• 关键词：PM_2.5  时间变化  空间分布  阅兵  春节

• 基金项目：国家重点基础研究发展计划（No.2014CB447900）；中国科学院战略性先导专项B（No.XDB05020501）；环保公益性行业科研专项（No.201409001）

• 郭家瑜
• 中国科学院大气物理研究所, 大气边界层物理和大气化学国家重点实验室, 北京 100029

• 张英杰
• 1 中国科学院大气物理研究所, 大气边界层物理和大气化学国家重点实验室, 北京 100029;2 南京信息工程大学, 大气物理学院, 南京 210044

• 郑海涛
• 中国科学院大气物理研究所, 大气边界层物理和大气化学国家重点实验室, 北京 100029

• 王自发
• 中国科学院大气物理研究所, 大气边界层物理和大气化学国家重点实验室, 北京 100029

• 孙业乐
• 中国科学院大气物理研究所, 大气边界层物理和大气化学国家重点实验室, 北京 100029

• 摘要：近年来,随着雾霾事件的频发,人们逐渐提高了对雾霾的关注度,PM_2.5作为其首要污染物对大气能见度及人体健康造成了严重影响.因此,本文利用2015年北京12个环境监测站点的PM_2.5、PM₁₀、NO₂、SO₂、CO和O₃的浓度数据和气象数据,综合研究了北京2015年大气细颗粒物的空间变化特征及分布规律.同时,利用空间差异率（COD）统计方法评估了不同地区细颗粒物浓度的差异程度,并结合2015年2次特殊事件（春节和阅兵）,对大气污染特征及其与排放源控制的关系进行了深入对比分析.结果发现,重污染天气集中发生在秋冬季,且污染程度高、持续时间长.城区PM_2.5浓度比郊区高约12 μg·m^-3.东城区与对照区差异最大,COD值为0.24；东城区与西城区差异最小,COD值为0.05.春、夏、秋季颗粒物PM_2.5、PM₁₀浓度日变化较为平稳,在中午有所升高,冬季颗粒物质量浓度明显呈现出夜间高于日间的污染模式.近3年PM_2.5与PM₁₀保持显著的相关性,但PM_2.5/PM₁₀比值呈降低趋势.阅兵期间采取的空气质量管控措施和气象要素共同作用导致PM_2.5浓度下降约72%,市中心的首要污染物为NO₂,郊区首要污染物为O₃和PM₁₀.春节期间烟花燃放对PM_2.5的瞬时贡献量很大,对比春节假期和非假期2个阶段的大气污染特征发现,人口和机动车减少及餐馆暂停营业并没有使北京局地空气质量得到明显改善.该研究结果提示在进行PM_2.5控制的同时也要对O₃浓度有所关注,同时也进一步支撑了北京空气质量改善需要京津冀协同控制这一重要结论.

• Abstract：The frequent occurrence of severe haze episodes has attracted great concerns in recent years. PM_2.5, as a primary pollutant of haze, has serious impacts on atmospheric visibility and human health. In this study, hourly concentrations of PM_2.5, PM₁₀, NO₂, SO₂, CO, O₃ and meteorological data in 2015 were obtained from 12 monitoring sites in Beijing to investigate the characteristics of spatial distribution and variations of atmospheric fine particles in Beijing. The coefficient of divergence (COD) was used to further evaluate the spatial differences of PM_2.5 between different regions. We also examined two special events (the Military Parade and the Spring Festival) in 2015 to analyze the relationships between air pollution and source control. The results showed that severe pollution events predominantly occurred in autumn and winter with high concentration levels and long duration. The average concentration of PM_2.5 in urban area was 12 μg·m^-3 higher than that in the suburban area. The most significant difference in COD value was observed between traffic and background site and the smallest variation was between Dongcheng District and Xicheng District (COD=0.05). The diurnal profiles of PM_2.5 and PM₁₀ concentrations were relatively stable with small increases at noon in spring, summer and autumn. However, pronounced diurnal cycles in winter showed much higher concentration at nighttime than those during daytime. PM_2.5 was tightly correlated with PM₁₀ during the past three years, yet the average PM_2.5/PM₁₀ ratio showed a decreasing trend. The average PM_2.5 concentration decreased by approximately 72% during the Military Parade due to the combined effects of emission controls and favorable meteorological conditions. As a result, the primary pollutant was changed from PM_2.5 to NO₂ in the downtown area, while O₃ and PM₁₀ were primary pollutants in the countryside. During the Spring Festival, fireworks made a significant but short-term contribution to PM_2.5 concentration. By comparing the holiday and non-holiday periods, we found that the decreases in population and motor vehicles and temporary closed restaurants did not lead to an obvious improvement in air quality during the Spring Festival. These results indicated that we should pay attention to O₃ when controlling PM_2.5. In addition, this study supports the conclusion that cooperative control among Beijing, Tianjin and Hebei is of great importance to improve the air quality in Beijing.

• Key words：PM_2.5  temporal variation  spatial distribution  military parade  the Spring Festival

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