Delhi pollution to spike again, brace for foggy mornings and fouler air in coming days
The Met has predicted low wind, poor ventilation coefficient and stable atmospheric conditions that are likely to affect air quality, particularly in the evening and night till December 29.delhi Updated: Dec 27, 2017 10:05 IST
The capital saw another day of shallow fog with the visibility at 600 metres at 8.30am on Wednesday morning. The air quality remained “very poor” as the air quality index (AQI) — a measure of pollutants in the air — at 338 at 8am. It was worse than the average air quality index of 335 on Tuesday which was another “very poor” day in Delhi with the weather department forecasting heavy fog and fouler air quality for the next few days.
Tuesday’s average air quality index was 335, classified as “very poor” by the CPCB. It was better than Monday, when the AQI was 372.
On Sunday, the reading was 305. 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, too, saw a slight dip throughout the day. While PM10 concentration went down from 381μg/m3 at 6am to 334.2μg/m3 at 6pm, the level of PM2.5 saw a decrease from 262.8μg/m3 at 6am to 221.6μg/m3 at 6pm.
Both PM10 and PM2.5 are ultra fine particles, 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 100μg/m3 and 60μg/m3, respectively.
According to Met officials, the concentration of pollutants fell slightly because of good wind speed during the day.
“During the daytime on Tuesday, the wind speed was 12-15km/hour and there was an improvement in the air quality. However, since evening, the wind speed has been decreasing and can become 0 in the night. For that reason, moderate to dense fog is expected on Wednesday morning with visibility to go down to around 200m,” Kuldeep Srivastava, a senior Met department scientist, said.
The foggy conditions will remain for the coming 3-4 days and air quality will stay foul.
According to the Central Pollution Control Board (CPCB), the Met has predicted low wind, poor ventilation coefficient and stable atmospheric conditions that are likely to affect air quality, particularly in the evening and night till December 29.
“In view of this, agencies concerned have been requested to remain alert and take all necessary measures to prevent an emergency situation,” an official said.
CPCB air laboratory chief Dipankar Saha, however, said there was no reason to panic. “Low wind and calm weather during the morning and evening will see a dip in air quality. We are likely to have dense fog, which is natural during these days of the year. However, the air quality is not likely to reach emergency levels like it did in November,” Saha said.
On Wednesday, partly cloudy sky is expected and the maximum and minimum temperatures would be around 23 and 7 degree Celsius respectively.
On Tuesday, the maximum temperature was 23.7 degree Celsius, three notches above normal, while the minimum temperature notched 7.1, one degree below what is normal this time of the year.