Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Biogeochemical accumulation of heavy metals at waste dump of former uranium and coal mine at Bečkov near Žacléř
AbstractThe waste rock dumped at abandoned coal and uranium mine in Bečkov was found to contain enhanced contents of uranium and other elements. During spontaneous ignition of the dump some metals, particularly Cd, As, Pb, U, then Zn, Se, Ag, Sn and Sb were remobilized and accumulated in the summit part of the burnt dump. Many anthropogenic mineral phases were identified in the heavy fraction of dump material (density > 2,9): lead, tin, alloy of Pb and Sn, galenite, PbSn-oxide, two Pb-oxides, Sn-oxide, anglesite, metallic selenium, Pb-selenate or selenite, Fe-oxides ± Cu, Zn, As, unidentfied mineral of Cu-As-O. Anglesite (incrustations and skeleton-like crystals) and Fe-oxides (magnetite, hematite) predominate. The metals are progressively extracted and absorbed by vegetation, mostly by birch and beech trees. Coefficients of biogeochemical enrichment of metals in leaves of trees increase in a sequence U^Pb^Cu^ Mo^ As^ Cd^Zn. High contents of zinc and cadmium were also identified in humic layer that originates on the dumps. However, because of low age of the humic layer, the majority of other metals are still depleted in humus relative to dumped waste rock. The degree of depletion decreases as follows: U^(Mo, Cu, Ni) ^Pb^As. As a consequence, the contents of arsenic and lead in humic layer are expected to grow faster in future than those of uranium and other elements.