Vertical Observations and Analysis of PM2.5,O3,and NOx at Beijing and Tianjin from Towers during Summer and Autumn 2006

During the period between 18 August and 22 September 2006,an ultraviolet photometric O 3 analyzer,a NO-NO 2-NO x chemiluminescence analyzer,and a quartz micro-oscillating-scale particle concentration analyzer were simultaneously used for monitoring at three different heights each at Beijing(325-m tower) and Tianjin(255-m tower).These towers belong to the Institute of Atmospheric Physics(IAP) of the Chinese Academy of Sciences(CAS) and to the Tianjin Municipal Meteorological Bureau,respectively.These measurements were used to continuously measure the atmospheric O 3 and NO x volume-by-volume concentrations and the PM 2.5 mass concentration within a vertical gradient.When combined with meteorological data and information on the variation of vertical characteristics of the various atmospheric pollutants in the two cities,analysis shows that these two cities were seriously polluted by both PM 2.5 and O 3 during summer and autumn.The highest daily-average concentrations of PM 2.5 near the ground in Beijing and Tianjin reached 183 μg m ?3 and 165 μg m ?3 ,respectively,while the O 3 concentrations reached 52 ppb and 77 ppb,and NO x concentrations reached 48 ppb and 62 ppb for these two cities,respectively.The variations in the daily-average concentrations of PM 2.5 between Beijing and Tianjin were demonstrated to be consistent over time.The concentrations of PM 2.5 measured in Beijing were found to be higher than those in Tianjin.However,the overall O 3 concentrations near the ground in Tianjin were higher than in Beijing.NO x concentrations in Tianjin were consistently lower than in Beijing.It was also found that PM 2.5 pollution in Beijing’s atmosphere may also be affected by the pollutants originating in and delivered from Tianjin,and that Tianjin was impacted by Beijing’s pollutants at a significantly reduced level.