Characteristics of Atmospheric Pollutants at Dinghushan Station During the Asian Games in Guangzhou

To understand the air quality status and influences of meteorological factors on concentrations of regional background pollutants in Southern China, online measurements of nitrogen oxide, sulfur dioxide, ozone, PM₁₀ and PM_2.5 observations are conducted in Mount Dinghu Background Monitoring Station in November of 2010. MICAPS data, NCEP FNL data and HYSPLIT model are used to deeply analyze the relationship between synoptic circulation, divergence and vorticity, meteorological factors, pollutant source regions and variation characteristics of pollutants in different periods. The results show that the average concentrations of NO₂, SO₂ and O₃ in Mount Dinghu area are (7.2±3.1)×10^-9, (8.5±3.8)×10^-9 and (28.7±9.8)×10^-9, respectively, during the Asian Games period.The aerosol pollution in this region is serious, with the monthly average concentration of PM₁₀ for 113 μg·m^-3 and PM_2.5 for 81 μg·m^-3, and the daily average concentration of PM_2.5 exceeds the WHO IT.1 air quality standard for 13 days. The analyses on air pollutants during high-level pollution periods show that the average concentrations of NO_x and O₃ are 13.2×10^-9 and 20.9×10^-9, which decreases by 41.3% and 10.7% than those in 2009, but the average concentration of SO₂ hardly changes in 2010 compared with that in 2009. All the results suggest that the air quality control measure is effective in some degree. However, the concentrations of PM₁₀ and PM_2.5 during the period of the Asian Games are higher than those during the same period in 2009, due to relatively stable meteorological conditions, fine weather and high temperature, while the continuous precipitations leads to the lower values of PM₁₀ and PM_2.5 during the same period in 2009. High temperature and humidity caused by uniform pressure and temperature fields of the generation of high pressure, continued convergence, weak rising mechanism, the weak surface wind at the surface layer and regional transport lead to the accumulation of primary air pollutants and fine particles. Backward trajectory simulation results show that the flows, originating from east, lead an obvious increase in primary air pollutants, fine particles and atmospheric oxidation in the areas of Mount Dinghu, which pass the industrial areas in Pearl River Delta. In summary, higher concentrations of PM_2.5 in Pearl River Delta regional background area are attributed to adverse meteorological condition and pollutant transport.