Delhi’s air quality in ‘poor’ category, mercury expected to touch 40° C

New Delhi: Delhi’s air quality was in the “poor” category on Tuesday morning as the mercury was expected to touch 40 degrees Celsius. The hourly Air Quality Index (AQI) was 272 at 7 am. The average 24-hour AQI was 251 on Monday.

An AQI between zero and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 “severe”.

The mercury crossed the 40-degree mark in parts of Delhi for the first time this year on Monday. It was as high as 42 degrees Celsius in Narela, prompting the India Meteorological Department (IMD) to declare “severe heatwave” conditions in some areas for the next two days.

The average maximum temperature on Monday was 39.1 degrees Celsius, seven degrees above normal. The minimum temperature on Monday was 22.2 degrees Celsius, four notches above normal.

On Tuesday, air quality monitoring agency System of Air Quality and Weather Forecasting And Research (Safar) said the AQI indicated “poor” air quality with the dominance of dust (~62% in PM10). The AQI was likely to be within the same category on Wednesday. “For the next two days (30th and 31st) AQI is likely to degrade to be within ‘Poor’ or ‘lower end of ‘Very Poor’ due to low wind speeds (<6km/h),” said Safar.

High mixing layer height was expected to enhance ventilation and offset the effect of low wind speed. “There is also a possibility of dust intrusion from the western region… From 1st [April] onwards, AQI is expected to improve but likely to be within ‘Poor’ due to moderate wind speed (12-18km/h) that improves ventilation of pollutants,” said Safar.