Spatiotemporal Variations of Air Pollutants before and after the COVID-19 Pandemic in Chengdu

Abstract

The pandemic of coronavirus disease 2019 (COVID-19, caused by the SARS-CoV-2 virus) had severe health, social, and economic impacts across the globe. However, the reduction in air pollution resulting from travel restrictions emerged as a beacon of hope. This study focused on Chengdu, China, using a generalized additive model and time series analysis to assess air quality changes during the lockdown. The research revealed a notable decrease in the Air Quality Index, nitrogen dioxide (NO2), and particulate matter concentrations, with NO2 showing the most pronounced response to reduced emissions from control measures. However, Chengdu experienced a relatively smaller decline in air pollution compared to other major Chinese cities. After the implementation of Class B measures in response to COVID-19, air pollutant concentrations in Chengdu significantly increased in February and March 2023 compared to the same period in 2022 and model-predicted values, despite little difference in annual average levels between the two years. The study suggested that the topography of the Sichuan Basin, with unique meteorological conditions such as temperature inversions and humidity anomalies, hindered pollutant dispersion and potentially reduced the likelihood of airborne virus transmission.