@article {14656,
	title = {Fine particle pH during severe haze episodes in Northern China.},
	journal = {Geophys. Res. Lett.},
	volume = {44},
	year = {2017},
	pages = {5213-5221},
	abstract = {Aerosol acidity plays an important role in atmospheric chemistry. China emits large amounts\&nbsp;of SO2, NOx, and NH3 into the atmosphere, but aerosol acidity is poorly characterized. In this\&nbsp;study, simultaneous 1-h measurements of particulate and gaseous compositions along with\&nbsp;the ISORROPIA-II thermodynamic equilibrium model were used to study aerosol acidity\&nbsp;during severe haze episodes in northern China. The summed concentration of sulfate, nitrate\&nbsp;and ammonium was 135 {\textpm} 51 μg/m3 with a maximum of 250 μg/m3, and the gas-phase NH3\&nbsp;mixing ratio was 22 {\textpm} 9 ppb. Fine particles were moderately acidic, with a pH range of\&nbsp;3.0-4.9 and an average of 4.2, which was higher than those in the United States and Europe.Excess NH3 and high aerosol water content are responsible for the relatively lower aerosol\&nbsp;acidity. These results suggests that the new pathways for sulfate production in China\&nbsp;proposed by recent studies should be revisited.},
	author = {MX Liu and Y* Song and T  Zhou and ZY  Xu and CQ Yan and M* Zheng and ZJ Wu and Hu M and Y.S. Wu and T. Zhu}
}
