Zmeny obsahu vybranych prvku v uplynulych dvaceti letech v pudach na uzemi hlavniho mesta Prahy

Results of recent geochemical mapping of the Prague urban agglomeration (Poňavič et al. 2018) were compared with corresponding results obtained 20 years ago (Ďuriš 1996), both mapping projects were realized by the Czech Geological Survey, Prague. The aim of this study is not only a presentation of the distribution of selected elements in topsoil environment (As, Co, Cr, Cu, Ni, Pb, V, and Zn), but also a comparison of their inter-relationships in separate types of urban environment during the last 20 years. The first geochemical mapping took place on the whole territory of Prague. Creation of geochemical maps of distribution of selected trace elements in soils was one of the aims of this activity. The study results proved unambiguously, that the city centre was most loaded by all elements measured (Ďuriš 1996). The anomalous concentrations were probably caused by aerial fallout, coming from emissions from energy sources, industrial plants and traffic. The localization of such anomalous places was influenced by directions of air-flows and by the city surface morphology with dominant influence of the Vltava river valley (Ďuriš 2011). The second mapping was concentrated on the central part of Prague (see Fig. 1). The iterative geochemical mapping is a part of the European project Urban Geochemistry (UrGe), organized by the Geochemistry Expert Group of EuroGeoSurveys.
For the second study we divided the samples according to the type of site where they were taken: traffic affected areas, parks, residential and other urban environment groups, see Tab. 1.
When comparing heavy metal contents from different environment settings in separate sample sets, it was noted that no significant difference between “residential” and “traffic affected areas” environment was recognized, see Fig. 2. However, in case of other types of environment as “traffic affected areas” vs. “parks” significant differences were recorded. We registered a significant enrichment of Cu and Zn and slight enrichment of As and Cr in traffic affected areas. On the contrary, no significant difference between Pb, V and Ni was observed. All differences in contents, relations and presence of separate heavy metals discussed above seem to be the result of change of city environment exploitation. During the last 20 years, significant decrease of industrial activities, traffic organization changes (by-pass roads and tunnels) through the Prague territory took place; while a number of brownfield revitalization programmes were successfully completed.

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