2016年夏季南京大气污染特征观测分析

为研究南京夏季大气复合污染的特征，2016年8月15日~9月15日期间开展了强化观测实验，本文利用仙林、鼓楼80m楼顶2个站点的强化观测资料，结合草场门常规监测资料，统计分析了南京不同地区夏季O₃和颗粒物（PM_2.5、PM₁₀）的浓度特征和相关性，以及郊区水溶性离子与其气态前体物的转化率变化特征.研究表明：3个站点O₃平均小时浓度为100.3μg/m³.PM_2.5和PM₁₀浓度分别为41.1和67.8μg/m³，郊区夜间存在颗粒物浓度高值.SO₄^2-、NO₃^-、NH₄⁺浓度总和占PM_2.5浓度的比值达到61%，OC（有机碳）/EC（元素碳）比值范围为0.8~4.0，日均值超过2.0的天数占77%，城、郊均存在二次污染.白天O₃与颗粒物（PM_2.5）浓度呈显著正相关变化，硫转化率（SOR）、氮转化率（NOR）分别与O₃浓度、湿度显著正相关.HONO主要在夜间积累，HCl和HNO₃浓度峰值出现在下午.与其它无机盐相比，NH₄⁺在总氨中所占比例明显偏低，大气中的氨主要以气态NH₃存在.观测期间O₃污染较重，O₃与颗粒物的正相关关系显著，化学反应在颗粒物积累过程中具有重要贡献，此外还可能存在城区向郊区的污染输送.

Observation and analysis of the characteristics of air pollution in Nanjing in summer 2016

To study the characteristics of air pollution in Nanjing during the summer, an intensive observational experiment was carried out from August 15th to September 15th, 2016. Data from three sites (Xianlin, Caochangmen, and Gulou) were collected to analyze the characteristics and correlation between O₃ and particulate matter (PM_2.5, PM₁₀) concentrations. Xianlin, Caochangmen, and Gulou each represented suburban, urban, and urban upper air respectively. In addition, at the Xianlin site, conversion characteristics of water-soluble ions and their gaseous precursors were also analyzed. The study showed that the hourly average concentration of O₃ was 100.3μg/m³. Average hourly concentrations of PM_2.5 and PM₁₀ were 41.1μg/m³ and 67.8μg/m³, respectively, and a peak was observed during the nights at the suburban site. The sum of the SO₄^2-, NO₃^- and NH₄⁺ to PM_2.5 ratios reached 0.61 and the OC (organic carbon) to EC (elemental carbon) ratio ranged from 0.8 to 4.0, with 77% of the days being greater than 2.0. The high OC/EC ratio indicated the existence of secondary pollution. The correlation between O₃ and PM concentrations was significantly positive, especially at the daytime. Similarly, the conversion rate of sulfur (SOR) and nitrogen (NOR) was correlated with daylight O₃ and nighttime humidity, respectively. Also, the accumulation of HONO mainly occurred during the night, while that of HCl and HNO₃ occurred in the afternoon. Compared with other inorganic salts, the ratio of NH₄⁺ in total ammonia was quite small, which showed that gaseous NH₃ was the main phase state. In conclusion, the potentially important role of chemical reactions in the accumulation of PM_2.5, especially involving secondary particles, and transport of air pollution from urban to suburban is addressed.