The science of the total environment

Diurnal and temporal changes in air pollution during COVID-19 strict lockdown over different regions of India.

The coronavirus-19 (COVID-19) pandemic led to government interventions to limit the spread of the disease which are unprecedented in recent history;for example, stay at home orders led to sudden decreases in atmospheric emissions from the transportation sector In this review article, the current understanding of the influence of emission reductions on atmospheric pollutant concentrations and air quality is summarized for nitrogen dioxide (NO2), particulate matter (PM25), ozone (O3), ammonia, sulfur dioxide, black carbon, volatile organic compounds, and carbon monoxide (CO) In the first 7 months following the onset of the pandemic, more than 200 papers were accepted by peer-reviewed journals utilizing observations from ground-based and satellite instruments Only about one-third of this literature incorporates a specific method for meteorological correction or normalization for comparing data from the lockdown period with prior reference observations despite the importance of doing so on the interpretation of results We use the government stringency index (SI) as an indicator for the severity of lockdown measures and show how key air pollutants change as the SI increasesThe observed decrease of NO2 with increasing SI is in general agreement with emission inventories that account for the lockdown Other compounds such as O3, PM25, and CO are also broadly covered Due to the importance of atmospheric chemistry on O3 and PM25 concentrations, their responses may not be linear with respect to primary pollutants At most sites, we found O3 increased, whereas PM25 decreased slightly, with increasing SI Changes of other compounds are found to be understudied We highlight future research needs for utilizing the emerging data sets as a preview of a future state of the atmosphere in a world with targeted permanent reductions of emissions Finally, we emphasize the need to account for the effects of meteorology, emission trends, and atmospheric chemistry when determining the lockdown effects on pollutant concentrations Copyright: © 2021 The Author(s)

/pdf/the-global-impacts-of-covid-19-lockdowns-on-urban-air-44wnyuozcg.pdf

The global impacts of COVID-19 lockdowns on urban air pollution: A critical review and recommendations

Human mobility behavior in COVID-19: A systematic literature review and bibliometric analysis

A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions.

Exceedances and trends of particulate matter (PM2.5) in five Indian megacities.

. We have estimated the spatial changes in NO 2 levels over different
regions of India during the COVID-19 lockdown (25 March–3 May 2020) using the satellite-based tropospheric column NO 2 observed by
the Ozone Monitoring Instrument (OMI) and the Tropospheric Monitoring
Instrument (TROPOMI), as well as surface NO 2 concentrations obtained
from the Central Pollution Control Board (CPCB) monitoring network. A
substantial reduction in NO 2 levels was observed across India during
the lockdown compared to the same period during previous business-as-usual
years, except for some regions that were influenced by anomalous fires in
2020. The reduction (negative change) over the urban agglomerations was
substantial ( ∼  20 %–40 %) and directly proportional to the
urban size and population density. Rural regions across India also
experienced lower NO 2 values by ∼  15 %–25 %. Localised
enhancements in NO 2 associated with isolated emission increase
scattered across India were also detected. Observed percentage changes in
satellite and surface observations were consistent across most regions and
cities, but the surface observations were subject to larger variability
depending on their proximity to the local emission sources. Observations
also indicate NO 2 enhancements of up to ∼  25 % during
the lockdown associated with fire emissions over the north-east of India
and some parts of the central regions. In addition, the cities located near the
large fire emission sources show much smaller NO 2 reduction than other
urban areas as the decrease at the surface was masked by enhancement in
NO 2 due to the transport of the fire emissions.

/pdf/covid-19-lockdown-induced-changes-in-no2-levels-across-india-2pd6cypf3i.pdf

Shweta Singh

Papers

Diurnal and temporal changes in air pollution during COVID-19 strict lockdown over different regions of India.

Exceedances and trends of particulate matter (PM2.5) in five Indian megacities.

COVID-19 lockdown-induced changes in NO2 levels across India observed by multi-satellite and surface observations