Source Apportionment and Composition of Fine Particulate Matter in Delhi, India

Chronic exposure to fine particulate matter (PM) leads to premature death and increases the risk of cardiopulmonary disease. Industrialization and urbanization in developing countries like India and China present unique air quality challenges, where dense populations are routinely exposed to high levels of atmospheric pollutants. Pollutant composition and source profiles remain poorly characterized and lack temporal resolution in such settings. A better understanding is required to devise effective control and remediation policies to combat air pollution challenges in megacities such as Delhi, India.

Ambient measurements of submicron aerosol (PM₁, d_p < 1 µm) were carried out at The Indian Institute of Technology Delhi during the winter of 2017. Bulk chemical composition, number, size distribution, black carbon content, and concentration of PM₁ were measured by a suite of instruments, including an Aerosol Chemical Speciation Monitor (ACSM). Results show high PM concentrations dominated by organic species, exceeding 50 μg/m³ on average during the campaign. Speciated diurnal profiles highlight a unique morning (6:00–9:00) particulate chloride peak, as shown in the figure below. A literature survey was conducted to identify potential local and regional chloride sources. Complimentary laboratory studies were performed to improve chloride quantification. Source apportionment was carried out via Positive Matrix Factorization of ACSM mass spectra. Results indicate significant contribution from hydrocarbon-like organic aerosol (HOA) sources. This study provides time-resolved information on particulate matter concentrations, sources, and characteristics in Delhi, India.  

Figure 1: Preliminary diurnal PM₁ profile in Delhi, India from February 2017, as measured by ACSM. Unity collection efficiency was used.