Lake Três Irmãs (LTI), the largest upland lake in the Brazilian Amazonia, located in Serra dos Caraj as, was characterized using multi-elemental and isotope geochemistry (d 13 C and d 15 N) to understand the significance of organic and inorganic sources, weathering and sedimentary processes on the distribution of elements in lake bottom (surficial) sediments. Carbon and nitrogen isotopes from sedimentary organic matter suggest C3 terrestrial plants (forests > canga vegetation), macrophytes and freshwater DOC as the main sources. Sediments are depleted in most of the major oxides (except Fe 2 O 3 and P 2 O 5) when compared to upper continental crust (UCC) and their spatial distribution is highly influenced by catchment lithology. Principal Component Analysis revealed that most of the trace elements (Ba,

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Stable isotope analyses have helped in assessing dietary switches if the diet undergoes metabolic alteration (isotopic exchange). However, when considering the effects over time of switching from one diet to another, one can assess how quickly the new diet is incorporated into tissues via the isotopic renewal or incorporation rate, or turnover. Turnover is obtained using exponential curves that fit the original data, allowing the determination of practical order parameters such as the half-life (T) and the turnover constant (k). Researchers have found that metabolic incorporation can be fractionated. The resulting fractions, called metabolic pools, are identified using the linearization of the isotopic exchange model and its linear fit. This fractionation methodology is still not well defined. The objective of this study was to assess the behaviour of the metabolic renewal rate (turnover) in fractionated form, explain the theory, and apply it to data from the avian duodenal mucosa and albumen. We concluded that the duodenal mucosa has one metabolic pool, with a half-life of 1.23 days, and that the albumen has two metabolic pools, with half-lives of 1.89 and 6.32 days.

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Bark is a residue that can be used as fuel by the industry. One of the problems of its use is the impurity that it may contain. This study aimed to characterize physically and thermo-chemically the eucalyptus bark used as a fuel in a wood panel industry, relating the high heating value (HHV) with the ash content. Six treatments were provided according to particle size and washing process of the bark: T1 (850 μm to 425 μm/unwashed), T2 (retained on 250 μm/unwashed), T3 (< 150 μm/unwashed), T4 (850 μm to 425 μm/washed), T5 (retained on 250 μm/washed), T6 (< 150 μm/washed). The material was assessed regarding moisture content. The treatments were subjected to HHV and proximate analysis. The ashes were analyzed under SEM-EDS to identify the components/impurities. The data obtained in this study were statistically analyzed using the software R. The material presented moisture content of 70% on a dry basis, which is considered high for use in bioenergy. It was identified the presence of silica and calcium in the ash, which indicates the presence of soil in the material. The process of washing the bark was efficient for the reduction in ash content only in particle size < 150 μm. The separation of the bark in particle size was a better technique to reduce the impurities. The proximate analysis showed a significant difference among treatments. The ash content presented values from 2.63% (T1) to 13.86% (T3). The HHV was 18 828 J g −1 (T1) and 15 757 J g −1 (T3). The separation in particle size reduced 81.02% in the ash content, which represented an increase of 21.05% in the HHV. This result showed the effect of the ash content in the energy potential.