Inorganic Chemical Characteristics of PM2.5 During Pollution Events in Jinan, China

A one-year observation campaign from December 2020 to December 2021 was carried out in Jinan, a city that previously suffered from severe fine particulate matter (PM2.5) pollution. The meteorological parameters and ambient concentrations of the air pollutants were recorded, and PM2.5 samples were collected during the campaign. The inorganic chemical compositions of the PM2.5 samples were measured, identifying 8 water-soluble ions (WSIs) and 15 trace metals. Pollution events, including 7 dust events (DEs) and 19 secondary inorganic events (SIEs), were identified and classified. The inorganic chemical compositions of the pollution events were characterized, summarized, and concluded. The low ratio of WSIs to PM2.5, high concentrations of Ca2+ and Mg2+, and significant increases in trace metals were the dominant characteristics of PM2.5 during DEs. The high concentrations of SO42-, NO3-, and NH4+; the high ratio of secondary ions to WSIs; and the high ratio of WSIs to PM2.5 were the dominant characteristics of PM2.5 during SIEs. Even though, recently, the PM2.5 pollution in Jinan has not been as severe as pollution from a dozen years ago, it still exists, just at lower frequencies and pollution levels. This investigation provides the characteristics of PM2.5 pollution under dramatically improved conditions and various ideas for the management and control of PM2.5 pollution.