Chloride-rich particles responsible for visibility reduction over Delhi, claims IIT-M study

A study led by researchers from the prestigious Indian Institute of Technology-Madras (IIT-M) has found chloride to be the highest inorganic fraction in particulate matter, which is blamed as the reason for haze and fog over New Delhi and other parts of north India.

The findings of the study have been published in the prestigious peer-reviewed journal International Journal Nature Geoscience. Though many studies in the past had identified PM2.5 (particulate matter or aerosol particles with diameter less than 2.5 micrometre) as a major pollutant, the role of PM2.5 and detailed chemistry of haze and fog formation over national capital was poorly understood.

“This study now greatly enhances our understanding about the precise role of PM2.5 in chemistry of fog formation, which will help policy makers to frame the better policies for improving the air quality and visibility over national capital,” the institute said in a statement.

The study, led by IIT-M and carried out in collaboration with Max Planck Institute for Chemistry, Germany; Harvard University, USA; Georgia Institute of Technology, USA, and Manchester University, UK, not only provides the scientific explanation for source of high chloride in PM2.5 mass over Delhi but also quantifies its role in haze and fog formation and visibility reduction.

“This work put forward importance of measurements and modelling approaches to scientifically conclude that half of the water uptake and visibility reduction by aerosol particles around Delhi is caused by the HCl emissions, which is locally emitted in Delhi potentially due to plastic contained waste burning and other industrial processes,” Dr Sachin S Gunthe, Associate Professor, Department of Civil Engineering, IIT Madras, said.

The study identifies waste burning as a major source of pollution, which is responsible for emissions of aerosol precursors as well as other toxic substances such as chlorinated dioxins and other persistent pollutants that affect human health.

The study also emphasised the need to improve the policies related to air pollution, solid waste management including e-waste, and food safety to systematically address the environmental issues in India.