Investigating the impact of emission reductions and traffic sector emissions on ambient PAH and nitrated PAH concentrations

Polycyclic aromatic hydrocarbons (PAHs) pose a health risk as hazardous air pollutants, with nitrated PAHs (nitro-PAHs) being notably more toxic. However, limited research has explored how spatial PAH and nitro-PAH concentrations have evolve over time and the specific impact of traffic emissions on ambient PAH and nitro-PAH levels.

This study investigates the effects of decreasing anthropogenic emissions and traffic-related emissions on both PAH and nitro-PAH concentrations using a high-resolution regional chemical transport model. The research introduces a new nitro-PAH species, 2-Nitrofluoranthene (2-NFLT), into the Global Environmental Multiscale model – Modelling Air quality and CHemistry (GEM-MACH), enhancing our understanding of regional air quality trends. By simulating 2-NFLT concentrations for varying emission levels over three decades, we aim to identify the changes in 2-NFLT concentrations compared to primary PAH concentrations. Additionally, we quantify the contribution from traffic sector to ambient PAH concentrations by conducting sensitivity simulations under a traffic-free scenario.

This work underscores the significance of fine spatial resolution in nitro-PAH modeling and provides critical insights into the co-benefits of reducing primary PAH and NOX emissions over the past two decades. The findings have implications for informing policies aimed at improving air quality and safeguarding public health.