New results of the Ecorc’Air citizen science project: Biomonitoring of Vehicular Air Pollution in Cologne, Germany

Airborne particulate matter (PM) is known to have serious effects on human health. Unfortunately, assessing spatial variability of PM at high resolution remains challenging due to limitations in the number of existing regulatory air quality stations in cities. As an alternative approach, biomonitoring using vegetation within cities has been proposed in recent years.

In the framework of the Ecorc’Air citizen science project, a robust protocol has been developed based on the annual collection of plane tree bark, which serves as a passive airborne PM collector using magnetic susceptibility as a proxy parameter to estimate PM abundance in cities (Carvallo et al. 2024). This has been used to create annual maps showing the variations in magnetic particle concentrations. Since the project started in Paris (France) in 2016, there has been a growing participation of inhabitants, associations, and municipalities and it has recently grown beyond national borders.

In Germany, sampling took place downtown Cologne in spring 2025 as part of the DFG-funded project “Mapping the concentration of particles in the air in the city of Cologne using environmental magnetic techniques – a first step towards participation in the European science network Euro'Air”. In this presentation, we focus on the results obtained from analyzing the collected plane bark samples. We show the spatial distribution of magnetic susceptibility and frequence dependent magnetic susceptibility. Additionally, our preliminary results from attempts to characterize the particles by magnetic hysteresis parameters and first order reversal curves (FORC) as well as scanning electron microscopy (SEM/EDX) analyses. The outcome will be discussed with respect to the spatial distribution of the PM concentrations in Cologne.