Impact of trace metals on denitrification in estuarine sediments of the Douro River estuary,Portugal   总被引：1，自引：0，他引：1  

Catarina Magalhães  Joana Costa  Catarina Teixeira  Adriano A. Bordalo 《Marine Chemistry》2007

Denitrification influences the nitrogen budget in estuaries by removing fixed nitrogen from the inorganic pool; rates are dependent on both geological and geographic conditions as well as increasing anthropogenic impacts. In this study the effects of copper (Cu), chromium (Cr), zinc (Zn), cadmium (Cd) and lead (Pb), on the denitrification pathway were evaluated in subtidal and intertidal sediments of the Douro River estuary. Dinitrogen, N₂O and NO₂⁻ production rates were measured in triplicate slurries of field samples under different treatments of metal concentrations. Results demonstrated that similar metal amendments led to different site responses for denitrification, suggesting that variations in sediment properties (metal concentrations, grain size, organic matter content, etc.) and/or differences in denitrifying community tolerance modulate the level of metal toxicity. Denitrifying communities in subtidal muddy sediments were not affected by increasing concentrations of metals. In contrast, intertidal sandy sites revealed high sensitivity to almost all trace metals tested; almost complete inhibition by Cr (95%) and Cu (85%) was observed for 98 and 79 μg per gram of wet sediment respectively, and by Zn (92%) at the highest concentration added (490 μg per gram of wet sediment). Moreover, the addition of trace metals stimulated N₂O and NO₂⁻ accumulation in intertidal sandy (Zn, Cu, Cr and Cd) and muddy sediments (Cu and Zn), demonstrating a pronounced inhibitory effect on specific steps within the denitrification enzymatic system. In summary, the results obtained suggest that, according to the type of estuarine sediment, trace metals cannot only reduce total N removal from an estuary via denitrification but also can enhance the release of N₂O, a powerful greenhouse gas.  相似文献   

Long-Term Changes in Abundance of Yellowfin and Skipjack off the Coast of Angola     

de Campos Rosado  J. M. 《ICES Journal of Marine Science》1971,34(1):65-75

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Galaxy number counts – V. Ultradeep counts: the Herschel and Hubble Deep Fields     

N. Metcalfe  T. Shanks  A. Campos  H. J. McCracken †  R. Fong 《Monthly notices of the Royal Astronomical Society》2001,323(4):795-830

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Validation of Arenicola marina in field toxicity bioassays using benthic cages: biomarkers as tools for assessing sediment quality     

Ramos-Gómez J  Martins M  Raimundo J  Vale C  Martín-Díaz ML  DelValls TA 《Marine pollution bulletin》2011,62(7):1538-1549

Sediment toxicity assessments using caged organisms present advantages over using laboratory and native community studies. The use of caged Arenicola marina in sediment toxicity assessments was evaluated. Lugworms were exposed in situ to sediments from coastal and port areas in Spain for seven days, and the activities of the biotransformation enzymes ethoxyresorufin O-deethylase, dibenzylfluorescein dealkylase and glutathione S-transferase, the activities of the antioxidant enzymes glutathione reductase and glutathione peroxidase and lipid peroxidation were then analyzed as biomarkers. Biomarker results and sediment physicochemical data were integrated. Cádiz Bay (SW Spain) sediments presented metal contamination that was not linked to a biochemical response. In LPGC Port (SW Spain), Pb contamination exhibited a moderate toxic potential, while PAHs, and presumably pharmaceuticals, provoked biochemical responses that efficiently prevented lipid peroxidation. In Santander Bay (N Spain), exposure to PAHs and, presumably, pharmaceuticals induced biomarker responses, but lipid peroxidation occurred nevertheless. These results indicated that caged A. marina were effective for the assessment of sediment quality and that the selected biomarkers were sufficiently sensitive to identify chemical exposure and toxicity.  相似文献   

Instrumental and digital coronagraphy for the observation of the Uranus satellites’ upcoming mutual events     

M. Assafin  R.P. Campos  D.N. da Silva Neto  A.H. Andrei 《Planetary and Space Science》2008,56(14):1882-1887

Ground-based observations of faint satellites nearby their planets with 1-2 m class telescopes usually do not allow for high quality astrometry and photometry, due to saturation by the primary or to poor S/N ratio on the satellite images, generally embedded on the scattered light of the planet. Earth-based observations of the Uranus satellites’ upcoming mutual events in 2007-2008 are no exception. In most cases, the event will take place at 4 arcs or less from the planet, with “planet minus satellite” brightness differences of 10 magnitudes. So as to make feasible the observations of these important phenomena, we have developed a prototype of a coronagraph of simple design making use of good quality commercial optical systems. Pilot tests made with this coronagraph with a telescope of show that it is possible to obtain S/N ratios of 50 or higher for 10 s exposures, for satellites as close as 2 Uranus radii from the planet center. We have also developed numerical algorithms which perform digital coronagraphy in the images, with the elimination of the influence of the planets’ scattered light. This procedure considerably improves the S/N ratio of the satellite images (with or without a coronagraph instrument) and shall be applied in the reduction of the observations of the Uranus events so as to achieve the highest possible photometric and astrometric quality.  相似文献   

Mapping Soils,Vegetation, and Landforms: An Integrative Physical Geography Field Experience*   总被引：2，自引：0，他引：2  

Joseph P. Hupy  Stephen P. Aldrich  Randall J. Schaetzl  Pariwate Varnakovida  Eugenio Y. Arima  Juliegh R. Bookout  Narumon Wiangwang  Annalie L. Campos  Kevin P. McKnight 《The Professional geographer》2005,57(3):438-451

Students in a graduate seminar at Michigan State University produced a series of detailed vegetation, soils, and landform maps of a 1.5‐square‐mile (3.9 km²) study area in southwest Lower Michigan. The learning outcomes (maps) and skill development objectives (sampling strategies and various GIS applications) of this field‐intensive mapping experience were driven by the assumption that students learn and understand relationships among physical landscape variables better by mapping them than they would in a classroom‐based experience. The group‐based, problem‐solving format was also intended to foster collaboration and camaraderie. The study area lies within a complex, interlobate moraine. Fieldwork involved mapping in groups of two or three, as well as soil and vegetation sampling. Spatial data products assembled and used in the project included topographic maps, a digital elevation model (DEM), aerial photographs, and NRCS (National Resource Conservation Service) soil maps. Most of the soils are dry and sandy, with the main differentiating characteristic being the amount of, and depth to, subsurface clay bands (lamellae) or gravelly zones. The presettlement (early 1830s) vegetation of the area was oak forest, oak savanna, and black oak “barrens.” Upland sites currently support closed forests of white, black, and red oak, with a red maple, dogwood, and sassafras understory. Ecological data suggest that these oak forests will, barring major disturbance, become increasingly dominated by red maple. This group‐based, problem‐solving approach to physical geography education has several advantages over traditional classroom‐based teaching and could also be successfully applied in other, field‐related disciplines.  相似文献   

Reply to ��Comment on Sousa, M.L. and Costa, A.C., ��ground-motion scenarios consistent with probabilistic seismic hazard disaggregation analysis. Application to Mainland Portugal��?�� by Jo?o F. B. D. Fonseca and Susana P. Vilanova     

Maria Lu��sa Sousa  Alfredo Campos Costa 《Bulletin of Earthquake Engineering》2011,9(4):1297-1307

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The effect of carbon steel-wool in removal of arsenic from drinking water     

V. Campos 《Environmental Geology》2002,42(1):81-82

. This paper attempts to prove that the removal of arsenic in drinking water is a combination of the granular activated carbon and carbon steel-wool. The steel-wool filter is the most important in residential applications. The single most important consideration is the empty bed contact time. Removal of inorganic arsenic to parts per million (ppm) or parts per billion (ppb) levels within 15 to 30 min is fairly common. Immobilization techniques are likely to continue to gain importance in the world.  相似文献   

Diagenesis of English Lower Jurassic limestones as inferred from oxygen and carbon isotope analysis     

H.S. Campos  A. Hallam 《Earth and Planetary Science Letters》1979,45(1):23-31

Fifty-seven samples of mostly Liassic limestones and calcite spar were subjected to mass spectrometer analysis to determine δ¹³C and δ¹⁸O. The results are used to compare and interpret the changing isotopic composition through time of calcite-precipitating pore fluids and to assess the influence of rate and type of sedimentation, diagenetic reactions and meteoric water influx. In general microsparite beds and concretions formed sooner after deposition in Dorset than in Yorkshire, where sedimentation rates were usually higher. Calcite horizons in the Bridport Sands Formation of Dorset are entirely diagenetic in origin. Carbon isotope data from concretions in the Jet Rock Formation of Yorkshire support a model of changing organic reactions with increasing depth of burial. The influence of meteoric waters is substantially restricted to the formation of post-Liassic veins.  相似文献   

Overheated, Cu-bearing magmas in the Zaldívar porphyry-Cu deposit, Northern Chile. Geodynamic consequences     

E. Campos  J. L. R. Touret  I. Nikogosian  J. Delgado 《Tectonophysics》2002,345(1-4)

The Zaldívar porphyry copper deposit, Northern Chile, consists of two major intrusions, the 290 Ma Zaldívar, and the more recent Miocene (38.7 Ma) Llamo porphyry. Five types of inclusions have been identified in quartz phenocrysts from Llamo porphyry, including melt inclusions (M), and four types of fluid inclusions, called MS (multi solids), B (brines), G (vapor-rich) and W (aqueous), respectively.Melt remnants, well preserved as M-inclusions, homogenize around 1000 °C. They show a rhyolitic composition, comparable to the most evolved acidic rhyolitic end member found elsewhere in the regional magmatism and to worldwide volcanic rhyolitic glass. High silica content in some inclusions can, however, be due to partial remelting of the quartz host during the heating run. Copper content in the same inclusions ranges between 0.03 and 0.57 wt.%, with an average concentration of 0.10 wt.%, suggesting a major magmatic source for the copper (orthomagmatic model).MS inclusions, which contain a number of solids at room temperature, mostly H₂O-bearing phases (system NaCl–KCl–((Fe, Mg, Cu)Cl)–H₂O, average salinity 70 wt.% NaCl equiv.), homogenize at magmatic temperatures (around 1000 °C). They represent the first fluids to have exsolved from the magma at depth, at a pressure of about 2 kbar. Their high homogenization temperature, comparable to values measured for melt inclusions (1000 to 1050 °C), may indicate trapping of MS and M inclusions in host phenocrysts from an immiscible mixture of silicate melt and highly saline fluids expelled from the magma during the early stage of quartz crystallization.The data indicate a magmatic origin for copper, as well as extremely high melt temperatures. These features are interpreted by magmatic differentiation of mantle-derived primitive melts, corresponding to major changes in the tectonic regime of the Andean margin, which occurred in Miocene times.  相似文献