In situ measurements of SO2, NOx, NOy, and O3 in Beijing, China during August 2008 Original Research Article

The measurement of SO2, O3, NO, NO2, and NOy mixing ratios was conducted from Jul 28, 2008 to Sep 2, 2008 at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP, CAS) station, which is 2 km southwest to the Beijing National Stadium (Birdʹs Nest/Olympic Stadium). Photochemical pollution was detected during the measurement on Aug 2, 2008, and the maximum hourly average [O3] reached 128 ppbv, caused by both the local photochemical reactions and regional transportation of pollutants. The NOx Ozone Production Efficiency (OPE (NOx)) values were 6.9 and 20.2 on Aug 2 and Aug 24, 2008 respectively, which were the two days with highest O3 pollution. The OPE (NOx) of 6.9 on Aug 2 was within a typical range in city area, and it implied that the high O3 could be due to local sources. While OPE (NOx) of 20.2 on Aug 24 was larger than the typical value in the region, but lower than that of the surrounding clean area during 2008 Beijing Olympics Closing Ceremony. It indicated that the pollution was because of regional transportation of pollutants. In addition, 60% of the extent of the Smog Production Model (SPM) data was less than 0.6 and the rest was slightly larger than 0.6, with maximum of 0.78. It indicated that the sensitivity of O3 generated was volatile organic compounds (VOCs) control during the observation period. The SPM results also implied that O3 product in high-O3 day is a transition state from VOCs sensitivity to NOx sensitivity. Lastly, the analysis of the wind direction and extent of SPM showed that the photochemical pollution of this region was mostly subject to the influence of southeastern air flow in the summer.