Heavy metal contamination in the Aries river catchment, western Romania: Implications for development of the Rosia Montand gold deposit

The Abrud-Aries river system, western Romania, is subject to ongoing mining activity associated with Cu, Pb and Zn ore extraction. The catchment contains what is believed to be Europe's largest unutilized Au deposit at Rosia Montana that is planned to be exploited by open-cast mining techniques. The magnitude and environmental significance of metal (Cd, Cu, Pb, and Zn) concentrations in surface water and river channel sediment have been investigated along a 140 kin reach of the Rivers Abrud and Aries and 9 tributaries affected by mining. The speciation of sediment-bound metals was established using a 4-stage sequential extraction procedure (SEP) that identified four chemical phases: (1) exchangeable, (2) Fe/Mn oxides, (3) organic matter/sulphides and (4) residual. Peak solute and sediment-bound metal concentrations were found to occur in the River Abrud downstream of the EM Bucium mine and in mining-affected tributaries, with up to 71% of sites containing sediment metal concentrations in excess of Dutch intervention values. The River Aries was found to be much less polluted than the River Abrud, with only Cu showing concentrations above guideline values, as a consequence of porphyry Cu mineralization in the catchment. The magnitude and spatial extent of metal pollution is influenced by local physico-chemical conditions and hydrological linkages between mining and local river systems. Sediment-bound Cd and Zn were found to be predominantly associated with the exchangeable phase of the sediment (9-74% and 6-65%, respectively), whilst Fe/Mn oxides (5-76%) and organic matter/sulphides (1-45%) generally accounted for a majority of Pb and Cu partitioning, respectively. Sites of environmentally significant sediment-metal pollution were identified in the Rivers Abrud and Aries where exchangeable metal concentrations exceeded Dutch intervention values. The implications of metal contamination in the Aries river basin to the proposed mining development at Rosia Montana are discussed in relation to other contaminated Romanian catchments and with the EU Water Framework Directive. (C) 2005 Elsevier B.V. All rights reserved.