After rain, Delhi gets its cleanest air since Sept ’17

With the arrival of the monsoon, the air in Delhi on Thursday was the cleanest since September last year.

The Air Quality Index (AQI) value for the Capital was a ‘satisfactory’ 76 at 4 pm on Thursday. It touched the ‘satisfactory’ level on Wednesday following heavy pre-monsoon showers. The last time Delhiites breathed air so clean was nine months ago.

Depending on AQI values, air quality is classified as good, satisfactory, moderate, poor, very poor and severe. Last year, the only satisfactory days too were during monsoon.

Pre-monsoon showers hit the Capital this week, with light rain on Monday and Tuesday and heavier showers on Wednesday.

On Thursday, the India Meteorological Department (IMD) declared that the monsoon had reached most parts of northern India. The rains are expected to cover the whole country in the next two to three days, according to the IMD.

Air quality has improved across India as the monsoon set in. None of the 57 cities for which data was available reported poor, very poor or severe levels on Thursday. Six cities were at moderate levels while the rest of the cities enjoyed satisfactory, and even good, air quality.

NEWDELHI:

Good 0-50 Poor 201-300 Satisfactory 51-100 Very Poor 300-400

Particulate matter is the major pollutant in Delhi NCR and also in the northern plains. The Capital and surrounding areas witness a spike in pollution levels during winters when meteorological conditions trap pollutants near the surface, and crop burning adds to the problem.

In the monsoon season between June and September, Moderate 101-200 Severe 401-500 the rains settle air pollutants and improve air quality.

“Air pollution starts rising after October,” AK Shukla, who heads the air lab at the Central Pollution Control Board, said. “Monsoon months are generally the best.”

“The rains wash out pollutants, especially particulate matter,” Shukla added “Some gases are soluble so there is some impact on gaseous pollutants (as well), but the major impact is on particulates.” In mid-June the capital experienced an unexpected drop in air quality due to dust-carrying winds from Rajasthan, Haryana and Punjab. The strong winds also stirred up dust already present in DelhiNCR, causing the air quality to drop to severe levels.

IN THE MONSOON SEASON BETWEEN JUNE AND SEPTEMBER, THE RAINS SETTLE AIR POLLUTANTS AND IMPROVE AIR QUALITY