The latest freshwater giants: a new Peltocephalus (Pleurodira: Podocnemididae) turtle from the Late Pleistocene of the Brazilian Amazon.

Overkill of large mammals is recognized as a key driver of Pleistocene megafaunal extinctions in the Americas and Australia. While this phenomenon primarily affected mega-mammals, its impact on large Quaternary reptiles has been debated. Freshwater turtles, due to the scarcity of giant forms in the Quaternary record, have been largely neglected in such discussions. Here we present a new giant podocnemidid turtle, Peltocephalus maturin sp. nov., from the Late Pleistocene Rio Madeira Formation in the Brazilian Amazon, that challenges this assumption. Morphological and phylogenetic analyses of the holotype, a massive partial lower jaw, reveal close affinities to extant Amazonian species and suggest an omnivorous diet. Body size regressions indicate Pe. maturin possibly reached about 180 cm in carapace length and is among the largest freshwater turtles ever found. This finding presents the latest known occurrence of giant freshwater turtles, hinting at coexistence with early human inhabitants in the Amazon.

A low-cost portable system for elemental mapping by XRF aiming in situ analyses.

This work presents the development of a portable system that allows 2D elemental mapping of large areas (maximum of 35.0 × 35.0 cm2) by XRF. A measuring head, composed of an x-ray source and a detector, is mounted on a 3-axis stage with movement reproducibility better that 0.03 mm. The final elemental map resolution of 1.4 mm was experimentally determined in the best condition of collimation, and the same experiments indicate that the resolution is fully dominated by the x-ray beam spot size. The main goal of this new setup is to perform analyses of historical, archaeological and geological objects. Because it's lightweight, our setup has the potential to be of great utility for in situ analyses, given the great difficulty and high costs transporting the artifacts from the museum to a laboratory. The importance of this instrumentation is related to the need to identify the distribution of the chemical elements in large surface areas of cultural heritage objects by a nondestructive method.

Assessment of metal sorption mechanisms by aquatic macrophytes using PIXE analysis.

In this work, a study of the metal sorption mechanism by dead biomass has been performed. All batch metal biosorption experiments were performed using the aquatic macrophyte Egeria densa as biosorbent. Divalent cadmium and zinc solutions were used to assess the sorption mechanisms involved. Using a suitable equilibrium time of 2h and a mixture of 300 mg biosorbent and 50 mL metal solution at pH 5, monocomponent sorption experiments were performed. In order to determine the residual amounts of metals in the aqueous solutions and the concentrations of removed metals in the dry biomass, Particle Induced X-ray Emission (PIXE) measurements in thin and thick target samples were carried out. Based on the strong experimental evidence from the mass balance among the major elements participating in the sorption processes, an ion exchange process was identified as the mechanism responsible for metal removal by the dry biomass.

Thin and thick target PIXE analyses to assess the mechanism of Cu2+ removal by Egeria densa.

In this work the PIXE technique was used to study the mechanism of metal sorption by dead biomass. Several batch copper-sorption experiments were performed by using Egeria densa biomass. PIXE measurements were performed in solid and liquid samples. Element concentrations in biosorbent samples were determined using the Clara software. Based on the mass balance among the major elements in the liquid and solid phases before and after the Cu-removal experiments, an ion exchange process is suggested as the main mechanism.

Evaluation of trace element levels in muscles, liver and gonad of fish species from São Francisco River of the Paraná Brazilian state by using SR-TXRF technique.

This study is focused on the analysis of an accumulation of inorganic elements in muscles, liver and gonad of seven fish species from São Francisco River located in the Paraná state of Brazil. Concentrations of the elements were determined using the SR-TXRF technique. In the muscles of fish species, negative length dependent relationships were observed for chromium and zinc ion absorption. The obtained results showed that accumulated Cr ions values are above the limits defined in the Brazilian legislative norm on food.

Inhibition effect on the Allium cepa L. root growth when using hexavalent chromium-doped river waters.

The effect of Cr(6+) on Allium cepa root length was studied using both clean and polluted river waters. Seven series of Cr(6+)-doped polluted and non-polluted river waters were used to grow onions. Chromium concentration (Cr(6+)) of 4.2 mg L(-1)(EC(50) value), doped in clean river water caused a 50% reduction of root length, while in organically polluted samples similar root growth inhibition occurred at 12.0 mg Cr(6+) L(-1). The results suggested that there was a dislocation to higher values in toxic chromium concentration in polluted river water due to the eutrophization level of river water.