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Breather over? Falling temperature, low wind speed pushing up Delhi pollution levels

The average daily air quality index (AQI) rose from 322 on Saturday to 352 on Sunday.

delhi Updated: Nov 26, 2017 23:43 IST
HT Correspondent
HT Correspondent
New Delhi, Hindustan Times
Air pollution,Delhi pollution,Air quality
Buildings shrouded by heavy smog in New Delhi on November 16.(AFP file)

Falling temperature and low wind speeds pushed up pollution levels in the National Capital Region on Sunday, with the air quality expected to get worse over the next few days, experts from different government departments said.

The average daily air quality index (AQI) rose from 322 on Saturday to 352 on Sunday. An AQI value between 301 and 400 is considered as “very poor”. The AQI had hit a peak of 486 on November 9 when pollution levels in Delhi stayed in the “severe” zone for a week, leading to a public health emergency.

Levels of particulate matter – the primary pollutants in Delhi’s air – were also on the rise. The PM10 reading shot up to 370ug/m3 at 7pm on Sunday from 276 at 3pm on Saturday.

The level of the smaller and deadlier PM 2.5 particulate matter also hit 226ug/m3 on Sunday from 171 the previous day. A PM2.5 level of 300 and above falls in the emergency “severe+” zone.

“Falling wind speed and increasing moisture levels are among the culprits. The wind speed dropped from around 7km per hour on Saturday to less than 3km per hour on Sunday. Pollutants are accumulating again as the winds with very low speed are not being able to flush them out,” D Saha, head of the air quality laboratory at the Central Pollution Control Board (CBCB), told Hindustan Times.

Officials in the Regional Weather Forecasting Centre (RWFC) said that they were expecting foggy days later this month because of the rising moisture levels. “More moisture and low wind speeds could lead to fog by November 29 or 30. Visibility is likely to drop to less than 1 km,” said Kuldeep Srivastava, a senior scientist at RWFC.

SAFAR, the country’s pollution forecasting agency maintained by the union ministry of earth sciences, is also predicting a dip in air quality over the next two or three days. “The last two days of the month, in particular, could be bad,” said Gurfan Beig, the body’s project director.

The minimum temperature, which had dropped to a season-low 7.6 degrees Celsius on Friday, hovered around 8.5 degrees on Sunday.

“Falling wind speed and increasing moisture levels are among the culprits. The wind speed dropped from around 7km per hour on Saturday to less than 3km per hour on Sunday. Pollutants are accumulating again as the winds with very low speed are not being able to flush them out,” D Saha, head of the air quality laboratory at the Central Pollution Control Board (CBCB), told Hindustan Times.

Officials in the Regional Weather Forecasting Centre (RWFC) said that they were expecting foggy days later this month because of the rising moisture levels. “More moisture and low wind speeds could lead to fog by November 29 or 30. Visibility is likely to drop to less than 1 km,” said Kuldeep Srivastava, a senior scientist at RWFC.

SAFAR, the country’s pollution forecasting agency maintained by the union ministry of earth sciences, is also predicting a dip in air quality over the next two or three days. “The last two days of the month, in particular, could be bad,” said Gurfan Beig, the body’s project director.

The minimum temperature, which had dropped to a season-low 7.6 degrees Celsius on Friday, hovered around 8.5 degrees on Sunday.

First Published: Nov 26, 2017 23:29 IST