Distribution and speciation of mercury in mine waste dumps.

Mine waste dumps of historic mercury mines represent environmental threat. In the central Czech Republic, Hg ores were mined at two sites for more than 150 years. Mine wastes collected from dumps near Hg mines were elevated in total Hg (up to 120 microg(-1)). Thermal-desorption method revealed that most of Hg (>80%) in studied waste material was present as cinnabar (HgS), that is relatively stable in soils and resistant to formation of highly toxic methyl-Hg. Nevertheless minor part (<14%) of total Hg was identified as mineral surface bound Hg, which might undergo methylation and thus represents potential long-term environmental risk.