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Thursday, Sep 19, 2019

Gurugram air worsens in absence of rain, no hope of improvement

Privately owned air monitors in the city, however, recorded a much higher pollution level in several parts of the city. As per a monitor in South City 1, the AQI on Wednesday morning was 401 (severe) and 360 (very poor) in Sector 30.

gurugram Updated: Sep 05, 2019 02:10 IST
Sonali Verma
Sonali Verma
Hindustan Times, Gurugram
Bad air quality days are here and, if experts are to be believed, air might continue to be as polluted, unless it rains.
Bad air quality days are here and, if experts are to be believed, air might continue to be as polluted, unless it rains. (Yogendra Kumar/HT PHOTO)
         

Bad air quality days are here and, if experts are to be believed, air might continue to be as polluted, unless it rains. Weather experts said only isolated rainfall is on cards for the city, where rainfall was deficient by 38% for August.

On Wednesday, a thick haze of suspended dust engulfed Gurugram pushing up the AQI (air quality index) to 162 (moderate) from Tuesday’s 124.

Privately owned air monitors in the city, however, recorded a much higher pollution level in several parts of the city. As per a monitor in South City 1, the AQI on Wednesday morning was 401 (severe) and 360 (very poor) in Sector 30. At least seven other private monitors, whose data is available on mobile apps, recorded an AQI of more than 300 on Wednesday morning.

“From Tuesday evening, dust flying in from the north-western regions has led to the accumulation of particulate matter over the national capital region (NCR). Because of the high humidity, the particles aren’t dispersing uniformly. The low wind speed is also a reason behind the haze,” said Dipankar Saha, former head of the CPCB’s air quality lab.

Gurugram recorded relative humidity of 72% at 5.30pm on Wednesday and wind speed of 5 kilometres per hour (kmph), as per the India Meteorological Department (IMD). Experts predicted that Thursday would be no better. A minimum wind speed of 14kmph is needed to disperse particulate matter.

For more than a month, the city has been witnessing ‘good’ (0-50) and ‘satisfactory’ (51-100) AQI days as a result of the monsoon rainfall which washed away pollutants. August did not record a single day of ‘moderate’ (101-200) or ‘poor’ AQI (201-300), shows the CPCB data. However, according to experts, the good air quality days are all but gone for the city.

“The middle of September, when the south-west monsoon makes its exit, is usually when the AQI starts to dip. As the weather starts cooling down around the end of the month, the density of air increases and particulate matter settles at a lower level in the atmosphere,” said Niranjan Raje, former member of the Environment Pollution Control Authority (EPCA). He added that the air quality is likely to become worse towards the end of September.

CPCB data shows that last year, however, the AQI remained in the ‘satisfactory’ category for most part of September due to intermittent rain.

According to experts, the difference in the AQI between the CPCB’s monitors and private monitors was because of the difference in their method of calculation. “The CPCB accounts for an average AQI of the past 24 hours. The increase in dust particles started around Tuesday night,” said Sachin Pawar, an air quality expert who has a monitor. He added that most private monitors also don’t have a correction for humidity levels, and increased humidity translates to higher AQI.

Experts also said that the CPCB AQI monitor in Vikas Sadan is likely to not be accurate for the entire city. “This reading can’t be accurate for all parts of the city as the monitor is stationed at one place and accounts for the AQI there,” said EPCA’s Raje. Factors such as the level of local vehicular traffic emissions also affects the AQI reading, experts said.

According to experts, Gurugram’s AQI is likely to be in the ‘moderate’ category for most of this month. “Unless the concentration of ground-level pollutants rises in the air, the AQI would likely be moderate and not worsen. October is when stubble burning starts in district’s neighbouring areas and the AQI falls to the ‘poor’, ‘very poor’ and ‘severe’ categories,” Saha said.

First Published: Sep 04, 2019 21:40 IST