Rain Improves Air Quality, Brings It Under "Good" Category In Delhi

Rainfall in the national capital on Monday brought the much needed respite from air pollution with farm fires contributing only one percent to PM 2.5 in the city's air.

Delhi's air quality index (AQI) was recorded at 46 in the 'good' category with PM 2.5 as the lead pollutant, said Ministry of Earth Sciences' forecast body SAFAR.

"Local land surfaces are wet and so dust re-suspension is minimum which led to low PM10. Presence of western disturbance has led to scattered rainfall over north India, leading to low biomass burning. This condition improved AQI with low PM2.5.

"Fire counts have been reduced to 170 and its share is only 1% to PM2.5. Moist surfaces inhibit re-suspension of dust which will keep AQI in 'good' category for next 24 hours and after that AQI will degrade to 'satisfactory' for Delhi," said SAFAR.

According to the data from the Indian Agricultural Research Institute (IARI), 60 farm fires were recorded collectively in the six northern states out of which Punjab recorded 57 incidents, Haryana had one and Rajasthan had two fire incidents.

There were no fires in Delhi, Uttar Pradesh and Madhya Pradesh.

On October 17, satellites detected 54 residue burning events in the six study states with 14 in Punjab, zero in Haryana, 39 in UP, zero in Delhi, zero in Rajasthan and one in MP. The number of fires decreased from 741 on October 16 to 54 the next day.

However, IARI said detection of burning events by satellites was hampered due to clouds over all the study states. This was also corroborated by IITM-Pune's Decision Support System (DSS).

Total 4,146 burning events were detected in the six states between September 15 and October 17, which are distributed as 2,389, 1,026, 620, zero, 27 and 84 in Punjab, Haryana, UP, Delhi, Rajasthan and MP, respectively.

Overall, the total burning events recorded in the six states are 50.7 per cent less than in 2020 till date, IARI said.

It said Punjab recorded 50.8 per cent reduction, Haryana recorded 10.9 per cent increase, UP recorded 63.6 per cent increase, Delhi recorded 100 per cent reduction, Rajasthan recorded 88.7 per cent reduction and MP recorded 78.1 per cent reduction, in the current season than in 2020.

The air quality in the national capital was in the 'very poor' category on Sunday but the stubble burning contribution to Delhi's air came down by two per cent, authorities said.

Stubble burning in the neighbouring states significantly contributes to the air pollution in Delhi.

The active fire events due to rice residue burning were monitored using satellite remote sensing, following the new "Standard Protocol for Estimation of Crop Residue Burning Fire Events using Satellite Data".

Punjab had recorded 1.02 lakh incidents of stubble burning in 2016. The number decreased to 67,079 in 2017; 59,684 in 2018 and 50,738 in 2019 from October 1 to November 30. The state logged 79,093 such incidents last year, according to the IARI.

Haryana saw 15,686 farm fires in 2016; 13,085 in 2017; 9,225 in 2018; 6,364 in 2019 and 5,678 in 2020.

Punjab and Haryana attract attention during the paddy harvesting season in October and November.

Farmers set their fields on fire to quickly clear off the crop residue before cultivating wheat and potato. It is one of the main reasons for the alarming spike in pollution in Delhi-NCR.

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