Changes of chemical composition and source apportionment of PM2.5 during 2013–2017 in urban Handan, China

Abstract China implemented the National Air Pollution Prevention and Control Action Plan since 2013, aiming at significantly improving air quality in major areas and cities in 2017. To investigate the changes of the characteristics of PM 2.5 and its major chemical components, formation mechanisms, and sources apportionment during 2013–2017 in urban Handan, which was one of the top polluted cities in China, we analyzed the chemical compositions of PM 2.5 samples for the entire year of 2013 and 2017, as well as a comprehensive dataset including continuous online hourly observations of the meteorological parameters and major air pollutants, i.e., SO 2 , NO 2 , and O 3 in this study. Potential Source Contribution function (PSCF) analysis was applied to investigate the potential source regions contributing to high PM 2.5 pollution episodes. The results showed that the concentration of major air pollutants except ozone decreased, and the proportion of PM 2.5 decline in Handan (37.0%) had reached the requirements (25%) of the National Air Pollution Prevention and Control Action Plan. The major chemical compositions of PM 2.5 decreased significantly, but the percentage of secondary organic aerosols increased from 37.0% in 2013 to 40.0% in 2017. The higher proportion of secondary components implied more severe secondary pollution. The PSCF analysis indicated that the significant local contribution and short-range transport in the surrounding areas were the major sources of heavy pollution episodes in Handan. This study highlights the importance of emission reduction of atmospheric organic compounds and joint control actions on a regional basis during heavy pollution episodes.