Chemical compositions of atmospheric particulate matter during differences air quality conditions in each month

Abstract

Ambient Particulate Matter (PM) can vary in size, shape, charge, and composition, as influenced by the surrounding environment, season, and even time of day. In addition to the complex composition of atmospheric aerosol particles, there are extremely active and highly reactive transient free radicals, such as hydroxyl radicals (•OH) and superoxide radicals (O2•–), and persistent free radicals (PFRs). Persistent free radicals (PFRs) are extremely active and highly reactive transients. PFRs which also exist for several days, months, and even many years, accompanied by the existence of particles of different sizes and interrelated with the chemical composition of aerosols, are regarded as an emerging environmentally harmful substance. The present study collected samples using Personal Environmental Monitors at Chia Nan University of Pharmacy and Science, Tainan, Taiwan, to examine the free radicals and chemical composition of aerosols. The sampling was conducted during the winter from January 25th to February 9th, 2022, summer from June 30th to July 11th, 2022, and early winter from November 21st to November 30th, 2022. Samples were collected twice per day, during the daytime and nighttime. It was found that the average concentrations of persistent free radicals of PM10 at nighttime are more than at daytime. Across the three seasons, in early winter, the highest average concentrations of persistent free radicals were 16.70 ± 8.13 ×1014 spins/m3 in PM10 and 7.72 ± 1.19 ×1014 spins/m3 in PM2.5. Persistent free was 14.71 ± 7.13 ×1014 spins/m3 in PM10 and 12.13 ± 4.47 ×1014 spins/m3 in PM2.5, and the lowest average concentrations of persistent free found in summer were 9.58 ± 3.51 ×1014 spins/m3in PM10 and 8.11 ± 4.77 ×1014 spins/m3 in PM2.5. The relationship between PFRs and NH4+, nss-K+, nss-NO3-, nss-SO42-, and PO43- was found in water-soluble ions. An association was found between PFRs and formate, glutarate, maleate, fumarate, oxalate, and phthalate in carboxylate. An association was also found between PFRs and myo-inositol, erythritol, levoglucosan, and mannitol in saccharides. This indicates the source from the mixture of inorganic salts from burning fossil fuels that burn coal Vehicle exhaust from traffic from thermolysis of cellulose during the combustion activity of plants and from pyrolysis of hemicellulose. The ratio was also found to OC/EC is proposed as a potential marker to distinguish between fossil and non-fossil fuel sources. The A/F ratio was also found to be a good indicator of differentiation from sources obtained from in situ emission or from in situ synthesis through photochemical processes. The ratio of malonate to succinate was also observed, indicating that photochemical reactions are the main source of aerosol production in the atmosphere or traffic emissions are the main sources of aerosol production in the atmosphere. The main sources of PM in this study were fossil fuel combustion, in situ photochemical synthesis, and traffic emissions. The levels of PFRs exhibit a marked seasonal variation, with elevated concentrations observed during the winter months. The highest concentrations of these pollutants are typically observed in the early winter period, suggesting an association with increased combustion activities. Biomass burning is recognized as a major contributor to air pollution, which in turn poses significant health risks to human populations. The findings of this study underscore the elevated levels of air pollution associated with biomass combustion during the early winter and winter months, as compared to the summer season.