Riccardo Biddau

Rare earth elements in waters from the albitite-bearing granodiorites of Central Sardinia, Italy

With the aim of contributing to the knowledge of the geochemical behaviour and mobility of the rare earth element (REE) in the natural water systems, the ground and surface waters of the Ottana–Orani area (Central Sardinia, Italy) were sampled. The study area consists of albititic bodies included in Hercynian granodiorites. The waters have pH in the range of 6.0–8.6, total dissolved solid (TDS) of between 0.1 and 0.6 g/l, and major cation composition dominated by Ca and Na, whereas predominant anions are Cl and/or HCO3. The pH and the major-element composition of the waters are the factors affecting the concentration of REE in solution. The concentrations of ∑REE+Y in the samples filtered at 0.4 μm vary between 140 and 1600 ng/l, with La of between 14 and 314 ng/l, and Yb of between <6 and 12 ng/l. A negative Ce anomaly, especially marked at high pH, is observed in the groundwaters. The surface waters show lower REE concentrations, which are independent of pH, and negligible Ce anomaly. Speciation calculations, carried out with the EQ3NR computer program, showed that the complexes with the CO32− ligand are the dominant REE species at pH in the range of 6.7–8.6. The REE3+ ions dominate the speciation at pH <6.7 and only in the light REE (LREE). The relative concentrations of REE in water roughly reflect those in the aquifer host rocks. However, when concentrations of REE in water are normalised relative to the parent rocks, a preferential fractionation of heavy REE (HREE) into the water phase can be observed, suggesting the greater mobility and stability of HREE in aqueous solution.

Antimony in the soil-water-plant system at the Su Suergiu abandoned mine (Sardinia, Italy): strategies to mitigate contamination.

This study was aimed to implement the understanding of the Sb behavior in near-surface environments, as a contribution to address appropriate mitigation actions at contaminated sites. For this purpose, geochemical data of soil (8 sites), water (29 sites), and plant (12 sites) samples were collected. The study area is located at Su Suergiu and surroundings in Sardinia (Italy), an abandoned mine area heavily contaminated with Sb, with relevant impact on water bodies that supply water for agriculture and domestic uses. Antimony in the soil horizons ranged from 19 to 4400 mg kg(-1), with highest concentrations in soils located close to the mining-related wastes, and concentrations in the topsoil much higher than in the bedrock. The Sb readily available fraction was about 2% of the total Sb in the soil. Antimony in the pore water ranged from 23 to 1700 μg L(-1), with highest values in the Sb-rich soils. The waters showed neutral to slightly alkaline pH, redox potential values indicating oxidizing conditions, electrical conductivity in the range of 0.2 to 3.7 mS cm(-1), and dissolved organic carbon ≤2 mg L(-1). The waters collected upstream of the mine have Ca-bicarbonate dominant composition, and median concentration of Sb(tot) of 1.7 μg L(-1) (that is total antimony determined in waters filtered through 0.45 μm), a value relatively high as compared with the background value (≤0.5 μg L(-1) Sb) estimated for Sardinian waters, but below the limits established by the European Union and the World Health Organization for drinking water (5 μg L(-1) Sb and 20 μg L(-1) Sb, respectively). The waters flowing in the mine area are characterized by Ca-sulfate dominant composition, and median concentrations of 7000 μg L(-1) Sb(tot). Extreme concentrations, up to 30,000 μg L(-1) Sb(tot), were observed in waters flowing out of the slag materials derived from the processing of Sb-ore. The Sb(III) was in the range of 0.8 to 760 μg L(-1) and represented up to 6% of Sb(tot). In the waters collected downstream of the mine, median Sb(tot) concentrations decreased as distance from the mine area increases: 1300 μg L(-1) Sb(tot) in the stream Rio Ciurixeda at 3 km distance, and 25 μg L(-1) Sb(tot) in the main River Flumendosa 15 km further downstream. Attenuation of Sb contamination was mainly due to dilution. Results of modeling, carried out by both EQ3 and Visual MINTEQ computer programs, suggest that sorption of dissolved Sb onto solid phases, and/or precipitation of Sb-bearing minerals, likely give a minor contribution to attenuation of Sb contamination. The slightly alkaline pH and oxidizing conditions might favor the persistence of inorganic Sb(V)-bearing species at long distance in the studied waters. Concentrations of Sb in the plants Pistacia lentiscus and Asparagus ranged from 0.1 to 22 mg kg(-1), with maximum values in plants growing very close to the mining-related wastes. The P. lentiscus grows well on the soils highly contaminated with Sb at Su Suergiu and might be used for revegetation of the Sb-rich heaps, thus contributing to reduce the dispersion of contaminated materials. Major effects of contamination were observed on the water bodies located downstream of the Su Suergiu abandoned mine. The maximum load (16.6 kg Sb per day) to the Flumendosa, the main aquatic recipient, was observed after heavy rain events. Therefore, priorities of mitigation actions should be focused on minimizing the contact of rain and runoff waters on the heaps of mining wastes.

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

GRIDA3—a shared resources manager for environmental data analysis and applications

GRIDA3 (Shared Resources Manager for Environmental Data Analysis and Applications) is a multidisciplinary project designed to deliver an integrated system to forge solutions to some environmental challenges such as the constant increase of polluted sites, the sustainability of natural resources usage and the forecast of extreme meteorological events. The GRIDA3 portal is mainly based on Web 2.0 technologies and EnginFrame framework. The portal, now at an advanced stage of development, provides end-users with intuitive Web-interfaces and tools that simplify job submission to the underneath computing resources. The framework manages the user authentication and authorization, then controls the action and job execution into the grid computing environment, collects the results and transforms them into an useful format on the client side. The GRIDA3 Portal framework will provide a problem-solving platform allowing, through appropriate access policies, the integration and the sharing of skills, resources and tools located at multiple sites across federated domains.

AQUAGRID: an extensible platform for collaborative problem solving in groundwater protection

AQUAGRID is the subsurface hydrology computational service of the Sardinian GRIDA3 infrastructure, designed to deliver complex environmental applications via a user-friendly Web portal. The service aims to provide to water professionals integrated modeling tools to solve water resources management problems and aid decision making for contaminated soil and groundwater. In this paper, the AQUAGRID application concept and enabling technologies are illustrated. At the heart of the service are the computational models to simulate complex and large groundwater flow and contaminant transport problems and geochemical speciation. AQUAGRID is built on top of compute-Grid technologies by means of the EnginFrame Grid framework. Distributed data management is provided by the Storage Resource Broker data-Grid middleware. The resulting environment allows end-users to perform groundwater simulations and to visualize and interact with their results, using graphs, 3D images and annotated maps. The problem solving capability of the platform is demonstrated using the results of two case studies deployed.

Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining

Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1-20 μg L(-1) working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1-100μgL(-1) working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100-10,000 μg L(-1) working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO3. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO3, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L(-1)), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO3 appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).

Source and fate of nitrate in contaminated groundwater systems: Assessing spatial and temporal variations by hydrogeochemistry and multiple stable isotope tools

Intensive farming usually imply a degradation of groundwater resources worldwide. In particular, nitrate concentrations exceeding the 50 mg L-1 limit established for drinking water pose the human health at risk. Therefore, assessing the impact of farming on groundwater, in terms of space and time, is of fundamental importance for policy decision makers and land managers. This study was aimed at assessing the nitrate source and fate in groundwater by combining hydrogeochemical and isotopic tools. The study area is located in the coastal plain of Arborea (Italy), a nitrate vulnerable zone (NVZ) due to intensive farming and animal husbandry (28,000 bovine livestock units). This area represents Mediterranean environments where groundwater resources are of relevant importance. In order to assess the present level of groundwater contamination and evaluate temporal variations, 6 hydrogeochemical surveys were carried out bimonthly at 13 sampling sites located in an area of 6 km2. Additional samples were collected in specific surveys (82 water samples in total). The physical-chemical parameters, nitrogen species concentrations, major and minor components were determined, together with the boron, hydrogen, oxygen, nitrogen, and sulfur isotopic delta values. Results showed that groundwater samples were of meteoric origin, as indicated by the δ2H and δ18OH2O values. The groundwater showed near-neutral pH (6.8-7.9) and different values of redox potential (0.2 ÷ 0.5 V), dissolved oxygen (2 ÷ 6 mg L-1), electrical conductivity (0.8 ÷ 2.1 mS cm-1) and chemical composition (sodium-chloride ÷ calcium-bicarbonate). Nitrate was not homogeneously distributed in groundwater, being observed a large range of concentrations, from <1 up to 162 mg L-1. The above differences reflected the variability of groundwater circulation at small scale, which in turn controlled the interaction of water with different sediments (sands and/or clays). The shallow wells (about 5 m depth), screened in groundwater interacting mainly with sands, showed marked variations under the monitoring period, with nitrate peaks reflecting high leaching of nitrate in correspondence of fertilization and irrigation periods. The deeper wells (15-37 m depth) showed high to moderate nitrate when screened in sandy aquifer, whereas they had very low nitrate and relatively high ammonium (up to 1.8 mg L-1) when clay layers were intercepted. Trends of δ15N and δ18ONO3 values in the nitrate of shallow groundwater were related to the nitrate concentration observed over the monitored period. This dual isotope systematic showed a likely source of nitrate in groundwater from either manure or sewage. The δ11B signature coupled to δ15N values clearly identified the manure as the predominant source of nitrate in the shallow and deep groundwater at Arborea. Relative enrichments in heavy nitrogen coupled to high concentrations of nitrate in groundwater were mainly attributed to volatilization processes occurring during the storage of animal wastes prior to application on the soil. Mixing of groundwater with seawater was not recognized, whereas mixing between shallow and deep groundwater may have occurred locally. Natural attenuation of nitrate contamination was observed in the deep groundwater interacting with lagoon clays rich in organic matter. Heterotrophic denitrification processes were highlighted by relatively high δ15N, δ18ONO3, δ34S and δ18OSO4 values in association with low SO42-/Cl- and high HCO3-/SO42- molar ratios observed in the groundwater with low concentration of nitrate. Results of this study showed that site-specific investigations are required for designing the best practices aimed at preserving groundwater resources under Mediterranean conditions. The spreading of animal waste on soils affects groundwater systems and likely extends over long time, strongly depending on the time lag of nutrient transport from source areas to receptor wells. Therefore, adequate monitoring of groundwater quality is required in areas of intensive farming.

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.

Groundwater Contamination: Environmental Issues and Case Studies in Sardinia (Italy)

In this study, the arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) contamination has been evaluated in the groundwater of Sardinia (Italy). Contamination by such chemical species is among the most relevant risks for many populations, thus giving general interest to the case studies presented in this chapter. A brief introduction about the European legislative framework is given, followed by a description of the analytical methods used and a discussion of the results. Two areas were selected as case studies: the Osilo area, devoted to geogenic degradation, and the Iglesiente–Fluminese mining district mainly affected by anthropogenic contamination. The geochemical controls on the natural baselines of As, Cd, Pb, and Zn are generally related to natural sources, mostly derived from water–rock interaction processes in areas of known mineral occurrences. In fact, median concentrations of the investigated elements in the mineralized areas are much higher than those of the corresponding median regional values and sometimes exceed the Italian limits for drinking water. In the Iglesiente–Fluminese mining district very high concentrations of Cd, Pb, and Zn were measured in groundwater that circulates in areas affected by past mining activities.