Behaviour of mercury and mercury compounds at the underground disposal in salt formations and their potential mobilisation by saline solutions

Within the next 40 years, in the European Union approximately 11,000 t of metallic mercury has to be disposed that is no longer used in the chlor-alkali industry or is gained from non-ferrous metal production or the cleaning of natural gas. One disposal option is permanent storage in underground storage sites in salt rock. As a liquid, metallic mercury has been ex-cluded from this disposal option so far. Prior to a permit, it is necessary to investigate the par¬ticular challenges for the disposal practice that originate from the specific properties of me¬tallic mercury (liquid state, formation of toxic gases, laborious clean-up of contaminated areas). On the base of present knowledge a safe permanent storage of metallic mercury in under-ground storage sites is principally feasible.