Project

  • Lock-Down’s Impact on India’s Air Quality
  • Client: Govt of India
  • Project date: 30 Augest, 2021
  • Project URL:
  • Investigation of the impact of lockdown on NO2 concentrations before and during different phases of lockdown.
  • Used Sentinel-5P NRTI NO2: Near Real-Time NO2 dataset for analysis, imported from GEE Image-Collection.
  • GeeMap, a Python package for interactive mapping with Google Earth Engine API, is used for the analysis.
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Lock-Down’s Impact on India’s Air Quality

Introduction:

Air pollution has become a severe problem in Indian cities due to rapid urbanization and industrialization, causing numerous health-related issues for humans and the environment. Nitrogen Dioxide (NO2), one of the major pollutants, results from vehicular, industrial, and thermal power plant emissions. During the COVID-19 pandemic, a nationwide lockdown was imposed into four phases from March 25 - May 31, 2020; Phase-I (25/03/2020 - 14/04/2020), Phase-II (15/04/2020 - 03/05/2020), Phase-III (04/05/2020 - 17/05/2020) and Phase-IV (18/05/2020 – 31/05/2020). All major anthropogenic activities contributing to atmospheric pollution (such as industries, vehicles, and other activities) were restricted during the lockdown. The current report examines the impact of the lockdown on tropospheric NO2 concentrations before and during the different phases of lockdown through satellite (Sentinel 5P) and ground- based (CPCB) measurement across India and two major cities Delhi and Bangalore.

Results:

Long-term Analysis over India:

(a)

(b)

Fig-1. (a) Average tropospheric NO2 (µmol/m2) level for the year 2019, (b) Average tropospheric NO2 (µmol/m2) level for the year 2020.

In 2020, the lockdown was imposed for a shorter period, but it contributed to a significant reduction in NO2 concentration throughout the year compared to the previous year (Fig-1). For a more detailed study, the average NO2 concentration is also compared for the lockdown period

(March 25 to May 31) for 2019 and 2020. A huge reduction in tropospheric NO2 level is observed during the lockdown period in 2020 compared to 2019.

Lockdown Impact on tropospheric NO2:

During the pre-lockdown period, tropospheric NO2

analysis over India depicted that the hotspots are observed from the most

urbanized locations

(megacities) or the locations dominated by the presence of thermal power plants and other

industries. At the urbanized locations, the high NO2

concentration can be attributed to vehicular

emission, domestic

combustion, industrial emission and many other anthropogenic activities.

During the first phase of

lockdown, most of the urbanized locations (cities) shows a huge reduction in NO2 level that may be associated with a strict restriction in

transportation activities. Another major reason is the closure of industrial activities around the major cities, which is also a major source of air pollution, particularly NO2. However, some locations still show higher NO2 level. That were identifiesd as thermal power plant emissions in Jharkhand, Chhattisgarh, West- Bengal, Orisa and south-eastern of UP, which were operational to accomplish the electricity demand of the country.

After

the

first

phase

lockdown,

NO2

level

gradually

increases

from

second phase to fourth phase lockdown because an ease in the upcoming lockdown phases compared to first phase lockdown.

In the third and fourth phase of lockdown,

higher NO2 level is

observed over the Western UP, Punjab and Haryana states. These higher NO2 levels culd be attributed to the crop

residueburning

activities in the respected states.

NO2 analysis over the megacities Delhi and Bangalore:

Delhi

Bangalore

Pre-Lockdown

(01/03/2020 – 24/03/2020)

Phase-I Lockdown

(25/03/2020 – 14/04/2020)

Phase-II Lockdown

(15/04/2020 – 03/05/2020)

Phase-III Lockdown

(04/05/2020 – 17/05/2020)

Phase-IV Lockdown

(18/05/2020 – 31/05/2020)

From the above spatial plots, It is observed that both the cities have the same trend in NO2 level during the study period. Both Delhi and Bangalore show the highest NO2 in the pre-lockdown phase while the lowest in the first phase of lockdown. It is also experienced that Delhi shows a continuous increase in NO2 level with a higher rate than Bangalore from the second phase to the fourth phase of lockdown.

Time-Series Analysis

Delhi

For the time series analysis, Satellite NO2 values have been extracted at the Lodhi Road IMD (CPCB station;[ 28.70, 77.10]) location for the lockdown duration (March 1 – May 31) for the years 2019 and 2020. Kaggle Air Quality Index(AQI) data has also been analyzed with the NO2 level at the respective locations and durations. It has been observed that the NO2 level remains much lower in 2020 compared to 2019. Throughout the lockdown duration, 2020 shows significantly improved Air Quality compared to 2019.

**breaks in plots are due to the missing data

Bangalore

A similar analysis has been performed for Bangalore, India. At BTM Layout, Banglore-CPCB station [12.91, 77.59] location. A large data gap has been observed in satellite observation at the Bangalore location during the study period, But it shows better air quality.