Enhancing Polycyclic Aromatic Hydrocarbons (PAHs) Quantification through High-Resolution Aerosol Mass Spectrometry for Mobile Sampling
OLADAYO OLADEJI, Albert Presto, Carnegie Mellon University
Abstract Number: 251
Working Group: Urban Aerosols
Abstract
Polycyclic Aromatic Hydrocarbons (PAHs), a subset of air toxics, pose severe health risks even at low concentrations due to their carcinogenic and reproductive effects. They are semi volatile organic compounds, generated from the incomplete combustion of organic compounds. Despite their significance, spatial distribution studies of PAHs remain limited, largely due to the absence of real-time, chemically specific methods.
This study applies high-resolution aerosol mass spectrometry (AMS) for enhanced quantification and spatial analysis of particle-phase PAHs. Sampling was done in Pittsburgh in which a mobile laboratory was driven over defined routes in areas of varying source activity (e.g., the downtown core, residential areas, and industrial areas).
Laboratory validation utilizing PAH standards and NIST database comparison demonstrated robustness, yielding a 95% correlation coefficient. Moreover, a fragmentation table was devised based on NIST database analysis, enhancing methodological accuracy in identifying PAHs.
Quantification of PAHs, including acenaphthene and acenaphthylene, alongside other PAHs revealed spatial and temporal variability. For instance, the mean concentration of acenaphthene varied by a factor of 3 between neighborhoods. Most of the detected PAHs had low background concentrations and the time series of concentration was dominated by short intense concentration spikes.
PAH concentration spikes were correlated with black carbon (BC), suggesting vehicle emissions as a major source. Ratio-ratio plots (e.g., PAH/BC) suggest that most of the observed spikes can be attributed to emissions from nearby gasoline and diesel vehicles.
Ongoing efforts involve refining the methodology to quantify the Relative Ionization Efficiency of various PAHs, aiming to enhance analytical precision and broaden applicability. This methodological framework advances PAH quantification and offers insights into spatial distribution and emission sources, crucial for air quality management and public health.