title: Geochemical behavior of an acid drainage system: the case of the Amarillo River, Famatina (La Rioja, Argentina).
abstract: The Amarillo River (Famatina range, Argentina, ~29° S and ~67° W) is unusual because acid mine drainage (AMD) is superimposed on the previously existing acid rock drainage (ARD) scenario, as a Holocene paleolake sedimentary sequence shows. In a markedly oxidizing environment, its water is currently ferrous and of the sulfate-magnesium type with high electrical conductivity (>10 mS cm-1in uppermost catchments). At the time of sampling, the interaction of the mineralized zone with the remnants of mining labors determined an increase in some elements (e.g., Cu ~3 to ~45 mg L-1; As ~0.2 to ~0.5 mg L-1). Dissolved concentrations were controlled by pH, decreasing significantly by precipitation of neoformed minerals (jarosite and schwertmannite) and subsequent metal sorption (~700 mg kg-1As, 320 mg kg-1Zn). Dilution also played a significant role (i.e., by the mixing with circumneutral waters which reduces the dissolved concentration and also enhances mineral precipitation). Downstream, most metals exhibited a significant attenuation (As 100 %, Fe 100 %, Zn 99 %). PHREEQC-calculated saturation indices (SI) indicated that Fe-bearing minerals, especially schwertmannite, were supersaturated throughout the basin. All positive SI increased through the input of circumneutral water. PHREEQC inverse geochemical models showed throughout the upper and middle basin, that about 1.5 mmol L-1of Fe-bearing minerals were precipitated. The modeling exercise of mixing different waters yielded results with a >99 % of correlation between observed and modeled data.
authors: Centro de Investigaciones en Ciencias de la Tierra (CICTERRA) CONICET, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016CGA, Córdoba, Argentina. karina.lecomte@unc.edu.ar.
authors: K L
authors: KL
authors: Lecomte
authors: Centro de Investigaciones en Ciencias de la Tierra (CICTERRA) CONICET, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016CGA, Córdoba, Argentina.
authors: S N
authors: SN
authors: Maza
authors: Centro de Investigaciones en Ciencias de la Tierra (CICTERRA) CONICET, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016CGA, Córdoba, Argentina.
authors: G
authors: G
authors: Collo
authors: Dpto. Geodinámica y Paleontología, Universidad de Huelva, 21071, Huelva, Spain.
authors: A M
authors: AM
authors: Sarmiento
authors: Centro de Investigaciones en Ciencias de la Tierra (CICTERRA) CONICET, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X5016CGA, Córdoba, Argentina.
authors: P J
authors: PJ
authors: Depetris
mesh_terms: D001118:Argentina; D004784:Environmental Monitoring; D005290:Ferric Compounds / Q000032:analysis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000032:analysis / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry; D008903:Minerals / Q000032:analysis / Q000737:chemistry; D008906:Mining; D045483:Rivers / Q000737:chemistry*; D013431:Sulfates / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D058085:Iron Compounds; D019216:Metals, Heavy; D008903:Minerals; D013431:Sulfates; D014874:Water Pollutants, Chemical; C492331:jarosite; C511969:schwertmannite
keywords: Acid mine drainage; Acid rock drainage; Efflorescent sulfate salts; Fe-bearing minerals; Natural attenuation; PHREEQC modeling