Delhi’s air quality shows signs of improvement after evening rain

Experts said that pollution levels are likely to dip further on Tuesday as light rain and drizzle, triggered by a western disturbance, is expected to continue till Tuesday morning.

The air quality in Delhi, which spiked throughout Monday, showed signs of marginal improvement from late Monday evening, as rain lashed the National Capital bringing down the concentration of particulate matter – the dominant pollutants in Delhi’s air.

Showers in New Delhi on Monday evening. (Sanchit Khanna/HT PHOTO)

Experts said that pollution levels are likely to dip further on Tuesday as light rain and drizzle, triggered by a western disturbance, is expected to continue till Tuesday morning.

The day’s average Air Quality Index (AQI) dropped to 361 on Monday from 377 on Sunday. But this improvement was not because of the drizzle. The average AQI is calculated around 4 pm and the rain started around 6 pm.

The improvement, because of the rain, was reflected better in the levels of PM10 and PM2.5 which started dipping soon after the drizzle started.

While PM10 concentration dropped from around 422 at 2 pm to around 400 around 9pm, the level of PM2.5 also came down from around 245 at 5 pm to 238 at 9pm

“There will be further improvement on Tuesday as the rain will wash away some more pollutants in the air. The layer of dust on the roads, trees and constructions sites will also be washed away. The dust particles, which used to rise from these surfaces and mix with the air, will not be able to do so, allowing Delhiites to breathe some cleaner air,” said D Saha head of the air quality laboratory at CPCB.

But pollution levels could spike marginally once again from Wednesday and continue to deteriorate till Friday because of the calm winds and high moisture levels left back by the rains.

“We are expecting some shallow fog on Wednesday and Thursday morning as there would be a lot of moisture in the air. The winds would be calm too,” said Kuldeep Srivastava, a senior scientist with the RWFC.

MeT experts, however, said that the sky is likely to clear up from Friday as the cold and dry north westerly winds are expected to pick up speed.

“Once we get a clear sky, a good sunshine and some strong winds from the north and northwest, air quality would definitely improve,” said Saha.