Air quality remains poor, mercury spike expected to alleviate pollution

Air quality in the city remained in the poor category of the Central Pollution Control Board’s air quality index (AQI) for the third consecutive day on Monday, with a reading of 296 on the daily pollution bulletin — the same as that recorded a day prior

Air quality in the city remained in the poor category of the Central Pollution Control Board’s air quality index (AQI) for the third consecutive day on Monday, with a reading of 296 on the daily pollution bulletin — the same as that recorded a day prior. As per official forecasts, pollution levels are expected to remain in the upper end of the poor to the lower end of the very poor category till February 24, after which the AQI is expected to start improving.

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The average level of ultrafine particulate matter having a diameter of 2.5 microns or less (PM 2.5), the city’s primary pollutant, was 277 micrograms per cubic metre (µg/m³) on Monday, as per the CPCB’s air quality monitor at Vikas Sadan in Sector 11. This is up from 206 µg/m³ the previous day. At the official monitor in Sector 51, the PM 2.5 concentration stood at 335µg/m³, up from 305µg/m³ the previous day.

Kuldeep Srivastava, head of India Meteorological Department’s (IMD) regional forecasting centre in Delhi-NCR, said that pollution levels will continue to improve over the next week, with rising temperatures expected to lead to higher wind speeds and increased mixing height of pollutants — the vertical height at which suspended particles mix with the air.

While the IMD’s automatic weather station (AWS) for Gurugram did not record the minimum temperature on Monday, the IMD’s AWS at the Palam observatory in Delhi recorded the day’s minimum temperature at 12.8 degrees Celsius, up from 11.6 degrees the previous day, and the maximum temperature at 26.7 degrees Celsius, up from 26 degrees Celsius the previous day.

“The wind speed is expected to touch about 15 kilometres per hour, and increasing temperatures will cause upward movement of air and increase the ventilation index, which indicates the rate of dispersal,” said Srivastava.

As per the early air quality warning system for Delhi-NCR, the ventilation index is likely to increase from approximately 4,000 m²/s on Monday to 9,000 m²/s on February 24. A ventilation index of 6,000 m²/s or more is necessary for the effective dispersal of pollutants.

As per the IMD’s weekly forecast, the maximum and minimum temperatures are expected to hover around 30 degrees Celsius and 16 degrees Celsius, respectively, over the next few days. Shallow to moderate episodes of fog will continue during the morning, despite it being an atypical weather phenomenon for this time of the year.