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Smog makes a comeback in Delhi, air quality might get worse today

Wednesday’s Air Quality Index (AQI) clocked 359, which falls under ‘very poor’ category — a huge shift from 300 on Tuesday. On Monday, it recorded 234, while on Sunday, it was ‘moderate’ at 197.

delhi Updated: Dec 21, 2017 09:44 IST
HT Correspondent
HT Correspondent
Hindustan Times
delhi,smog,weather
Wednesday’s Air Quality Index (AQI) clocked 359, which falls under ‘very poor’ category — a huge shift from 300 on Tuesday. On Monday, it recorded 234, while on Sunday, it was ‘moderate’ at 197. (Burhaan Kinu/HT PHOTO)

A layer of shallow fog encompassed the national capital on Wednesday morning, resulting in a layer of smog in the air throughout the day.

Wednesday’s Air Quality Index (AQI) clocked 359, which falls under ‘very poor’ category — a huge shift from 300 on Tuesday. On Monday, it recorded 234, while on Sunday, it was ‘moderate’ at 197.

The AQI is calculated on a scale of 0-500. 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.

The levels of PM10 and PM2.5 saw steady increase throughout the day. While PM10 concentration went up from 325.9 micrograms per cubic metre (μg/m3) at 7am to 396.6 μg/m3 at 7pm, the level of PM2.5 saw a nominal hike from 196.1 μg/m3 at 7am to 249.1 μg/m3 at 7pm.

Both PM10 and PM2.5 are ultra fine particles that are the dominant pollutants in Delhi. The acceptable levels of PM10, the larger particulate matter, and PM 2.5, which measures the finer and more dangerous particulate matter, are 100 μg/m3 and 60 μg/m3 respectively. The PM2.5 particulates, which can measure up to 30 times tinier than the width of a human hair, can reach the bloodstream of a person through the respiratory system and pose serious health risks.

According to the MeT department, this hazy condition was smog. Slow wind speed is largely responsible for this. “This is fog and along with local emissions it is became smog. Calm conditions are not allowing the pollutants to get dispersed. The wind speed, which was 15-16km/hour a couple of days back, is now 5-6km/hour,” Kuldeep Srivastava, a senior MeT department scientist, said.

According to him, the air will get fouler on Thursday due to similar weather conditions.

“Things will improve after a couple of days once the wind speed increases,” Srivastava said.

On Wednesday, the minimum temperature was recorded at 9.6 degrees Celsius, two notches above normal for this time of the year. The maximum was 21.4, a degree below normal, the MeT office said.

The foggy morning resulted in 54 north-bound trains running behind schedule while departure of 12 trains were rescheduled keeping in mind the bad weather conditions.

The MeT has forecasted mainly cloudy sky for the day on Thursday, with dense fog in the morning and mist during the day. The maximum and minimum temperatures are expected to settle at 23 and 11 degrees Celsius.

First Published: Dec 20, 2017 23:27 IST