Abstract:lockdown in China reduced long-range transport of air pollution to Taiwan.• OMI NO2 over central-north China reduced by 24% compared to previous years.
• PM2.5 concentration in northernTaiwan 2 times lower compared to similar episode • CMAQ simulation with 50% reduced emission in China matches measured PM2.5 in Taiwan. • Avoided PM2.5 pollution equivalent to 0.5 μg m −3 reduction for entire winter season
“… Fig. 6 Comparison of pollutant concentration changes associated to lockdowns in Almaty ( Kerimray et al, 2020 ), Beijing, Delhi, Dubai, Mumbai, Shanghai, Rome, Zaragoza ( Chauhan and Singh, 2020 ), Malaysian cities ( Kanniah et al, 2020 ), Northern China ( Shi and Brasseur, 2020 ), Seoul, several cities in China, Tehran, Brussels, Madrid, Milan (a), Paris, New York (a) ( Bauwens et al, 2020 ), several cities in China ( Zambrano-Monserrate et al, 2020 ), Taiwan ( Griffith et al, 2020 ), the Yangtze River Delta ( Li et al, 2020 ), Barcelona ( Tobías et al, 2020 ), Milan (b) ( Collivignarelli et al, 2020 ), Western Europe ( Menut et al, 2020 ), California ( Bashir et al, 2020 ), New York (b) ( Zangari et al, 2020 ), Rio de Janeiro (a: Dantas et al, 2020 ; b: Siciliano et al, 2020 ), and Sao Paulo (a: Krecl et al, 2020 , b: Nakada and Urban, 2020 ). …”
Lockdown measures led to air pollution decrease in several countries around the world such as China and India, whereas other regions experimented an increase in pollutant concentrations. Northern South America (NSA) was one of those areas where pollution changed during lockdown due to high fire activity. This study aims to analyze, for the first time in NSA, the behavior of selected criteria air pollutants during the implementation of the SARS-CoV-2 lockdown in two high populated cities of the region: Bogotá and Medellín in Colombia. A set of tools including surface measurements, as well as satellite and modeled data were used. 24-hour average concentrations of PM
10
, PM
2.5
, and NO
2
were collected from air quality stations for the lockdown period ranging from February 21 to June 30, 2020. The Copernicus Atmosphere Monitoring Service (CAMS) was used to analyze the fire flux OC as a biomass burning (BB) indicator, and tropospheric NO
2
concentrations were retrieved from TROPOMI. The HYSPLIT model was used to analyze back trajectories and fire data were obtained from MODIS sensor measurements. Our analysis shows short-term background NO
2
, PM
10
, and PM
2.5
concentration reductions of 60%, 44%, and 40%, respectively, for the strict lockdown; and 62%, 58%, and 69% for the relaxed lockdown. Corresponding long-term reductions were of 50%, 32%, and 9% for the strict lockdown; and 37%, 29%, and 19% for the relaxed lockdown. Regional BB increased PM
2.5
concentrations by 20 μg/m
3
during the strict lockdown, and the Saharan dust event increased PM
10
concentrations up to 168 μg/m
3
in Bogotá, and 104 μg/m
3
in Medellín, bringing an additional risk of morbidity and mortality for population. Regional BB has several causes that need to be properly managed to benefit local air quality improvement plans. Future cleaner transport policies equivalent to reduced lockdown mobility could bring pollution close to WHO guidelines.
“… Fig. 6 Comparison of pollutant concentration changes associated to lockdowns in Almaty ( Kerimray et al, 2020 ), Beijing, Delhi, Dubai, Mumbai, Shanghai, Rome, Zaragoza ( Chauhan and Singh, 2020 ), Malaysian cities ( Kanniah et al, 2020 ), Northern China ( Shi and Brasseur, 2020 ), Seoul, several cities in China, Tehran, Brussels, Madrid, Milan (a), Paris, New York (a) ( Bauwens et al, 2020 ), several cities in China ( Zambrano-Monserrate et al, 2020 ), Taiwan ( Griffith et al, 2020 ), the Yangtze River Delta ( Li et al, 2020 ), Barcelona ( Tobías et al, 2020 ), Milan (b) ( Collivignarelli et al, 2020 ), Western Europe ( Menut et al, 2020 ), California ( Bashir et al, 2020 ), New York (b) ( Zangari et al, 2020 ), Rio de Janeiro (a: Dantas et al, 2020 ; b: Siciliano et al, 2020 ), and Sao Paulo (a: Krecl et al, 2020 , b: Nakada and Urban, 2020 ). …”
Lockdown measures led to air pollution decrease in several countries around the world such as China and India, whereas other regions experimented an increase in pollutant concentrations. Northern South America (NSA) was one of those areas where pollution changed during lockdown due to high fire activity. This study aims to analyze, for the first time in NSA, the behavior of selected criteria air pollutants during the implementation of the SARS-CoV-2 lockdown in two high populated cities of the region: Bogotá and Medellín in Colombia. A set of tools including surface measurements, as well as satellite and modeled data were used. 24-hour average concentrations of PM
10
, PM
2.5
, and NO
2
were collected from air quality stations for the lockdown period ranging from February 21 to June 30, 2020. The Copernicus Atmosphere Monitoring Service (CAMS) was used to analyze the fire flux OC as a biomass burning (BB) indicator, and tropospheric NO
2
concentrations were retrieved from TROPOMI. The HYSPLIT model was used to analyze back trajectories and fire data were obtained from MODIS sensor measurements. Our analysis shows short-term background NO
2
, PM
10
, and PM
2.5
concentration reductions of 60%, 44%, and 40%, respectively, for the strict lockdown; and 62%, 58%, and 69% for the relaxed lockdown. Corresponding long-term reductions were of 50%, 32%, and 9% for the strict lockdown; and 37%, 29%, and 19% for the relaxed lockdown. Regional BB increased PM
2.5
concentrations by 20 μg/m
3
during the strict lockdown, and the Saharan dust event increased PM
10
concentrations up to 168 μg/m
3
in Bogotá, and 104 μg/m
3
in Medellín, bringing an additional risk of morbidity and mortality for population. Regional BB has several causes that need to be properly managed to benefit local air quality improvement plans. Future cleaner transport policies equivalent to reduced lockdown mobility could bring pollution close to WHO guidelines.
“…Obviously, the various forms of lockdown had an essential impact on the whole transport sector worldwide (see, for instance, reference [5] for the impact on logistics and reference [6] for the impact on air transport) and consequently on the environment and energy savings where side benefits were observed [7][8][9], as well as on economic and social activities [10,11]. The impact of COVID-19 was also intense in the field of urban mobility.…”
The COVID-19 pandemic had a significant effect in urban mobility, while essential changes are being observed in travelers’ behavior. Travelers in many cases shifted to other transport modes, especially walking and cycling, for minimizing the risk of infection. This study attempts to investigate the impact that COVID-19 had on travelers’ perceptions towards bike-sharing systems and whether the pandemic could result in a greater or lesser share of trips that are being conducted through shared bikes. For that reason, a questionnaire survey was carried out in the city of Thessaloniki, Greece, and the responses of 223 people were analyzed statistically. The results of the analysis show that COVID-19 will not affect significantly the number of people using bike-sharing for their trips. However, for a proportion of people, bike-sharing is now more attractive. Moreover, the results indicate that bike-sharing is now more likely to become a more preferable mobility option for people who were previously commuting with private cars as passengers (not as drivers) and people who were already registered users in a bike-sharing system. The results also provide evidence about the importance of safety towards COVID-19 for engaging more users in bike-sharing, in order to provide them with a safe mobility option and contribute to the city’s resilience and sustainability.
“…Because of this, it is difficult to determine the direct influence of the anthropogenic effects of COVID-19 on PM 2.5 concentrations observed in February and March 2020, and air pollutant concentration reduction trends during the COVID-19 period have only been confirmed by data such as surface observations and satellite images in most studies 7,20,21 . Alternatively, air quality modeling has been performed after assuming reduced emissions and the influences on the air pollutant concentration estimated 5,22,23 . Until now, there has been no study to quantitatively present the reduction of observed air pollutant concentrations influenced by COVID-19, separated from the influences of meteorological conditions and emission reduction policies.…”
In January 2020, anthropogenic emissions in Northeast Asia reduced due to the COVID-19 outbreak. When outdoor activities of the public were limited, PM2.5 concentrations in China and South Korea between February and March 2020 reduced by − 16.8 μg/m3 and − 9.9 μg/m3 respectively, compared with the average over the previous three years. This study uses air quality modeling and observations over the past four years to separate the influence of reductions in anthropogenic emissions from meteorological changes and emission control policies on this PM2.5 concentration change. Here, we show that the impacts of anthropogenic pollution reduction on PM2.5 were found to be approximately − 16% in China and − 21% in South Korea, while those of meteorology and emission policies were − 7% and − 8% in China, and − 5% and − 4% in South Korea, respectively. These results show that the influence on PM2.5 concentration differs across time and region and according to meteorological conditions and emission control policies. Finally, the influence of reductions in anthropogenic emissions was greater than that of meteorological conditions and emission policies during COVID-19 period.
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