Immobilization of toxic elements in mine residues derived from mining activities in the Iberian Pyrite Belt (SW Spain): Laboratory experiments

In the mining environments of the Iberian Pyrite Belt (IPB), the oxidation of sulphide wastes generates acid drainage with high concentrations of SO₄, metals and metalloids (Acid Mine Drainage, AMD). These acid and extremely contaminated discharges are drained by the fluvial courses of the Huelva province (SW Spain) which deliver high concentrations of potentially toxic elements into the Gulf of Cádiz. In this work, the oxidation process of mine tailings in the IPB, the generation of AMD and the potential use of coal combustion fly ash as a possible alkaline treatment for neutralization of and metal removal from AMD, was studied in non-saturated column experiments. The laboratory column tests were conducted on a mine residue (71.6 wt% pyrite) with artificial rainfall or irrigation. A non-saturated column filled solely with the pyrite residue leached solutions with an acid pH (approx. 2) and high concentrations of SO₄ and metals. These leachates have the same composition as typical AMD, and the oxidation process can be compared with the natural oxidation of mine tailings in the IPB. However, the application of fly ash to the same amount of mine residue in another two non-saturated columns significantly increased the pH and decreased the SO₄ and metal concentrations in the leaching solutions. The improvement in the quality of leachates by fly ash addition in the laboratory was so effective that the leachate reached the pre-potability requirements of water for human consumption under EU regulations. The extrapolation of these experiments to the field is a promising solution for the decontamination of the fluvial courses of the IPB, and therefore, the decrease of pollutant loads discharging to the Gulf of Cádiz.     

A physically-based method for removing pits in digital elevation models

Spurious pits in digital elevation models (DEMs) are traditionally removed by filling depressions, often creating flat regions that lead to inaccurate estimation of landscape flow directions. In this study, a physical approach based on a simple landscape evolution model is proposed for DEM pit removal. This method, an alternative to traditional geometrical procedures, enforces more realistic slopes and flow directions on topography. The procedure is compared with the method most commonly used in the literature and distributed with commercial GIS software where, generally, elevations of a depression are increased up to the lowest value among neighbouring cells. Several tests are performed and parameters sensitivity is carried out in order to demonstrate the performance of the proposed model as compared to traditional methods.     

Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry

With the objective of investigating the windwind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9 III+B1 III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50° i 70°.     

Exploring the time geography of public transport networks with the gtfs2gps package

Journal of Geographical Systems - The creation of the General Transit Feed Specification (GTFS) in the mid-2000s provided a new data format for cities to organize and share digital information on...     

The use of GIS tools to support decision-making in the expansion of chain stores

This article deals with a network competitive localization problem in which a firm seeks to determine the location of a new facility, which competes with all the facilities operating in the market, both belonging to the same firm and to the competing firms. In this context, two frequently conflicting objectives are involved: maximization of the total market share captured by the firm and minimization of market share losses for its existing facilities due to being captured by the new facility (cannibalization). We formulate the location problem as a multi-objective optimization model. Some GIS tools that provide some maps representing the market share and the cannibalization effect are proposed. This allows for the visualization of the effects produced by the opening of a new facility in the market and the trade-offs between the objectives. Finally, the advantages of using these tools have been shown by means of an application to a real data case.     

Assessment of phosphogypsum impact on the salt-marshes of the Tinto river (SW Spain): role of natural attenuation processes

About 120 Mton of phosphogypsum from the fertiliser industry were stack-piled on the salt-marshes of the Tinto river (Spain). This paper investigates the capacity of salt-marshes to attenuate contamination due to downward leaching from phosphogypsum. Solids and pore-waters were characterized at different depths of the pile to reach the marsh-ground. In superficial zones, metals were highly mobile, and no reduced sulphur was found. However, pollutant concentration decreased in the pore-water in deeper oxygen-restricted zones. Metal removal occurred by precipitation of newly formed sulphides, being this process main responsible for the contamination attenuation. Pyrite-S was the main sulphide component (up to 2528 mg/kg) and occurred as framboids, leading to high degrees of pyritization (up to 97%). The sulphidization reaction is Fe-limited; however, excess of acid-volatile sulphide over other metals cause precipitation of other sulphides, mainly of Cu and As. This decrease in metal mobility significantly minimises the impact of phosphogypsums on the salt-marshes.     

Multidisciplinary approach of the hyperarid desert of Pampas de La Joya in southern Peru as a new Mars-like soil analog

The distribution of living organisms, organic matter, and chemical properties in Mars-like environments on Earth can be used as a model to guide the investigation of possible habitable environments on Mars. This work aims to demonstrate that the place known informally as the “Mar de Cuarzo” (Sea of Quartz) in the Pampas de La Joya desert southern Peru (between 16°S and 17°S latitude), contains soils with characteristics similar to those found on the Martian surface. Using a multidisciplinary approach, we studied the environmental data, geology, organic matter content, oxidant activity, and microbiology of this area. Our data show that (1) Mar de Cuarzo is a hyper arid area with a lower concentration of organic matter than those found in the Mars-like soils from Yungay area (Atacama Desert in Chile), while at the same time having, comparable extreme environmental conditions, and very low levels of microorganisms. (2) The detrital components of the soils come essentially from the Andean volcanic chain and local outcrops of Precambrian gneisses and Cretaceous granitic batholiths. (3) The presence of microclimates, geomorphological features, and the high influence of the “El Niño Southern Oscillation (ENSO)” allowed the formation of exotic and heterogeneous chemical deposits in these soils, including iron oxides, sulfates, and other evaporites. (4) Thermal volatilization in these soils (using methods similar to the Viking and Phoenix instruments) shows high oxidant activity. (5) Labeled release experiment (similar to the Viking instrument) shows high degradation of nutrients added in these soils.Altogether, the Mar de Cuarzo area in the Pampas de La Joya is an interesting place for astrobiological studies as a new analog to Mars, and for comparative analyses with other hyperarid analogs as Yungay.     

Basis for a streamflow forecasting system to Rincón del Bonete and Salto Grande (Uruguay)

This paper presents the basis for the design of streamflow prediction systems for the hydroelectric dams of Rincón del Bonete (Uruguay) and Salto Grande (Uruguay–Argentina). The prediction is made, independently, for each reservoir and each month of the year with two methodologies: data-driven statistical models and hybrid downscaling that includes atmospheric predictors. We determine a set of potential predictors and then fit linear models coupled with variable selection techniques, under the hypothesis of perfectly known predictors. The predictive skill of the schemes outperforms the climatological forecast throughout the year in both reservoirs (except August in Rincón del Bonete). This remains the case even when the forecast lead does not allow for the use of preceding flows as predictors. While in Rincón del Bonete it is not possible to distinguish a period of high predictability, in Salto Grande, there is a robust signal in March–May and October–December.     

On the motion of three rigid bodies: Central configurations

In the present paper, the motion of three rigid bodies is considered. With a set of new variables, and the 10 first integrals of the motion, the problem is reduced to a system of order 25 and one quadrature. The plane motions are characterized, and finally, an equation for the existence of central configurations (in particular, Lagrangian and Eulerian solutions) has been found. Besides, the case of three axisymmetric ellipsoids is studied.