ABSTRACT
In this work, the relationships between air quality and pollutant emissions were investigated during the COVID-19 pandemic in Shandong Province. During the quarantine period (from January 24 to February 7, 2020), the concentrations of atmospheric pollutants decreased significantly relative to the period before controls were imposed (from January 15 to 23, 2020). Specifically, except for an increase in the concentration of O3, concentrations of PM10, PM2.5, NO2, SO2, and CO decreased for 72.6 µg·m-3 (45.86%), 47.4 µg·m-3(41.24%), 25.6 µg·m-3 (58.00%), 3.0 µg·m-3 (17.71%), and 0.5 mg·m-3 (31.40%), respectively. RAMS-CMAQ simulation showed that meteorological diffusion had an essential role in improving air quality. Influenced by meteorological factors, emissions of PM10, PM2.5, NO2, SO2, and CO were reduced 26.04%, 33.03%, 28.35%, 43.27%, and 23.29%, respectively. Furthermore, the concentrations of PM10, PM2.5, NO2, SO2, and CO were reduced by 19.82%, 8.21%, 29.65%, -25.56%, and 8.12%, respectively, due to pollution emissions reductions during the quarantine period. O3 concentrations increased by 20.51% during quarantine, caused by both meteorological factors (10.47%) and human activities (10.04%). These results indicate that primary pollutants were more sensitive to emissions reductions; however, secondary pollutants demonstrated a lagged response the emissions reduction and were significantly affected by meteorological factors. The linear relationship between ozone and the emissions reduction was not significant, and was inverse overall. Further investigation are now required on the impact of emissions reduction on ozone pollution control.