Abstract. To improve the air quality, Beijing government has employed several air pollution control measures since 2008 Olympics. In order to investigate the organic aerosol sources after the implementation of these measures, ambient fine particulate matters were collected at a regional site Changping (CP) and an urban site Peking University Atmosphere Environment MonitoRing Station (PKUERS) during the Photochemical Smog in China field Campaign in summer of 2016. A chemical mass balance (CMB) modeling and the tracer yield method were used to apportion the primary and secondary organic sources. Our results showed that the particle concentration decreased significantly during the last a few years. The apportioned primary and secondary sources explained 62.8 ± 18.3 % and 80.9 ± 27.2 % of the measured OC at CP and PKUERS, respectively. Vehicular emissions served as the dominant sources. Except gasoline engine emission, the contributions of all the other primary sources decreased. Besides, the anthropogenic SOC, i.e. toluene SOC, also decreased, implying that deducting primary emission can reduce anthropogenic SOA. Different from the SOA from other regions in the world, where biogenic SOA was dominant, anthropogenic SOA was the major contributor to SOA, implying that deducting anthropogenic VOCs emissions is an efficient way to reduce SOA in Beijing. Back trajectory cluster analysis results showed that high mass concentrations of OC were observed when the air mass was from south. However, the contributions of different primary organic sources were similar, suggesting the regional particle pollution. The ozone concentration and temperature correlated well with the SOA concentration. Different correlations between day and night samples suggested the different SOA formation pathways. Significant enhancement of SOA with increasing particle water content and acidity were observed in our study, suggesting the aqueous phase acid-catalyzed reactions may be the important SOA formation mechanism in summer of Beijing.
Synthesis of an advanced Pd-Rh bimetallic catalyst for gasoline engine emission control
