Chemical characterization of fine particulate matter, and source apportionment of organic aerosol at three sites in New Delhi, India

Atmospheric particulate matter has adverse effects on human health, and causes over 4 million deaths per year globally. New Delhi was ranked as world’s most polluted megacity with annual average PM_2.5 concentration of ~140 ug.m^-3. Thus, real time chemical characterization of fine particulate matter and identification of its sources is important for developing cost effective mitigation policies.

Highly time resolved real-time chemical composition of PM_2.5 was measured using Long-Time of Flight-Aerosol Mass Spectrometer (L-ToF-AMS) at Indian Institute of Technology Delhi and Time of Flight-Aerosol Chemical Speciation Monitor (ToF-ACSM) at Indian Institute of Tropical Meteorology, Delhi, and PM₁ using High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS) at Manav Rachna International University, Faridabad, Haryana located ~40 km downwind of Delhi during Jan-March, 2018. Black carbon concentration was measured using Aethalometer at all three sites. Unit mass resolution (UMR) and high resolution (HR) data analysis were performed on AMS and ACSM mass spectra to calculate organics, nitrate, sulfate and chloride concentrations. Positive Matrix Factorization (PMF) (Paatero and Tapper, 1994) of organic mass spectra was performed by applying multilinear engine (ME-2) algorithm using Sofi (Source finder) for identifying sources of OA.