The volcanic rocks of the Colíder and Roosevelt formations are extensively exposed in the south-central portion of the Amazonian Craton where effusive and pyroclastic rocks have been mapped. Both units, topped by chemical sediments and oceanic facies as rhyolite and andesite lavas, rhyodacite, and porphyritic dacite, with frequent intercalations of pyroclastic and epiclastic deposits. Whole-rock geochemistry for 55 samples of rhyolitic to andesitic composition suggests the involvement of fertile mantle-derived components with E-MORB to OIB compositions. The analyzed rocks display calc-alkaline to shoshonitic affinity consistent with generation related to an active continental margin. The whole-rock Sm-Nd isotope data from selected felsic volcanic rocks of the Colíder and Roosevelt formations yield negative initial εNd values between –3 and –9, indicating the predominantly crustal nature of the parental magmas with early Archean to late Paleoproterozoic (ca. 2.5–2.0 Ga) depleted mantle model ages.
In this work, 8‐hydroxyquinoline is used as the active sites in cross‐linked chitosan beads with epichlorohydrin (CT‐8HQ). The CT‐8HQ material was shaped in bead form and used for heavy metal removal from aqueous solution. The study was carried out at pH 5.0 with both batch and column methods and the maximum adsorption capacity of metal ions by the CT‐8HQ was attained in 4 h in the batch experiment. The adsorption capacity order was: Cu2+ > Ni2+ > Zn2+ for both mono‐ and multi‐component systems with batch conditions. From breakthrough curves with column conditions, the adsorption capacity followed the order Cu2+ > Zn2+ > Ni2+ for both mono‐ and multi‐component systems. The CT‐8HQ beads maintained good metal adsorption capacity for all five cycles with absorbent restoration achieved with the use of 1.0 mol L–1 HCl solution, with 90% regeneration. 相似文献
Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer. 相似文献
Recently, the increasing demand for biofuels triggered a new phase for the sugar‐alcohol sector. In Brazil, as well as in other tropical countries, this process raised worries regarding the possible direct and indirect effects of the crop's expansion on the conversion of native vegetation coverings. Therefore, the modeling of spatial‐economic surfaces, representing the potential rent variation in its spatial component, for economic activities, may be a useful tool in the decision‐making process. Hence, here we propose and present the results of a combined framework composed of two modules using the modeling platform Dinamica EGO. The first module simulates sugarcane's growth, calculating the daily response of the crop to environmental conditions during the stages of the plant's development. The second module estimates rents for sugarcane cultivation in Brazil, identifying areas where this activity would bring higher economic return, looking at simulated productivity, production costs and selling prices in a way that is spatially explicit for Brazil. Two different scenarios for production costs were tested, and results ranged from negative values to maxima of R$/ha 929 and R$/ha 1176 for standard and efficient costs of production, respectively. The model successfully indicated non‐profitable and profitable areas, and regions where high expected economic return overlaps endangered ecosystems. 相似文献
Heavy rainfall trends in a region of south-eastern South America during 1959–2002 were discussed using daily data of 52 meteorological stations of Argentina, Brazil and Uruguay. Changes in intensity and frequency were both studied with different statistical tests and approaches to check the significance of trends of single and regional aggregated rainfall series. There were predominant positive trends in the annual maximum rainfalls, as well as a remarkable increment in the frequency of heavy rainfalls over thresholds ranging from 50 to 150 mm. However, significant positive trends were not shown in the series of annual maximums and shown only in 15% to 30% of the series of frequencies over thresholds. This lack of significance is due to the high variability of heavy rainfalls in space and time, which makes difficult their capture by single rain gauges. Thus, when the assessment of the heavy rainfall indicators of intensity and frequency were conducted at the regional and sub-regional level, it showed significant trends, both in intensity and frequency over thresholds, with a clearer signal in central and eastern Argentina between 30° and 40° S. 相似文献
Many nickel deposits are known in Brazil, accounting for about 350 · 106 tons of ore with an average of 1.5% Ni. All are of the lateritic type. These deposits are scattered throughout the country, being rarer in the Northeastern Region and in the South, below 25 °S latitude. They are mainly associated with mafic-ultramafic massifs of large dimensions and ultramafic alkaline complexes, and occur in climatic regions of contrasting seasons. The weathering profile developed over the fresh rock consists, from bottom to top, of the following horizons: altered rock, coarse saprolite, argillaceous saprolite, ferruginous saprolite and lateritic overburden. The thickness of each horizon varies from one deposit to another, the whole profile generally exceeding 20 m. The saprolitic horizons with inherited minerals (serpentine, chlorite) or neoformed minerals (smectites) constitute the silicated nickel ore and are thicker were climatic conditions are drier; the ferruginous upper horizons made up of iron oxide-hydroxides are more developed in more humid regions. In Brazil, the silicated ore generally prevails over the oxidized ore. The main Ni-bearing minerals are serpentine, smectite, garnierite and goethite. The lateritic nickel deposits of Brazil may be correlated with two erosion surfaces, corresponding to the Sul Americano (Lower Tertiary) and Velhas (Upper Tertiary) levelling cycles. The degree of dismantling of the higher and more ancient surface and the consequent development of the Velhas Surface control the position of the nickel accumulation in the landscape. Thus, the deposits may be found either in the lowlands or in the highlands, where they are always covered by a silcrete layer. The alteration profiles in the Brazilian lateritic nickel deposits are broadly similar to those described elsewhere in the world. However, they present two characteristic features: the silicated ore prevails over the oxidized ore, and a silicified layer covers the profies developed on the highlands. 相似文献
The two-dimensional response of a viscoelastic half-space containing a buried, unlined, infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane SH, P, SV and Rayleigh waves is obtained by an indirect boundary integral method based on the two-dimensional Green's functions for a viscoelastic half-space. An extensive critical review of the existing numerical results obtained by other techniques is presented together with some new numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity for P, SV, SH and Rayleigh waves. 相似文献
A method to obtain the three-dimensional harmonic response of a infinitely long cylindrical shell of circular cross-section embedded in a layered viscoelastic half-space and subjected to harmonic plane waves impinging at an oblique angle with respect to the axis of the shell is presented. The procedure combines an indirect integral representation for the field in the exterior half-space with a model of the pipeline or tunnel based on Donnell shell theory. The integral representation for the soil is based on the use of moving Green's functions for the layered viscoelastic half-space. The accuracy of the formulation is tested by comparison of results obtained by using different discretizations. Extensive comparisons with previous two- and three-dimensional results for the case of a shell embedded in a uniform half-space and some new numerical results for a shell embedded in a multilayered half-space are presented in a companion paper. 相似文献