Spatial representativeness of NO2 monitoring stations with respect to Sentinel-5P satellite based estimates

Nitrogen dioxide (NO₂) pollution is one of the most significant environmental threats to human health. To mitigate the negative effects of NO₂ and other air pollutants, it is essential to monitor pollution through a wide and reliable network. This study aimed to demonstrate the feasibility of using estimated NO₂ concentrations derived from Sentinel-5P, which is a mission that is part of the European Earth Observation Programme Copernicus.satellite data, combined with meteorological factors, to support NO₂ pollution monitoring. Unlike point ground measurements, this approach provides data for the entire area of interest. The main objective of this work is to determine what fraction of Poland is covered by spatially representative (SR) surface NO₂ concentrations measured at ground-based stations. Additionally, the study investigated how many people live in areas not covered by SR NO₂ measurements and identified potential locations for new stations to improve the spatial representativeness of the NO₂ monitoring network across Poland. Four methods for determining SR were tested: Global Moran's I, variability of the correlation coefficient with distance from the station, variability of semivariance with distance from the station, and similarity threshold. It was revealed that approximately 74–94 % of the urban population and 10–30 % of the rural population, where the yearly NO₂ limit was exceeded (>10 μg/m³), are covered by the representative NO₂ measurement network, depending on the method used. Finally, it was proposed to add 10–17 new urban stations and 0–5 new rural stations. This would ensure that 91–98 % of the population is covered by the SR monitoring network.