Spartina densiflora demonstrates high tolerance to phenanthrene in soil and reduces it concentration     

Redondo-Gómez S  Andrades-Moreno L  Parra R  Valera-Burgos J  Real M  Mateos-Naranjo E  Cox L  Cornejo J 《Marine pollution bulletin》2011,62(8):1800-1808

The present study was conducted to investigate the tolerance of Spartina densiflora to phenanthrene, and to test its ability in phenanthrene dissipation. A glasshouse experiment was designed to investigate the effect of phenanthrene from 0 to 1000 mg kg⁻¹ on growth and photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters, gas exchange and photosynthetic pigments. We also performed chemical analysis of plant samples, and determined the concentration of phenanthrene remaining in soil. S. densiflora survived to concentrations as high as 1000 mg kg⁻¹ phenanthrene in soil; in fact, there was no significant difference in RGR among the treatments after 30 days. Otherwise, phenanthrene affected photosynthetic apparatus at 100 and 1000 mg kg⁻¹; thus, the lower Φ_PSII could be explained by the declined photosynthetic pigment concentrations. Soil extraction indicated a more marked rate of phenanthrene disappearance in the soil in the presence of S. densiflora.  相似文献   

Groundwater salinization in the Azores archipelago (Portugal)   总被引：1，自引：1，他引：0  

J. Virgílio Cruz  Rui Coutinho  Dina Pacheco  Raquel Cymbron  Paulo Antunes  Pedro Freire  Sandra Mendes 《Environmental Earth Sciences》2011,62(6):1273-1285

Groundwater salinization in coastal regions causes severe constraints to water supply and economic losses to society worldwide. In the Azores archipelago, groundwater abstraction in wells drilled in coastal aquifers is very important for water supply, and quality problems have been reported. Therefore, a groundwater chemistry dataset from wells was compiled to study groundwater salinization in these aquifers. Waters are mainly of the Na–Cl type, presenting a slightly acidic to slightly alkaline character, with a pH between 5.63 and 8.50 (median 7.40). Electrical conductivity measurements range from 127 to 9,670 μS/cm (median 862), suggesting highly variable mineralization, with higher values observed on Santa Maria, São Miguel, Pico, Graciosa, and São Jorge islands. The major-ion composition reflects the contribution of seawater to the groundwater compositional evolution, which is essentially explained by seawater intrusion into wells. In many samples, exchange reactions of Na⁺ + K⁺ for Ca²⁺ + Mg²⁺ are associated with salinization. The seawater fraction in groundwater composition reaches a maximum of 22.5%. These results are extremely challenging to water managers in the Azores because failure to comply with national water quality regulations and with European Union groundwater directive requirements often occurs.  相似文献   

On the Effect of Thermally Induced Stresses in Failures of Some Rock Slopes in Rio de Janeiro, Brazil   总被引：1，自引：0，他引：1  

Euripedes do Amaral Vargas Jr.  Raquel Quadros Velloso  Leonardo Erik Chávez  Luiz Gusmão  Claudio Palmeiro do Amaral 《Rock Mechanics and Rock Engineering》2013,46(1):123-134

Previous studies have indicated that many rock slope failures in Rio de Janeiro, Brazil, occur during relatively dry periods when there is little, if any, rainfall. In the present paper, we describe these events and propose possible mechanisms for their occurrence. It is believed that daily fluctuations in temperature may create thermally induced stresses of enough magnitude to propagate fractures already existing in the rock mass. Laboratory experiments were conducted in order to measure temperature variations in a fractured rock system. Using the experimentally obtained data, we carried out numerical analyses in order to verify whether temperature-related stresses were indeed able to propagate fractures existing in the rock mass. The results obtained indicate that cycles of temperature change over time, especially during the colder months of the year can indeed create stress conditions in the rock mass able to propagate existing non-persistent joints, and ultimately lead to failure of the rock slope.  相似文献   

Paying as the urban areas grow – implementing and managing urban development charges using a GIS application     

Jorge Baptista e Silva  Raquel Faria de Deus  José António Tenedório 《International journal of geographical information science》2013,27(9):1689-1705

Urban development charges (UDC) are considered relevant taxation instruments that can improve the economic sustainability of urban areas and the financial health of the respective local governments. The economic formulation and justification based on the ‘direct benefit principle,’ the ‘accountability principle,’ and the ‘proportionality principle’ requires a methodology that can be supported by a geographic information system (GIS) application. This article presents the research output of a real case study – the municipality of Aljezur, Portugal – and the fundamentals of the GIS tool that was designed. This GIS-based methodology comprises a multi-annual infrastructure capital plan and an accurate zoning map for spatial differentiation of values combining municipal-wide and site-specific approaches, following ‘pay as the urban areas grow’ perspective applied to urban development and new buildings. It requires data integration of the urban planning process with infrastructure and urban growth data in order to manage and monitor the computation of this charge over time, thereby increasing the accuracy, the objectivity and the clarity of the process. The results obtained show that this UDC-GIS application seems well adapted to small municipalities. Its possible replication and use in other contexts require adaptations derived from different urban and taxation policy options and from different legal, organizational, technological, and informational local systems.  相似文献   

Magnetorotational instability in stratified, weakly ionized accretion discs     

Raquel Salmeron  Mark Wardle 《Monthly notices of the Royal Astronomical Society》2003,345(3):992-1008

We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionized accretion discs, such as protostellar and quiescent dwarf novae systems. The method includes the effects of the magnetic coupling, the conductivity regime of the fluid and the strength of the magnetic field, which is initially vertical. The conductivity is treated as a tensor and is assumed to be constant with height.
We obtained solutions for the structure and growth rate of global unstable modes for different conductivity regimes, strengths of the initial magnetic field and coupling between ionized and neutral components of the fluid. The envelopes of short-wavelength perturbations are determined by the action of competing local growth rates at different heights, driven by the vertical stratification of the disc. Ambipolar diffusion perturbations peak consistently higher above the midplane than modes including Hall conductivity. For weak coupling, perturbations including the Hall effect grow faster and act over a more extended cross-section of the disc than those obtained using the ambipolar diffusion approximation.
Finally, we derived an approximate criterion for when Hall diffusion determines the growth of the magnetorotational instability. This is satisfied over a wide range of radii in protostellar discs, reducing the extent of the magnetic 'dead zone'. Even if the magnetic coupling is weak, significant accretion may occur close to the midplane, rather than in the surface regions of weakly ionized discs.  相似文献   

Radial and vertical angular momentum transport in protostellar discs     

Raquel Salmeron  Arieh Königl  Mark Wardle 《Astrophysics and Space Science》2007,311(1-3):81-85

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Anomalous heat flow belt along the continental margin of Brazil     

Hamza  Valiya M.  Vieira  Fabio P.  Silva  Raquel T. A. 《International Journal of Earth Sciences》2018,107(1):19-33

International Journal of Earth Sciences - A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB)....  相似文献   

Exploring the interactions between vulnerability,resilience and adaptation to extreme temperatures     

Nunes  Ana Raquel 《Natural Hazards》2021,109(3):2261-2293

Natural Hazards - Proposed ways of improving adaptation to climate change have most often been supported by narrowly framed and separate analysis. This article investigates how different levels of...  相似文献   

Individual and population plasticity of the seagrass Zostera noltii along a vertical intertidal gradient     

Susana Cabaço  Raquel Machás  Rui Santos 《Estuarine, Coastal and Shelf Science》2009,82(2):301-308

The seasonal plasticity of individual Zostera noltii architectural, reproductive and elemental content features, of plant epiphyte load and of meadow biomass–density relationships was investigated along a vertical intertidal gradient at Ria Formosa lagoon, southern Portugal. The vertical variability of the seagrass environment was evident in the sediment characteristics, which showed coarser grain size, less organic matter, lower N content and higher ammonium concentration in the low intertidal than in medium and high intertidal. A clear vertical differentiation in Z. noltii morphology was observed from longer and wider leaves, longer and wider internodes and shorter roots at low intertidal, to shorter and narrow leaves, shorter and narrower internodes and longer roots at high intertidal. The leaf size was negatively related to light availability and positively related to nutrient availability whereas the root size was negatively related to nutrient availability. The lower leaf N and P content found in low intertidal plants may reflect a dilution effect of the nutrients due to higher growth rates. Lower N content of low intertidal leaves supports previous findings that the nitrate reductase activity is lower in plants from this level. The higher epiphyte load observed in Z. noltii leaves of the low intertidal may be a consequence of the lower exposure period, but also of higher hydrodynamics that increase the availability of nutrients. No evidence of the influence of the intertidal level on the flowering shoot density was found. The cyclic temporal pattern of the biomass–density relationship was much wider at low and medium intertidal than at high intertidal. At low intertidal, the decline in shoot density during fall and winter was coincident with a biomass decrease and its increase in spring and summer coincided with the biomass increase. In medium and high intertidal, the biomass and density seasonal variations were decoupled. As a result, only at low intertidal there was a significant positive relationship between biomass and density. This suggests that Z. noltii population structure along the intertidal is regulated by different factors. Light is probably the most important factor regulating the population structure in the low intertidal, whereas desiccation is probably the main factor regulating the populations in upper intertidal. Zostera noltii showed a considerable plasticity at a physiological-, plant- and population-level along the intertidal zone, indicative of the species acclimation to the steep environmental gradient of this particular ecosystem.  相似文献   

Constraining the degree of the dominant mode in QQ Vir     

Andrzej Baran  John Telting  Roy Østensen  Maciej Winiarski  Marek Drożdż  Dorota Kozieł  Mike Reed  Raquel Oreiro  Roberto Silvotti  Michał Siwak  Uli Heber  Peter Papics 《Astrophysics and Space Science》2010,329(1-2):199-203

We present early results of the application of a method which uses multicolor photometry and spectroscopy for ? discrimination. This method has been successfully applied to the pulsating hot subdwarf Balloon?090100001. Here we apply the method to QQ?Vir (PG1325+101). This star was observed spectroscopically and photometrically in 2008. Details on spectroscopy can be found in Telting et al. (Astrophys. Space Sci. 2010, this volume), while photometry and preliminary results on ? discrimination are provided here. The main aim of this work was to compare the value of the ? parameter derived for the main mode in QQ?Vir to previously published values derived by using different methods.  相似文献