The AQI at almost all locations in Mumbai improved from moderate to satisfactory during lockdown, stated the report. (File)A study by the Maharashtra Pollution Control Board (MPCB) to see the impact of the lockdown on the environment across the state has shown that Mumbai’s Chhatrapati Shivaji International Airport recorded the sharpest decline in pollution levels, followed by Sion in the city and Vasai West in Palghar.
The study titled ‘Impact Evaluation of Covid-19 Pandemic on Environmental Attributes’ was commissioned by MPCB and the report was released on July 31. It was conducted twice – pre-lockdown, between March 1 and March 20 and during lockdown, between March 21 and June 1.
Even before Prime Minister Narendra Modi announced a 21-day nationwide lockdown from March 25, Maharashtra had announced a lockdown from March 23, with the government closing majority of shops and offices in Mumbai, Pune, Pimpri Chinchwad and Nagpur from March 21. To analyse air quality data for the study, 22 online ambient air quality monitoring stations across Maharashtra was recorded.
Silver lining amid pandemic
While the pandemic led to a clampdown on all non-essential activities from March 21 to June 1, a silver lining has been the effect of these regulations on the environment. The lockdown led to a significant decline in air pollution levels in major cities of Maharashtra. The AQI at almost all locations in Mumbai remained between 50 and 80 during this period, a rarity for the city.
The average AQI (air quality index) recorded at the international airport during the pre-lockdown period was 153.05, which falls in the “moderate” category. The average AQI recorded at the station during lockdown was 54.41, falling in the “satisfactory” category. The AQI at almost all locations in Mumbai improved from moderate to satisfactory during lockdown, stated the report.
In Vasai, there was a significant reduction in average AQI during lockdown – moving from the “moderate” to the “good” category. However, AQI at Airoli in Navi Mumbai was found to be slightly increased during lockdown. “The increase in pollution concentrations at locations may be due to higher percentage or density of essential services or industries,” noted the report.
The average AQI moved from “moderate” to “satisfactory” at 11 locations in Mumbai and Solapur. The report stated, “From the trend analysis of AQI across five phases, it can be clearly seen that before any initial declaration of Covid-19 pandemic, the AQI values are fairly high in range of 100 to 200. However, at the end of this phase, increased AQI values up to 250 are observed, which might be due to increased activity of panic migration of people.”
The study also included impact of lockdown on pollutants’ concentration — PM 10 (atmospheric particulate matter that have a diameter of less than 10 micrometers); Nox, which is mainly released through combustion processes like heating, power generation and engines in vehicles and ships; and SO2, produced by burning of sulfur-containing fossil fuels for power generation and vehicles.
Significant reduction in PM 10 and NOx concentration was recorded in majority of the stations. However, SO2 concentration reduced at 13 stations and increased by nearly 2 per cent in eight stations.
As per emission inventory of Mumbai, 39 types of industries (excluding power plants) contribute to over 50 per cent of SO2 in the city. During the third and fourth phases of the lockdown, Khadakpada-Kalyan station showed very high concentration of SO2. While the average SO2 levels recorded during the overall lockdown period was 54.32 µg/m3, it was 27.44 µg/m3 in pre-lockdown times.
The report noted that during lockdown, few activities were permitted, including inter-state travels. “The Khadakpada-Kalyan is a location on the busy Nashik-Thane highway with maximum traffic of heavy duty vehicles, which uses higher Sulphur content fuels. On the other hand, thousands of migrant workers travelled from this route to reach MP, UP and other parts of North India as most of the Shramik trains and buses departed from Nashik and Dhule to these places. Thereby, it can be predicted that higher concentration at this location is a result of these heavy duty vehicles’ movement,” it added.