- Pollution levels recorded in the National Capital Region on Deepavali and the two following days were in keeping with forecasts
Pollution levels recorded in the National Capital Region on Deepavali and the two following days were in close agreement with forecasts that assumed that the entire stock of unsold firecrackers in the city was used.This data indicates that a October 9 Supreme Court ban on the sale of firecrackers in the city had no effect, and partly explains why air pollution remained severe despite it.The idea behind the Supreme Court judgment was to test whether reduced firecracker use could alleviate the noxious pollution in Delhi during winter.
To forecast pollution levels on October 19, 20 and 21 as a result of this ban, Goa-based research group, Urban Emissions, simulated three scenarios using weather and emissions data.In the first, the ban led to no reduction in firecracker use; in the second, there was a 25% reduction while in the third, the drop was 50%.“The pollution peaks only matched at 0%. This means that there was no effect of the ban on what people managed to burst,” said Sarath Guttikunda, the director of Urban Emissions.
For example, the peak forecast for PM 2.5, or fine particulate matter, in the 0% scenario was 580 micrograms/cubic metres for October 20, the day after Deepavali, while the actual number averaged from 20 monitoring stations on the same day was 617.3 micrograms/cubic metre. Similarly, PM 10, carbon monoxide, nitrous oxide and sulphur dioxide trends under the 0% scenario also matched actual numbers.
To arrive at the forecast, Mr. Guttikunda’s team modelled emissions across Delhi and its satellite cities from bursting 50,00,000 kg of firecrackers, a number cited by firecracker distributors in documents submitted to the Supreme Court after the ban. The colouring of firecracker explosions comes from the salts of chemicals such as magnesium and aluminium, while the fuel is gunpowder made from charcoal and sulphur. “When burst, all salts that produce colours end up straight into PM2.5 and PM10, and sulphur in the gunpowder ends up in SO2,” said Mr. Guttikunda.