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Ecology & Environment
Mahesh

28/10/24 13:30 PM IST

Air quality in Delhi

In News
  • With the withdrawal of the southwest monsoon and the onset of winter, the air quality in Delhi has started to nose-dive.
Stubble burning
  • Stubble burning refers to a traditional practice of farmers burning  the remnants of paddy stalks after harvesting.
  • This method is often the quickest way, as farmers in Punjab and Haryana have a narrow window of October and November to clear their fields and sow wheat for the winter.
  • The environmental impact of stubble burning has been known since the 1990s.
  • Agricultural researchers, while analysing the economics of rice-wheat cropping pointed out that rising labour costs made it expensive for farmers to collect rice stalks strewn across the field that resulted from the use of mechanical devices such as rice shredders and combine harvesters.
  • Though the burning of rice stalk was initially condemned as a waste of valuable manure, concerns were also raised about its harm to farmers’ health.
  • However, its link to worsening air quality in Delhi was quantified only over the last decade and a half.
  • Today, the use of sophisticated instruments, modelling studies, and computational methods have enabled the estimation, almost daily, of stubble burning’s contribution to air quality in Delhi.
  • In the case of Punjab, during winter, 54% of the time the wind from the State blew towards Delhi, it led to a spike in air pollution; when the wind originated from Haryana, the figure stood at 27%.
Other Factors
  • Stubble burning was responsible for nearly 15% of Delhi’s air pollution.
  • On the same day, ‘Delhi transport’ which includes particulate matter from vehicles and vehicles crossing into Delhi was responsible for about 18% of the PM 2.5 load, according to the IITM’s air quality forecast system.
  • The IIT Kanpur, IIT Delhi, and Teri consortia analysis of the sources of pollution in Delhi found that the real-time source apportionment of PM 2.5 results show secondary inorganic aerosols (SIA), which travel from beyond Delhi, contribute the highest to Delhi’s pollution load.
  • The average of winter pollution source apportionment shows SIA (32% ) and biomass burning within and outside Delhi (24%) contribute the most followed by vehicles at 17%.
  • The SIAs form when gaseous precursors like sulfur dioxide (SO2), nitrogen oxides (NOx), and ammonia (NH3) react to form ammonium sulfate or ammonium nitrate.
  • In winter, the mean contribution of SIA from the sources within Delhi is 16% and the rest 84% from outside Delhi.
  • In the last few years, policymakers have realised that the sources of air pollution can be tackled only via an airshed approach that requires coordinated action by multiple States including those beyond Delhi to evolve a joint response to the pollution crisis.
Source- The Hindu

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