Modelling the variability of particle concentrations from tyre and brake wear for Hamburg

Air pollution is a global threat to human health, especially in densely populated areas. Pollutant concentrations in European countries have been decreased due to legislative actions. However, non-exhaust emissions, consisting of tyre, brake and road wear, as well as road dust resuspension, remain and even tend to increase.
This study quantifies tyre and brake wear emissions using a bottom-up model for the city of Hamburg in 2018. The concentrations of these particles are simulated with the urban scale chemistry transport model EPISODE-CityChem. For this purpose, EPISODE-CityChem 1.8 has been extended to include six new particle components representing different size classes for tyre and brake wear.
The size classes are PM_2.5, PM_2.5-10 and PM₁₀₊, particles larger than 10 μm. The emission factors are based on the emission factor from the UK national atmospheric emission inventory for PM₁₀ for tyre and brake wear, respectively. These are combined with the mass size distribution of the total suspended particles according to EMEP to derive the emission factors for the other size classes.
The contribution of PM_2.5 from tyre and brake wear to the total PM_2.5 concentrations varies throughout the months between 9% and 16% at traffic stations and between 2% and 6% at urban background stations.
The particle concentrations from tyre and brake wear show local and seasonal differences, which could be a difficulty in adhering to the recommended guideline values for particle concentrations. 
The results of this study can be transferred to other large European cities with high traffic volumes and can help to understand the problem's scope, as measurements rarely differentiate between particles caused by exhaust vs. non-exhaust emissions.