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This study investigated the physicochemical properties of PM2.5, especially among secondary aerosols, based on the particulate matter and gaseous precursors in Yongin, Korea measured between February and June 2022. A comparative analysis of PM composition across two seasons highlighted the atmospheric characteristics of this suburban area. As observed, the average PM2.5 concentrations in February and March were higher than those in May and June, with NO3− being particularly predominant during the colder months when PM2.5 levels were elevated. During this period, the high levels of gaseous precursors such as NOX, HNO3, and NMHC likely contributed to secondary aerosol formation. The intermediate oxidation states of organic matter in Yongin indicate its suburban characteristic, which is intermediate between urban and rural areas. Inorganic aerosols were enriched with (NH4)2SO4 with sufficient NH3 availability, and then the formation of NH4NO3 was promoted through the reaction of the same phase (gas–gas) HNO3 with NH3. Additionally, the temperature variations influenced the PM2.5 composition, promoting the production of NH4NO3 in February–March. In Yongin, HNO3 acted as a limiting factor in NH4NO3 production. Thus, the management of precursor gases such as HNO3 and NO2 is crucial during periods of high PM2.5 in the colder seasons. [ABSTRACT FROM AUTHOR]

In recent years, the amount of construction waste and recycled aggregate has been increasing every year in Korea. However, as the recycled aggregate is poor quality, it is not used for concrete, and the Korean government has strengthened the quality standards for recycled aggregate for concrete. In this study, research was conducted on the mechanical and durability characteristics of concrete using recycled aggregate, after developing equipment to improve the quality of recycled aggregate to increase the use of recycled aggregate for environmental improvements. The results illustrated improvements in the air volume, slump, compressive strength, freezing and thawing resistance, and drying shrinkage. Furthermore, this study is expected to contribute to the increased use of recycled aggregate in the future. [ABSTRACT FROM AUTHOR]