New Delhi: Vehicles were the single largest contributor to Delhi’s PM2.5 pollution Saturday, accounting for 25%, according to data generated by the Indian Institute of Tropical Meteorology’s (IITM) newly inaugurated Integrated Atmospheric Chemistry and Aerosol Toxicity Analysis Laboratory (AATAL). Secondary organic aerosols contributed 18.4%, followed by secondary inorganic aerosols (16.5%), road dust (10.9%) and waste burning (5%).The laboratory, which provides real-time source-apportionment data, was inaugurated in New Rajendra Nagar by Union minister of state Jitendra Singh Saturday. Equipped with 25 advanced instruments and built at an estimated instrument cost of Rs 79.5 crore, the facility is designed to identify pollutants, trace their sources, understand how they transform in the atmosphere and assess their potential health impacts.AATAL will complement IITM’s existing Air Quality Early Warning System (EWS), which provides AQI forecasts, and the Decision Support System (DSS), which estimates the contribution of local and regional pollution sources. A revamped EWS was also launched.Officials said the laboratory would strengthen research on the interaction of aerosols with moisture, fog and haze, particularly during winter in northern India.Data generated over the past five days show that vehicles, secondary organic aerosols and secondary inorganic aerosols have consistently been the top contributors to Delhi’s PM2.5 levels, although their shares have varied.On Friday, when Delhi’s AQI was in the poor category, secondary organic aerosols were the largest contributor at 24.6%, while vehicles and secondary inorganic aerosols each accounted for 20.7%. Road dust remained a significant contributor, accounting for 5-10% of PM2.5 in recent days.Secondary organic aerosols form when volatile organic compounds (VOCs) released by vehicles, industries, solvents and vegetation react in the atmosphere to form particulate matter. Secondary inorganic aerosols are formed through chemical reactions involving gases such as sulphur dioxide, nitrogen oxides and ammonia, producing sulphates and nitrates.Singh said, “Earlier, the discussion would largely revolve around whether the pollution level was 100 or 200. This facility will help us understand the composition of pollution as well as the contribution of different sources. This ensures that action is based on scientific evidence.”He added that the facility would provide insights into the smaller constituents of air pollution, including metallic elements and other potentially harmful components. Understanding not only pollutant concentrations but also their composition and toxicity was important because different pollutants could have different health impacts, he said.Sachin Ghude, project director, said the initial findings show that around 40% of Delhi’s PM2.5 is primary particulate matter, while 60% is secondary. “Unlike primary particles, which are emitted directly into the air, secondary aerosols form when gases undergo chemical reactions in the atmosphere and get converted into particles. The findings indicate that primary particles, secondary inorganic aerosols and secondary organic aerosols each account for around 30% of the total PM2.5, while the remaining 10% comprises metals, toxic elements and other components,” he told TOI.The facility restores real-time source-apportionment data for Delhi after a gap of nearly three years. The previous system operated by IIT Kanpur ceased in Nov 2023 after Delhi govt halted the project. Officials said the initiative would now be resumed with the help of IIT Delhi.The laboratory is expected to support the Commission for Air Quality Management (CAQM) and other agencies in identifying major pollution sources, prioritising interventions and assessing their effectiveness. It will provide measurement-based evidence to pinpoint sectors and locations contributing to deteriorating air quality and support coordinated action across Delhi-NCR.
