Variation of the concentration of particulate matter in the atmosphere and rainwater quality during precipitation at an urban site of southeast Korea

This study investigated the wet deposition of particulate matter (PM) for six precipitation events at Daeyeon dong, Busan, South Korea, from February 2020 to July 2020. The concentration of PM₁₀ in the atmosphere was steadily measured before and after the precipitation. Rainwater samples were collected every 50 mL of each precipitation event using rainwater collecting devices and rainwater qualities (pH, electrical conductivity (EC), water-soluble ions (SO₄^2-, NO₃^-, NH₄⁺, Ca²⁺, etc.) were analyzed. For heavy rain events with strong rainfall intensities (>7.5 mm/h), the average PM₁₀ reduction efficiency reached more than 68%. For the relatively weak (<5 mm/h) rainfall intensities, the PM₁₀ reduction efficiencies were less than 40%. In all rainfall events, the average rainwater pH gradually increased over time from 4.3 to 5.0, while the average EC decreased from 81.9 to 12.1 µS/cm. The concentrations of all ions in the rainwater samples gradually decreased during precipitation. For heavy rain events, the acidity, EC, and concentrations of total water-soluble ions of initial rainwater samples were higher than those of later samples. This result indicates that the concentration of PM₁₀ in the atmosphere was reduced by wet deposition.