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排序方式: 共有96条查询结果,搜索用时 15 毫秒
1.
Abbondanzi F Campisi T Focanti M Guerra R Iacondini A 《Marine environmental research》2005,59(5):419-434
A study was conducted to determine polycyclic aromatic hydrocarbons (PAHs) distribution and microbial population changes in brackish sediments from an Italian lagoon included in the Ramsar List of Wetlands of International Importance. The presence and level of PAH-degrading bacteria were estimated by the most probable number (MPN) enumeration technique, whereas degradation capability towards target compounds was checked against loss of spiked PAHs (Phenanthrene, Anthracene and Fluoranthene) in MPN tubes after incubation in optimal conditions. Chemical analyses and microbiological counts suggested a potential for PAHs biodegradation by natural occurring populations of sediment microorganisms, thus indicating an "optimal range" in sediment PAHs concentrations, outside of which the natural selection of the indigenous microflora did not occur. The MPN procedure here described, provided an effective and reliable way to simultaneously determine microbial population densities and subsequent confirmation of the biodegradation capability of sediment indigenous microflora when exposed to laboratory and environmental concentrations of PAHs. 相似文献
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Federica Marcolini 《Mathematical Geology》2006,38(6):667-678
Fourier analysis was used in this study to help a specific determination of some Mimomys (Arvicolidae, Rodentia, Mammalia)
species. Several Pliocene and Pleistocene Central and Western European Mimomys species first lower molar contours have been
decomposed by Complex Discrete Fourier Transform. Inter- and intra-specific comparisons have been performed on the harmonics
obtained from the decomposition and some problematic specimens have been classified. 相似文献
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Massimiliano Barbolini Federica Cappabianca Fabrizio Savi 《Surveys in Geophysics》2003,24(5-6):587-601
A crucial point in any methodology for avalanche hazard assessment is the evaluation of avalanche distance exceeded probability, i.e., the annual probability that any assigned location along a given path is reached or exceeded by an avalanche. Typically this problem is faced by estimating the snow volume in the starting zone that is likely to accumulate an average every T years by statistical analysis of snowfall record, and then using this volume as input to an appropriately calibrated avalanche dynamics model to determine the runout distancesfor this design event. This methodology identifies the areas that canbe affected by an avalanche for the considered value of the return period (i.e. the average interval of time for a certain event to repeat itself), ¯T. However, it does not allow us to evaluate the actual avalanche encounter probability for any given point in the runout zone. In the present work this probability is computed by numerical integration of the expression P(x) = ∫0 ∞ P*(V)f(V) dV, where f is the probabilitydensity function (PDF) of the avalanche release volume V, and P* is the probability of the point x being reached or passed by an avalanche if the release volume is V; this latter probability is calculated by avalanche dynamics simulations. The procedure is implemented using a one-dimensional hydraulic-continuum avalanche dynamic model, calibrated on data from different Italian Alpine ranges, and is applied to a real world hazard mapping problem. 相似文献
6.
Pressure-Dependence of Rare Earth Element Distribution in Amphibolite- and Granulite- Grade Garnets. A LA-ICP-MS Study 总被引:4,自引:0,他引:4
Fernando Bea Pilar Montero Giorgio Garuti Federica Zacharini 《Geostandards and Geoanalytical Research》1997,21(2):253-270
Using an excimer (KrF) laser ablation ICP-MS system, we studied the distribution of REE in garnets from metapelites and metabasites from Ivrea-Verbano (Western Alps, Italy) and from the Peña Negra Anatectic Complex (Central Iberia), finding systematic variations that correlate well with the metamorphic grade. Chondrite-normalized REE patterns of garnets from amphibolite-grade metapelites have lower-than-chondrite levels from La to Sm, a very small or no Eu anomaly, and a steep rise in the abundance of heavy REE as the atomic number increases. Metapelitic garnets from the amphibolite-granulite transition have a marked Eu negative anomaly and are enriched in MREE such that Sm is 10-15 times chondrite and the pattern is almost flat from Dy to Yb-Lu. In garnets from granulite-grade metapelites, the intensity of the Eu anomaly and the relative concentration of Nd, Sm, Gd and Tb increase, with almost flat chondrite-normalized patterns from Sm to Lu. Garnets from mafic granulites are remarkably similar to those of metapelitic garnets equilibrated at the same pressure, except for the Eu anomaly. The apparent paradox of enhanced uptake of larger REE ions with increasing pressure is attributed to the 3M2+ 2REE3++ vacancy substitution, which produces a net decrease in the dimensions of the unit-cell of garnet. Variations in REE patterns depend essentially on the pressure and have little dependence on either temperature, bulk-composition of garnet, or REE whole-rock composition, so they could represent a new approach for geobarometric studies. The best numerical parameter to express pressure-related variations of REE distribution in garnets is the Gd/Dy ratio which does not seem perceptibly affected by disequilibrium partitioning. The regression equation between GASP pressure and the average Gd/Dygarnet is P = 3.6 + 5.6 Gd/Dy. This equation seems to be reliable for garnets: (1)equilibrated within a pressure range of 4-9 kbar, (2) coexisting with modal monazite; and (3) with unit-cell dimensions under 11.46 Å. 相似文献
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Carlos M. Alonso-Hernández Fabio Conte Cristina Misic Mattia Barsanti Miguel Gómez-Batista Misael Díaz-Asencio Anabella Covazzi-Harriague Federica G. Pannacciulli 《Continental Shelf Research》2011,31(7-8):749-757
The main environmental features of the Gulf of Batabanó, Cuba, Caribbean, were investigated through the analyses of surface sediments collected at 23 sites. In order to highlight the potential threats affecting the sedimentary compartment of this area, samples were analysed for: granulometry, mineralogy, heavy metals concentration (As, Cd, Cu, Mn, Ni, Pb, Zn), organic carbon, total nitrogen and radionuclides. Findings were compared with published data and “grey” literature.Results showed: granulometric homogeneity and a widespread carbonatic condition all over the gulf, probably due to stable bathymetry and lack of terrigenous input (except for the La Coloma basin); a rather pristine environment for what concerns heavy metals pollution, except for La Coloma where a large arsenic input was recorded; very low levels of natural and artificial radioactivity; a relevant quantity of sedimentary organic matter, providing biota with useful substrate for feeding and enhancing the food-web development while indirectly supplying lobster fisheries. Combined data highlighted the impact of the Dique Sur in reducing terrigenous input in the coastal area.Future studies should focus on dating of sediment cores for identifying and quantifying the changes acting in the gulf and on investigating the origins of the large arsenic input to La Coloma. 相似文献
10.
Angela Marinoni Paolo Laj Pierre Alexandre Deveau Federica Marino Grazia Ghermandi Fabien Aulagnier Hlne Cachier 《Atmospheric Research》2005,74(1-4):565-580
The physical and chemical properties of aerosol particles were investigated at Plan d'Aups, one of the ESCOMPTE sites located in the St. Baume mountain area (700 m a.s.l.), 50 km east of Marseilles (France). The site is ideally located for assessing the vertical and horizontal extent of the pollution plume from the Marseilles–Berre area.Our study showed that polluted air masses from the Marseilles–Berre area are advected to Plan d'Aups in the early afternoon. Average daily concentration of particles reaches up to 40 μg m−3 while 1-h average particle number concentration is greater than 30,000 cm−3. Most of the particle mass is composed of SO42− and organic carbon (OC). The chemical properties of the particles revealed that an additional source, possibly from the industrial area of Gardanne, contributes to the aerosol mass. This last source is characterised by significant emissions of elements, such as Zn, V, Al and Si.In addition to transport, we found that gas-to-particle conversion takes place at the interface between the free troposphere and the boundary layer. We estimated that on average, 30% of the particle number is accounted for by direct nucleation. This is potentially a major aerosol source to the free troposphere. 相似文献