Case Study 4 Metal fluxes from mine waste to rivers Falun Copper Mine

Mixed sulphidic ores (mainly containing Fe, Cu, Pb and Zn) were mined for more than a millennium at the Falun Copper Mine, central Sweden. The exploitation was conducted in industrial scale for 450 years, until the operations ceased in 1992. The great importance of the Falun Mine for the technical, economic, social and political history of Sweden and Europe was recognized by the designation of the Mine and parts of Falun city as a World Heritage Site by UNESCO. But the long history of heavy environmental pollution from the mining and metallurgical activities is also unique and deserves recognition and assessment. As an element of the large-scale "Falun Project" aiming at a general clean-up of the Falun region and near-by River Dalalven, a book entitled "The Environmental History of the Falun Mine" was prepared by L. Lindestrom and published in 2003.

According to current estimates, a total of 6 Mt of SO2 and 15 kt of Cu was emitted to the atmosphere, while 0.5-1.0 Mt of Cu, Pb, Zn and Cd were discharged to the surrounding forest soils and watercourses during the operations in Falun. In the small stream flowing through the city of Falun, the total concentration of Cu was enhanced about 140 times (reaching 70

jg/l) and that of Zn about 1,000 times (reaching 2,000 jug/l) relative to reference levels upstream of Falun, even after purification of the mine water had been initiated.

The assessment of the Falun environment showed that the soils and the terrestrial ecosystems surrounding Falun had recovered to a remarkable degree during the 20th century. The aquatic environment had much less time to respond to pollution abatement measures, since the treatment of the mine water did not start until the late 1980s. Nonetheless, a clear recovery has taken place in the aquatic ecosystems close to Falun during the 1990s. To explain this rapid environmental improvement, it is necessary to understand the speciation and bioavailability of the toxic metals, as well as the antagonistic effects of some metals (such as Zn) towards the manifestation of harmful effects of other, more toxic metals.

0 0

Post a comment