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      Impact of Covid-19 lockdown on PM 10, SO 2 and NO 2 concentrations in Salé City (Morocco)

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          Abstract

          Covid-19 was first reported in Morocco on March 2, 2020. Since then, to prevent its propagation, the Moroccan government declared a state of health emergency. A set of rapid and strict countermeasures have taken, including locking down cities, limiting population's mobility and prohibiting almost all avoidable activities. In the present study, we attempted to evaluate the changes in levels of some air pollutants (mainly PM 10, NO 2 and SO 2) in Salé city (North-Western Morocco) during the lockdown measures. In this context, a continuous measurement of PM 10, SO 2 and NO 2 was carried before and during the Covid-19 lockdown period. As a consequence of the security measures and control actions undertaken, the emissions from vehicle exhaust and industrial production were significantly reduced, which contribute to the decrease in the concentrations of the studied pollutants. The obtained results showed that the difference between the concentrations recorded before and during the lockdown period were respectively 75%, 49% and 96% for PM 10, SO 2 and NO 2. PM 10 levels were much less reduced than NO 2. The three-dimensional air mass backward trajectories, using the HYSPLIT model, demonstrated the benefits of PM 10 local emission reductions related to the lockdown were overwhelmed by the contribution of long-range transported aerosols outside areas. In addition, noteworthy differences in the air mass back trajectories and the meteorology between these two periods were evidenced.

          Graphical abstract

          Daily average concentrations of SO 2 and NO 2 from March 11th to April 2nd in Salé city.

          Highlights

          • •

            PM 10, NO 2 and SO 2 concentrations were reduced by more than half during the covid-19 lockdown period.

          • •

            Covid-19 countermeasures contribute to reduce all pollutant concentrations but with significant differences among them.

          • •

            Long-range transported aerosols contributions overcame the PM 10 local emission reductions benefits related to the lockdown.

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          Changes in air quality during the lockdown in Barcelona (Spain) one month into the SARS-CoV-2 epidemic

          Aurelio Tobías, Cristina Carnerero, Cristina Reche … (2020)
          Lockdown measures came into force in Spain from March 14th, two weeks after the start of the SARS-CoV-2 epidemic, to reduce the epidemic curve. Our study aims to describe changes in air pollution levels during the lockdown measures in the city of Barcelona (NE Spain), by studying the time evolution of atmospheric pollutants recorded at the urban background and traffic air quality monitoring stations. After two weeks of lockdown, urban air pollution markedly decreased but with substantial differences among pollutants. The most significant reduction was estimated for BC and NO2 (−45 to −51%), pollutants mainly related to traffic emissions. A lower reduction was observed for PM10 (−28 to −31.0%). By contrast, O3 levels increased (+33 to +57% of the 8 h daily maxima), probably due to lower titration of O3 by NO and the decrease of NOx in a VOC-limited environment. Relevant differences in the meteorology of these two periods were also evidenced. The low reduction for PM10 is probably related to a significant regional contribution and the prevailing secondary origin of fine aerosols, but an in-depth evaluation has to be carried out to interpret this lower decrease. There is no defined trend for the low SO2 levels, probably due to the preferential reduction in emissions from the least polluting ships. A reduction of most pollutants to minimal concentrations are expected for the forthcoming weeks because of the more restrictive actions implemented for a total lockdown, which entered into force on March 30th. There are still open questions on why PM10 levels were much less reduced than BC and NO2 and on what is the proportion of the abatement of pollution directly related to the lockdown, without meteorological interferences.
          Article 0 comments Cited 351 times – based on 0 reviews     Review now
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            Severe air pollution events not avoided by reduced anthropogenic activities during COVID-19 outbreak

            Pengfei Wang, Kaiyu Chen, Shengqiang Zhu … (2020)
            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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              Sources and properties of non-exhaust particulate matter from road traffic: a review.

              Harry A. Thorpe, Nicholas Harrison (2008)
              While emissions control regulation has led to a substantial reduction in exhaust emissions from road traffic, currently non-exhaust emissions from road vehicles are unabated. These include particles from brake wear, tyre wear, road surface abrasion and resuspension in the wake of passing traffic. Quantification of the magnitude of such emissions is problematic both in the laboratory and the field and the latter depends heavily upon a knowledge of the physical and chemical properties of non-exhaust particles. This review looks at each source in turn, reviewing the available information on the source materials and particles derived from them in laboratory studies. In a final section, some of the key publications dealing with measurements in road tunnels and the roadside environment are reviewed. It is concluded that with the exception of brake dust particles which may be identified from their copper (Cu) and antimony (Sb) content, unequivocal identification of particles from other sources is likely to prove extremely difficult, either because of the lack of suitable tracer elements or compounds, or because of the interactions between sources prior to the emission process. Even in the case of brake dust, problems will arise in distinguishing directly emitted particles from those arising from resuspension of deposited brake dust from the road surface, or that derived from entrainment of polluted roadside soils, either directly or as a component of road surface dust.
              Article 0 comments Cited 229 times – based on 0 reviews     Review now
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                Author and article information

                Contributors
                Abdelfettah Benchrif
                Journal
                Journal ID (nlm-ta): Sci Total Environ
                Journal ID (iso-abbrev): Sci. Total Environ
                Title: The Science of the Total Environment
                Publisher: Published by Elsevier B.V.
                ISSN (Print): 0048-9697
                ISSN (Electronic): 1879-1026
                Publication date PMC-release: 19 May 2020
                Publication date (Print): 15 September 2020
                Publication date (Electronic): 19 May 2020
                Volume: 735
                Page: 139541
                Affiliations
                [a ]Faculty of Sciences, Ibn Tofail University, Kenitra, Morocco
                [b ]National Centre for Nuclear Energy, Science and Technology (CNESTEN), Morocco
                [c ]Laboratoire National des Études et de Surveillance de la Pollution (LNESP), Morocco
                [d ]Direction Régionale de la Culture, Ministère de la Culture, Morocco
                Author notes
                [* ]Corresponding author at: National Centre for Nuclear Energy, Science and Technology (CNESTEN), BP 1382, 10001 Rabat, Morocco benchrif@ 123456cnesten.org.ma
                Article
                Publisher ID: S0048-9697(20)33058-8 Publisher ID: 139541
                DOI: 10.1016/j.scitotenv.2020.139541
                PMC ID: 7235599
                PubMed ID: 32445829
                SO-VID: 5efea7e1-9b7c-46ba-b6a2-8c81273d89f5
                Copyright © © 2020 Published by Elsevier B.V.
                License:

                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
                Date received : 10 May 2020
                Date revision received : 15 May 2020
                Date accepted : 17 May 2020
                Categories
                Subject: Article

                ScienceOpen disciplines: General environmental science
                Keywords: covid-19,pm10,no2,so2,lockdown,morocco
                Data availability:
                ScienceOpen disciplines: General environmental science
                Keywords: covid-19, pm10, no2, so2, lockdown, morocco

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