Induction of a geochemical barrier for As, Fe and S immobilization in a sulfide substrate

Acid mine drainage (AMD) is an environmental concern due to the risk of element mobilization, including toxic elements, and inclusion in the food chain. In this study, three cover layers were tested to minimize As, Fe and S mobilization from a substrate from former gold mining, containing pyrite and arsenopyrite. For this purpose, different layers (capillary break, sealant and cover layer) above the substrate and the induction of a geochemical barrier (GB) were used to provide suitable conditions for adsorption and co-precipitation of the mobilized As. Thirteen treatments were established to evaluate the leaching of As, Fe and S from a substrate in lysimeters. The pH, As, Fe, S, Na, and K concentrations and total volume of the leachates were determined. Mineralogical analyses were realized in the substrate at the end of the experimental period. Lowest amounts of As, Fe and S (average values of 5.47, 48.59 and 132.89 g/lysimeter) were leached in the treatments that received Na and K to induce GB formation. Mineralogical analyses indicated jarosite formation in the control treatment and in treatments that received Na and K salts. However, the jarosite amounts in these treatments were higher than in the control, suggesting that these salts accelerated the GB formation. High amounts of As, Fe and S (average values of 11.7, 103.94 and 201.13 g/lysimeter) were observed in the leachate from treatments without capillary break layer. The formation of geochemical barrier and the use of different layers over the sulfide substrate proved to be efficient techniques to decrease As, Fe and S mobilization and mitigate the impact of acid mine drainage.

Replication of an ivg protocol to estimate bioaccessible arsenic in materials from a gold mining area in Brazil

Tests for bioaccessibility are useful in human health risk assessment. No research data with the objective of determining bioaccessible arsenic (As) in areas affected by gold mining and smelting activities have been published so far in Brazil. Samples were collected from four areas: a private natural land reserve of Cerrado; mine tailings; overburden; and refuse from gold smelting of a mining company in Paracatu, Minas Gerais. The total, bioaccessible and Mehlich-1-extractable As levels were determined. Based on the reproducibility and the accuracy/precision of the in vitro gastrointestinal (IVG) determination method of bioaccessible As in the reference material NIST 2710, it was concluded that this procedure is adequate to determine bioaccessible As in soil and tailing samples from gold mining areas in Brazil. All samples from the studied mining area contained low percentages of bioaccessible As.

Division of Soil Conservation Soil and Water Quality Review, January 2010

Special Points of Interest: • The Division of Soil Conservation celebrated its 70th anniversary July 1, 2009. The Iowa Soil Conservation Laws were enacted in 1939 creating the state soil conservation agency and governing committee and providing for the creation of Iowa’s 100 soil and water conservation districts. • The Mines & Minerals Bureau, through the federal Abandoned Mine Land (AML) Program, worked with various watershed groups to again secure an additional $1 million dollars in funding for the construction on projects in Marion, Mahaska and Monroe Counties. • Iowa hosted the Mississippi River/Gulf of Mexico Hypoxia Task Force tour and meeting in September 2009.

Low molecular weight carboxylic acids in oxidizing porphyry copper tailings

The distribution of low molecular weight carboxylic acids (LMWCA) was investigated in pore water profiles from two porphyry copper tailings impoundments in Chile (Piuquenes at La Andina and Cauquenes at El Teniente mine). The objectives of this study were (1) to determine the distribution of LMWCA, which are interpreted to be the metabolic byproducts of the autotroph microbial community in this low organic carbon system, and (2) to infer the potential role of these acids in cycling of Fe and other elements in the tailings impoundments. The speciation and mobility of iron, and potential for the release of H+ via hydrolysis of the ferric iron, are key factors in the formation of acid mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of the Piuquenes tailings, Fe(III) is the dominant iron species and shows high mobility. LMWCA, which occur mainly between the oxidation front down to 300 cm below the tailings surface at both locations (e.g., max concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01 mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and 16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(111) hydroxides are depleted. Our data suggest that LMWCA may influence the mobility of iron in two ways. First, complexation of Fe(III), through formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate, oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III) chelate complexes which may be mobilized downward and convert to Fe(II) by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate and formate) can be used by iron-reducing bacteria as electron donors (e.g., Acidophilum spp.), with ferric iron as the electron acceptor. These processes may, in part, explain the low abundances of secondary Fe(III) hydroxide precipitates below the oxidation front and the high concentrations of Fe(II) observed in the pore waters of some low-sulfide systems. The reduction of Fe(III) and the subsequent increase of iron mobility and potential acidity transfer (Fe(II) oxidation can result in the release of H+ in an oxic environment) should be taken in account in mine waste management strategies.

[Voyage en Italie : 1824-1830]. , [Plan d'un couvent] : [plans du premier étage et du rez-de-chaussée] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 191

[Voyage en Italie : 1824-1830]. , Tombeau de Théron à Agrigente : détails au huitième de l'Exécution : [détails d'élévation, avec plusieurs profils, plan partiel] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 192

[Voyage en Italie : 1824-1830]. , [Vue du port] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 200

[Voyage en Italie : 1824-1830]. , Montenero, près Livourne : [vue perspective] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 201

[Voyage en Italie : 1824-1830]. , [Vue présumée de la Punta Nera, port et] rue en pente à Porto Ferrajo : [deux vues perspectives, un plan d'ensemble] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 106

[Voyage en Italie : 1824-1830]. , Madona del Soccorso : [vue perspective, plan et coupe longitudinale] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 106

[Voyage en Italie : 1824-1830]. , S. Alessandro en marbre : [élevation principale] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 204

[Voyage en Italie : 1824-1830]. , [Vue perspective d'un palais] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 205

[Voyage en Italie : 1824-1830]. , [Vestibule d'un palais] : [plan et vue perspective] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 204

[Voyage en Italie : 1824-1830]. , [Deux palais ou maisons privées] : [deux plans du rez-de-chaussée] : [dessin] / h. L. [Henri Labrouste]

Référence bibliographique : Weigert, 207