Effect of phosphorus on the attenuation of lead and chromium

This study analyses the adsorption of Pb(II) and Cr(III) in soils. These metals are commonly found together in nature in urban wastes or industrial spillages, and the theoretical approach of the work was to evaluate the response of the soil to continuous Cr and Pb spillages to soil in terms of several physicochemical parameters. The influence of an anthropogenic input of phosphorus was evaluated. Continuous flow experiments were run in duplicates in acrylic columns (25 cm × 3.2 cm). The influent Cr(III) and Pb(II) solutions of 10 mg l−1 and 25 mg l−1 at pH 5 were pumped upward through the bottom of the columns to ensure saturation flow conditions. Also, successive experiments were run with the above concentrations of Cr(III) and Pb(II) and NaH2PO4, keeping metal to phosphorus ratio of 1:0, 1:0.1 and 1:1. Modelling parameters included Freundlich and Langmuir equations, together with the Two-site adsorption model using CXTFIT code. Results obtained allowed concluding that Pb(II) adsorption presents a certain degree of irreversibility and the continued spillages over soil increment the fraction which is not easily desorbed. Cr(III) desorption was almost complete, evidencing its high mobility in nature. The presence of an anthropogenic input of phosphorus leads to a marked increase of both Pb(II) and Cr(III) adsorption in soils. Z-potential measurements allow to discard the electrostatic attraction of Cr(III) and Pb(II) with the surface charged soil as the dominant process of metal sorption. Instead, CheaqsPro simulation allows to identify PbH2PO4 +, PbHPO4 (aq) and CrHPO4 + as the dominant species which regulate Cr(III) and Pb(II) transport in soils.Fundação para a Ciência e a Tecnologi

Comparative analysis of 14C and tgatechniques for the quantification of the biomass content of end-of-life tires

Thermogravimetric analysis (TGA) and 14Ctechniques were compared for the determination of the biomass content of end-of-life tires (ELTs). Samples of different types (of ELTs) were prepared, and the biomass fraction of each sample was measured using the two methods (TGA and 14C). Six reference samples were also prepared with known quantities of natural rubber and stearic acid in order to establish the calibration curve necessary for the thermogravimetric analysis and to verify the accuracy of the results of the 14C analysis. The conclusions were that the 14C technique is the more valid, reliable, and precise method for determining the biomass content of end-of-life tires, since the results of the 14C tests of the reference samples coincided perfectly with the actual natural rubber and stearic acid content. On the other hand, the results of the thermogravimetric method differed considerably from the known natural rubber content of the reference samples as well as from the results of the 14C technique. This method is therefore not appropriate for use in determining the biomass content of end-of-life tires.Peer Reviewe

Hunting Blinds in the Southern End of the Deseado Massif: Collective Hunting Strategies During the Late Holocene

The Southern End of the Deseado Massif (SDM, Patagonia, Argentina) is part of a morphostructural region with seasonal shallow lakes and streams highly dependent on rainfall. The area is rich in rock shelters and both primary and secondary sources of high-quality siliceous rocks. To the South there are basaltic plateaus and open plains where no such sources have been identified. Although a relatively big space was explored, rock structures forming groups were located in only a small part of it. In this paper we seek to analyze the reasons for their location and the way in which they were used. In order to do this, we present information related to their frequency, characteristics, and the archaeological context recovered. In addition, in order to understand the way in which they were used, the visibility of nearby environments was analyzed with Geographical Information Systems, using a DEM (Digital Elevation Model) developed by the Argentine Instituto Geográfico Nacional(IGN). Results obtained indicate that the rock structures were built in places higher than the surroundings, using immediately available rocks. According to the visibility analysis, they worked in an articulated way as part of collective hunting strategies. The characteristics and composition of the artifact assemblages recovered indicate that different activities took place at these sites during the Late Holocene. The identification of the hunting blinds in a specific area within the SDM and their absence in the remaining study area to the North and South suggest that this area was selected for planned collective hunting.Fil: Franco, Nora Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Departamento de Ciencias Antropológicas; ArgentinaFil: Vetrisano, Lucas Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; ArgentinaFil: Gilio, Brenda Ludmila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Cirigliano, Natalia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; ArgentinaFil: Bianchi, Pablo Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentin