High NO2 Concentrations Measured by Passive Samplers in Czech Cities: Unresolved Aftermath of Dieselgate?

This work examines the effects of two problematic trends in diesel passenger car emissions—increasing NO2/NOx ratio by conversion NO into NO2 catalysts and a disparity between emission limit actual emissions everyday driving—on ambient air quality Prague. concentrations were measured 104 membrane-closed Palmes passive samplers at 65 locations Prague March–April September–October 2019. city stations during those periods comparable with average values 2016–2019. The selected locations, after correcting for 18.5% positive bias co-located monitoring station, 36 µg/m3 (range 16–69 µg/m3, median 35 µg/m3), EU annual 40 exceeded 32% locations. have correlated well (R2 = 0.76) 2019 daily vehicle counts, corrected additional due to uphill travel intersections. In addition expected “hot-spots” busy intersections center, new ones identified, i.e., along six-lane road V Holešovičkách. Comparison data from six 15 March–30 April 2020 restrictions same period 2016–2019 revealed an overall reduction even larger NO. spatial analysis time both demonstrate consistent correlation traffic intensity along/near path. slow pace reductions suggests that stricter NOx limits, introduced last decade or two, so far failed sufficiently reduce concentrations, there is no clear sign remedy Dieselgate excess emissions.