Delhi’s air quality remains ‘very poor’ day after 2nd stage Grap was invoked

Delhi’s air quality remained in the “very poor” category on Tuesday a day after the authorities invoked the second stage of the Graded Response Action Plan (Grap) to curb pollution amid unfavourable meteorological conditions, calm winds during the night, high local emissions, and the illegal use of firecrackers.

An air quality index (AQI) of 318 was recorded at 9am on Tuesday, compared to 303 (very poor) at 11pm on Monday. The 24-hour average AQI was 310 on Monday compared to 277 (poor) on Sunday. The air quality deteriorated to the “very poor” zone on Monday for the first time since June 19 when the AQI was 306.

The Commission for Air Quality Management (CAQM), which monitors pollution in the Capital, on Monday cited a review of the air quality, meteorological conditions, and forecasts and said the AQI in Delhi was likely to remain in the very poor category until Thursday. It added the CAQM sub-committee for operationalisation of the Grap invoked 11-point action plan as per the second stage of the revised plan to prevent further deterioration of air quality.

The curbs included stricter monitoring of the use of diesel generators not equipped with emission mitigation devices, an increase in parking fees to discourage private transport, and strengthening bus and Metro services.

CPCB classifies AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.

According to the Decision Support System (DSS) forecasting model, pollution in Delhi would rise primarily due to local pollutants and pollution from the neighbouring towns. It estimated the contribution of stubble burning to Delhi’s PM 2.5 (particulate matter having a diameter of 2.5 microns or less) load to be around 3.2% on Monday. The contribution of Delhi’s vehicular emissions was around 11%. Gautam Budh Nagar accounted for an estimated 8.8% and Ghaziabad 7.5%.

DSS estimates the share of stubble burning in Delhi’s air to be around 3.5% on Tuesday. This was expected to rise to 11.2% on Wednesday and around 15.1% on Thursday. Additional emissions from sources such as stubble/waste burning were likely to deteriorate air quality significantly.

The ban on firecrackers was flouted in Delhi and neighbouring areas on Sunday as part of the Karva Chauth celebrations, sparking concerns about poor enforcement ahead of Diwali when the air quality usually worsens.

The Delhi government on September 9 said all types of firecrackers, including green crackers, cannot be sold, purchased, stocked, or manufactured in the capital. Firecrackers have been banned since 2017 to check the pollution. Despite the ban, sales of firecrackers have continued.

There has been a consistent spike in AQI the day after Diwali in seven of the last eight years, barring 2022 when strong winds and rain helped disperse firecracker emissions. In 2021, the AQI shot up from 382 (very poor) on Diwali day to 462 (severe) the following day.