Despite the reduction of economic activities during the pandemic-related lockdown, there was no respite in air pollution in most parts of India, as satellite observations show. Many parts of central-western India and north India showed an increase in pollution in contrast to the general trend.
Scientists at the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science and Technology (DST), Government of India, utilised the EUMETSAT and NASA satellite observations for the years 2018, 2019 and 2020, and investigated the influence of significant cut-off of anthropogenic activities on the changes in the vertical and columnar distribution of ozone, CO, and NO2 during the lockdown period. They identified that regions in the central-western part of India and north India are prone to higher air pollution exposure based on state-of-the-art satellite observations and hence are exposed to a greater risk of respiratory problems.
The study published in Environmental Science and Pollution Research led by Prajjwal Rawat, a senior research fellow at ARIES Nainital, and his research supervisor Dr Manish Naja, showed that ozone, carbon monoxide, and NO2 showed an increase of about 15% over the central-western part of India. According to the study, carbon monoxide showed a consistent increase (as high as 31%) of concentration at higher heights during the lockdown. The long-range transport and downward transport from the stratosphere significantly increased ozone concentrations over north India during the lockdown, and remote regions like the Himalayas and coastal cities showed the bare minimum influence of lockdown in air quality, with a tendency to increase in criteria air pollutants.
The satellite-based observation of toxic trace gases, ozone, NO2 and carbon monoxide near the surface and in the free troposphere, mostly showed a reduction of the pollutants over India. However, over some regions like western-central India, some parts of Northern India, and Remote Himalaya, an increase of ozone and other toxic gases was observed. This could have aggravated respiratory health risks around those regions during the pandemic.
Multi-satellite remote sensing of air pollutants has evolved dramatically over the last decade. Synergic measurements of satellite and in-situ observation provide a more comprehensive understanding of air pollution episodes. In 2020, a complete nationwide lockdown was imposed over India to impede the spread of coronavirus disease. This enormously disrupted the economy with a single positive side effect, a short-term improvement in the air quality near the surface.
According to the ARIES team, the study helped to identify the regions prone to higher air pollution exposure and, hence, can identify areas at a greater health risk. The team previously, with scientists from the ISRO, showed INSAT-3D as a valuable Indian geostationary satellite to study ozone pollutions over India; however, for other criteria, air pollutants (i.e., NO2, SO2, CO, VOCs, etc.), India is lacking in space-based observations and need air quality monitoring indigenous satellite in orbit.