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      Effect of restricted emissions during COVID-19 on air quality in India

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          Abstract

          The effectiveness and cost are always top factors for policy-makers to decide control measures and most measures had no pre-test before implementation. Due to the COVID-19 pandemic, human activities are largely restricted in many regions in India since mid-March of 2020, and it is a progressing experiment to testify effectiveness of restricted emissions. In this study, concentrations of six criteria pollutants, PM 10, PM 2.5, CO, NO 2, ozone and SO 2 during March 16th to April 14th from 2017 to 2020 in 22 cities covering different regions of India were analysed. Overall, around 43, 31, 10, and 18% decreases in PM 2.5, PM 10, CO, and NO 2 in India were observed during lockdown period compared to previous years. While, there were 17% increase in O 3 and negligible changes in SO 2. The air quality index (AQI) reduced by 44, 33, 29, 15 and 32% in north, south, east, central and western India, respectively. Correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years, indicating more significant regional transport than previous years. The mean excessive risks of PM reduced by ~52% nationwide due to restricted activities in lockdown period. To eliminate the effects of possible favourable meteorology, the WRF-AERMOD model system was also applied in Delhi-NCR with actual meteorology during the lockdown period and an un-favourable event in early November of 2019 and results show that predicted PM 2.5 could increase by only 33% in unfavourable meteorology. This study gives confidence to the regulatory bodies that even during unfavourable meteorology, a significant improvement in air quality could be expected if strict execution of air quality control plans is implemented.

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          Highlights

          • The effect of restricted human activities due to the COVID-19 pandemic in India on air quality in 22 cities was estimated.

          • PM 2.5 had maximum reduction in most regions.

          • Correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years.

          • The substantial reduction in concentrations resulted in a 4 times reduction in total ER.

          • PM 2.5 could increase due to unfavourable meteorology but the average concentration would still be under CPCB limits.

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          Most cited references16

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          Anthropogenic drivers of 2013–2017 trends in summer surface ozone in China

          Significance Drastic air pollution control in China since 2013 has achieved sharp decreases in fine particulate matter (PM2.5), but ozone pollution has not improved. After removing the effect of meteorological variability, we find that surface ozone has increased in megacity clusters of China, notably Beijing and Shanghai. The increasing trend cannot be simply explained by changes in anthropogenic precursor [NOx and volatile organic compound (VOC)] emissions, particularly in North China Plain (NCP). The most important cause of the increasing ozone in NCP appears to be the decrease in PM2.5, slowing down the sink of hydroperoxy radicals and thus speeding up ozone production. Decreasing ozone in the future will require a combination of NOx and VOC emission controls to overcome the effect of decreasing PM2.5.
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            Severe air pollution events not avoided by reduced anthropogenic activities during COVID-19 outbreak

            Due to the pandemic of coronavirus disease 2019 in China, almost all avoidable activities in China are prohibited since Wuhan announced lockdown on January 23, 2020. With reduced activities, severe air pollution events still occurred in the North China Plain, causing discussions regarding why severe air pollution was not avoided. The Community Multi-scale Air Quality model was applied during January 01 to February 12, 2020 to study PM2.5 changes under emission reduction scenarios. The estimated emission reduction case (Case 3) better reproduced PM2.5. Compared with the case without emission change (Case 1), Case 3 predicted that PM2.5 concentrations decreased by up to 20% with absolute decreases of 5.35, 6.37, 9.23, 10.25, 10.30, 12.14, 12.75, 14.41, 18.00 and 30.79 μg/m3 in Guangzhou, Shanghai, Beijing, Shijiazhuang, Tianjin, Jinan, Taiyuan, Xi'an, Zhengzhou, Wuhan, respectively. In high-pollution days with PM2.5 greater than 75 μg/m3, the reductions of PM2.5 in Case 3 were 7.78, 9.51, 11.38, 13.42, 13.64, 14.15, 14.42, 16.95 and 22.08 μg/m3 in Shanghai, Jinan, Shijiazhuang, Beijing, Taiyuan, Xi'an, Tianjin, Zhengzhou and Wuhan, respectively. The reductions in emissions of PM2.5 precursors were ~2 times of that in concentrations, indicating that meteorology was unfavorable during simulation episode. A further analysis shows that benefits of emission reductions were overwhelmed by adverse meteorology and severe air pollution events were not avoided. This study highlights that large emissions reduction in transportation and slight reduction in industrial would not help avoid severe air pollution in China, especially when meteorology is unfavorable. More efforts should be made to completely avoid severe air pollution.
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              Temporal variations of six ambient criteria air pollutants from 2015 to 2018, their spatial distributions, health risks and relationships with socioeconomic factors during 2018 in China

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                Author and article information

                Contributors
                Journal
                Sci Total Environ
                Sci. Total Environ
                The Science of the Total Environment
                Elsevier B.V.
                0048-9697
                1879-1026
                22 April 2020
                1 August 2020
                22 April 2020
                : 728
                : 138878
                Affiliations
                [a ]Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
                [b ]Department of Environmental Science and Engineering, Fudan University, Shanghai, China
                [c ]Engineering Technology Development Center of Urban Water Recycling, Shenzhen Polytechnic, Shenzhen, China
                Author notes
                Article
                S0048-9697(20)32395-0 138878
                10.1016/j.scitotenv.2020.138878
                7175882
                32335409
                b9e15fde-13f2-4dab-bc80-a670dfd6b39c
                © 2020 Elsevier B.V. All rights reserved.

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

                History
                : 16 April 2020
                : 19 April 2020
                Categories
                Article

                General environmental science
                covid-19,india,aqi,pm2.5,aermod
                General environmental science
                covid-19, india, aqi, pm2.5, aermod

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