Evolution characteristics of air pollutants and their meteorological influencing factors in Macao

With the development of the Guangdong-Hong Kong-Macao Greater Bay Area, the air quality of Macao, as an international tourism and leisure center, has drawn increasing attention. Based on the hourly observation data from the Taipa Ambient Air Quality Monitoring Station (2013–2023) in Macao, trend and correlation analyses were conducted to assess the long-term variations of six common air pollutants (O₃, PM₁₀, PM₂.₅, SO₂, NO₂ and CO) and their relationships with meteorological factors. Results show that the concentrations of PM₁₀, PM₂.₅, SO₂, NO₂, and CO have generally declined over the past decade, while the O₃ level has experienced a significant increase since 2016 and showed a marked increase in 2023, indicating that O₃ pollution is replacing primary pollutants as the dominant concern. Seasonal variation characteristics show that the concentrations of all pollutants are the lowest in summer, while the concentration of O₃ peaks in autumn and the concentrations of other pollutants are the highest in winter. Affected by photochemical reactions, O₃ shows a single peak in the afternoon, NO₂ exhibits a typical double-peak feature related to traffic emissions, and the concentrations of PM₁₀, PM₂.₅ and SO₂ are generally higher during the day and lower at night. Correlation analysis reveals a strong positive correlation between PM₂.₅ and PM₁₀, and a significant negative correlation between O₃ and NO₂. Pollutant concentrations show a positive association with air pressure but a negative relationship with relative humidity. Temperature exhibits a positive correlation with O₃ yet is negatively correlated with other pollutants. In contrast, the relationship between pollutants and wind speed remains weak. This study systematically reveals the differences in the temporal evolution of common pollutants in Macao, highlighting that while the overall air quality has improved, the risk of O₃ pollution is increasing significantly.