Trace Elements Speciation in Mining Affected Waters

Abstract

The trace element species distribution in the waters of Maresh and Luda Yana Rivers flowing the region of Cu—Mo Asarel-Medet mine, Bulgaria, were determined during a high-flow May 2007 by a combination of monitoring studies and a thermodynamic modeling. The mining activities, the weathering and the oxidation processes in the East dump were found to affect strongly the composition, physico-chemical characteristics and behaviour of trace elements in the whole water system. High levels of SO42⁻, Cu, Mn, Fe, Al and acidity were determined in the affected stations. In the reference and mining affected waters different species were calculated. Cu²⁺ and CuCO₃° species (1:1) existed in the reference waters and Cu²⁺ and CuSO₄° species (1:1) in the polluted and affected waters. Cu²⁺ species was dominating downstream. Hydroxy species Fe(OH)₂ ⁺, Al(OH)_n ^3–n (n = 2—4) (responsible for the formation of a suspended phase) and Me²⁺ ions followed by sulphate species MeSO₄° (Me = Mn, Zn, Cd and Pb), and carbonate species PbCO₃° and PbHCO₃ ⁺ were predominant in the system. Some more sulphate species, such as MeSO₄ ⁺, Me(SO₄)₂ ⁻ (Me = Fe, Al), Me(SO₄)₂ ²⁻ (Me = Zn, Cd, Pb), Me(SO₄)₃ ⁴⁻ (Me = Zn, Cd) and Cd(SO4)₄ ⁶⁻ also appeared in mining polluted and affected waters. Although the trace elements concentration decreased downstream However, the quota of their free metal species, which are more toxic, increased.