Environmental spatial heterogeneity of the impacts of COVID-19 on the top-20 metropolitan cities of Asia-Pacific

Abstract

This study investigated the environmental spatial heterogeneity of novel coronavirus (COVID-19) and spatial and temporal changes among the top-20 metropolitan cities of the Asia-Pacific. Remote sensing-based assessment is performed to analyze before and during the lockdown amid COVID-19 lockdown in the cities. Air pollution and mobility data of each city (Bangkok, Beijing, Busan, Dhaka, Delhi, Ho Chi Minh, Hong Kong, Karachi, Mumbai, Seoul, Shanghai, Singapore, Tokyo, Wuhan, and few others) have been collected and analyzed for 2019 and 2020. Results indicated that almost every city was impacted positively regarding environmental emissions and visible reduction were found in Aerosol Optical Depth (AOD), sulfur dioxide (SO₂), carbon monoxide (CO), and nitrogen dioxide (NO₂) concentrations before and during lockdown periods of 2020 as compared to those of 2019. The highest NO₂ emission reduction (~ 50%) was recorded in Wuhan city during the lockdown of 2020. AOD was highest in Beijing and lowest in Colombo (< 10%). Overall, 90% movement was reduced till mid-April, 2020. A 98% reduction in mobility was recorded in Delhi, Seoul, and Wuhan. This analysis suggests that smart mobility and partial shutdown policies could be developed to reduce environmental pollutions in the region. Wuhan city is one of the benchmarks and can be replicated for the rest of the Asian cities wherever applicable.

Figure 1

Comparison of daily changes in AOD concentration of the cities in 2019 and 2020.

Figure 2

Spatial patterns indicating a drastic drop in average NO₂ concentration in March 2019 and 2020 in the Asia-Pacific region. Maps were created through Google Earth Engine (https://earthengine.google.com/V.2020) by a co-author, Sawaid Abbas.

Figure 3

Periodic changes of NO₂ concentration of the cities in 2019 and 2020 during the P1 (Jan 1–Jan 22), P2 (Jan 23–Feb 22), P3 (Feb 23–Mar 22), P4 (Mar 23–Apr 22) and P5 (Apr 23–May 22). The black and red dotted lines indicate mean NO₂ concentration (Jan 1–May 22) in 2019 and 2020 and the dots indicate outliers, respectively.

Figure 4

Comparison of daily changes in CO concentration of the cities in 2019 and 2020.

Figure 5

Patterns of changes in mobility in different cities due to lockdown implementation. The anomalies are computed with respect to base period from 1st January to 14th February 2020.