ALBERT

Description: Nutrient (nitrate, phosphate, silica) and dissolved metal (Al, Cu, As, Cd, Ni, Zn, Fe, U) distributions were studied in the mixing zones of the Tinto and Odiel rivers which drain the South Iberian pyrite belt. Phosphate distribution is strongly influenced by discharges from the fertiliser industry, especially in the Tinto mixing zone. The increase of silica content in this zone is related to a release of biogenic silica from diatoms. Nitrate concentrations which are influenced by urban and industrial effluents showed an important maximum in the early stages of mixing in the Tinto (as do the metals). Compared to the Odiel river, the metal concentrations in the Tinto river reached higher values in relation to more intensive mining activities. Dissolved Fe, Mn, Al, Cu, Cd and Zn concentrations were correlated in the mixing zones of both rivers. This suggests that they have the same source and are subjected to the same controlling processes in the estuary. A maximum concentration for these metals was observed in the early stage of mixing in the Tinto and reflects a decrease of redox in a low pH (〈3) environment. Downstream in the Odiel system, metals showed a slight removal. Dissolved uranium, present at a low level (0.05 μmol l-1) in the rivers, is introduced by the phosphate fertiliser industry in the estuary and trapped in sedimentation areas. As a consequence, waters of the Gulf of Cadiz have a U content similar to that of the open seawater. Copyright (C) 1999 Elsevier Science B.V. All rights reserved.

Description: The Rio Tinto and Rio Odiel drain the Iberian Pyrite Belt, an important metal-rich sulphide deposit. The rivers are highly acidic (pH 2.2-3.6) and have milli-molar SO4 and Fe concentrations and micro-molar Co, Cu, Mn and Zn concentrations. Observed dissolved metal levels were at a maximum during autumn and early winter surveys (e.g. Rio Tinto: 460-856 μM Cu), and lower in late winter, spring and summer (121-175 μM Cu). This variability is attributed to the production of concentrated acid mine drainage (AMD) during periods of enhanced microbial activity at higher temperatures in summer, and a subsequent run-off of the AMD into the rivers with the first rain in the autumn. Lower temperatures and dilution by winter floods resulted in a reduction of river metal concentration towards the end of the wet season. Metal distributions in the estuarine mixing zones of the Tinto and Odiel were governed by the acidity. The lack of metal transfer from the dissolved to the particulate phase in the low salinity region is attributed to the electrostatic repulsion between the metal cations and positive charges on particle surfaces, and/or to the protonation of adsorption sites at low pH. Dissolved Pb was an exception and showed marked removal in the low salinity zone at low pH (pH 2.5), due to its particle reactive nature. The gross metal fluxes from the Rio Tinto and Rio Odiel are important on a global scale, for example amounting to 8.1 and 1.6 of the estimated global riverine dissolved Zn and Cu fluxes. The fluxes of metals from the estuary contribute to enhanced dissolved metal concentrations observed in the Gulf of Cadiz. © 2003 Elsevier Ltd. All rights reserved.

Description: On April 25, 1998, a spill at the Los Frailes mine in southern Spain resulted in a very high input of metals (including Ag, As, Cd, Cu, Fe, Pb, Tl and Zn) into the river Guadiamar. Calculations indicate that the discharges into the Guadiamar of Cu (5100t), Pb (24,700t), Zn (26,200t) and Ag (138t, based on mud only) were higher than the annual production by the Los Frailes mine for Ag and Pb, and ca. two times less for Cu and Zn. For many metals, the increase in concentration in the affected river (Guadiamar), 2days after the initial discharge, was by several orders of magnitude. However, 6months after the incident, no evidence of the spill could be observed in the plume of the river (Guadalquivir) which discharged the mine waters into the coastal waters of the Gulf of Cadiz. This observation can possibly be explained by low rainfall, natural metal removal processes in the river and estuarine environments and by human interventions. Copyright (C) 1999 Elsevier Science Ltd. On April 25, 1998, a spill at the Los Frailes mine in southern Spain resulted in a very high input of metals (including Ag, As, Cd, Cu, Fe, Pb, Tl and Zn) into the river Guadiamar. Calculations indicate that the discharges into the Guadiamar of Cu (5100 t), Pb (24,700 t), Zn (26,200 t) and Ag (138 t, based on mud only) were higher than the annual production by the Los Frailes mine for Ag and Pb, and ca. two times less for Cu and Zn. For many metals, the increase in concentration in the affected river (Guadiamar), 2 days after the initial discharge, was by several orders of magnitude. However, 6 months after the incident, no evidence of the spill could be observed in the plume of the river (Guadalquivir) which discharged the mine waters into the coastal waters of the Gulf of Cadiz. This observation can possibly be explained by low rainfall, natural metal removal processes in the river and estuarine environments and by human interventions.