Factors influencing improvements in air quality in Guanzhong cities of China, and variations therein for 2014-2020

It is interesting and important to know what factors cause improvements in regional air quality. This study analyzed the factors that improved the air quality in cities in the Guanzhong region of China-in terms of meteorology and controlling emissions-following the implementation of the "Action Plan for Air Pollution Prevention and Control" in 2013. The average air quality index (AQI) values, PM2.5, PM10, SO2, CO, and NO2 in these cities in 2020 decreased by 45.1%, 43.8%, 82.9%, 57.3%, and 31.6%, respectively, compared to the values in 2014, while the O3 concentration increased by 16.7%. During the COVID-19 pandemic of February to May 2020, lockdown measures in cities in Guanzhong resulted in reductions of approximately 18.4%, 24.2%, and 17.9% in the AQI, PM2.5, and PM10 concentrations compared to the same period in 2019. Principal component analysis showed that the yearly reduction in AQI in cities in Guanzhong was attributed mainly to reductions in industrial emissions, followed by reductions in emissions from homes and motor vehicle exhausts. We propose the strengthening of measures to control particulate matter, O3 and greenhouse gas to see the improvement of air quality among this region in the future