Winds too slow to rid Gurugram air of PM2.5. AQI ‘severe’, might deteriorate further by Thursday
Air quality in the city deteriorated back to the “severe” category on Tuesday, recording 402 on the Central Pollution Control Board’s air quality index (AQI) bulletin at 4pm. Conditions are likely to deteriorate further in the coming few days.
Tuesday’s air quality was up from 326 (“very poor”) the previous day. This is the first time that air quality touched “severe” levels since November 3, when the AQI touched a season-high of 486. Experts attributed Tuesday’s uptick in pollutants to a combination of factors including farm fires, winds and falling temperatures.
According to data from the city’s official air quality monitor at Vikas Sadan, ultrafine particulate matter less than 2.5 microns in size (PM2.5) concentration on Tuesday touched a maximum of 498µg/m³, with a daily average of 410µg/m³ at 6 pm. This is almost seven times the national safe limit of 60µg/m³ and 41 times the World Health Organisation’s safe limit of 10 µg/m³. On Monday, the average was 244 µg/m³. Prolonged to exposure to such ultrafine matter can lead to a host of respiratory illnesses among those with pre-existing conditions and also cause distress in healthy people.
Privately owned air quality monitors across Gurugram recorded similarly alarming levels of particulate matter. In Sector 30, one monitor recorded a daily average AQI of 395, with PM2.5 concentrations exceeding 400 µg/m³ and PM10 exceeding 500 µg/m³. Another monitor near Ghata village saw PM10 concentrations almost reach 600 µg/m³.
Conditions are likely to deteriorate further by Thursday and enter the “severe+” or “emergency” zone (AQI 500+), according to the ministry of earth sciences’ air quality early warning system for Delhi NCR.
“Temperatures have fallen quite sharply, and wind speed is low, between eight to 10 kmph, which is causing particles to accumulate quite quickly as we saw on Tuesday. This accumulation will continue till Thursday at least,” said a senior CPCB scientist. For pollutant dispersal, surface wind speed in Delhi NCR should be at least 10kmph.
In Gurugram, the minimum temperature fell from 13.2°C on Monday to 11°C on Tuesday, while maximum temperatures also fell from 28.2 to 27°C.
Another significant contributor is the spate of farm fires in Punjab and Haryana. Smoke from these fires are transported by winds ( the northwesterlies) in the upper layers towards Delhi NCR, said both experts and officials.
“While the number of fires detected by satellite image seems to be less than last year, the reduction hasn’t been enough to mitigate the contribution of stubble burning in Delhi-NCR, which is currently at about 20 percent,” said Sachin Panwar, a city-based air quality scientist.
The predicted AQI for Gurugram on Wednesday is 394, which is in the very poor category of the index, but just short of being in the ‘severe’ category.