Risk assessment and proposed remedial actions in coastal tailings disposalsites in Romania

Intensive mining and ore processing activities over the last fifty years co ncerning phosphate and polymetallic sulphidic ores at Navodari and Baia, by the Romanian Black Sea coast, have resulted in the production of millions of tonnes of hazardous wastes which contain high residual concentrations of heavy elements and radionuclides in mobile forms. At Navodari, where a che mical plant for the production of sulphuric acid and superphosphates operat es, over 3,000,000 m(3) of phosphogypsum and 1,000,000 m(3) of pyritic cind ers have been disposed of in several stacks and dumps. At Baia, over 1,200, 000 t of copper tailings from the nearby located flotation plant have been disposed of since 1965 in three decantation ponds. Under the action of seve ral physicochemical mechanisms, toxic elements contained in the tailings ar e mobilised, migrate to the surroundings and cause severe and widespread co ntamination of soils, surface and ground waters and the Black Sea. In this paper, all the above mentioned sources of pollution that are curren tly directly or indirectly affecting humans, soils, freshwater ecosystems a nd the Black Sea, are identified and characterised. Furthermore, in order t o assess the level of risk posed by each source of pollution at each affect ed area, a complete environmental characterisation study was undertaken fol lowed by a risk analysis carried out on a source-pathway-target basis. Base d on experimental and risk analysis data, a rehabilitation scheme is propos ed for all affected areas, aiming at deactivating the pollution sources and rehabilitating the contaminated areas with remedial actions. This scheme i nvolves mainly: removal of toxic and heavy elements from sulphidic tailings and leachates with biosorption and biosolubilisation techniques and develo pment of a vegetative cover on phosphogypsum, cinders and sulphidic tailing s. (C) 1998 Elsevier Science Ltd. All rights reserved.