Delhi’s air quality remained in the very poor category on Monday a day after it deteriorated to this level for the first time this season due to a combination of low temperature, calm winds, and farm fires in neighbouring states.
An air quality index (AQI) of 305 was recorded at 8:05am in Delhi, 246 (poor) in Ghaziabad, 354 (very poor) in Greater Noida, 255 (poor) in Gurugram, and 304 (very poor) in Noida. The AQI in Delhi was 313 on Sunday compared to 248 (poor) a day earlier. Delhi last recorded air quality in this category on May 17 when the AQI was 336 due to dusty winds from Rajasthan.
Delhi’s AQI was likely to remain very poor until at least Wednesday with no significant change in meteorological factors expected immediately. Farm fires in Punjab and Haryana were likely to impact the air quality severely.
Two of the 36 air stations in Delhi— Ashok Vihar and Aya Nagar— recorded severe air quality on Sunday. AQI between 0-50 is considered good, between 51 and 100 as satisfactory, between 101 and 200 as moderate, between 201 and 300 as poor, between 301 and 400 as very poor, and over 400 as severe.
A jump in farm fires in northern states has been blamed among the reasons for the spike in pollution levels. According to data from the National Aeronautics and Space Administration (Nasa), 265 farm fires were reported in Punjab and Haryana on Saturday, compared to 206 a day earlier. An average of 90 such fires were lit in the week preceding that.
In October, 2,436 reported farm fires in the two states were 75% fewer than the 2012-2022 average of 9,775 reported in the same time period. The fires have started earlier than last year but the count is yet to spike significantly. They tend to spike significantly by the end of October and in the first week of November.
Data from the earth sciences ministry estimated the contribution of biomass burning to be around 16.4% on Sunday. It was forecast to rise to around 30.6% on Monday and around 32.8% by Tuesday. The persisting lack of strong winds was expected to trap local sources of pollutants.
The transport sector’s contribution to local emissions was estimated to be the highest (15.2%) on Sunday. This was expected to rise to 16.1% on Monday and dip to 13.6% on Tuesday. The source of around 27.8% of Sunday’s PM 2.5 concentration was in Delhi. The remaining came from biomass burning and transboundary pollution.
Low temperatures and calm winds at night led to the accumulation of pollutants in the region. Delhi’s minimum temperature dipped to the season’s lowest of 15.6°C on Sunday, three degrees below normal. It was 17.2°C on Monday.
The visibility was down to around 1500-1800 metres during the day on Sunday while it is over 4,000 metres normally. The predominant northwesterly wind direction carried pollutants from farm fires to the capital.
Calm winds at night were expected to become more common as temperatures dip further. The mixing height will dip too and poor air is expected to continue unless strong winds blow.
On Saturday, measures under Stage II or the very poor category, including enforcement of the ban on diesel generator sets, ensuring an uninterrupted power supply, enhancing parking fees to discourage the use of public transport and augmenting bus and metro services, of the Graded Response Action Plan were implemented in anticipation of deterioration in air quality.
Source: Hindustan Times
