Spatiotemporal characteristics of air pollutants in Seoul: How seasonal variation shapes weekly pollution cycles

Abstract

Air pollution in temperate cities changes regularly with seasons and human activities. Previous studies have explored seasonal patterns and weekday–weekend differences in Seoul’s air quality. However, most studies discuss seasonal changes and weekly pollution trends separately, without focusing on their interactive effects. This study aims to analyze how weekday–weekend pollution differences vary in cold and warm seasons. It also explores the seasonal changes in correlations among major air pollutants in Seoul. This research uses three years (2017–2019) of hourly data from 25 monitoring stations in Seoul. It applies tidy data processing and visual analysis to compare the diurnal variation, weekly patterns and relationships of PM2.5, PM10, NO2 and O3 in different seasons. The results show that seasons strongly influence weekly pollution characteristics. PM₂.₅, PM₁₀ and NO₂ present higher concentrations in the cold season, whereas O₃ is higher in the warm season. Traffic related pollutants have clearer weekday weekend differences in cold seasons. Ozone levels in warm seasons may be related to active photochemical reactions. The correlations between particulate matter and ozone also change obviously across different seasons. This study proves that single-dimensional analysis cannot fully reflect urban air pollution features. By combining seasonal and weekly comparison, this research provides useful references for seasonal and targeted air quality management in temperate metropolitan cities.