The air quality in the National Capital Region is expected to be bad over the next few days, the Hindustan Times reported quoting the Central Pollution Control Board on Wednesday. The air quality will continue to be in the “very poor” category because of low wind speeds.
According to the Central Pollution Control Board, the level of PM 2.5 – particulate matter in the air that is smaller than 2.5 microns – has increased the most between 9 am and 10 am over the last 10 days. The sudden drop in night temperature and high moisture content are also responsible for this, the report said, quoting scientists. Besides, the low wind speed cannot scatter the pollutants early in the day. Pollution levels were lowest between 5 pm and 6 pm.
“As the sun rises and air gets heated up, dew starts evaporating...Moisture level rises and the air’s capacity to carry pollutants increases,” the head of the Central Pollution Control Board’s air laboratory, D Saha, was quoted as saying. “The pollution level, however, drops later when the temperature rises further.”
Wind speed of 5 metres per second is needed to dissipate pollutants. But, Delhi’s wind speed has been hovering around 1.5 metres per second for the last few days, the report said. Saha said that the situation is expected to get worse over the next few days, mostly because of the low wind speed. “On Tuesday, the wind speed dropped to around 0.9 m/s,” Saha added.
Delhi pollution this year
The air quality in the Capital this Diwali season was the cleanest in the past three years, according to a report released by the System of Air Quality and Weather Forecasting And Research. However, the city’s air quality had turned “severe” the day after Diwali, for the first time this year.
In 2016, an alarming post-Diwali smog in Delhi-NCR had forced schools to be closed for three days and the National Green Tribunal to declare an environmental emergency in Delhi, Haryana, Punjab, Rajasthan and Uttar Pradesh.