Search

This study reports the annual amount of heavy metals discharged by industrial activity into the estuary of the Ría of Huelva (SW Spain). The findings showed that the discharged metals found in highest amounts were Fe (11 t y⁻¹), Zn (3.4 t y⁻¹) and Mo (0.88 t y⁻¹). There were other metals with high pollutant charge, such as Ti (232 kg y⁻¹), As (228 kg y⁻¹), Ni (195 kg y⁻¹), Pb (100 kg y⁻¹), Cr (39 kg y⁻¹) and Cd (33 kg y⁻¹). These results were compared with pollutants transported via the Tinto and Odiel rivers from abandoned mining activities in the Iberian Pyrite Belt (IPB), and it was deduced that the amounts spilled exclusively by industries were less than 1% in relation to the total discharge. Hence, the treatment of residues from the IPB should be the priority goal to improve water quality in the estuary., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems.

Abstract: Intensive mining has taken place in the Iberian Pyrite Belt since 3000 B.C. generating Acid Mine Drainage (AMD) and releasing high amounts of SO4, acidity, metals and metalloids into surface water. Concentrations of elements in AMD-impacted waters are regulated by the precipitation of Fe-rich materials and particulate matter can influence the mobility and the bioavailability of metals. In this paper a study on the dissolved As species concentration along a polluted stream has been performed. Two sampling campaigns were conducted during the dry and the rainy seasons. Concentrations of dissolved elements are higher during the dry season and increase progressively along the water course in both seasons. Concentrations up to 80μgL−1 of As3+ and 5mgL−1 of As5+ were determined. The concentration of As species increases and the As3+/As5+ ratio decreases downstream. The Fe2+/Fe3+ and As3+/As5+ ratios show the same pattern with respect to pH for all the examined samples, except those taken from Au cyanidation wastes. The particulate phase is mainly composed of Fe, As and Pb, with As being associated with the Fe minerals while Pb seems to be associated with the clay colloids. [Copyright &y& Elsevier]

Abstract: Arsenic is very abundant in the Iberian Pyrite Belt (IPB) and it might have hazardous consequences for plants. The chemical speciation is an important factor to take into account in toxicity evaluations. Arsenate is analogous to phosphate and it can seriously interfere with cellular processes. In the present study we have analysed by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) the arsenic speciation in soils from São Domingos mine area (IPB) and arsenate resulted to be the major species. The arsenic content and speciation analysis have been carried out also in two metal tolerant species from that area: Erica andevalensis, endemic heather from the mining areas of the Southwest Iberian Peninsula, and Erica australis, a widely distributed species. The total content of arsenic ranged in soils from 194 to 7924mgkg−1 (dry mass), and from 1 to 24.4mgkg−1 in E. andevalensis and from 2.7 to 11.6mgkg−1 in E. australis. The organic forms of arsenic were almost absent, with only dimethylarsinate (DMA) found in some samples of E. andevalensis. These plant species must possess different tolerance mechanisms, as E. australis accumulates mainly arsenite, while in E. andevalensis arsenate is the most abundant species in some cases. [Copyright &y& Elsevier]

Abstract: Fifteen tailings samples were investigated for mineralogy by scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), 12 for geochemical distribution by sequential extractions successively attacking water-soluble, adsorbed-exchangeable-carbonate, Fe (oxy)hydroxide, Fe oxide and sulfide fractions, as well as 13 tailings pore water and two groundwater samples for geochemical composition and physicochemical conditions at the former Ylöjärvi Cu–W–As mine in SW Finland. Mineralogical observations and sequential extractions demonstrated the depletion of arsenopyrite and other sulfide minerals from the superficial and deeper coarse-grained tailings resulting in high concentrations of As in pore water and groundwater beneath the tailings heap (5140 and 14 500μgL−1, respectively), and lowering the pore pH (from ca. 7.8 to 5.3). The solubility of As was controlled by pH (and Eh) as well as precipitating Fe(III) (oxy)hydroxides and Fe(III) arsenates. Although these phases are an important sink for As, it accumulates in the percolating water. Further acidification of the tailings after the consumption of scarce neutralizing calcite is probable and will affect the stability of the remaining arsenopyrite and As-bearing secondary phases. [Copyright &y& Elsevier]

Abstract: Simultaneous analysis of micro-X-ray diffraction (μ-XRD) and micro-X-ray fluorescence (μ-XRF) based on synchrotron light sources, and electron microprobe (EMP) analyses, were performed on iron terrace samples taken from Tinto-Odiel river system from the Iberian Pyrite Belt (IBP, SW Iberian Peninsula). Iron terraces are formed during the oxidation and precipitation of dissolved iron along the riverbeds impacted by acid mine drainage (AMD). This paper includes the study of actively-forming current terraces and fossil terraces isolated from the stream courses due to the river migration over time. The results of the study of current terrace samples from AMD-affected streams of two IPB abandoned mines (Tinto Santa Rosa and Cueva de la Mora) showed that fresh precipitates at the surface are composed primarily of metastable schwertmannite, which is gradually transformed at depth over short-time scales into goethite. Sediments of ancient terraces are composed mainly of goethite, which most likely originated from the re-crystallization of a precursor schwertmannite. However, at century-time scale, goethite partially re-crystallizes to hematite due to diagenetic processes. The transformation rate of goethite into hematite is negatively correlated with grain size and the crystallinity of goethite. Moreover, this transformation is accompanied by an increase in grain size and a decrease in surface area of hematite, and a concomitant decrease in arsenic trapped in the solid. This increase in the arsenic mobility during the diagenetic maturation should be considered in the development of conceptual and analytical models describing long-term fate, transport and bioavailability of arsenic in environmental systems. [ABSTRACT FROM AUTHOR]