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HomeEnvironmentGovt agencies can’t agree if Delhi's air quality after Diwali was 'severe'...

Govt agencies can’t agree if Delhi’s air quality after Diwali was ‘severe’ or ‘very poor’

CPCB said Delhi's Air Quality Index the morning after Diwali was a 'very poor' 368, while SAFAR reported a 'severe' reading of 506.

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New Delhi: The two major government agencies that monitor pollution seem to disagree on the air quality index (AQI) levels recorded in Delhi the morning after Diwali, releasing two completely different estimates Monday. 

The Central Pollution Control Board (CPCB), which falls under the Ministry of Environment, Forests and Climate Change, estimated an AQI of 368, which falls in the ‘very poor’ category and indicates that air quality deteriorated only marginally after Diwali night. 

This data is based on 37 monitoring stations placed throughout Delhi.

However, Ministry of Earth Sciences’ SAFAR (System of Air Quality and Weather Forecasting & Research) showed an overall AQI of 506, which would put air quality in the ‘severe’ category, or higher in the pollution spectrum. SAFAR collects data from 11 monitoring stations in Delhi.

While SAFAR officials could not be reached for comment, their website explains that AQI calculations are based on data collected every five minutes. The CPCB, meanwhile, collects readings on an hourly basis. This may have resulted in lower average values for CPCB as the peak readings may have been missed.


Also read: Pollution monitors max out on Diwali night, CPCB says it’s studying impact of firecrackers


Weather conditions different

CPCB official P. Krishnamurthy, who is involved in monitoring pollution as a first-aider, said AQI measurements can vary with location, and do not paint a complete picture. However, he added that the levels of pollution this Diwali were much lower than in the last three years.

Apart from the fact that fewer firecrackers were burst, weather conditions also played a role in dissipating pollutants, he added.

“Last year, the temperatures were very low on Diwali, but this time the average temperature was around 26 degrees (Celsius),” he said.

Lower temperatures cause a reduction in what is known as the ‘mixing height’ — the height at which suspended particles disperse into the air. 

Between 9 pm Diwali night and 6 am the next day, the mixing height dipped to 120 metres, as opposed to the usual 500-600 metres, Krishnamurthy said. This caused the AQI to shoot up significantly in many areas.

Air quality in certain areas turned hazardous as pollution monitors hit the maximum reading of 999 late at night in some areas, including Patparganj. By morning, however, wind speed picked up and helped disperse the pollutants, bringing the AQI down to levels similar to those seen before Diwali.

Krishnamurthy said apart from low temperatures and poor wind speed, humidity was also high on Diwali in 2018, which caused a thick layer of smoke to engulf Delhi for days.

While the Supreme Court’s ban on firecrackers was flouted in many parts of Delhi, the CPCB’s ‘First Aiders’, who were monitoring noise pollution levels through the night, reported that noise pollution from fireworks was significantly lower than what is usually seen on Diwali nights.

The Modi government had announced earlier this month that ‘green crackers’ — which are designed to emit 30 per cent less pollution than traditional variants — would be available in the market this year, but consumers have complained that they were hardly available. 

SAFAR reported Sunday that fire counts from stubble burning in Haryana and Punjab — one of the primary contributors to Delhi’s infamous smog — almost doubled over the previous 48 hours, from 1,200 to 2,700. The share of pollution from biomass is also likely to increase over the next few days, the report said.


Also read: Why Kejriwal and Modi govt can’t agree on source of Delhi’s air pollution


 

 

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