广州亚运会期间鼎湖山站大气污染特征

为了解广州亚运会期间华南区域大气质量状况以及气象条件对区域本底浓度值的影响，2010年11月对鼎湖山站主要污染物NO_x，SO₂，O₃，PM₁₀和PM_2.5进行了连续在线观测。利用MICAPS，NCEP FNL资料及后向轨迹模拟对观测时段大气污染物变化特征进行了分析。结果表明:观测时期鼎湖山区域NO₂，SO₂和O₃平均体积分数分别为 (7.2±3.1)×10-9，(8.5±3.8)×10-9和 (28.7±9.8)×10-9。PM₁₀和PM_2.5的月平均质量浓度分别达到113 μg·m-3和81 μg·m-3，PM_2.5超标日数达13 d (标准为世界卫生组织第1阶段值，日平均值为75 μg·m-3)。不同时段日变化分析表明，广州亚运会期间高值时段 (定义为PM_2.5质量浓度超过世界卫生组织的IT.1标准的时段) NO_x和O₃平均体积分数为13.2×10-9和20.9×10-9，较2009年同期分别下降了41.3%和10.7%。不利气象要素影响和污染物区域传输作用是形成珠江三角洲区域大气本底 (鼎湖山地区) 细粒子污染偏高的主要原因。

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.