Investigating Organic Aerosol Composition, Phase State, and Miscibility Across Two Cities with Evolving Vehicle Fleets
Kinjal Kolhe, Kamal Sahu, Harish C Phuleria, JENNA DITTO, Washington University in St. Louis
Abstract Number: 506
Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene
Abstract
In this work, we assess chemical composition, properties, and heterogeneity of urban aerosols measured in two cities: St. Louis, USA and Mumbai, India. While electric and hybrid vehicles are on the rise globally, their sales vary by country. In the U.S., this growth of hybrid and electric vehicles currently represents about 15-20% of new car sales, while in India this growth is closer to 5-10%. With urban aerosol composition transforming as a result of vehicle fleet electrification, we aim to explore whether this transition impacts the chemical/physical properties of urban organic aerosol mixtures, focusing on aerosol phase state with additional analyses of aerosol thermodynamic mixing favorability (miscibility). We performed a comparative analysis across urban background and roadway-adjacent PM2.5 samples collected in St. Louis and Mumbai across several seasons. Additional paired indoor-outdoor samples were collected in St. Louis at an urban residence. All PM2.5 samples were analyzed by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry tools, following both targeted and non-targeted approaches. Initial analyses of the urban aerosol’s hydrocarbon composition focused on polycyclic aromatic hydrocarbons (PAHs), as US EPA-classified priority pollutants, and diagnostic ratios revealed the dominance of PAHs from pyrogenic sources in both environments. Total PAH concentrations in Mumbai were 3-4 times higher than in St. Louis, including for species like benzo[a]pyrene (a group 1 carcinogen), and showed predominance of pyrene in both cities. Leveraging non-targeted analyses beyond the aerosol mixtures’ hydrocarbon components, our study investigates the transformation and evolution of urban outdoor aerosol in two different vehicle fleet electrification scenarios, and investigates resulting composition-dependent aerosol phase state and miscibility. Finally, paired indoor-outdoor samples are used to assess changes to chemical composition and phase state or miscibility properties upon indoor infiltration to residential environments.