Dispersion of antimony from oxidizing ore deposits

The solubilities of brandholzite, [Mg(H2O)6][Sb(OH)6]2, and bottinoite, [Ni(H2O)6][Sb(OH)6]2, at 25 °C in water have been measured. Solubilities are 1.95(4) × 10-3 and 3.42(11) × 10-4 mol dm-3, respectively. The incongruent dissolution of romeite, Ca2Sb2O7, and bindheimite, Pb2Sb2O7, at 25 °C in 0.100 mol dm-3 aqueous HNO3 was also investigated. Equilibrium dissolved Sb concentrations were 3.3 ± 1.0 × 10-7 and 7.7 ± 2.1 × 10-8 mol dm-3, respectively. These values have been used to re-evaluate the geochemical mobility of Sb in the supergene environment. It is concluded that the element is geochemically immobile in solution and in soils. This was in part validated by an orientation soil geochemical survey over the Bayley Park prospect near Armidale, New South Wales, Australia. Anomalous soil Sb levels are confined to within 100 m of known stibnite mineralizatio

Una puesta fósil de tortuga terrestre en el Pleistoceno

A fossil clutch from the Pleistocene of Pujol d'es Fum (Formentera, Balearic Islands) is studied. From its structure, egg morphology and eggshell microstructure, belonging to the ootaxon Testudoolithus, it is attributed to a tortoise. According to the present-day testudinids correlation between egg width and caparace length, this tortoise caparace is estimated to be less than 78.9 cm long. Stratigraphical data and palaeoecological evidence indicate a retrodunar environment of Upper Pleistocene age. The tortoise could have been related to another giant form previously found in Eivissa. Key words: Tortoise fossil eggs, semigiant testudinid, Upper Pleistocene, Balearic Islands, Spain.Se presenta el estudio de un nido fósil, con presencia de huevos, hallado en el mes de Julio de 1996 en el acantilado de Es Pujol d'es Fum de la isla de Formentera (Islas Pitiusas, Archipiélago Balear). Por la estructura del nido, la morfología de los huevos y la microestructura de la cáscara, se le atribuye a una tortuga de tierra, ootaxa Testudoolithus. Por la correlación entre la anchura de los huevos con la longitud del espaldar en los testudínidos, se estima perteneciente a una tortuga terrestre semigigante, de 78,9 cm como máximo. Los datos estratigráficos, los gasterópodos fósiles y los indicios paleoecológicos, sugieren que se trataba de un ambiente retrodunar terrestre del Pleistoceno superior. Atendiendo a los datos actuales parece ser la misma forma de quelonio hallada en el Pleistoceno de Ibiza en 1980. Palabras clave: Huevos fósiles de tortuga, testudínido semigigante, Pleistoceno superior, Islas Baleares, España

The role of titanium dioxide on the behaviour and fate of plastics in the aquatic environment.

Although titanium dioxide (TiO2) is the most widely used pigment in plastics, there is limited quantitative information available for consumer goods and environmental samples. Moreover, and despite its photocatalytic activity, the potential impacts of TiO2 on the behaviour and fate of environmental plastics has received little attention. This paper compiles measurements of Ti in plastic samples from aquatic environments and in consumer goods that are known to make important contributions to environmental pollution. These data, along with a critical evaluation of experimental studies using TiO2-pigmented plastics, are used to formulate an understanding of how the pigment modifies the properties and persistence of environmental plastics. Titanium is heterogeneously distributed amongst different categories and sources of plastic, with concentrations ranging from <1 mg kg-1 in transparent-translucent materials to over 50,000 mg kg-1 in brightly coloured samples. Concentrations towards the higher end are sufficient to change positively buoyant polyolefins into negatively buoyant plastics, suggesting that environmental fractionation based on Ti content might occur. Accelerated leaching of TiO2 from aged plastic has been demonstrated empirically, and while mobilised particles are reported within a size range greater than biotically-active titania nanoparticles, modeling studies suggest that the latter could be derived from TiO2 pigments in the environment. Although rutile appears to be the most important polymorph of TiO2 in non-fibrous plastics, the degree and type of engineered surface modification in consumer and environmental plastics are generally unknown. Surface modification is likely to have a significant impact on the photo-oxidative degradation of plastics and the mobilization of fine (and, possibly, nano-sized) TiO2 particles and requires further research