delhipollution

Steady breeze improves Delhi’s air; CPCB

DAINIK NATION BUREAU

A steady breeze helped keep the city’s air pollution levels in check today, letting people breathe relatively easy on a day thousands took part in the Delhi Half Marathon.

The National Air Quality Index (AQI) had a score of 292 for the national capital, which is classified as ‘poor’ by the Central Pollution Control Board (CPCB), a marginal improvement over yesterday’s 298 which was the best in over a month.

‘Poor’ sits after ‘severe’ and ‘very poor’ in the CPCB- maintained index. It may trigger breathing discomfort to most people on prolonged exposure, says the corresponding advisory of the agency.

The main factor that saved Delhi the blushes was “wind speed” and its consistency, said, Dipankar Saha, air lab chief of CPCB.

“There is a consistent flow of wind from north towards the south. And the winds are dry and cold. The winds from north do not carry dust or moisture and its free flow through the city acts as a natural cleansing agent,” Saha said.

Earlier, when pollution had touched ’emergency’ levels, there were calls for the cancellation of the half marathon and appeals to authorities, including the judiciary, to call it off.

However, the Delhi High Court refused to postpone it.

The System of Air Quality and Weather Forecasting and Research (SAFAR) recorded 24-hour average (rolling) of PM2.5 and PM10 at 121 and 201 micrograms per cubic metres respectively, as against the prescribed standards 60 and 100.

Private weather forecast agency Skymet said pollution levels, which have decreased significantly over the capital, are not likely to spike anytime soon.

However, as temperatures drop, the inversion layer (the height beyond which pollutants cannot escape) also comes close to the surface, thus hindering the effective dispersion of particulate matter into the upper layers of the atmosphere.

The monitoring centres of the Delhi Pollution Control Committee at Major Dhyan Chand National Stadium and Jawaharlal Nehru Stadium, located close to the half marathon’s route, had PM2.5 and PM10 marginally above the safe limits, even in real-time.

The DPCC monitors capture pollution in real-time which, often, is erroneously compared with 24-hour standards of these particulates.

The AQI is basically a figure and a series of colour codings shared by agencies on the level of pollution. For example, the one CPCB shares ranges between 0 and 500.

An AQI between 0-50 is considered Good, 51-100 Satisfactory, 101-200 Moderate, 201-300 Poor, 301-400 Very Poor, and 401-500 Severe.

note–credit goes to PTI

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