Seasonal variation, formation mechanisms and potential sources of PM2.5 in two typical cities in the Central Plains Urban Agglomeration, China

Huanjia Liu; Hezhong Tian; Kai Zhang; Shuhan Liu; Ke Cheng; Shasha Yin; Yongli Liu; Xiangyang Liu; Yiming Wu; Wei Liu; Xiaoxuan Bai; Yong Wang; Panyang Shao; Lining Luo; Shumin Lin; Jing Chen; Xingang Liu

doi:10.1016/j.scitotenv.2018.12.068

Seasonal variation, formation mechanisms and potential sources of PM_2.5 in two typical cities in the Central Plains Urban Agglomeration, China

Sci Total Environ. 2019 Mar 20:657:657-670. doi: 10.1016/j.scitotenv.2018.12.068. Epub 2018 Dec 6.

Authors

Huanjia Liu¹, Hezhong Tian², Kai Zhang³, Shuhan Liu¹, Ke Cheng⁴, Shasha Yin⁵, Yongli Liu⁴, Xiangyang Liu¹, Yiming Wu¹, Wei Liu¹, Xiaoxuan Bai¹, Yong Wang¹, Panyang Shao¹, Lining Luo¹, Shumin Lin¹, Jing Chen¹, Xingang Liu¹

Affiliations

¹ State Key Joint Laboratory of Environmental Simulation & Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China; Center for Atmospheric Environmental Studies, Beijing Normal University, Beijing 100875, China.
² State Key Joint Laboratory of Environmental Simulation & Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China; Center for Atmospheric Environmental Studies, Beijing Normal University, Beijing 100875, China. Electronic address: hztian@bnu.edu.cn.
³ Department of Epidemiology, Human Genetics and Environmental Sciences, University of Texas Health Science Center Houston, School of Public Health, Houston, TX 77030, United States.
⁴ School of Environment, Henan Key Laboratory of Environmental Pollution Control, Key Laboratory of Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Normal University, Xinxiang 453007, China.
⁵ College of Chemistry and Molecular Engineering, Research Institute of Environmental Science, Zhengzhou University, Zhengzhou 450001, China.

PMID: 30677932
DOI: 10.1016/j.scitotenv.2018.12.068

Abstract

In order to probe the seasonal variation, formation mechanisms as well as geographical origins of fine particles and its chemical components in two cities (Zhengzhou, ZZ and Xinxiang, XX) in Central Plains Urban Agglomeration, daily PM_2.5 aerosol samples were collected for four consecutive seasons during 2017-2018. The annual average concentrations of PM_2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm) were calculated at 70.5 ± 50.8 and 69.0 ± 46.3 μg m^-3 at ZZ and XX, respectively. Daily ambient PM_2.5 concentrations ranged from 18.2 to 303.0 μg m^-3, among which >81% of the total sampling days exceeded the National Ambient Air Quality Standard of China (NAAQS, 35 μg m^-3 as an annual average). Additionally, concentrations of PM_2.5 and its major chemical components were seasonally dependent, usually with the highest mass concentration in winter. Compared with previous studies, higher NO₃^-/SO₄^2- were observed in this study depicted that air pollution caused by motor vehicle exhaust cannot be ignored. OC concentration was higher at ZZ than XX during sampling campaign likely partially caused by larger number of motor vehicles, chemical pesticide and solvent used in ZZ. Both homogeneous and heterogeneous reactions played an important role in the formation of nitrate, while heterogeneous reactions dominated the formation of sulfate. We also found a faster increase in nitrate than in sulfate during the evolution of haze. The characteristics of long-range transportation of PM_2.5 and its major chemical components and gaseous precursors were observed at both sites through back trajectories and WPSCF analysis, suggesting the complexity of air pollution and the multi-influence among cities.

Keywords: Chemical components; Formation mechanisms; Geographical origin; PM(2.5); Seasonal variation; Zhengzhou-Xinxiang region.