Hydrogeochemistry of circum-neutral mine waters in the Anglès old mining area, North Eastern Spain

Circum-Neutral mine drainage may constitute a significant environmental problem due to the mobilization of metalloids such as As, Sb, Se, and metals such as Cd, Pb, and Zn. The neutral pH conditions of these waters may be attributed to the dissolution of acid-consuming carbonate minerals associated with carbonate gangue or host rocks. In the abandoned Anglès mining district, mine water from Coral adit (Osor area) and mine shafts (Bonmatí area), generally, had neutral pH from carbonate and silicate dissolution, and showed high concentrations of Fe, Mn, Ni, Pb and Zn. Mine water samples showed high concentrations of Ca (116-189 mg/L), HCO3 - (290-377 mg/L), SO4 - 2 (156-288 mg/L) and an elevated pH (7.08-7.68), which may indicate calcite dissolution through the Coral adit. In addition, the elevated concentrations of Mn (0.19-1.8 mg/L) and Zn (>0.25-2.8 mg/L) suggest the dissolution of sphalerite and Mn oxides. Moreover, mine water showed elevated concentrations of some cations, such as Na (31.4-42.5 mg/L), Mg (18.0-28.0 mg/L), and K (4.5-6.2 mg/L), above their concentrations in surface water. Geochemical modeling showed that albite and other aluminosilicates are not stable in these waters and likely dissolve; equilibrium with kaolinite also is a main processes controlling water chemistryPeer Reviewe