Temporal Changes in Mountain Slope Gradients in the Concentrations of Pollutants and Pb Isotope Ratios Near the Ostrava Conurbation (Upper Silesia, Czech-Polish Border)

Abstract

The Upper Silesian basin belongs to the largest industrial pollution sources in Europe and the city of Ostrava ranks among the worst-polluted urban areas in the European Union. To assess temporal and spatial trends in atmospheric pollution, we determined concentrations of S, Pb, Cu, Zn, As, Cd, Sb, and Al in snow in downtown Ostrava and at the Lysa Hora Mt. (LH), situated 33 km southeast. Snowpack surfaces were sampled in February 2011/2012, 2018, and 2019. At LH, we collected snow samples at four elevations (700, 900, 1100, and 1300 m) in order to quantify mountain slope gradients in the pollution that, in turn, might reflect vertical stratification of air masses in a region frequently affected by temperature inversions. 206Pb/207Pb and 208Pb/207Pb isotope ratios and back trajectories of air masses were used for pollution source apportionment. In year 1, there were clear-cut upslope decreases in concentrations of soluble pollutants. By year 3, the concentrations of soluble pollutants at LH decreased by 90% and the concentration gradients ceased to exist. Because annual precipitation totals at LH increase upslope by 75%, rates of deposition of soluble pollutants are now higher at the summit than those at the foot of the mountain. Hydrological control of deposition rates of soluble pollutants thus plays a more important role under lower pollution levels. Concentrations of soluble pollutants in Ostrava were up to 36 times higher compared with those at LH and also decreased by 90%. Lead isotopes indicated the continuing presence of gasoline Pb in the atmosphere, despite its ban in 2000.