 ppb, OPE decreases with NOx. The correlation analysis indicates that the concentration of aromatics is best correlated to OPE, followed by those of biogenic VOCs and OVOCs. However, the propylene-equivalent concentration of OVOCs is best correlated to OPE.Backward trajectories of air parcel were calculated and used to characterize the influences of the air parcel trajectory on pollutants and OPE. The results show that both in the emission control period of Olympic Games in Beijing and in the period before, the OPE value was highest when relatively clean air parcels were from the northwest sector. In the April-June period about 31.9% of the trajectories were affected by the Beijing City and the corresponding OPE was 4.7±3.3, while in the July-September period about 26.1% of the trajectories were affected by the city, and the corresponding OPE was 6.6±5.5.