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City records month’s worst air quality on Sunday

UPDATED ON JAN 27, 2020 07:01 PM IST

The city recorded its worst air quality for the month so far on Sunday with air quality index (AQI) at 265, which falls under ‘poor’ category. The pollution, however, declined on Monday, with AQI at 178 (moderate) for PM2.5 pollutant (particulate matter of 2.5 micron size that can easily enter the lungs and cause ailments), according to the System of Air Quality Weather Forecasting and Research (SAFAR).

AQI entered the ‘moderate’ category on Monday after ‘poor’ air quality for a week (since January 19). “Warm conditions combined with high moisture in Mumbai’s air, plus easterly winds over the past week kept AQI in ‘poor’ category,” said Gufran Beig, project director, SAFAR. “Now the wind direction is slowly changing to northeasterly to northerly, which will lower temperatures and moisture, and increase wind speed over the city. As a result, the pollutant boundary layer will not be able to suspend close to the surface, thus leading the AQI to ‘moderate’ or ‘satisfactory’ category in the coming days.”

On Sunday, Navi Mumbai and Bandra-Kurla Complex (BKC) both recorded its highest pollution levels of the season with AQI at 374 and 355, both under ‘very poor’ category. Malad and Mazagaon also recorded ‘very poor’ AQI while Bhandup had the cleanest air in the city with an AQI of 99 (satisfactory). All other locations recorded ‘poor’ air quality.

SAFAR categorises AQI for pollutants in the 0-50 range as good; 51-100 as satisfactory; 101-200 as moderate; 201-300 as poor; 301-400 as very poor and above 400 as severe.

On Monday, Navi Mumbai was the only location in the city to record ‘very poor’ AQI at 306 while all other locations were either in the ‘moderate’ or ‘poor’ category. Bhandup continued to have the cleanest air at 96 (satisfactory).

On Sunday, the concentration of PM2.5 was 123 microgrammes per cubic metre (µg/m3) against the safe limit of 60 µg/m3, and concentration for PM10 (larger coarser particles) was 192 µg/m3 against the safe limit of 100 µg/m3. On Monday, the concentration dropped to 79 µg/m3 for PM2.5 and 141 µg/m3 for PM10.

“The AQI was strongly dependent on the maximum temperature and that’s why an immediate dip was noticed on Monday following a reduction in the maximum temperature,” said Akshay Deoras, meteorologist and PhD researcher department of meteorology, University of Reading, the UK. “Significant deterioration of AQI is unlikely in the remaining days of this month due to reduced maximum temperatures and moisture.”

Minimum temperature on Monday was 20 degrees Celsius, both in the suburbs and south Mumbai, which was 2.5 degrees Celsius above normal. The maximum temperature was above the 30 degrees Celsius mark, almost 2 degrees Celsius above normal. Humidity levels were 91% in the suburbs and south Mumbai.

The maximum temperature on Monday dropped below the normal mark. The suburbs recorded 30.4 degrees Celsius, 1.2 degree Celsius below normal while south Mumbai recorded 30 degrees Celsius, close to the normal mark.

Deoras said the Mumbai Metropolitan Region will witness cloudy weather conditions on Tuesday and a possibility of light drizzle cannot be ruled out. “The AQI might start deteriorating in early February since temperatures and moisture are expected to go up,” he said.

The India Meteorological Department (IMD) predicted that minimum temperature is likely to drop to 16 degrees Celsius on Tuesday morning while the maximum is expected to be 29 degrees Celsius, owing to cool northerly winds under the influence of a western disturbance over northern parts of the country. An AQI of 165 (moderate) has been forecast for Tuesday.

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