Extreme air pollution in the Ganges valley

In an article published in Aerosol and Air Quality Research in December 2017, Hiren Jethva wrote: "The mass concentration of PM 2.5 escalates from ~50 µg m–3 measured prior to the onset of residue burning in early October to as high as 300 µg m–3 (24-hour averaged, 7-day running mean) during the peak burning period in early November. A linear regression analysis reveals that the variations in PM 2.5 over New Delhi can be attributed to the concurrent changes in the satellite retrievals of fire counts and aerosols over the crop burning area. The back-trajectory analysis shows that most clusters (>80%) of the northwesterly flow near the ground intercepted the crop burning region before arriving at the receptor location in New Delhi; this further corroborates the transport patterns inferred from the satellite data."

"The seasonal crop residue burning over the northwestern states of Punjab and Haryana in India is a major source of pollution over the greater Indo-Gangetic Plain region. The burning of waste material resulted from the harvest of rice crop produces aerosols and trace gases in large quantities, which affects the air quality locally and across the region downwind of the sources. The correlation analysis suggests a strong influence of crop residue fires and associated smoke aerosols observed by MODIS and OMI sensors over Punjab on the concentration of PM 2.5 measured on the ground in New Delhi."

This massive source of pollution comes on top of everyday (factories, daily motorised traffic), seasonal (low wind, cold temperatures, higher air moisture and fossil fuel based heating) and occasional pollution. Die Deutsche Welle specifies the effects of one of these particular occasion, Diwali: "Air pollution in New Delhi has spiked after India's biggest fireworks party of the year. Residents woke up to a pall of grey left behind by acrid smoke from fireworks that remained trapped in the city's cool air."

"Air pollution in New Delhi and several other Indian cities deteriorated on Monday to the worst recorded level, a day after revelers set off firecrackers and rockets to celebrate the Hindu festival of lights, Diwali. The smoke from fireworks added to emissions from cars and trucks as well as stubble fires by farmers around Delhi that have made it the world's most polluted capital."

"The air quality index, which measures the concentration of poisonous particulate matter, touched 500 in several parts of Delhi, including the international airport, in the early hours of Monday, the maximum recorded by the government's Central Pollution Control Board. Anything above 401 is classified as "severe." Air pollution at that level can seriously affect those with existing respiratory illnesses, and even those who are healthy. The levels have remained above 300 since early Monday morning, or "very poor," which can cause respiratory illness after prolonged exposure."

"The overall air quality index across the city, however, was at its lowest in three years due to favorable wind speeds and some reduction in the use of fireworks during Diwali, according to SAFAR, a government-run monitor. In an effort to limit pollution over the festival period, India's Supreme Court had ordered residents to only use safe and environmentally-friendly fireworks that emit less smoke and soot. It also stipulated that the fireworks could only be set off for a maximum of two hours, and only in designation areas such as parks — a ruling that appeared to go largely ignored."

In metro.co.uk, Jimmy Nsubuga reports another attempt to change behaviours: "The New Delhi government held a four-day laser show starting Saturday to encourage residents to skip firecrackers altogether."

Die Deutsche Welle continues: "The government has taken a slew of measures, including shutting down thermal power plants and banning construction during the pollution season. In November, a bid to reduce road traffic will be introduced with odd and even registration plates allowed on Delhi roads on alternate days. Several other Indian cities have initiated some pollution control action in recent years, but there has been little or no political will to enforce anti-pollution laws."