Stefania Da Pelo

Benthic foraminifera as bio-indicators of trace element pollution in the heavily contaminated Santa Gilla lagoon (Cagliari, Italy)

In order to assess the response of benthic foraminifera to trace element pollution, a study of benthic foraminiferal assemblages was carried out into sediment samples collected from the Santa Gilla lagoon (Sardinia, Italy). The lagoon has been contaminated by industrial waste, mainly trace elements, as well as by agricultural and domestic effluent. The analysis of surficial sediment shows enrichment in trace elements, including Cr, Cu, Hg, Ni, Pb and Zn. Biotic and abiotic data, analyzed with multivariate techniques of statistical analysis, reveal a distinct separation of both the highly polluted and less polluted sampling sites. The innermost part of the lagoon, comprising the industrial complex at Macchiareddu, is exposed to a high load of trace elements which are probably enhanced by their accumulation in the finer sediment fraction. This area reveals lower diversity and higher percentages of abnormalities when compared to the outermost part of the lagoon.

The Palaeocene–Middle Eocene deposits of Sardinia (Italy) and their palaeoclimatic significance

Abstract The Palaeocene of southern Sardinia includes a continental ferruginous sedimentation, with a high content of Al and Fe, indicative of a subhumid tropical climate. The subsequent microcodium carbonated detrital microcodium levels, containing an abundant quartzose fraction, rather suggest semiarid conditions. In SW Sardinia, the marine deposits, referred to Late Thanetian–Lower Ypresian (=Ilerdian) times, are limestones including larger foraminifers and contain significant amounts of quartz. A lower content of detrital kaolinite points a sediment source from the surrounding areas with a semiarid climate. The occurrence, at the top of this unit, of small trochospiral rotaliids and larger amount of detrital kaolinite suggests a transition to a rainy tropical climate in the adjacent areas. These limestones pass gradually to carbonate sediments characterized by large amounts of detrital kaolinite and intercalated coal layers, with pollen of tropical palms, attributed to the Late Ypresian (=Cuisian)–Early Lutetian and referred to a humid-subhumid tropical climate.

Legacy of Cyanide and ARD at a Low-Scale Gold Mine (Furtei, Italy)

A gold deposit was exploited from 1997 to 2003 at Furtei, Sardinia (Italy). Gold and silver were recovered from oxidized ores by cyanidation; copper concentrates were separated from the sulfide ores by flotation. Following unplanned closure, sulfide-rich materials derived from mining and processing residues were left on site. During operation, cyanide solutions were disposed of in a tailings impoundment. The cyanide underwent natural degradation so that by 2011, cyanide concentrations in the tailings impoundment and seeps were below the Italian limit for industrial effluents. However, during the rainy season, sulfide-rich materials in the waste rock dumps produce extreme acidic solutions and concentrations of some dissolved contaminants, especially ammonium, aluminum, arsenic, copper, iron and manganese, still exceed discharge criteria in the tailings impoundment and seeps. Highly contaminated drainage flows downstream from the mine and poses a hazard to agricultural areas.ZusammenfassungBei Furtei auf Sardinien (Italien) wurde zwischen 1997 und 2003 eine Goldlagerstätte abgebaut. Gold und Silber wurden durch Cyanidlaugung der oxidierten Erze gewonnen; Kupferkonzentrate wurden durch Flotation aus den Sulfiderzen separiert. Nach der unplanmäßigen Schließung verblieben sulfidreiche Bergematerialien sowie Aufbereitungsrückstände am Standort zurück. Während des Betriebes wurden die Cyanidlösungen in einen Schlammteich verbracht. Cyanid unterlag dem natürlichen Abbau, sodass in 2011 die Cyanidkonzentrationenen im Schlammteich sowie in den Sickerwässern den italienischen Grenzwert für Industrieabwässer unterschritten. Jedoch bilden die sulfidreichen Bergehalden während der Regenzeit extreme Sauerwässer, sodass die Konzentrationen einiger Wasserinhaltsstoffe, speziell die von Ammonium, Aluminium, Kupfer, Eisen und Mangan, im Schlammteich und in den Sickerwässern noch immer über den Einleitwerten liegen. Der hoch kontaminierte Abstrom des Bergwerks stellt eine Gefahr für landwirtschaftlich genutzte Flächen dar.ResumenUn depósito de oro fue explotado desde 1997 hasta 2003 en Furtei, Cerdeña (Italia). Oro y plata fueron recuperados de minerales oxidados por cianuración; los concentrados de cobre fueron separados por flotación. Tras el cierre no planificado, los materiales ricos en sulfuros derivados de los residuos de las operaciones mineras y de procesamiento, fueron dejados en el sitio. Durante la operación, las soluciones cianuradas fueron dispuestas en embalses de relaves. El cianuro fue sometido a degradación natural de modo que hacia 2011, las concentraciones de cianuro en los embalses de relaves y en los filtrados, fueron menores que los limites italianos para efluentes industriales. Sin embargo, durante la estación lluviosa, los minerales ricos en sulfuros en las escombreras de mineral estéril, producen soluciones extremadamente ácidas y con concentraciones especialmente de amonio, aluminio, arsénico, cobre, hierro y manganeso que exceden los criterios de descargo en los embalses de relaves y en las filtraciones. Ese drenaje altamente contaminado flujo corriente abajo desde la mina y representa un peligro para las áreas agrícolas.抽象意大利撒丁岛Furtei金矿开采时间为1997-2003年。该金矿采用氰化物氧化含金矿物的方法实现金、银提取,通过浮选法从硫化物中提取铜。当金矿闭坑时,采矿和选矿过程中产生的富含硫化物废矿石遗留于采场,残留氰化物溶液仍被圈闭于尾矿坝。至2011年,氰化物经过自然降解在尾矿坝渗出液中的浓度已经降至意大利工业废水排放标准以下。但是,在雨季,富含硫化物废矿石仍能产生强酸废水,尾矿坝渗出液溶解性污染物如铵、铝、砷、铜、铁和锰等仍然超标。从矿区向下游排放的高度污染废水对下游农业构成严重威胁。

Enargite by XPS

X-ray photoelectron spectroscopy was used for characterizing the enargite surface. Freshly cleaved samples were analyzed at liquid nitrogen temperature. Enargite is a copper arsenic sulfide of formula Cu3AsS4; it is used as a minor ore of copper. Enargite is a potential source of arsenic and may create environmental problems through the release of toxic elements upon oxidation.

Nitrate occurrence in groundwater hosted in hard-rock aquifers: estimating background values at a regional scale

This study was aimed at assessing the occurrence of nitrate in poorly anthropized areas at a regional scale, as an attempt to estimate the nitrate background in areas far from intense agriculture, farming, industrial activities and urban areas. Nitrate concentrations, together with physical-chemical parameters and major anions and cations, were determined in 49 spring waters flowing out of granitic and metamorphic rocks in Sardinia (Italy). Nitrate in the spring waters was in the range of

The reaction of enargite with alkaline NaClO solutions: an AFM and flow-through study

The reaction of enargite, Cu 3 AsS 4 , with alkaline NaClO solutions is of interest for hydrometallurgical applications. In this study, the surface of cleavage fragments was observed ex situ by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) after sequential interaction (up to 240 min) with a 0.27 M NaClO/0.03 M NaOH solution (pH 12.2) at room temperature (295 ± 2 K). Likewise, the evolution of the reaction of enargite powder (25 < size fraction < 53 μm) interacting with the same solution was investigated in a flow-through experiment. AFM images show the progressive formation of protrusions, preferentially along surface features such as steps and cracks. XPS analyses of the surface after 240 min reaction indicate the establishment of Cu(II)-O, As(III)-O and As(V)-O bonds. SEM images and EDS analyses show that a newly formed, highly porous phase is composed of a copper oxide, identified as tenorite (CuO) by X-ray diffraction. In the flow-through experiment, arsenic and sulphur are released in nearly stoichiometric proportions (As/S molar ratio = 0.27 ± 0.01). Release of As and S decreases slightly with time, whereas Cu depletion in the output solution occurs, because of the formation of CuO. Based on sulphur and arsenic release, the steady-state dissolution rate (normalized to initial surface area) is estimated to be on the order of 10 -8 mol m -2 s -1 .

Electrical Resistivity Tomography for the identification of the alluvium-Triassic boundary in Medenine Region (SE Tunisia)

The Jeffara Plain, in Medenine region (SE Tunisia), suffers of dry climatic conditions. Lower Triassic sandstones widely outcrop within the Plain and they host a strategic aquifer exploited for drinking and irrigation purposes. An insufficient natural recharge and an increasing water demand have led to an overexploitation of such aquifer. Water harvesting techniques and particularly Managed Aquifer Recharge (MAR) systems can be useful tools for restoring groundwater resources. To better design the MAR system and to characterize the local geological setting, an Electrical Resistivity Tomography survey was conducted in six selected sites in the Jeffara Plain, within the frame of EU WADIS-MAR project.

Preliminary characterization of slope stability in a small basin in the South-West of Sardinia (Italy)

The assessment of slope instability in small drainage basins is relevant because their impacts affecting population and infrastructure are usually very fast and sometimes destructive. This study presents the methodological approach to assess the stability of a small granitic river basin located in the South-West of Sardinia (Italy). In the drainage area two different kinds of slope deposits, originated at different times, were analysed. In order to determine the origin and evolution of the different deposits, the bodies of the moved masses and the head scarps were respectively characterized through profiles, grain size analysis and geomechanic classification. The profiles were surveyed using Jacob staff or Abney level. The survey tape method was applied to determine the grain size distribution (GSD) in cross sections at each slope deposit. The GSD was analysed using standard statistics. The geomechanical characterization of the cliffs in the headscarps above the deposits were made using Bieniawski (1979) and Romana (1985) methods. The former deposits have a regular longitudinal profile. The plan form can be convex or slightly concave. They are formed by cobbles and boulders and they are matrix free. They were classified as debris slope (DS).The cliff above the DS was evaluated vulnerable to plane failure and completely unstable. The new deposit hillslope gradient and transversal sections are irregular. It is formed by cobbles, boulders and pebbles, it has matrix of granules sand and silt. It is a complex mass movement between rock fall and rock avalanche (RF-RA).The cliff above the RF-RA is vulnerable to plane failure and toppling and is partially stable.

Hydrogeological and hydrogeochemical modelling in the freatic aquifer of the Cixerri plain (Sardinia, Italy)

A hydrogeological modelling, supported by geological and hydrogeochemical data was performed. The proposed methodology was applied to the strategic aquifer of the Cixerri area (SW Sardinia, Italy). The knowledge-base system will provide a suitable and effective tool for understanding and monitoring pollutants transfer dynamics into groundwater to better manage water resources and mitigate desertification processes. In particular, this study aims to evaluate the potential risk of nitrate pollution in aquifers from agricultural practices by combining intrinsic aquifer vulnerability to contamination.

3D hydrogeological modelling supported by geochemical mapping as an innovative approach for management of aquifers applied to the Nurra district (Sardinia, Italy)

A hydrogeological 3D modelling, supported by hydrogeochemical mapping and integrated interpretation of available data, was performed. The proposed methodology was applied to the strategic aquifer of the Nurra district (NW Sardinia, Italy). The finding of this work highlighted that structural history of the Nurra district exerts a relevant control on the hydrogeology and hydrochemistry of groundwater. The local connection of Triassic and Jurassic aquifers was proposed. The knowledge-base system will provide a suitable and effective tool for understanding and monitoring pollutants transfer dynamics into groundwater to better manage water resources and mitigate desertification processes.