NEW DELHI: The capital is yet to see a “good-air” day this year despite recording intense rain activity on a few days in July. Last year, Delhi saw its only “good-air” day, when the overall Air Quality Index (AQI) is below 50, in October due to incessant rain. Five such days were recorded in 2020.
Though the AQI this month has been mostly hovering in the “satisfactory” category with the lowest being recorded at 61 on July 17, experts say background emissions are high in the city.
Data of Central Pollution Control Board (CPCB), which started measuring AQI in 2015, shows “good-air” days were mostly recorded when rain or lockdown helped in cleaning the air. Though no such day was reported in 2015, 2016 and 2018, Delhi witnessed two “good-air” days in 2017 on July 30 and 31.
Two “good-air” days were registered in 2019 when AQI touched 49 on two days, August 18 and 19. In 2020, there were five such days, one in March during the lockdown and four in August during the monsoon period. The capital saw only one “good-air” day in 2021 on October 18 when AQI dipped to 46.
When the monsoon arrived on June 30, Delhi recorded its first heavy rain day. India Meteorological Department’s data showed that Safdarjung and some other weather stations witnessed “moderate” to “heavy” rainfall on a few days this month. Safdarjung, the city’s base station, has logged 253.6mm of rainfall in July so far against the monthly normal of 210.6mm.
Though July has recorded “excess” rainfall this year, experts said rain intensity and duration were important factors. LS Kurinji, programme associate, Council on Energy, Environment and Water (CEEW), said, “Delhi typically experiences better air quality during the monsoon season as rain clears particulates from the atmosphere. But, rainfall has been seen only on 31 days this monsoon compared with 46 days in 2021 and 49 days in 2020. Arid weather during summer, followed by a late arrival of monsoon and less rainfall in the last two months, have resulted in increased dust contribution.”
An analysis done by CEEW on PM2.5 levels showed only 40 days had “good” and “satisfactory” air quality days in June and July compared with 51 days in 2021 and 55 in 2020.
“Poor air quality during the summer and monsoon months reinforces the message that for improving air quality, proactive measures are needed throughout the year. Delhi government must use the Decision Support System round the year, which is currently operational only during the winter months, to plan and roll out actions in advance to avert high pollution levels. Further, urban local bodies must ensure year-round vigilance and action against sources like waste burning, dust from unpaved roads and construction activities,” said Kurinji.
Dipankar Saha, former head of CPCB’s air laboratory, said intensity, magnitude, frequency and duration of rain were key deciding factors to suppress and precipitate emissions in the atmosphere and on the ground. “Meteorological conditions and emissions can’t be uniform, so they are not comparable,” he added.
