Mercury in the Town of Idrija (Slovenia) After 500 Years of Mining and Smelting

Abstract

Due to mining and smelting processes, and due to the naturally increased contents of mercury in soil, the wider surroundings of Idrija are contaminated with mercury. The Idrija ore deposit contains rocks enriched with cinnabar originating from periods up to Middle Triassic. Native mercury can be found primarily in Carboniferous clastic rocks which reach the surface in the western part of the ore deposit. In the 1970s, when the production of mercury reached its peak, the first intensive studies of the ecological cycle of mercury were made. New analytical techniques and improved methods for determining the total mercury and methylmercury contents were introduced in order to study the uptake and distribution of this element in the ground, air, water, plants, animals and man. After 20 years, systematic determinations of total mercury in environmental and biological samples were started again. In our work, total mercury in air, lichens sampled in situ, transplanted lichens, carrots and beans were determined, using gold amalgamation cold vapour atomic absorption spectrometry (CV AAS) after acid decomposition under pressure, or in the case of air measurements, the double amalgamation technique followed by CV AAS. Measured concentrations of total gaseous mercury in air varied from to to 277 ng Hg m 3. The total mercury contents in lichens sampled in situ were in the interval between 3 to 23 μg Hg g 1 dry sample (d.s.). The total mercury content in carrot ranges from approximately 60 to 760 ng Hg g 1 d.s. The concentrations of total mercury in beans were in the interval between 2 to 23 ng Hg g −1 d.s.