Delhi's air quality dips to season’s worst, may turn ‘poor’ next week

New Delhi: Delhi’s air quality is gradually deteriorating and may turn “poor” by the first week of October, with stubble burning likely to start contributing soon. Delhi’s overall Air Quality Index (AQI) touched 177 (moderate) on Tuesday— the highest so far this monsoon season. The AQI was recorded at 159 (moderate) on Monday, according to Central Pollution Control Board (CPCB)’s daily bulletin.

The capital’s air quality has been deteriorating over the past 48 hours due to an increase in dust pollution.

Kuldeep Srivastava, scientist at IMD and head of Regional Weather Forecasting Centre in Delhi, said that local dust was the primary factor now, with north-westerly winds raising dust over the past couple of weeks. “Delhi has seen no rain recently and conditions are dry. Local sources are also contributing, leading to a spike in pollution. Stubble burning is not playing a significant role yet, but may contribute next month,” added Srivastava.

System of Air Quality and Weather Forecasting And Research (SAFAR) on Tuesday said the withdrawal of monsoon had started in the region with PM10 currently the primary pollutant.

“The overall Delhi AQI is in the middle-end of the moderate category as forecast. PM10 is the lead pollutant and dust is the main contributor. High surface winds and good ventilation conditions are expected for the next two days, which are likely to keep Delhi AQI in the high moderate category. By October 2, AQI may reach the higher end of moderate to lower end of the poor category,” said SAFAR on Tuesday.

“An increase in stubble burning fires was observed on Monday around Punjab, Haryana, and neighbouring border regions. However, significant impact is not expected for Delhi in the next two days,” SAFAR added.

LS Kurinji, a research analyst at Council on Energy, Environment and Water (CEEW), said north-westerly winds generally tend to contribute to Delhi’s air, whereas Delhi usually records south-westerly winds at this time of the year.

“Stubble burning has started in some regions of Punjab and Haryana. Similar fire events were observed in late September in 2019 as well, but it did not impact Delhi’s air quality as the region experiences southwesterly winds during the time. Satellite-derived fire events’ data over the last few years indicates that stubble burning reaches a peak between end-October and early-November. During this period, the wind direction changes to northwesterly, which aids in carrying smoke from farm fires in Punjab and Haryana to NCR and beyond,” added Kurinji.

An AQI is classified as “good” when it is 50 or below, “satisfactory” between 51 and 100, “moderate” between 101 and 200 and ‘poor’ when it is between 201 and 300 on the CPCB’s index.

Delhi has been witnessing its cleanest year in terms of air quality, with the lockdown contributing to a major extent. The capital has already recorded five “good” air days this year, the most since 2015, when the AQI was launched. Four such days were recorded in the month of August alone.