Cheng Zhen, Ma Xin, He Yujie, Jiang Jingkun, Wang Xiaoliang, Wang Yungang, Sheng Li, Hu Jiangkai, Yan Naiqiang
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
National Meteorological Center of China, Beijing 100081, China.
Environ Res. 2017 Jul;156:239-246. doi: 10.1016/j.envres.2017.03.022. Epub 2017 Mar 28.
The ambient PM pollution problem in China has drawn substantial international attentions. The mass extinction efficiency (MEE) and hygroscopicity factor (f(RH)) of PM can be readily applied to study the impacts on atmospheric visibility and climate. The few previous investigations in China only reported results from pilot studies and are lack of spatial representativeness. In this study, hourly average ambient PM mass concentration, relative humidity, and atmospheric visibility data from China national air quality and meteorological monitoring networks were retrieved and analyzed. It includes 24 major Chinese cities from nine city-clusters with the period of October 2013 to September 2014. Annual average extinction coefficient in urban China was 759.3±258.3Mm, mainly caused by dry PM (305.8.2±131.0Mm) and its hygroscopicity (414.6±188.1Mm). High extinction coefficient values were resulted from both high ambient PM concentration (68.5±21.7µg/m) and high relative humidity (69.7±8.6%). The PM mass extinction efficiency varied from 2.87 to 6.64m/g with an average of 4.40±0.84m/g. The average extinction hygroscopic factor f(RH=80%) was 2.63±0.45. The levels of PM mass extinction efficiency and hygroscopic factor in China were in comparable range with those found in developed countries in spite of the significant diversities among all 24 cities. Our findings help to establish quantitative relationship between ambient extinction coefficient (visual range) and PM & relative humidity. It will reduce the uncertainty of extinction coefficient estimation of ambient PM in urban China which is essential for the research of haze pollution and climate radiative forcing.
中国的环境细颗粒物污染问题已引起国际社会的广泛关注。细颗粒物的质量消光效率（MEE）和吸湿性因子（f(RH)）可用于研究其对大气能见度和气候的影响。中国此前的少数研究仅报告了试点研究结果，缺乏空间代表性。本研究收集并分析了中国国家空气质量和气象监测网络的小时平均环境细颗粒物质量浓度、相对湿度和大气能见度数据。研究涵盖了2013年10月至2014年9月期间九个城市群中的24个中国主要城市。中国城市的年平均消光系数为759.3±258.3Mm，主要由干细颗粒物（305.8±131.0Mm）及其吸湿性（414.6±188.1Mm）造成。高消光系数值源于高环境细颗粒物浓度（68.5±21.7µg/m）和高相对湿度（69.7±8.6%）。细颗粒物质量消光效率在2.87至6.64m²/g之间变化，平均为4.40±0.84m²/g。平均消光吸湿因子f(RH = 80%)为2.63±0.45。尽管24个城市之间存在显著差异，但中国的细颗粒物质量消光效率和吸湿因子水平与发达国家相当。我们的研究结果有助于建立环境消光系数（视程）与细颗粒物和相对湿度之间的定量关系。这将降低中国城市环境细颗粒物消光系数估算的不确定性，这对于雾霾污染和气候辐射强迫研究至关重要。
