Cotton Fiber/ZrO2, A New Material for Adsorption of Cr(VI) Ions in Water     

Alfredo Alberto Muxel  Sonia Maria Nobre Gimenez  Flaveli Aparecida de Souza Almeida  Rení Ventura da Silva Alfaya  Antonio Alberto da Silva Alfaya 《洁净——土壤、空气、水》2011,39(3):289-295

The natural cotton fiber was used to synthesize an anion exchange, containing ZrO₂ film on its surface, NCFZC (natural cotton fiber/ZrO₂ composite). This anion exchanger was produced by the reaction of the zirconium oxychloride and hydroxyl groups on surface of the natural cotton fiber. The material was used for Cr(VI) ions adsorption studies. Adsorption equilibrium time and optimum pH for Cr(VI) adsorption were found to be 6 h and 4.0, respectively. The Langmuir and Temkin isotherms were used to models adsorption equilibrium data. The adsorption capacity of NCFZC was found to be 1.33 mmol/g. Kinetic studies showed that the rate of adsorption of Cr(VI) on NCFZC obeyed a pseudo‐second‐order kinetic model.  相似文献   

Geology and geochronology of the Betara region in south-southeastern Brazil: Evidence for possible Statherian (1.80–1.75 Ga) and Calymmian (1.50–1.45 Ga) extension events     

Oswaldo Siga  Leonardo Fadel Cury  Ian McReath  Ligia Maria de Almeida Leite Ribeiro  Kei Sato  Miguel Ângelo Stipp Basei  Cláudia Regina Passarelli 《Gondwana Research》2011,19(1):260-274

The results of geological mapping, chemical analysis and radiometric dating of metabasic rocks of Betara Formation, and mapping and dating of those present in the Betara basement nucleus together with mylonitic granodiorite and syenogranite are reported here. U–Pb analysis of bulk zircon fractions from the metabasic rocks of the basement nucleus yielded a Statherian age of 1790 ± 22 Ma, while the metabasic rocks from the upper part of the Betara Formation yielded a Calymmian age between 1500 and 1450 Ma. This age is a minimum for the deposition of the Betara Formation. The older metabasic rocks are associated with post-tectonic, possibly anorogenic syenogranite, while the younger ones are gabbro or very porphyritic ankaramite whose REE patterns are consistent with crystallization from an N-MORB parent magma. The observations and data point to the probable events associated with extensional processes of the end of Paleoproterozoic and early Mesoproterozoic. Similar registers of Statherian (1.80–1.75 Ga) and Calymmian (1.50–1.45 Ga) extensional events are recorded in other parts of the South American and African continents. The Neoproterozoic witnessed the formation and junction of the tectonic slices which formed the Apiaí domain during the assemblage of western Gondwana.  相似文献   

Reproductive biology of Spondias tuberosa Arruda (Anacardiaceae), an endemic fructiferous species of the caatinga (dry forest), under different management conditions in northeastern Brazil     

A.L.S. Almeida  C.C. Castro 《Journal of Arid Environments》2011,75(4):330-337

In areas under different management conditions (management units, MUs) located either on a slope or at the base of a slope and either in a plantation or in a pasture, we compared the flower and fruit production, floral visitors, visitation rates and pre-emergent reproductive success (PERS) of Spondias tuberosa (Anacardiaceae) in an area of dry forest in NE Brazil. Individuals in the plantation MU produced more flowers per inflorescence than those in other MUs, but there were no statistical differences in mean fruit set among MUs. The only difference in mean visitation rates was between the plantation (65.83 ± 38.49) and the slope sites (11.5 ± 12.8). We observed visits by 19 insect species, including bees (31.6%), butterflies (31.6%), wasps (26.3%) and flies (10.5%). A clustering analysis based on the number of visits showed that a) the plantation site is most different from the other MUs, b) the pasture and the site at the base of the slope are similar to the slope site, and c) the higher frequency of visits of pollinators in the plantation MU was responsible for these differences. Of the 19 species of insects visiting the flowers, 12 were considered pollinators. The pollinator similarity analysis indicated a clear separation between areas and suggested that human activity has resulted in the replacement of native pollinators by exotic species. However, these changes apparently have not affected the pre-emergent reproductive success of S. tuberosa. Our results show that plant reproductive biology in semi-arid ecosystems may be modified by human action and that changes in floral production and pollinator guilds are the most conspicuous effects. However, the traditional management performed by local people may not affect the reproductive success of plant species.  相似文献   

Seasonal Diet Shifts and Overlap Between Two Sympatric Catfishes in an Estuarine Nursery     

David Valença Dantas  Mario Barletta  Jonas de Assis Almeida Ramos  André Ricardo Araújo Lima  Monica Ferreira da Costa 《Estuaries and Coasts》2013,36(2):237-256

This study describes the seasonal feeding habits of different size classes of Cathorops spixii and Cathorops agassizii along an estuarine ecocline and the food overlap when different size classes occur together. These species were essentially zoobenthivorous, feeding mainly on Polychaeta Nereis sp., Copepoda Pseudodiaptomus acutus, Ostracoda Asterope sp., Gastropoda: Littorinidae, and Bivalvia Mytilus sp. and Anomalocardia brasiliana. However, during their life cycle and between different habitats and seasons, their trophic guild can change to zooplanktivore. The competition for resources was observed among C. spixii and C. agassizii, but was significantly reduced due to the seasonal diference in habitat use by different ontogenetic phases in the main channel of the estuary. The food niche separation was strongly influenced by environmental fluctuations, principally of salinity, resulting from rainfall and river inflow. High abundance of some preys, such as P. acutus (all estuary), Asterope sp. (upper and middle estuary), and Littorinidae (upper and lower estuary), could influence the significant diet overlap, principally during the rainy season, and call for more detailed studies of the benthic community structure. Moreover, dietary overlap was observed mainly between smaller sizes (intraspecific and/or interspecific) or between corresponding ontogenetic phases (interspecific), suggesting some differentiation in the diet in relation to the size class. Differences in prey type and size between the different ontogenetic phases of these ariids, principally among juveniles and adults, could be related to the size of the mouth, since adults are able to successfully capture larger preys or larger quantities of particular items.  相似文献   

Emergent effects of heavy metal pollution at a population level: Littorina brevicula a study case     

Kim SJ  Rodriguez-Lanetty M  Suh JH  Song JI 《Marine pollution bulletin》2003,46(1):74-80

Changes in genetic variability and allele frequency can be responses from natural populations when encountering a novel contaminated environment. The genetic diversity and population structuring of natural populations of the gastropod Littorina brevicula from heavy-metal polluted and unpolluted environments along the southeast coast of Korea were examined using two mtDNA markers, cyt b and ND6. This study applied a nested clade analysis to test the existence of structuring association of haplotype distribution with environments (polluted and unpolluted). No genetic differences within cyt b mtDNA were detected between environments. On the other hand, differences in population haplotype diversity and structuring were found within ND6 mtDNA between polluted and unpolluted environments. The ND6-mtDNA haplotype (=genetic) diversity was significant lower in polluted environments. This decreased genetic diversity along with differences in the haplotype distribution within heavy-metal polluted environments compared to those unpolluted ones stand out as emergent effects from pollution at a population level. In this study, we propose the use of different approaches, such as the NCA, that takes into account the rare haplotypes, when assessing the effects of pollution on population genetic structuring.  相似文献   

Post-Last Glacial Maximum evolution of a “fjord-type” lake based on high-resolution seismic data: the Lago Roca/Acigami (southern Tierra del Fuego,Argentina/Chile)     

Donaldo Mauricio Bran  Jorge Gabriel Lozano  Dario Civile  Emanuele Lodolo  María E. Cerredo  Alejandro Tassone  Luca Baradello  Maurizio Grossi  Juan Vilas 《第四纪科学杂志》2020,35(3):396-409

Lago Roca/Acigami is a “fjord-type” lake located in the southernmost part of South America, in the proximity of the Beagle Channel. A high-resolution seismic survey was carried out to analyse the seismic stratigraphy of the lake and to shed some light on the post-Last Glacial Maximum history of the area. Six seismic units were recognised, and their nature and depositional context were interpreted using seismic stratigraphy and acoustic facies analysis. A buried large ridge was identified within the glacial unit (SU1), interpreted as a frontal moraine that indicates a stabilisation phase. After retreat of the glacier from the basin, the trough was flooded by meltwater and a lake developed (SU2). The seismic facies, from bottom to top, depict a transition from ice-contact (SU2; SU3) to ice-distal proglacial conditions (SU4). A thick draping unit (SU5) marks a marine transgressive event and the instauration of a fjord environment in the basin. The marine transgression was a rapid event preceded by a fall in the lake level that caused an erosional unconformity. During the fjord phase the sedimentation remained controlled by meltwater discharge. Sea level fall, and subsequent disconnection from the Beagle Channel was accompanied by a progradation of the glaciofluvial deltaic sediments and the occurrence of several mass-wasting deposits (SU6). © 2019 John Wiley & Sons, Ltd.  相似文献   

Hydraulic response of a tidally forced coastal aquifer, Pontal do Paraná, Brazil     

D. S. Suresh Babu  Atul Kumar Sahai  Mauricio Almeida Noernberg  Eduardo Marone 《Hydrogeology Journal》2008,16(7):1427-1439

The unconfined aquifer supported by the extensive Holocene coastal plain of southern Brazil is found dissected at several places by tidally forced streams. One such unit of coastal plain, falling within the watershed limits of Perequê Stream in Paraná state, was analyzed using MODFLOW to assess the surface and subsurface water components under different stress conditions. The steady-state simulation suggests that ~23,000 m³/day of water forms the total budget of the designated aquifer zone and this zone discharges ~16,000 m³/day across the interface between the freshwater aquifer zone and the sea as direct submarine discharge. The maximum evaporation loss was assumed to be 2,700 m³/day. Any change in effective aquifer storage was insignificant, as there is no large-scale exploitation of local groundwater reserves. A calibration exercise, based on field measurements lasting 1 year, supports validity of the model considered. Simulations representing two different transient conditions point to the dynamic hydraulic response exhibited by the aquifer. A schematic map, showing directions and velocity of subsurface flows, and a three-dimensional model of the groundwater reserve helped to visualize the hydrogeologic changes and to formulate management plans.  相似文献   

A local landscape in transition between production and consumption goals: can new management arrangements preserve the local landscape character?     

Teresa Pinto-Correia  Mara Almeida  Carla Gonzalez 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2016,116(1):33-43

Around towns in the Alentejo region, the landscape is dominated by a characteristic agricultural small-scale mosaic. These areas are central in the region landscape character – even if the large-scale latifundia landscape of the extensive silvo-pastoral systems is most commonly associated with the region. In the last two decades, these parcels became extremely attractive for new comers, who settle in the rural context as residents, week-end visitors, being often also lifestyle farmers. The paper presents a case study landscape, in Montemor-o-Novo, a small town 100 km from Lisbon, highly subject to the pressure for consumption uses, by urban users. The study shows that the new owners, even if they have settled in the area due to the tranquility and social bindings of the rural, end up doing farming, with new or reshaped production objectives, markets and models, but at the same time maintaining the traditional farm systems. Thus, the landscape character is maintained, so far. Nevertheless, the role of these neo-rurals and lifestyle farmers is still an unseen role, both by the agriculture and the planning sectors. And thus the question is, whether the combination of actors and land management drivers will continue maintaining the landscape in the future.  相似文献   

Post-LGM sedimentation on the outer shelf-upper slope of the northernmost part of the São Paulo Bight, southeastern Brazil     

Michel Michaelovitch de Mahiques  Ilson Carlos Almeida da SilveiraSilvia Helena de Mello e Sousa  Marcelo Rodrigues 《Marine Geology》2002,181(4):387-400

Sedimentary and isotope data as well as ¹⁴C AMS dating on 15 box cores were used to identify the main post-Last Glacial Maximum (LGM) processes in the outer shelf and upper slope of the northernmost part of the São Paulo Bight, southeastern Brazil. Results show slight but significant variations in calcium carbonate, total sulphur and nitrogen contents as well as carbon and oxygen isotope ratios. Sedimentation rates, varying from 5 to 184 mm kyr⁻¹ are controlled by the shelf and upper slope morphology, the Brazil Current meander dynamics, and the Coastal Water offshore motion.  相似文献   

Larval distribution and growth of the rockfish, Sebastes capensis (Sebastidae, Pisces), in the fjords of southern Chile     

Landaeta  Mauricio F.; Castro  Leonardo R. 《ICES Journal of Marine Science》2006,63(4):714-724

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