The firecracker-free Diwali observed in the national capital this year saw a 39 per cent decrease in PM 2.5 levels compared to 2016, data collected by the Central Pollution Control Board (CPCB) has shown. The data collected from three monitoring stations — Pitampura, Janakpuri and from CPCB’s headquarters’ at Parivesh Bhavan — further revealed reductions in 12 of the 13 elements usually found in firecrackers.
The data shows a 64 per cent decrease in Strontium — an element which gives firecrackers a red colour. However, the concentration of Titanium saw a marginal increase.
CPCB’s air laboratory chief D Saha Friday attributed the better air quality to the Supreme Court’s decision to ban the sale of firecrackers in the Delhi-NCR, stating that it was the apex court’s “foresight” which cushioned the blow in a year that also saw adverse weather conditions coincide with the festival.
The CPCB had also compared “air pollution episode days” in 2016 and 2017 and found that 2017 was more critical than the previous year with respect to meteorological conditions. “This year was more critical than last year with respect to mixing height, wind speed and relative humidity,” Saha said. “With higher humidity, the weight of the pollutants moving in the air increases and then fall closer to the ground level,” he said.
For instance, wind speed fell in the range of 1.0-3.0 m/s between October 30-November 7, 2016, compared to 1.0-1.3 m/s between November 7 and 12 this year. Further, mixing height was 146-618 m last year, compared to 336-479 m this year. While mixing height is the height of vertical mixing of air and suspended particles above the ground, a lower mixing height suggests worse air.
The relative humidity, too, fell in the 47.8-63.3 per cent range in 2016 compared to 60.2-75.8 per cent this year, which weighs down pollutants to bring them closer to the ground. Meanwhile, among the elements found in firecrackers, the data shows a 51 per cent decrease in Barium — which provides a green colour.
Reductions were also seen in iron concentrations (48%), Calcium (37.8%), Zinc (41%) among other elements. “Reduction was seen in most elements, including Aluminium, Potassium, Sulphur… and elements such as Calcium and Barium that provide the colours in firecrackers,” said CPCB scientist Abhijit Pathak. “Except, there was an increase in Titanium levels,” he said.
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