Pietro Marescotti

Genetic evolution of nanocrystalline Fe oxide and oxyhydroxide assemblages from the Libiola mine (eastern Liguria, Italy) structural and microstructural investigations

The Libiola Fe-Cu-sulphide mine, near Sestri Levante (eastern Liguria), represents one of the most extensively exploited sulphide deposits in Italy. In this area, active Acid Rock Drainage (ARD) processes are evident. The major resulting mineral phases are Fe oxides and oxyhydroxides, occurring in varicoloured crusts on the surface of waste rocks and in unconsolidated muds. In this study, the Fe assemblages of the waste rock were investigated by microchemical (SEM), structural (XRD), microstructural (TEM) and spectroscopic (DRS, IR, μ-Raman) techniques, in order to determine the phase composition, the textural relations among the minerals and their genetic evolution. They are characterized by intimate intergrowths of hematite and goethite with minor quartz and lepidocrocite; in some samples, the presence of very minor schwertmannite was detected. TEM and HR-TEM observations revealed that hematite is present within pseudo-elliptical bodies as pseudo-hexagonal to subrounded nanocrystalline lamellae (from 18.9 to 26.5 nm in diameter), whereas goethite occurs either as parallel intergrowths of acicular crystals (from 10 to 16.3 μm in length) or as sheaf-like assemblages. On the basis of the present data, the studied Fe oxide and oxyhydroxide assemblages are found to represent distinct spatial and temporal stages of a nano-scale evolution process.

Microfungi in highly copper-contaminated soils from an abandoned Fe-Cu sulphide mine: growth responses, tolerance and bioaccumulation.

Copper is one of the most dangerous soil contaminants. Soils affected by high copper concentrations show low biodiversity and, above all, inadequate environmental quality. Microorganisms such as fungi can play a key role in metal-polluted ecosystems via colonization and decontamination. The study is devoted to characterize the microfungal community in highly Cu-contaminated bare soil from derelict Fe-Cu sulphide mines and to isolate microfungal strains able to tolerate and accumulate Cu. 11 Different taxa to be isolated has been isolated during two sampling campaigns (in Autumn and in Spring). Among these, Clonostachys rosea, Trichoderma harzianum, and Aspergillus alliaceus were tested at increasing Cu(II) concentrations and showed a Cu(II)-tolerance capability ranging from 100 to 400 mg L(-1). Moreover, the strains of T. harzianum and C. rosea presented a high Cu(II)-bioaccumulation capability, 19628 and 22,222 mg kg(-1), respectively. These microfungi may be fruitfully exploited in mycoremediation protocols.

Clay mineral mixtures as alteration products in pillow basalts from the eastern flank of Juan de Fuca Ridge: a TEM-AEM study

Abstract Transmission electron microscope-analytical electron microscope analyses have been carried out on secondary minerals from pillow basalts with various degrees of alteration from the Juan de Fuca Ridge (ODP Leg 168). The electron microscopic data indicate that the alteration products consist mainly of phyllosilicate mixtures. The least altered sample shows poorly crystalline phyllosilicates occurrring as flakes with 10 Å-spaced lattice fringes. They have compositions of celadonite mixed with smectite and/or Fe oxyhydroxides and Mg-rich smectite. Proceeding towards older, more altered basalts, the alteration products consist of: (1) poorly crystalline celadonite mixtures and Mg-rich smectite; and (2) phyllosilicates with a higher degree of crystallinity, showing lattice fringes with 9.1 Å-spacing and with a talc-like composition. Changes in phyllosilicate association occur as the type of alteration changes from an oxidizing, water-dominated system (occurrence of celadonite mixtures with Fe hydroxides) to a reducing, rock-dominated system (occurrence of Fe-smectite and talc-like mixtures).

Native fungi as metal remediators: Silver myco-accumulation from metal contaminated waste-rock dumps (Libiola Mine, Italy)

ABSTRACT Metal contamination constitutes a major source of pollution globally. Many recent studies emphasized the need to develop cheap and green technologies for the remediation or reclamation of environmental matrices contaminated by heavy metals. In this context, fungi are versatile organisms that can be exploited for bioremediation activities. In our work, we tested silver (Ag) bioaccumulation capabilities of three microfungal strains (Aspergillus alliaceus Thom & Church, Trichoderma harzianum Rifai, Clonostachys rosea (Link) Schroers, Samuels, Seifert & W. Gams) isolated from a silver polluted site. The aim was to select silver tolerant native strains and test their potential silver uptake. Among the three species tested, T. harzianum was the most efficient strain to tolerate and accumulate silver, showing an uptake capability of 153 mg L−1 taken at the Ag concentration of 330 mg L−1. Our study highlights the potential use of native microfungi spontaneously growing in sulphide-rich waste rock dumps, for silver bioaccumulation and bioremediation.

Application of synchrotron radiation-based techniques (μ-XRD, μ-XRF, and μ-XANES) to study Fe-rich hardpans within waste-rock dump

Recently, several techniques based on synchrotron radiation have been applied to environmental sciences giving the possibility for non-destructive investigations with micrometer spatial resolution. In particular, a combination of synchrotron methods (μ-XRF, μ-XRD, and μ-XAS) have been undertaken to investigate the metals speciation in mine wastes and soils. With this work, after a review on the mineralogical aspects of sulphide-rich waste-rock deposits and the application of synchrotron- based techniques for their characterization, we present a combined synchrotron-based μ-XRD, μ-XRF, and μ-XANES study to determine the mineralogy and the elemental distribution of metals in partially altered sulphide-mineralization fragments deposited within an open-air waste-rock dump (Libiola mine, eastern Liguria, Italy). The selected samples are composed of heterogeneous assemblages of Fe-bearing precipitates formed as a consequence of Fe-Cu sulphide alteration processes that occur within the main waste rock dump of the mining area. The results evidenced that the authigenic iron-rich phases generally contain signifi cant amounts of hazardous elements such as Cu, Zn, Mo, As, and Se. Moreover, a signifi cant mineralogical control on the mobility of these elements have been observed; in particular, the goethite-rich assemblages show high affi nity for Cu and Zn, whereas hematite-rich assemblages selectively concentrate As, Se, Mo, Cu and Zn.

Structural studies on synthetic and natural Fe-Sb-oxides of MO2 type

Structural refinements were performed on synthetic and natural Fe-Sb-oxides of MO 2 type according to the Rietveld method. The refinement in the P4 2 / mnm space group confirms that the synthetic phase (Fe 3 + Sb 5 + )O 4 , corresponding to squawcreekite, is characterised by a rutile-type structure. In contrast to the compositional and structural data (ideally Fe 2 + Sb 5 + 2O 6 with a trirutile-type structure) implicitly accepted by the IMA Commission on New Minerals and Mineral Names, also tripuhyite seems to crystallize with a rutile-type structure in the P4 2 /mnm space group and its composition is based on an equimolar ratio between Fe and Sb.

Alteration of braunite ores from Eastern Liguria (Italy) during syntectonic veining processes mineralogy and fluid inclusions

The manganese ores of the Northern Apennine ophiolites (Val Gravegila, Eastern Liguria, Italy) occur within chert sequences, mainly as stratiform layers (0.1-1 m thick) or massive lenses (5-20 m thick). The ores originated in the Ligurian-Piedmont oceanic basin (Middle Callovian) during turbiditic resedimentation of hydrothermally Mn-enriched submarine muds. During Upper Cretaceous-Lower Cenozoic orogenic events, the primary sedimentary oxide assemblages were completely recrystallized to braunite + quartz assemblages under prehnite-pumpellyte facies conditions (T = 275 ± 25 °C; P = 2.5 ± 0.5 kbar). This tectonic event induced mobilisation of Mn and Si, and thickening of the mineralised layers. A complex network of sigmoidal quartz veins formed at this stage. The interaction between the Mn mineralisation and the circulating fluids generated centimetric to decimetric reaction rims in the wall rock, where the braunite + quartz assemblage is replaced by Mn silicates (mainly bementite, johannsenite, parsettensite and rhodonite) and carbonates (mainly Mn-bearing calcite and rhodochrosite) with a zoned distribution. Mineral zoning points to an early interaction between the Mn mineralisation and H 2 O-CO 2 fluids with high water activity. Two distinct types of fluids are present in syntectonic quartz veins, namely a low-salinity water-rich fluid, and a Mn-Ca-Na-Mg-Fe-bearing aqueous solution that in all probability represent a relict of an early fluid phase circulating during breakdown of braunite. The isochore distribution related to low-salinity fluids indicates that veining processes took place during the main tectono-metamorphic events, at peak P-T conditions.

Mineralogical and chemical variations of ochreous precipitates from acid sulphate waters (asw) at the Roşia Montană gold mine (Romania)

The mineralogical and chemical variations of ochreous precipitates forming from acid sulphate waters discharged from the lowest mine adit (“Sf. Cruci din Orlea”) of the Roşia Montană Gold Mine (Romania) were investigated by a multianalytical approach (XRPD, IR, TEM, ICP) applied to surface precipitates and associated waters. The mineralogy of the precipitates changed significantly as a consequence of the variations in the chemical parameters of the circulating solutions (mainly pH, Eh, and sulphate concentrations) which were mainly controlled by mixing with unpolluted waters of Roşia River. Ochreous precipitates are characterized by high concentrations of potentially toxic elements (PTEs; in particular Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) and consist of a mixture, in variable proportion, of jarosite and schwertmannite, which represent the stable secondary minerals along the investigated transect of Roşia River. Particular regard is given to the ability of authigenic phases to selectively scavenge selected PTEs from contaminated solutions during their genesis and minerogenetic evolution. Furthermore, laboratory kinetic batch experiments on natural heterogeneous samples of ochreous precipitates were carried out to investigate the release processes involving PTEs and to verify the type and the amount of elements that can be temporarily/permanently trapped by the solid phase from the contaminated solutions. The comparative analysis of the precipitates and waters of the Roşia Montană mining area indicated that the role of secondary minerals as “mitigating agents” can be limited because even minor pH–Eh oscillations would cause mineralogical transformations that could lead to trace elements mobilization in the environment.

Solid state miscibility in the pseudo-binary TiO2—(FeSb)O4 system at 1373 K

Abstract The tetragonal rutile-type (FeSb)O4 compound was synthesized reacting Fe2O3 and Sb2O3 in O2. Solid solubility in the pseudo-binary TiO2—(FeSb)O4 (rutile — tripuhyite) system was investigated annealing powder mixtures characterized by different TiO2/(FeSb)O4 molar ratios in an O2 flux. Complete miscibility was found in the whole compositional range at 1373 K. The crystal structures of (FeSb)O4 and selected terms of the (Ti2xFe1–xSb1–x)O4 solid solution (0 ≤ x ≤ 1) were refined from X-ray powder diffraction data using the Rietveld method. Selective broadening of the X-ray lines was observed and analyzed by means of the Gaussian quadratic plot. Line broadening is probably related to a phase transformation taking place at low temperature, as suggested by the excess molar volume of the solid solution. As a result local chemical inhomogeneity and microstrain in the direction perpendicular to the 00l lattice planes for compositions 0.2 ≤ x ≤ 0.6 are generated.

Plant Colonization on a Contaminated Serpentine Site

Abstract This study evaluated relationships between the serpentine soil from a waste-rock dump of the abandoned Libiola sulphide mine (NW Italy) and its pioneer vegetation. We identified the tolerance of various species to environmental conditions and evaluated physical or chemical factors that influenced the first plants to colonize this stressful environment. Thirteen sampling sites were identified in the rock dump from characterization of surface or near-surface oxidation zone and vegetation type. Sampling sites were analyzed for slope, pH, mineralogy, soil chemistry, floristic composition, and the percent coverage of each species. In all the plots, species richness and vegetation cover were extremely low. The flora showed an acidophilous character.