Severe wintertime haze events with exceedingly high levels of aerosols have occurred frequently in China in recent years, impacting human health, weather, and the climate. A better knowledge of the formation mechanism and aerosol properties during haze events is helpful for the development of effective mitigation policies. In this study, we present field measurements of aerosol properties at an urban site in Beijing during January and February 2015. A suite of aerosol instruments were deployed to measure a comprehensive set of aerosol chemical and physical properties. The evolution of haze events in winter, dependent on meteorological conditions, consistently involves new particle formation during the clean period and subsequently continuous growth from the nucleation mode particles to submicron particles over the course of multiple days. Particulate organic matter is primarily responsible for producing the nucleation mode particles, while secondary organic and inorganic components jointly contribute to the high aerosol mass observed during haze events. The average effective density and hygroscopic parameter (κ) of ambient particles are approximately 1.37 g cm?3 and 0.25 during the clean period and increase to 1.42 g cm?3 and 0.4 during the polluted period, indicating the formation of secondary inorganic species from the continuous growth of nucleation mode particles. Our results corroborate that the periodic cycles of severe haze formation in Beijing during winter are attributed to the efficient nucleation and secondary aerosol growth under high gaseous precursor concentrations and the stagnant air conditions, highlighting that reductions in emissions of aerosol precursor gases are critical for remedying secondary aerosol formation and thereby mitigating haze pollution.
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机译：近年来，中国在中国经常发生严重的冬季雾化事件，常常在中国经常发生，影响人类健康，天气和气候。更好地了解阴霾事件期间的形成机制和气溶胶特性有助于开发有效缓解政策。在本研究中，我们在2015年1月和2月在北京的城市地点出现了气溶胶特性的现场测量。部署了一套气溶胶仪器，以衡量一套全面的气溶胶化学和物理性质。冬季雾霾事件的演变，依赖于气象条件，始终如例在清洁时期期间的新颗粒形成，随后在多天的过程中从核切割模式颗粒到亚微米颗粒的延时生长。颗粒状有机物质主要负责产生成核模式颗粒，而二次有机和无机成分共同有助于在雾霾事件期间观察到的高气溶胶肿块。在清洁期间，环境颗粒的平均有效密度和吸湿参数（κ）约为1.37g cm = 3和0.25，在污染期间增加至1.42g cm = 3和0.4，表明来自中的二次无机物种成核模式颗粒的连续生长。我们的结果证实，冬季北京的严重雾度形成的周期性周期归因于高气态前体浓度下的高效成核和二次气溶胶生长，突出的空气条件突出，突出了气溶胶前体气体排放的减少对纠正仲裁至关重要气溶胶形成，从而缓解阴霾污染。
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