The effects of air mass transport, seasonality, and meteorology on pollutant levels at the Iskrba regional background station (1996–2014)

Our main goal was to estimate the effects of long-range air transport on pollutant concentrations measured at the Iskrba regional background station (Slovenia). We cluster back-trajectories into categories and simultaneously model the effects of meteorology, seasonality, trends, and air mass trajectory clusters using a Bayesian statistical approach. This simplifies the interpretation of results and allows us to better identify the effects of individual variables, which is important, because pollutant concentrations, meteorology, and trajectories are seasonal and correlated. Similar to related work from other European sites, we find that slow and faster moving trajectories from eastern Europe and the northern part of the Balkan peninsula are associated with higher pollutant levels, while fast-moving trajectories from the Atlantic are associated with lower pollutant concentration. Overall, pollutant concentrations have decreased in the studied period. •Joint model of meteorology, seasons, trends & air mass movement gives more insight.•Air mass from eastern Europe and northern Balkans leads to higher pollution levels.•Decrease in trajectory length suggest a decrease in wind speeds in past 15 years.•Bayesian approach to modelling leads to substantially easier-to-interpret results.