Seasonal Variability of Atmospheric Air Quality as a Factor in the Formation of Ecological Risks in Cities (On the Example of Frankfurt am Main)

The study investigates the seasonal characteristics of atmospheric air quality parameters in Frankfurt am Main based on stationary environmental monitoring data. Hourly observation datasets from three stations (Frankfurt Friedberger Landstraße, Frankfurt Ost, and Frankfurt Schwanheim) for the period 2018–2025 were analyzed to evaluate the concentrations of nitrogen oxide (NO), nitrogen dioxide (NO2), particulate matter (PM10, PM2.5), and ground-level ozone (O3).

The analysis revealed a distinct seasonal pattern for nitrogen oxides, with maximum values occurring during the winter period and minimums in summer, heavily driven by traffic loads. Particulate matter variations showed less uniformity; fine particles (PM2.5) exhibited a typical winter peak due to poor dispersion conditions and secondary aerosol formation, whereas PM10 dynamics were closely tied to localized conditions and dust resuspension. Conversely, ground-level ozone demonstrated a pronounced summer maximum reflecting its photochemical origin.

The findings indicate that the city's air quality status is determined by a combination of transportation density, seasonal meteorological factors, and photochemical transformations. Two critical periods for urban environmental safety management were identified: the winter season (characterized by elevated NO, NO2, and PM2.5 loads) and the summer season (marked by peak ozone accumulation). The results underscore the necessity for a differentiated, season-specific approach to urban environmental policy, focusing on traffic emission reductions in winter and photochemical pollution warning systems in summer.