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M. J. Matias J. M. Marques P. Figueiredo M. J. Basto M. M. Abreu P. M. Carreira C. Ribeiro A. Flambó J. Feliciano E. M. Vicente 《Environmental Geology》2009,56(6):1227-1235
Santa Margarida Military Camp (S.M.M.C.) is the only one Portuguese military training area, including firing ranges for tactical
military manoeuvres of mechanised divisions. For this reason, various negative effects on the environment were expected due
to the military activities, as the Military Camp’s area is classified as a high vulnerability area to pollution of its multilayer
porous aquifers. The aim of this study was to identify and characterise local/regional geochemical impacts caused by the continuing
military training activities performed at S.M.M.C. in the course of 52 years. An overview of the geochemical research issues
as a basis for risk assessment is presented. A special attention has been put on the quality of local and regional surface
waters, shallow groundwaters and groundwaters. Local soils and sediments as well as fragments of shells and bullets were sampled
and analysed. The results so far obtained, indicated that none pollution effects were a consequence of the military training
activities. Till now, the geochemical signatures such as, high levels of K, Cl and NO3 in waters, detected in particular sites, should be faced as tracers of diffuse pollution ascribed to urban waste disposal
and cattle breading. 相似文献
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An integrated methodology for evaluation of overwash vulnerability is developed with respect to the historical washover evolution
of a barrier island system. Three different aspects of overwash are addressed in the vulnerability indices developed: overwashed
shoreline ratio, maximum overwash intrusion recurrence, and complete barrier overwash. The indices were applied to the barriers
in the Ria Formosa system in Southern Portugal using an aerial photography catalogue covering the period 1947–2001. Historical
trends of washover evolution were observed to be different between the barriers analysed, but generally, there was a decrease
in washover number and dimensions throughout the analysed period. The final overwash diagnostic obtained allowed an integrated
overwash vulnerability rating to be defined for each barrier, with vulnerabilities ranging from low to extreme. The methodology
has produced results that may assist coastal managers with information concerning barrier island system overwash hazard, define
the temporal and geographical distributions of overwash, and provide indications as to where overwash is most likely to occur
in the future. 相似文献
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After living one of the most intense metal price cycles, several ongoing macroeconomic phenomena with the potential of structurally redefining the long-run supply and demand for metals, and raising divergency regarding where the metal prices are trending, it is suitable to evaluate the dynamics in the metal prices, especially focus on the long cyclical components. This article studies in detail the cyclical components of the real prices of base metals, iron ore, and gold, applying band-pass filters and a novel decomposition over time series with length as far as 1800. The main findings are: (1) the long cyclical components in real prices are highly correlated among them and with the proposed long economic cycles, (2) short and medium cyclical components are more relevant in explaining the price deviations from their trend, but the long cyclical component is not negligible, (3) co-movement in base metals is strong for all the cyclical components, but decreasing as cyclical frequency increases, and (4) prices are either sideways or upward-trending depending on the assumptions for correction of the US Consumer Price Index, which suggests that the supply side of these industries, in the best case, only offset the cost increases by depletion.
相似文献25.
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Matthew McQuinn Adam Lidz Matias Zaldarriaga Lars Hernquist Suvendra Dutta 《Monthly notices of the Royal Astronomical Society》2008,388(3):1101-1110
We show that near-infrared observations of the red side of the Lyα line from a single gamma-ray burst (GRB) afterglow cannot be used to constrain the global neutral fraction of the intergalactic medium (IGM), , at the GRB's redshift to better than . Some GRB sightlines will encounter more neutral hydrogen than others at fixed owing to the patchiness of reionization. GRBs during the epoch of reionization will often bear no discernible signature of a neutral IGM in their afterglow spectra. We discuss the constraints on from the z = 6.3 burst, GRB050904, and quantify the probability of detecting a neutral IGM using future spectroscopic observations of high-redshift, near-infrared GRB afterglows. Assuming an observation with signal-to-noise ratio similar to the Subaru FOCAS spectrum of GRB050904 and that the column density distribution of damped Lyα absorbers is the same as measured at lower redshifts, a GRB from an epoch when can be used to detect a partly neutral IGM at 97 per cent confidence level ≈10 per cent of the time (and, for an observation with three times the sensitivity, ≈30 per cent of the time). 相似文献
27.
Archaeological indications near Mugardos (Ferrol, NW Spain) suggest the existence of a Roman settlement. In fact, in the area were found pavements, walls with north-south and east-west orientations and some structures that endured heating. These remains are covered by soil, more than 1 m thick, and lie over schists. In order to determine the archaeological potential of the area and to delimit future excavations a geophysical survey, consisting of a joint resistivity and magnetic survey, was planned and carried out. The square array of electrodes was used and the data are discussed as apparent square array resistivity maps and azimuthal inhomogeneity ratio (AIR) maps. The magnetic survey included total field measurements using sensor heights of 0.30 and 2.30 m above the ground, so that a magnetic gradient could be computed.A combined interpretation of both resistivity and magnetic data is discussed. Later excavations have confirmed the geophysical interpretation. 相似文献
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González-Fernández A. Córdoba D. Matias L.M. Torné M. 《Marine Geophysical Researches》2001,22(3):207-223
The sedimentary structure in the Gulf of Cadiz has been extensively studied by oil exploration companies. However, up to now
little is known about its deep crustal structure. Moreover, the total thickness of the sedimentary layers remains unknown
in large areas. The purpose of this paper is the crustal-scale interpretation of deep seismic near-vertical reflection and
refraction/wide-angle reflection data obtained during the IAM (Iberian Atlantic Margins) project, carried out in 1993. Our
results indicate that a continental type crust is underlying the entire Gulf of Cadiz, with progressive thinning from east
to west. The sedimentary cover shows a great thickness, reaching 8 km in the center of the Gulf. Three main sedimentary units
can be recognized: Jurassic-Cretaceous calcareous rocks, continuation of Algarve outcrops; the Allochthonous Units of Guadalquivir/Gulf
of Cadiz, the offshore continuation of the inland Carmona nappe; and sub-horizontal post-Miocene marine sediments. The crystalline
crust is divided into three main layers: the upper crust is characterized by P-wave velocity values of 5.7–6.1 km/s; the middle
crust shows values of 6.3–6.4 km/s; the lower crust has a mean vertical velocity gradient of 0.02 km/s/km, with velocities
between 6.9 to 7.1 km/s. The total crustal thickness varies from 27 km for the eastern part of the studied area, to 20 km
for the westernmost part. The crustal thinning is more pronounced in a N-S direction than in an E-W direction. No major structures
related with a defined Iberia-Africa plate boundary could be found.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献