Seasonal Variations in the Correlation between Particulate Matter and Rainwater Quality in an Urban Area of Southeast Korea

This study investigates the seasonal variations in the relationship between particulate matter (PM) concentrations and rainwater quality in an urban area of South Korea. Rainwater samples (n = 216) were collected during summer (June to August 2020) and winter (December 2020 to February 2021) at Pukyong National University, Busan, and analyzed for pH and electrical conductivity (EC) in the field, and water-soluble ions (Na⁺, Mg²⁺, K⁺, Ca²⁺, NH₄⁺, Cl^-, NO₃^-, SO₄^2-) were determined using an Ion Chromatography (IC, HIC-ESP, Shimadzu, Japan) at the Integrated Analytical Center for Earth and Environmental Sciences of Pukyong National University. Atmospheric concentrations of PM₁₀ and PM_2.5 were obtained from the Automated Weather System (AWS) of the Korea Meteorological Administration (KMA). The results showed significant seasonal differences in PM concentrations and rainwater quality. In summer, daily average concentrations of PM₁₀ and PM_2.5 were relatively low (about 18 μg/m³ and 7 μg/m³) with higher rainwater EC (about 26 µS/cm) and moderate levels of cations (about 10 mg/L) and anions (8 mg/L). In contrast, winter showed increased PM₁₀ and PM_2.5 concentrations (27 μg/m³ and 18 μg/m³), accompanied by lower EC (15.6 µS/cm) but higher cation (15 mg/L) and anion (12 mg/L) concentrations. Rainfall intensity was markedly higher in summer (3.01 mm/h) than in winter (0.63 mm/h), reflecting seasonal differences in pollutant washout processes. Correlation analysis revealed stronger relationships between PM concentrations and rainwater quality in summer, particularly for pH (r = 0.75), NH₄⁺ (r = 0.67), and K⁺ (r = 0.43). These findings indicate that rainfall during summer plays a critical role in transporting atmospheric pollutants to the surface, while in winter, meteorological factors such as wind and humidity have a greater influence. This study highlights the importance of considering seasonal and meteorological variations when assessing the environmental impacts of PM.

This research was supported by Particulate Matter Management Specialized Graduate Program through the Korea Environmental Industry & Technology Institute(KEITI) funded by the Ministry of Environment(MOE)