Roles of Relative Humidity in Aerosol Pollution Aggravation over Central China during Wintertime

Lin Zang, Zemin Wang, Bo Zhu and Yu Zhang
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Lin Zang: Chinese Antarctic Centre of Surveying and Mapping, Wuhan University, Wuhan 430079, China
Zemin Wang: Chinese Antarctic Centre of Surveying and Mapping, Wuhan University, Wuhan 430079, China
Bo Zhu: Hubei Environmental Monitoring Centre, Wuhan 430079, China
Yu Zhang: School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China

IJERPH, 2019, vol. 16, issue 22, 1-12

Abstract: Aerosol pollution elicits considerable public concern due to the adverse influence on air quality, climate change, and human health. Outside of emissions, haze formation is closely related to meteorological conditions, especially relative humidity ( RH ). Partly due to insufficient investigations on the aerosol hygroscopicity, the accuracy of pollution prediction in Central China is limited. In this study, taking Wuhan as a sample city, we investigated the response of aerosol pollution to RH during wintertime based on in-situ measurements. The results show that, aerosol pollution in Wuhan is dominated by PM 2.5 (aerodynamic particle size not larger than 2.5 μm) on wet days ( RH ≥ 60%), with the averaged mass fraction of 0.62 for PM 10 . Based on the RH dependence of aerosol light scattering (f ( RH )), aerosol hygroscopicity was evaluated and shows the high dependence on the particle size distribution and chemical compositions. f ( RH = 80%) in Wuhan was 2.18 (±0.73), which is comparable to that measured in the Pearl River Delta and Yangtze River Delta regions for urban aerosols, and generally greater than values in Beijing. Ammonium (NH 4 + ), sulfate (SO 4 2− ), and nitrate (NO 3 − ) were enhanced by approximately 2.5-, 2-, and 1.5-fold respectively under wet conditions, and the ammonia-rich conditions in wintertime efficiently promoted the formation of SO 4 2− and NO 3 − , especially at high RH . These secondary ions play an important role in aggravating the pollution level and aerosol light scattering. This study has important implications for understanding the roles of RH in aerosol pollution aggravation over Central China, and the fitted equation between f ( RH ) and RH may be helpful for pollution forecasting in this region.

Keywords: aerosol pollution; hygroscopicity; relative humidity; secondary formation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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