Air quality improves, experts sceptical

The air quality of the city improved, with Gurugram recording an air quality index (AQI) of 258 (‘poor’) on Monday compared to an AQI of 317 (‘very poor’) on Sunday.

The air quality of the city improved, with Gurugram recording an air quality index (AQI) of 258 (‘poor’) on Monday compared to an AQI of 317 (‘very poor’) on Sunday. However, experts said the improvement is not “very significant”, attributing it to increased wind speed and Gurugram’s geography

HT Image

Gurugram’s AQI had stayed in the ‘very poor’ zone of the Central Pollution Control Board’s (CPCB) AQI bulletin for the last three days. However, on Monday, Gurugram was the least polluted city in the National Capital Region (NCR) with the AQI in neighbouring Delhi, Noida, and Ghaziabad staying in the ‘very poor’ zone.

The level of ultrafine particulate matter having a diameter of 2.5 microns or less (PM 2.5), the city’s primary pollutant, was 233.3 micrograms per cubic metre (µg/m³) on Monday, as per the CPCB’s air quality monitor at Vikas Sadan in Sector 11, way almost four times the safe limit of 60µg/m³.

According to the early air quality warning system for Delhi-NCR, the air quality is likely to improve marginally but remain in the ‘poor’ category on Tuesday. The air quality is expected to deteriorate again and remain in the ‘very poor’ category on Wednesday, a condition predicted to persist till Saturday.

Experts said that the marginal improvement in the reading could be attributed to improvement in atmospheric conditions.

Kuldeep Srivastava, a scientist with the India Meteorological Department (IMD), said that there had been a slight improvement in the wind speed in comparison to Sunday, which could have played a part in the dispersal of pollutants. “For the past few days, wind speed in the region had been slow and blowing at 5kmph. Today, the wind speed has picked up marginally. In the coming days, wind speed during the day might pick up more and air quality might improve,” said Srivastava. He added that variations in AQI in different parts of a city needed to be taken into account while comparing the AQI with neighbouring cities.

The data, on which the city’s reading was based, however, came only from three air quality monitoring stations, a relatively small sample size. While the city has four air quality monitoring stations, data from one of the stations was not considered sufficient for computing the AQI. In comparison, Delhi’s AQI reading was based on data from 36 monitors. Meanwhile, data from three air quality monitors were used to compute AQI in both Ghaziabad and Noida.

Sachin Panwar, a city-based air quality scientist, said that the improvement in air quality wasn’t very significant. “Gurugram is upwind, located at the edge of the valley. Due to the change in air pressure over the Gurugram region, the air is lighter due to which sunlight is able to pass easily. Delhi, meanwhile, is deep in the valley. Ghaziabad, meanwhile, has hot spots due to the presence of industrial areas, hard industries, due to which AQI there is often on the higher side. In Gurugram, Monday’s reading is simply due to the benefit of weather conditions. If one were to check private monitors, the reading would be similar to other cities. Even with 10-15 micrograms, the air quality can change from one zone to another, if the previous value is on the borderline of a zone,” said Panwar.

He added that while one could expect an improvement towards the end of the month, stubble burning continued to be a major cause of worry. “There is a disturbance right now which could lead to a higher wind speed in the area but we can’t be very certain about it. Farm fires are rampant all across due to which the air will continue to carry forward pollutants,” he said.

On Monday, the city recorded a maximum temperature of 32.6 degrees Celsius, while the minimum temperature was 12.8 degrees Celsius. While the maximum temperature is expected to hover around 33 degrees on Tuesday, the minimum temperature is expected to rise by two degrees and touch 15 degrees Celsius, as per the IMD forecast, as per which clear skies will prevail throughout the week.