Quantifying the impact of vehicle fleet electrification on local aerosol concentrations in Helsinki using high-resolution Large Eddy Simulation

Abstract. Urban air quality strategies increasingly rely on transitioning to battery electric vehicles (BEVs), yet their impact on non-exhaust aerosol emissions remains uncertain. This study uses high-resolution Large Eddy Simulation (LES) to investigate aerosol concentrations in a planned Helsinki neighborhood where a highway corridor is being converted into a residential boulevard. We consider three scenarios with varying BEVs shares: a baseline year 2022 (10 % of BEVs), and projected years 2035 (60 %) and 2040 (100 %).

The findings reveal a "dual impact" of vehicle electrification. Increased BEV shares significantly reduce particle number concentrations (PN_2.5), with a projected 60 % decrease by 2040 compared to the baseline. Conversely, fine particle mass (PM_2.5) is projected to increase by approximately 15 % by 2040. This divergence occurs because while BEVs eliminate tailpipe exhaust, their greater weight increases unregulated non-exhaust emissions (NEE) from tire and brake wear. Results show high spatial variation, with pollutants concentrated along boulevard roads and limited penetration into residential blocks. This study underscores the challenges of BEV adoption in realistic urban environments and provides vital insights for sustainable urban planning and pollution mitigation strategies.