Assessment of Air Pollution before, during and after the COVID-19 Pandemic Lockdown in Nanjing, China

Ahmad Hasnain,Yong Zha,Basit Nadeem,Muhammad Zaffar Hashmi,Uzair Aslam Bhatti,Geng Wei,Yehua Sheng

doi:10.3390/atmos12060743

Abstract

A unique illness, the coronavirus disease 2019 (COVID-19), emerged in Wuhan, People’s Republic of China, in December 2019. To reduce the spread of the virus, strict lockdown policies and control measures were put in place all over the world. Due to these enforced limitations, a drastic drop in air pollution and an improvement in air quality were observed. The present study used six air pollutants (PM10, PM2.5, SO2, NO2, CO and O3) to observe trends before, during and after the COVID-19 lockdown period in Nanjing, China. The data were divided into six phases: P1–P3, pre-lockdown (1 October–31 December 2019), lockdown (1 January–31 March 2020), after lockdown (1 April–30 June 2020), P4–P6: the same dates as the lockdown but during 2017, 2018 and 2019. The results indicate that compared with the pre-lockdown phase, the PM10 and PM2.5 average concentrations decreased by –27.71% and –5.09%. Compared with the previous three years, 2017–2019, the reductions in PM10 and PM2.5 were –37.99% and –33.56%, respectively. Among other pollutants, concentrations of SO2 (–32.90%), NO2 (–34.66%) and CO (–16.85%) also decreased during the lockdown, while the concentration of O3 increased by approximately 25.45%. Moreover, compared with the pre- and during lockdown phases, PM10, PM2.5 and NO2 showed decreasing trends while SO2, CO and O3 concentrations increased. These findings present a road map for upcoming studies and provide a new path for policymakers to create policies to improve air quality.

Highlights

A new type of virus, a novel coronavirus disease, was first identified at the end of December 2019 in the capital city of China’s Hubei Province, Wuhan
Our results demonstrate that during the COVID-19 pandemic lockdown phase in China, Nanjing experienced a significant change in PM10 and a reduction of approximately −27.71% compared with the pre-lockdown phase, due to the restricted traffic and shutdown of industries
The impact of the nationwide lockdown that was imposed in order to curb the rapid spread of COVID-19 in China, on the air quality of the capital city of Jiangsu Province, Nanjing, was evaluated based on six air pollutants

Summary

Introduction

A new type of virus, a novel coronavirus disease, was first identified at the end of December 2019 in the capital city of China’s Hubei Province, Wuhan. The World Health Organization (WHO) officially called it the coronavirus disease 2019 (COVID-19) [1]. After the first confirmed case, the number of infected people increased rapidly all over the country, and within just a few days, due to the spread of COVID-19, it turned into a national disaster [3,4]. At the end of June 2020, in 215 countries around the world, more than 10.6 million people had been infected and 514,315 people had died as a result of the spread of COVID-19. The WHO confirmed COVID-19 as worldwide public health emergency due to its large-scale spread and contagious effects [2]. By early August 2020, more than 19.46 million confirmed cases of COVID-19 were observed in over 200 countries and territories around the world, according to the WHO [4]

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