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. 2020 Aug 25:732:139282.
doi: 10.1016/j.scitotenv.2020.139282. Epub 2020 May 11.

Air quality changes during the COVID-19 lockdown over the Yangtze River Delta Region: An insight into the impact of human activity pattern changes on air pollution variation

Li Li  1 , Qing Li  2 , Ling Huang  2 , Qian Wang  2 , Ansheng Zhu  2 , Jian Xu  2 , Ziyi Liu  2 , Hongli Li  2 , Lishu Shi  2 , Rui Li  2 , Majid Azari  3 , Yangjun Wang  2 , Xiaojuan Zhang  2 , Zhiqiang Liu  2 , Yonghui Zhu  2 , Kun Zhang  2 , Shuhui Xue  2 , Maggie Chel Gee Ooi  4 , Dongping Zhang  2 , Andy Chan  5
Affiliations

Air quality changes during the COVID-19 lockdown over the Yangtze River Delta Region: An insight into the impact of human activity pattern changes on air pollution variation

Li Li et al. Sci Total Environ. .

Abstract

The outbreak of COVID-19 has spreaded rapidly across the world. To control the rapid dispersion of the virus, China has imposed national lockdown policies to practise social distancing. This has led to reduced human activities and hence primary air pollutant emissions, which caused improvement of air quality as a side-product. To investigate the air quality changes during the COVID-19 lockdown over the YRD Region, we apply the WRF-CAMx modelling system together with monitoring data to investigate the impact of human activity pattern changes on air quality. Results show that human activities were lowered significantly during the period: industrial operations, VKT, constructions in operation, etc. were significantly reduced, leading to lowered SO2, NOx, PM2.5 and VOCs emissions by approximately 16-26%, 29-47%, 27-46% and 37-57% during the Level I and Level II response periods respectively. These emission reduction has played a significant role in the improvement of air quality. Concentrations of PM2.5, NO2 and SO2 decreased by 31.8%, 45.1% and 20.4% during the Level I period; and 33.2%, 27.2% and 7.6% during the Level II period compared with 2019. However, ozone did not show any reduction and increased greatly. Our results also show that even during the lockdown, with primary emissions reduction of 15%-61%, the daily average PM2.5 concentrations range between 15 and 79 μg m-3, which shows that background and residual pollutions are still high. Source apportionment results indicate that the residual pollution of PM2.5 comes from industry (32.2-61.1%), mobile (3.9-8.1%), dust (2.6-7.7%), residential sources (2.1-28.5%) in YRD and 14.0-28.6% contribution from long-range transport coming from northern China. This indicates that in spite of the extreme reductions in primary emissions, it cannot fully tackle the current air pollution. Re-organisation of the energy and industrial strategy together with trans-regional joint-control for a full long-term air pollution plan need to be further taken into account.

Keywords: Air quality; COVID-19; Yangtze River Delta.

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Conflict of interest statement

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Unlabelled Image
Graphical abstract
Fig. 1
Fig. 1
Modelling domain and locations of the national observational sites (green triangle). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 2
Fig. 2
Scatter plots of observed and simulated PM2.5 concentrations during pre-lockdown, Level I and Level II response periods at 41 monitoring sites over the YRD region (locations are monitoring sites shown in Fig. 2).
Fig. 3
Fig. 3
Relative changes of PM2.5 during Pre-lockdown, Level I and Level II periods in YRD.
Fig. 4
Fig. 4
Yearly changes of PM2.5, PM10, CO, NO2, SO2 and O3-8h in 41 cities in the YRD during 1st January - 31st Mar, 2020.
Fig. 5
Fig. 5
PM2.5 potential source regions:air mass trajectory analysis during different stages in Shanghai.
Fig. 6
Fig. 6
Source contribuitons to PM2.5 at Shanghai, Hefei, Hangzhou and Nanjing during pre-lockdown, Level I and Level II response periods.
Fig. 7
Fig. 7
Sectoral contribuitons to PM2.5 during pre-lockdown, Level I and Level II response periods in YRD.
See this image and copyright information in PMC

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