11 - Mercury Isotopes in Soils and Ores at the Site of a Former Mercury Mine

Area around the town of Idrija is a site of high contamination with Hg. Since the be-ginning of 16th century up to the end of operation in the nineties of 20th century, more than 3 million m3 of ore were excavated and 147.000 tons of Hg was produced. In this study the relationship between the Hg ore and soils is examined using the isotopic fingerprint. Soil samples at two sides of the valley where the decommissioned Hg smelting plant is located were collected. Ores exhibit a δ202Hg of -0.32 ‰. The soils in the vicinity of the Hg smelting plant exhibit the δ202Hg of -0.41 ‰ and the ones on the hill above the plant exhibit the δ202Hg from -1.46 to -0.92 ‰. At the river bank opposite to the smelting plant soils exhibit positive δ202Hg of 0.23 ‰ and are the only ones with the observable mass independent fractionation of -0.14 ‰ for Δ199Hg. The concentrations of Hg in soils at the smeltery are up to 1500 µg/g while the ones at the top of the hill and the opposite bank are between 100 and 200 µg/g. From this data it seems that the pollution from the smeltery heavily influences the isotopic composition of the soils in its proximity. On the hill above the smeltery the abundance of lighter isotopes is increased which might be a consequence of outfall of the heavier ones on the way to the top. Differences in isotopic composition on the left bank might be explained by the different source of Hg. From this study it can be inferred that Hg from the smeltery influences the isotopic composition only in the direct vicinity, while further away some fractionation processes or local sources become the predominant factor influencing the isotopic composition in soils.

Authors: Dominik Božič,Y aroslav Shlyapnikov, Marta Jagodic Hudobivnik, Jože Kotnik, Tatjana Dizdarevič, Marko Štrok, Milena Horvat