Organochlorine compounds in sharks from the Brazilian coast     

Claudio Eduardo de Azevedo e Silva  Adriana de Cássia Lima Dias  José Lailson-Brito  Jean Remy Daveé Guimarães 《Marine pollution bulletin》2009,58(2):294-298

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Removal of Copper,Nickel and Zinc Ions from Aqueous Solution by Chitosan‐8‐Hydroxyquinoline Beads     

Francisco C. F. Barros  Francisco W. Sousa  Rivelino M. Cavalcante  Tecia V. Carvalho  Francisco S. Dias  Danilo C. Queiroz  Luiz C. G. Vasconcellos  Ronaldo F. Nascimento 《洁净——土壤、空气、水》2008,36(3):292-298

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   

The long-term residual circulation in Long Island sound     

Mário E. C. Vieira 《Estuaries and Coasts》2000,23(2):199-207

Current meter data were acquired in Long Island Sound over a period of about 6 mo in 1988 at six different transects. The averages of the low-passed residuals represent the contributions from tidal steering and density forcing. It is found that the long-term residual circulation starts out with a classical estuarine pattern at the Race. The flows into and out of the Sound are vertically partitioned by Long Sand Shoal; they gradually revert back to classical vertically layered estuarine circulation as the Central Basin is traversed. Further west, the bottom oceanic water becomes a westward flowing swift jet close to the Connecticut shore, while the East River water is constrained to flow eastward along the Long Island coast. Counterclockwise gyres, identified in the Eastern Narrows and Western Basin, may increase residence times of polluted East River water in the western Long Island Sound.  相似文献   

Impact of constitutive models on the numerical analysis of underground constructions   总被引：1，自引：0，他引：1  

Yousef Hejazi  Daniel Dias  Richard Kastner 《Acta Geotechnica》2008,3(4):251-258

The constitutive model frequently used in numerical calculations of tunnel excavation is linear-elastic perfectly plastic with a Mohr–Coulomb (MC) failure criterion. Generally, this leads to shallower and wider surface settlement troughs than those observed experimentally. It is therefore necessary to use adapted constitutive models for the design of underground works. In this paper, three constitutive models are implemented in a two-dimensional simulation of an underground excavation in plane strain: a linear-elastic perfectly plastic model (the MC model), an elastoplastic model with isotropic hardening [the hardening soil (HS) model, Schanz et al., Beyond 2000 in computational geotechnics, Balkema, Rotterdam, pp. 281–290, 1999] and an extension of this model which implies an evolution of the stiffness modulus in the small-strain range according to the strain level (the HS model with small-strain stiffness “HS-Small”, Benz, Small-strain stiffness of soils and its numerical consequences. Ph.D. thesis, Universitat Stuttgart, 189 pp., 2007). The study is based on the results of drained triaxial compression tests representing an overconsolidated clay (Gasparre, Advanced laboratory characterisation of London clay. Ph.D. thesis, Imperial College London, 598 pp., 2005); and is then applied to a shallow tunnel. The impact of the constitutive model is highlighted as well as the limits of the simplest constitutive model.  相似文献   

Geochemistry of a sediment push-core from the Lucky Strike hydrothermal field,Mid-Atlantic Ridge     

Á.S. Dias  R.A. Mills  R.N. Taylor  P. Ferreira  F.J.A.S. Barriga 《Chemical Geology》2008,247(3-4):339-351

Hydrothermal sediment mineralogy and geochemistry can provide insights into seafloor mineralization processes and changes through time. We report a geochemical investigation of a short (22 cm) near-vent hydrothermal metalliferous sediment core from the Lucky Strike site (LS), on the Mid-Atlantic Ridge (MAR). The sediment was collected from the base of an active white smoker vent and comprises pure hydrothermal precipitates, mainly chalcopyrite, sphalerite, pyrite and barite, with negligible detrital and biogenic inputs. Geochemically, the core is enriched in elements derived from high-temperature hydrothermalism (Fe, Cu, Zn and Ba) and depleted in elements derived from low-temperature hydrothermalism (Mn), and metasomatism (Mg). The U/Fe content ratio is elevated, particularly in the deeper parts of the core, consistent with uptake from seawater associated with sulphide alteration. Rare earth elements (REE) concentrations are low and chondrite-normalized patterns are characteristic of high-temperature vent fluids with an enrichment in light REE and a pronounced positive Eu anomaly. A stronger positive Eu anomaly associated with higher La_n/Sm_n at the core top is controlled by barite precipitation. The hydrothermal influence on the REE decreases downcore with some evidence for a stronger seawater influence at depth. Nd isotopes also exhibit an increased detrital/seawater influence downcore. Pb isotope ratios are uniform and plot on the Northern Hemisphere Reference Line in a small domain defined by LS basalts and exhibit no detrital or seawater influence. Lucky Strike sediments are derived from high-temperature mineralization and are overprinted by a weak seawater–sediment interaction when compared with other Atlantic hydrothermal sites such as TAG. The larger seawater input and/or a larger detrital contribution in deeper layers can be explained by variable hydrothermal activity during sediment formation, suggesting different pulses in activity of the LS hydrothermal system.  相似文献   

Sources of organic carbon in the Portuguese continental shelf sediments during the Holocene period     

D. Burdloff  M.F. Araújo  J.-M. Jouanneau  I. Mendes  A.M. Monge Soares  J.M.A. Dias 《Applied Geochemistry》2008

Organic C (OC) and total N (TN) concentrations, and stable isotope ratios (δ¹³C) in muddy deposit sediments of the Northern and Southern Portuguese continental shelf were used to identify sources of fine-sized organic matter (<63 μm) during the Holocene period. Sedimentary columns off the Guadiana (core CRIDA 05), Tagus (core MD 992332) and Douro (core KSGX 57) estuaries are characterised by elemental and isotopic values that reflect distinct sources of organic matter (OC/TN and δ¹³C ranging, respectively, from 8.5 to 21 and from −22.4‰ to −27‰). Intense supplies to the Guadiana continental shelf of fine terrigenous particles during the Younger-Dryas Event are closely linked with higher OC/TN values and lower δ¹³C ratios. During the postglacial transgression phase, an increasing contribution of marine supplies (up to 80%) occurred. Higher δ¹³C (up to −22.4‰) values and low OC/TN ratios (down to 8.5) are found as the sea level approaches the current one. The Upper Holocene records emphasize the return to enhanced terrestrial supplies except for the Little Climatic Optimum between the 11th and 15th centuries AD. This climatic event is especially obvious in the three cores as a return to marine production and a decrease in terrestrial sediment supply to the continental shelf. The return to a cooling event, the Little Ice Age, between the 15th and 19th centuries AD, is mirrored by decreased terrigenous supplies in core KSGX 57. Gradually increasing sedimentation in estuaries, as well as formation of coastal dune fields, have been hypothesized on the basis of increasing δ¹³C and decreasing OC, TN and OC/TN values.  相似文献   

Brazil's premier gold province. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero     

Lydia Lobato  Luiz Ribeiro-Rodrigues  Frederico Vieira 《Mineralium Deposita》2001,36(8):808-809

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Incidence and recurrence of large forest fires in mainland Portugal     

F. Ferreira-Leite  A. Bento-Gonçalves  A. Vieira  A. Nunes  L. Lourenço 《Natural Hazards》2016,84(2):1035-1053

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Flood-related leptospirosis outbreaks in Brazil: perspectives for a joint monitoring by health services and disaster monitoring centers     

Luciana de Resende Londe  Rodrigo Silva da Conceição  Tiago Bernardes  Mariane Carvalho de Assis Dias 《Natural Hazards》2016,84(2):1419-1435

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Production of Reactive Oxygen Species in the Rhizosphere of a <Emphasis Type="Italic">Spartina-</Emphasis>Dominated Salt Marsh Systems     

Dewamunnage Muditha C. Dias  Justin M. Copeland  Carrie L. Milliken  Xiangming Shi  John L. Ferry  Timothy J. Shaw 《Aquatic Geochemistry》2016,22(5-6):573-591

This paper reports the presence of a metastable mixture of Fe(II), O₂, superoxide and hydrogen peroxide in sediment pore water in organic carbon-rich sediments in Spartina alterniflora-dominated salt marsh systems. Field measurements at two different estuarine sites in South Carolina (one heavily urbanized and a protected research reserve) showed a broad region of reactive oxygen species (ROS) production more than 15 cm below the sediment surface within and immediately adjacent to the rhizospheres of S. alterniflora. Dissolved Fe(II) was positively correlated with hydrogen peroxide indicating a possible abiotic pathway to ROS production (r ² = 0.94). The null hypothesis was tested that Fe(II) inventories were maintained by protective ligands and thus unreactive with respect to O₂ consumption and ROS production. The addition of an Fe-binding ligand, DTPA, resulted in rapid decline of ROS in pore water, indicating that Fe(II) was labile. The half-life of superoxide under the measured solution conditions was calculated and found to be less than a second. The combination of high lability and persistent ROS was interpreted to indicate a high rate of Fe(II) and O₂ supply to the pore water. The ²²⁴Ra/²²⁸Th disequilibrium was measured to determine the potential for advective mass transfer of dissolved oxygen via pore water exchange. The estimated pore water exchange of 54 L m^?2 day^?1 was significant but could not support the measured production of ROS alone, the direct exchange of O₂ from the S. alterniflora root system may have contributed significantly to ROS production in the sediments.  相似文献