However, air quality in the city is forecast to deteriorate again in the next 2 days
Delhi got a breather from ‘poor’, ‘very poor’ or ‘severe’ air quality after almost a month and a half, thanks to strong winds and rainfall.
The air quality in the city improved significantly since November 16, 2020 and was finally under comparatively safer limits November 17, after a gap of 41 days.
The overall average air quality settled in the moderate category November 17 as the air quality index (AQI) was 171, according to Central Pollution Control Board (CPCB) data.
The last time the AQI was recorded in the moderate category was October 6, 2020 (178). Since then, the city has been witnessing ‘poor’, ‘very poor’ and ‘severe’ air quality days.
An AQI of 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’, 301-400 ‘very poor’, and 401-500 ‘severe’. Above 500 is the ‘severe-plus or emergency’ category.
The AQI value November 17 was also the best since October 1, 2020, when the value was 151.
The concentration of pollutants particulate matter (PM)2.5 and PM10 — which had increased sharply and had reached five times above their safe limits in the air — also reduced significantly though they were still marginally above their safe limits.
While the concentration of PM2.5 was 70 microgramme per cubic metre (μg / m3), PM10 was 114 μg / m3 — the safe limits were 60 μg / m3 and 100 μg / m3 respectively.
Nine out of a total 36 monitoring stations in Delhi, however, recorded ‘poor’ air quality. These were located in Ashok Vihar, Bawana, Jahangirpuri, Mundka, Najafgarh, Nehru Nagar, Okhla Phase 2, Rohini and Vivek Vihar.
Strong surface winds in the last two days and rainfall November 15 due to a western disturbance helped in flushing out the accumulated pollutants.
“Surface winds are west-southwesterly and energetic, very favourable for pollutant dispersion. Rainfall, along with stronger winds under the influence of a western disturbance helped to clean the build-up of pollution in the Indo-Gangetic Plain,” an analysis by SAFAR (System of Air Quality and Weather Forecasting and Research), a body under the Union Ministry of Earth Sciences, said.
The share of stubble burning in contributing PM2.5 to Delhi’s air was almost negligible and estimated at around three per cent for November 17.
However, this improvement is short-lived. The AQI is likely to deteriorate to the ‘poor’ category by November 18 and to the ‘very poor’ by November 19, according to a SAFAR forecast.
Air quality in areas of the National Capital Region such as Ghaziabad, Greater Noida, Noida, Faridabad and Gurugram also improved to ‘moderate’ November 17.
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