1,721,029 research outputs found
ARSENIC CONTAMINATION FROM PAST MINING: THE CASE STUDY OF BACCU LOCCI IN SARDINIA (ITALY)
No full textA mineralogical and geochemical approach to assess and contain pollution in abandoned mining areas of Sardinia
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Overview of the environmental geochemistry of mining districts in southwestern Sardinia, Italy
No full textIn southwestern Sardinia the areas around Iglesias and Guspini–Arbus represent the heart of the former mining industry. Lead and zinc ores were extensively exploited from 1850 to 1995. Geochemical studies in these areas have identified the main sources of contamination to be from drainage of flooded mines,mining wastes and tailings abandoned in settling ponds, and exposed ores. The transport of the fine materials eroded from the tailings ponds contributes to
spreading pollution over larger areas downstream. Concentrations of Pb, Cd and Zn in the streams draining the mining area (up to 1, 1.7, and 1000 mg/L, respectively)
are several orders of magnitude higher than those observed in rivers outside the
mining areas in Sardinia (Pb: <0.004 mg/L, Cd: <0.001 mg/L, and Zn: <0.02 mg/L), and greatly exceed the Italian drinking water standards (Pb:
0.01 mg/L, Cd: 0.005 mg/L, and Zn: 3 mg/L)
Refinement of solid-state arsenic speciation in complex environmental samples by means of TEM and XPS
No full textArsenic geochemistry – selected papers from the 10th Water-Rock Interaction symposium, Villasimius, Italy, 10-15 June 2001 (foreword)
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Il rischio di mobilizzazione dell’As nell’area mineraria dismessa di Montevecchio Levante (Sardegna).
No full textEffect of major anions on arsenate desorption from ferrihydrite-bearing natural samples
No full textThe influence of background electrolytes (Na2HPO4 center dot 2H(2)O, NaHCO3, Na2SO4, NaNO3 and NaCl) on arsenate (As(V)) desorption from 3 environmental samples (a tailings sample, a stream-bed sediment and a top soil) containing ferrihydrite as the main As-bearing phase has been studied by means of kinetic batch experiments and geochemical simulations. The experimental results indicate that As(V) release increases greatly in the presence of dissolved phosphate and carbonate species. Similarly to PO43+, a strong surface interaction of inner-sphere type between ferrihydrite and aqueous carbonate species is suggested. Nitrate and Cl- have negligible effects on the As(V) desorption reaction, whereas SO4_2- exhibits intermediate behavior depending on its dissolved concentration that probably influences the type of surface complex (i.e. outer-sphere or inner-sphere). The process of As(V) release follows the first-order rate equation of Lagergren modified for desorption; most values of the desorption rate constant k(des) are in the range of 0.0012-0.0030 min(-1). Modeling of the desorption experiments with PHREEQC, with ferrihydrite as the main As-bearing phase, indicates that the influence of pH is notably less important than the displacement action of carbonate species in determining the amount of As(V) released to solution. Simulation of As(V) desorption totally fails when the carbonate surface complexes are excluded from the model. In the NaHCO3 experiments with the tailings sample the best match between observed and calculated data is obtained also including dissolution of scorodite and arsenopyrite in the model. Moreover, modeling has stressed the poor quality of the adsorption constants for sulfate species that leads to strong overestimation of As(V) desorption at pH 4 and underestimation at pH 7.5. Although the findings of this study are consistent with the results of recent studies from other authors, they cannot be generalized or directly applied to natural systems. However, environmental implications concerning As mobility, as well as possible application in various fields (e.g. irrigation agriculture, soil decontamination, water treatment and mine site remediation), might be derived from these findings
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