Delhi’s AQI remains in ‘very poor’ category

Delhi’s 24-hour average air quality index (AQI) was recorded at 348 (very poor) at 4pm on Monday and a slight deterioration in the air quality has been observed overnight

Delhi’s air quality was in the ‘very poor’ category on Tuesday morning with the national Capital recording a 24-hour average AQI of 364 (very poor) at 8am, the Central Pollution Control Board (CPCB) said.

The city woke up to with shallow fog in the morning with general visibility of 1000m at 8am. (HT Photo)

The city woke up to with shallow fog in the morning with general visibility of 1000m at 8am and it is expected to have a mainly clear sky during the day, according to the India Meteorological Department (IMD).

Delhi’s 24-hour average air quality index (AQI) was recorded at 348 (very poor) at 4pm on Monday and a slight deterioration in the air quality has been observed overnight.

According to the IMD, the maximum temperature on Tuesday would be 26°C and the minimum temperature is 12°C.

The IMD said northwesterly winds – those that transport pollutants from farm fires in Punjab and Haryana to Delhi – had returned, however an increase in wind speed up to 15 km/hr is expected on Tuesday, which should help improve air quality once more.

“The pre-dominant wind direction on Sunday was easterly, but wind speed was not too strong, averaging around 6km/hour during the day and being fairly calm at night. This switched over to northwesterly on Monday,” said Kuldeep Srivastava, stating even though winds will continue to remain calm at night, they should increase to 15 km/hr during the day on Tuesday.

“This should help improve visibility fairly quickly”, he added.

Data from the Decision Support System (DSS) shows an estimated contribution of stubble burning to Delhi to be around 9.14% on Tuesday.

Delhi’s transport sector has an estimated share of 11.13% in Delhi’s PM 2.5 concentration. The biggest pollutant in Delhi’s air continued to be PM2.5.

Forecasts by the Early Warning System (EWS) for Delhi – a forecasting model used by the Commission for Air Quality Management (CAQM), shows despite stronger winds, AQI is likely to remain very poor.

“Delhi’s air quality is likely to remain in the ‘very poor’ category from November 21 till 23. The outlook for the subsequent six days shows air quality is likely to remain in the ‘very poor’ category once more”, it said.

Data also showed the farm fire count across the northern plains is gradually on the decline.

Data by the Indian Agricultural Research Institute (IARI) showed Punjab and Haryana recorded 634 and 38 farm fires on Monday.

The count was 740 and 33 fires respectively on Sunday and 637 and 21 fires on Saturday.

According to data from the Delhi government’s real-time source apportionment on Tuesday morning showed that the contribution of biomass burning to Delhi’s PM 2.5 was 41% and 20% from vehicles.

Secondary inorganic aerosols — particles formed in the air as a result of gases reacting with each other from combustion sources — had meanwhile contributed by 30% to PM 2.5 formation, it said.

In terms of temperature, Delhi recorded a maximum temperature of 27.1°C – one degree below normal.

The minimum was recorded at 12°C, which is around normal for this time of the year.