Trace metals and organic compounds in the benthic environment of a subtropical embayment (Ubatuba Bay, Brazil)     

Muniz P  Pires-Vanin AM  Martins CC  Montone RC  Bícego MC 《Marine pollution bulletin》2006,52(9):1098-1105

  相似文献   

Assessment of contamination by polychlorinated biphenyls and aliphatic and aromatic hydrocarbons in sediments of the Santos and São Vicente Estuary System, São Paulo, Brazil   总被引：1，自引：0，他引：1  

Bícego MC  Taniguchi S  Yogui GT  Montone RC  Moreira da Silva DA  Lourenço RA  de Castro Martins C  Sasaki ST  Pellizari VH  Weber RR 《Marine pollution bulletin》2006,52(12):1804-1816

  相似文献   

On the stability of the satellites of asteroid 87 Sylvia     

O. C. Winter  L. A. G. Boldrin  E. Vieira Neto  R. Vieira Martins  S. M. Giuliatti Winter  R. S. Gomes  F. Marchis  P. Descamps 《Monthly notices of the Royal Astronomical Society》2009,395(1):218-227

The triple asteroidal system (87) Sylvia is composed of a 280-km primary and two small moonlets named Romulus and Remus ( Marchis et al. 2005b ). Sylvia is located in the main asteroid belt, with semi-major axis of about 3.49 au, eccentricity of 0.08 and 11° of orbital inclination. The satellites are in nearly equatorial circular orbits around the primary, with orbital radius of about 1360 km (Romulus) and 710 km (Remus). In this work, we study the stability of the satellites Romulus and Remus. In order to identify the effects and the contribution of each perturber, we performed numerical simulations considering a set of different systems. The results from the three-body problem, Sylvia–Romulus–Remus, show no significant variation of their orbital elements. However, the inclinations of the satellites present a long-period evolution with amplitude of about 20° when the Sun is included in the system. Such amplitude is amplified to more than 50° when Jupiter is included. These evolutions are very similar for both satellites. An analysis of these results shows that Romulus and Remus are librating in a secular resonance and their longitude of the nodes are locked to each other. Further simulations show that the amplitude of oscillation of the satellites' inclination can reach higher values depending on the initial values of their longitude of pericentre. In those cases, the satellites get caught in an evection resonance with Jupiter, their eccentricities grow and they eventually collide with Sylvia. However, the orbital evolutions of the satellites became completely stable when the oblateness of Sylvia is included in the simulations. The value of Sylvia's J ₂ is about 0.17, which is very high. However, even just 0.1 per cent of this value is enough to keep the satellite's orbital elements with no significant variation.  相似文献   

Influence of traffic emissions on the composition of atmospheric particles of different sizes—Part 2: SEM–EDS characterization     

K. Slezakova  J. C. M. Pires  M. C. Pereira  F. G. Martins  M. C. Alvim-Ferraz 《Journal of Atmospheric Chemistry》2008,60(3):221-236

In urban areas traffic is the major contributor to atmospheric particulate matter and exposure to these particles currently represents a serious risk to human health. The attention has been recently focused more on the particles of smaller sizes (PM_2.5) which penetrate deeper in respiratory system causing severe health effects. Therefore, more information on PM_2.5 should be provided, namely concerning morphological and chemical characterization. Aiming further evaluation of the impact of traffic emissions on public health, this work evaluated the influence of traffic on the chemical and morphological characteristics of PM₁₀ and PM_2.5, collected at one site influenced by traffic emissions and at one reference site. Chemical and morphological characteristics of 1,000 individual particles were determined by scanning electron microscopy combined with energy dispersive spectrometer (SEM–EDS). Cluster analysis (CA) was used to identify different types of particles that occurred in PM, aiming the identification of the respective emission sources. Traffic PM_2.5 were dominated by particles composed of Fe oxides and alloys (67%) which were related to traffic emissions (this percentage was 3.7 times higher than at the background site); in PM_2.5–10 the abundance of Fe oxides and alloys were 20% and 0% for the traffic and background sites, respectively. Background PM_2.5 were mainly constituted by aluminum silicates (63%) related to natural sources (this percentage was 2.5 times higher than at the traffic site); the abundances of aluminum silicates in PM_2.5–10 were 74% and 73% for traffic and background sites, respectively. It was concluded that traffic emissions were mainly present in PM_2.5 (the percentage of particles associated to these emissions was 3.4 times higher than in PM_2.5–10), while coarse particles were dominated by material of natural origin (the percentage of particles associated was 1.2 and 3.0 times higher than in PM_2.5 for traffic and background sites, respectively). Previous results obtained by proton induced X-ray emission (PIXE) were consistent with SEM–EDS analysis that showed to be very useful to complement elemental analysis of different PM_2.5 and PM_2.5–10.  相似文献   

Tectonic control of the Tejo river fluvial incision during the late Cenozoic, in Ródão—central Portugal (Atlantic Iberian border)   总被引：2，自引：0，他引：2  

P. Proena Cunha  A. Antunes Martins  S. Daveau  P.F. Friend 《Geomorphology》2005,64(3-4):271-298

Staircases of strath terraces and strongly incised valleys are the most typical landscape features of Portuguese rivers. This paper examines the incision achieved during the late Cenozoic in an area crossed by the Tejo river between the border with Spain and the small town of Gavião. In the more upstream reach of this area, the Tejo crosses the Ródão tectonic depression, where four levels of terraces are distinguished. During the late Cenozoic fluvial incision stage, the Ródão depression underwent less uplift than the adjacent areas along the river. This is reflected by the greater thicknesses and spatial extent of the terraces; terrace genesis was promoted by impoundment of alluvium behind a quartzitic ridge and the local presence of a soft substratum. Outside this tectonic depression, the Tejo has a narrow valley incised in the Hercynian basement, with some straight reaches that probably correspond to NE–SW and NNW–SSE faults, the terraces being nearly absent. Geomorphological evidence of tectonic displacements affecting the Ródão dissected terrace remnants is described. Geochronological dating of the two younger and lower terrace levels of this depression suggests a time-averaged incision rate for the Tejo in the Ródão area, of ca. 1.0 m/ka over the last 60 thousand years. A clear discrepancy exists between this rate and the 0.1 m/ka estimated for the longer period since the end of the Pliocene. Although episodes of valley incision may be conditioned by climate and base-level changes, they may also have been controlled by local factors such as movement of small fault-bounded blocks, lithology and structure. Regional crustal uplift is considered to be the main control of the episodes of valley incision identified for this large, long-lived river. A model is proposed in which successive regional uplift events—tectonic phases—essentially determined the long periods of rapid river downcutting that were punctuated by short periods of lateral erosion and later by some aggradation, producing strath terraces.  相似文献   

Nd isotopic composition of Paleoproterozoic volcanic and granitoid rocks of Vila Riozinho: implications for the crustal evolution of the Tapajós gold province, Amazon craton     

Claudio Nery Lamaro  Roberto Dall'Agnol  Marcio Martins Pimentel 《Journal of South American Earth Sciences》2005,18(3-4):277-292

Nd data from the Paleoproterozoic magmatic rocks of Vila Riozinho and Jamanxim (Tapajós gold province) indicate that original magmas were not produced exclusively by the remelting of Archean sialic crust and point to dominant Paleoproterozoic sources. ε_Nd(T) values preclude derivation from mantle sources for the ca. 2.0 Ga Vila Riozinho volcanics and older São Jorge granite. They may represent a subduction-related magmatic arc with magmas modified by interaction with crust or a post- to late-orogenic remelting of an older Paleoproterozoic juvenile arc with minimal contribution from the Archean crust. The origin of the 1.88 Ga Parauari, Maloquinha, Iriri, and Moraes Almeida igneous associations and the Jamanxim rhyolites has been attributed to large-scale taphrogenesis that marked the breakup of a large Paleoproterozoic continent. Derivation of the original magmas from the remelting of crustal sources older than ca. 1.9 Ga is consistent with geochemical and Nd isotopic data. Archean remnants probably occur between the Paleoproterozoic terrains of the Ventuari-Tapajós province. Archean terrains of the Amazon craton extend from the Xingu to the Itaituba region but have not been identified in the southern Guyana shield. Thus, data reveal that the boundaries between the central Amazon and Ventuari-Tapajós provinces need better definition and more detailed field and geochronological work.  相似文献   

Vortons: Dark Matter from Cosmic Strings     

C.J.A.P. Martins  E.P.S. Shellard 《Astrophysics and Space Science》1998,261(1-4):325-326

  相似文献   

Nature and origin of the BIF-hosted São Bento gold deposit, Quadrilátero Ferrífero, Brazil, with special emphasis on structural controls     

Srgio Luiz Martins Pereira  Lydia Maria Lobato  Juliano Efigênio Ferreira  Eduardo Csar Jardim 《Ore Geology Reviews》2007,32(3-4):571

The orogenic banded iron formation (BIF)-hosted Au mineralization at São Bento is a structurally-controlled, hydrothermal deposit hosted by Archean rocks of the Rio das Velhas greenstone belt, Quadrilátero Ferrífero region, Brazil. The deposit has reserves of 14.3 t Au and historical (underground) production of 44.6 t Au between 1987 and 2001. The oxide-facies São Bento BIF is mineralized at its lower portion, where in contact with carbonaceous, pelitic schists, particularly in the proximity of sulfide-bearing quartz veins. Shear-related Au deposition is associated with the pervasive, hydrothermal sulfidation (mainly arsenopyrite) of the Fe-rich bands of the São Bento BIF. Auriferous, sulfide- and quartz-rich zones represent proximal alteration zones. They are enveloped by ankerite-dominated haloes, which reflect progressive substitution of siderite and magnetite within the BIF by ankerite and pyrrhotite, respectively. The São Bento BIF was intensely and extensively deformed, first into open, upright folds that evolved into tight, asymmetric, isoclinal folds. The inverse limb of these folds attenuated and gave way to sheath folds and the establishment of ductile thrusts. Mineralized horizons at São Bento result from early structural modifications imposed by major transcurrent and thrusts faults, comprising the Conceição, Barão de Cocais and São Bento shear zones. Dextral movement on the SW–NE-directed Conceição shear zone may have generated splays at a compressional side-stepping zone, such as the São Bento shear zone, which is the structural locus for the São Bento gold mineralization. Relaxation of the Conceição shear zone under more brittle conditions resulted in the development of dilatational zones where gold–sulfide–quartz veins formed. These structures are considered to have been generated in the Archean. Geochronological data are scarce, with Pb–Pb analyses of refractory arsenopyrite and pyrite from bedded and remobilized ore plotting on a single-stage growth curve at 2.65 Ga. A later compressional, ductile deformation of unknown age overprinted, rotated and flattened the original, N60E-directed structure of the whole rock succession, with development of planar and linear fabrics that appear similar to Proterozoic-aged structures. Fluid inclusion studies indicate low salinity, aqueous fluids, with or without CO₂ and/or CH₄, with extremely variable CO₂/CH₄ ratios, of probable metamorphic origin. Fluid evolution shows a paragenetic decrease in the carbonic phase from 10–15% to 5%, and increase in the H₂O/(CO₂ + CH₄) and CO₂/CH₄ ratios, suggesting important interaction with carbonaceous sediment. Trapping conditions indicate a temperature of 300 °C at 3.2 kbar.  相似文献   

An overview of results of processes impacting near-surface atmospheric pollutants (PINESAP) from the mid-Atlantic United States     

Douglas K. Martins  Jose D. Fuentes 《Journal of Atmospheric Chemistry》2015,72(3-4):183-195

  相似文献   

Combined effects of elevated [CO2] and high temperature on leaf mineral balance in Coffea spp. plants     

Lima D. Martins  Marcelo A. Tomaz  Fernando C. Lidon  Fábio M. DaMatta  José C. Ramalho 《Climatic change》2014,126(3-4):365-379

Modelling studies predicted that climate change will have strong impacts on the coffee crop, although no information on the effective impact of elevated CO₂ on this plant exists. Here, we aim at providing a first glimpse on the effect of the combined impact of enhanced [CO₂] and high temperature on the leaf mineral content and balance on this important tropical crop. Potted plants from two genotypes of Coffea arabica (cv. Icatu and IPR 108) and one from C. canephora (cv. Conilon Clone 153) were grown under 380 or 700 μL CO₂ L^?1 air, for 1 year, after which were exposed to an stepwise increase in temperature from 25/20 °C (day/night) up to 42/34 °C, over 8 weeks. Leaf macro???(N, P, K, Ca, Mg, S) and micronutrients (B, Cu, Fe, Mn, Zn) concentrations were analyzed at 25/20 °C (control), 31/25 °C, 37/30 °C and 42/34 °C. At the control temperature, the 700 μL L^?1 grown plants showed a moderate dilution effect (between 7 % and 25 %) in CL 153 (for N, Mg, Ca, Fe) and Icatu (for N, K and Fe), but not in IPR 108 (except for Fe) when compared to the 380 μL L^?1 plants. For temperatures higher than control most nutrients tended to increase, frequently presenting maximal contents at 42/34 °C (or 37/30 °C), although the relation between [CO₂] treatments did not appreciably change. Such increases offset the few dilution effects observed under high growth [CO₂] at 25/20 °C. No clear species responses were found considering [CO₂] and temperature impacts, although IPR 108 seemed less sensitive to [CO₂]. Despite the changes promoted by [CO₂] and heat, the large majority of mineral ratios were kept within a range considered adequate, suggesting that this plant can maintain mineral balances in a context of climate changes and global warming.  相似文献