title: Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China.
abstract: Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. Sulfate is a major component of fine haze particles. Record sulfate concentrations of up to ~300 μg m-3were observed during the January 2013 winter haze event in Beijing. State-of-the-art air quality models that rely on sulfate production mechanisms requiring photochemical oxidants cannot predict these high levels because of the weak photochemistry activity during haze events. We find that the missing source of sulfate and particulate matter can be explained by reactive nitrogen chemistry in aerosol water. The aerosol water serves as a reactor, where the alkaline aerosol components trap SO2, which is oxidized by NO2to form sulfate, whereby high reaction rates are sustained by the high neutralizing capacity of the atmosphere in northern China. This mechanism is self-amplifying because higher aerosol mass concentration corresponds to higher aerosol water content, leading to faster sulfate production and more severe haze pollution.
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Yafang
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.; State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Guangjie
authors.initials: G
authors.lastname: Zheng
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Chao
authors.initials: C
authors.lastname: Wei
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Qing
authors.initials: Q
authors.lastname: Mu
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zheng
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Engineering, University of Iowa, Iowa City, IA 52242, USA.; Center for Global and Regional Environmental Research, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Meng
authors.initials: M
authors.lastname: Gao
authors.affiliation: Center for Earth System Science, Tsinghua University, Beijing 100084, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Kebin
authors.initials: K
authors.lastname: He
authors.affiliation: College of Engineering, University of Iowa, Iowa City, IA 52242, USA.; Center for Global and Regional Environmental Research, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Carmichael
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Pöschl
authors.affiliation: Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China.; Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
authors.forename: Hang
authors.initials: H
authors.lastname: Su
keywords: Cu alloys; coefficient of friction; friction; gradient nanostructures; metals; nanostructures; surface roughening