Monsoon showers fail to clean up air in Delhi

New Delhi: Delhi might have recorded more rainfall than the season’s average in the last two months, but the ongoing showers have failed to give any “good” air quality day till now.

In fact, the national capital has not seen a single day in terms of “good” air quality this year. Even last year, Delhi didn’t witness a single day, which could be termed “good”, as per data provided by Safar (System of Air Quality and Weather Forecasting and Research), under ministry of earth sciences.

An Air Quality Index (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 maximum number of days (92) since January this year was recorded in “moderate” category, followed by “very poor” (40). The air quality has touched the “severe” level four times till now this year.

Meanwhile, the meteorological department has said that the rainfall Delhi has received till now is in excess of the seasonal average. The month of July has received 177.8 mm of rainfall till Saturday, while the average is 129.0 mm. Since June 1, when the monsoon season officially began here, Delhi has recorded 217.9 mm rainfall, more than the 194.5 mm average.  

However, the rains failed to wash away some of the deadly air pollutants in the city’s air and according to experts, that is due to the intermittent spells of rain.  

“During the monsoon season, air quality will be ‘good’ when there is continuous rain for a day or two so that it washes off all the pollutants in the air which is not happening right now. At least two days continuous rain is required to clean up the atmosphere. It will be in the ‘good’ category once it rains like that,” said Scientist Gufran Beig, Project Director, SAFAR.

For the most part of July, the level has remained within the “satisfactory” category (17 days). Four days were recorded in the “moderate” category.

Experts had also warned that there are some particulate matters (PM) whose size varies between 0.1 micron and one micron, which continue to be present in Delhi’s air even after heavy rains.

The Supreme Court mandated Environment Pollution (Prevention and Control) Authority (EPCA) had earlier said that the secondary particles like nitrates and sulphates, which form in the air from primary particles, might be difficult to wash off.

The continuing summer months are the only time when Delhiites can expect to breathe easy. However, this year, there was a dip in the air quality level on June 13 due to dust storms in western India that pushed the air quality level to ‘severe plus’, bringing to light that emergency level pollution could be a ‘summer-time problem’ too.

On Saturday, the air quality was in the ‘satisfactory’ category, with PM10 and PM 2.5 levels at 99 and 47 microgramme per cubic metre (ug/m3) respectively.

The national capital has not seen a single day in terms of ‘good’ air quality this year despite recording more rainfall than the season’s average.

  D13