Abstract
The study aimed to examine the change in the concentration of nitrogen dioxide due to the lockdown amid the COVID-19 pandemic in India at the district level using Sentinel-5P TROPOMI. The spatio-temporal characteristics of the tropospheric column NO2 concentration during 45 days of the lockdown were compared with the same days of 2019. Further, to model spatially varying relationships of NO2 during the lockdown period, it was given as a dependent variable whereas NO2 during the pre-lockdown period was considered as an independent variable. Results show that the mean NO2 concentration was reduced from 0.00406 mol/m2 before the lockdown (2019-03-25 to 2019-05-10) to 0.0036 mol/m2 during the lockdown period (2020-03-25 to 2020-05-10). The maximum decline of NO2 concentration was observed in Gautam Buddha Nagar and Delhi. This indicates the high level of atmospheric pollution due to the excess use of fuel in human activities. The results of the Ordinary Least Squares (OLS) method show a strong positive relationship between both variables. Positive standard residuals indicate that the concentration of NO2 has reduced more than expected as per the OLS model. The z-score (24.11) was obtained from spatial autocorrelation. It indicates that residuals are highly clustered and there is less than a 1% likelihood that this clustered pattern could be a result of a random chance. The highest decrease was observed in districts/urban agglomerations of Gautam Buddha Nagar (-40%), Delhi (-37%), Greater Bombay (-31%), Hyderabad (-29%), Faridabad (-29%), Bangalore Urban (-28%), Gandhinagar (-27%), Chennai (-27%) and Gurgaon (-26%) respectively.
Highlights
Nitrogen dioxide (NO2) is an ambient trace gas which originates from both natural and anthropogenic processes
The major hot spots were observed in the National Capital Region (NCR), parts of certain states such as Chhattisgarh, Orissa, West Bengal, and metropolitan cities namely Ahmadabad, Greater Mumbai and Bangalore (Figure 1)
Describing air pollution due to COVID-19 has perhaps offered up hope of a practical way to reduce the effects of the virus, even if the change in outcomes is highly uncertain (Lewis 2020)
Summary
Nitrogen dioxide (NO2) is an ambient trace gas which originates from both natural and anthropogenic processes. Long-term exposure to NO2 may cause a wide spectrum of severe health problems such as hypertension, diabetes, heart and cardiovascular diseases and even death (Ogen 2020). Breathing air with a high concentration of NO2 can damage human respiratory system. Such exposure over short periods can aggravate respiratory diseases, asthma, leading to respiratory symptoms such as coughing, wheezing or difficult breathing. Longer exposure to an elevated concentration of NO2 may contribute to the development of asthma and potentially increase susceptibility to respiratory infections. COVID-19 originated from Wuhan city of Hubei Province in China in December 2019. Since it has spread in more than 210 countries. More than 4.3 million cases of Covid-19 have been recorded worldwide, including at least 297,000 deaths as of 7th April 2020., According to the tally of deaths by Johns Hopkins University at least 300,074 people have died from COVID-19 across the world (Renton 2020)
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