Distribution pattern of mercury in the Slovenian soil: Geochemical mapping based on multiple geochemical datasets

A regional geochemical survey was conducted, covering the entire territory of Slovenia. Medium-density soil sampling was performed in a 5 × 5 km grid, mercury concentrations were analysed and a map of mercury spatial distribution was constructed. The determined mercury concentrations revealed an important difference between the western and the eastern parts of the country. A huge anomaly in the western part is the consequence of environmental contamination due to the 500-year history of mining and ore processing in the Idrija mercury mine and partly due to Hg containing rocks on outcrops. Slightly elevated Hg concentrations revealed in the Ljubljana-Kranj and Celje basins indicate urban pollution due to industry, traffic and the use of mercury-containing products. It was established that, besides anthropogenic impacts, lithological and climatic characteristics that determine the type of soil also influence the distribution of mercury in soils. The data were compared to a previously conducted low-density geochemical survey (sampling grid 25 × 25 km, n = 54) and to the regional geochemical data set supplemented by local high-density sampling data (irregular grid, n = 2835). Comparing high-, medium- and low-sample density surveys, it was shown that higher sampling density allows the identification and characterization of anthropogenic influences on a local scale, while medium- and low-density sampling reveal general trends in the mercury spatial distribution, but are not appropriate for identifying local contamination in industrial regions and urban areas.