Reduction in Aviation Volume due to COVID-19 and Changes in Air Pollution near the International Airport in Taiwan

Measures to contain COVID-19 pandemic in Taiwan included international travel restrictions since February 2020, which resulted in a nearly 80% reduction of aviation volume at the International Taoyuan Airport (TPE), while industry and ground traffic continued to operate unaffected by the pandemic. This study attempted to assess the contribution of aviation volume to air pollution measured by a monitoring station, located 2 km southwest to the airport. We applied cluster analysis to identify TPE contribution to the major air pollutants and estimated their relationship with the number of passengers as a proxy to the flights number. From the airport containing cluster, we observed significant reduction of air pollution concentrations after the travel restrictions. The reduction percentage of SO2 and NOx was higher in the airport cluster (17.7% and 7.3%, respectively) compared to the total station observation (14.7% and 6.8% respectively). Spearman's coefficients indicated positive significant correlations between the number of passengers and PM2.5 (0.06), PM10 (0.21), SO2 (0.24), especially after the travel restrictions. Such low correlations were found due to the distance of 2 km between the monitoring station and the airport runway. This distance could be too far to precisely detect the contribution of aviation to air pollution, which was masked by industrial activities and ground traffic. Measuring air pollution at a closer distance to the runways is required for a better catchment of aviation impact on air quality.