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At present, there is a very limited information on the levels and distribution of dissolved metals in Manila Bay. In this study, the horizontal and vertical distribution of operationally defined species (labile, bound and total) of dissolved copper (Cu), cadmium (Cd) and zinc (Zn) were determined using differential pulse anodic and cathodic stripping voltammetry in water samples obtained from 18 stations in November 1998. In addition, the 24-h variability in the concentrations of these species at different depths in the water column was determined. These measurements were complemented by the determination of temperature, salinity, dissolved oxygen, chlorophyll a, particulate organic carbon and nutrients. Results showed that more than 50% of total dissolved copper and cadmium were labile while 50% of total dissolved zinc was organically bound. Vertical profiles showed that Cu, Cd and Zn concentrations were generally high at the surface. Zinc and cadmium were characterised by the presence of a mid-depth minimum while copper did not show any clear vertical trend.
Dissolved Cu concentrations during the spatial and diurnal samplings ranged from 0.32 to 6.95 nM and 1.52 to 45.65 nM, respectively. For Cd, the concentrations in 18 stations ranged from 0.05 to 2.92 nM, and from 0.03 to 2.42 nM over a 24-h period. Zn concentrations ranged from 2.48 to 147.43 nM and 2.87 to 88.27 nM during the spatial and diurnal samplings, respectively. The large variation in the concentration of Cu, Cd and Zn in the bay was observed to be associated with the presence of a large vertical density gradient in the water column, which appeared to limit the exchange of materials between the surface and bottom waters. Elevated levels of these metals near point sources suggest anthropogenic inputs in the bay. 相似文献
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F. Valera C. Díaz-Paniagua J.A. Garrido-García J. Manrique J.M. Pleguezuelos F. Suárez 《Journal of Arid Environments》2011,75(12):1342-1351
Southern Spain’s semi-arid habitats are a Mediterranean ecosystem modelled mainly by historic factors which make them unique in comparison with North African deserts. Southern Spanish vertebrates have adapted to the recent emergence of semi-arid habitats in varying degrees of success. This paper reviews the current status of these terrestrial vertebrates (amphibians, reptiles, birds and mammals), their origins and their main features in relation to this biogeographic area. The vertebrate fauna of the semi-arid southeast of the Iberian peninsula differs widely from the one in the semi-arid Maghreb mainly because the former is composed by generalist vertebrates and much less so by species adapted to arid conditions. Moreover, a large fraction of the vertebrates in the semi-arid Iberia does not exploit the semi-arid areas but depends on riparian and human-managed habitats. The species diversity is rather low since only a small fraction of Palaearctic, European or Mediterranean species can adapt to the ecological limitations imposed by aridity and dwell in these semi-arid habitats. Such adaptations comprehend features like trophic plasticity, low morphological specialization, high dispersal ability, shortened life cycles and behavioural mechanisms to exploit the limited resources available. This paper identifies major conservation issues and proposes specific courses of action. 相似文献
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Juan-Luis Valera Ana-María Negredo Antonio Villaseñor 《Pure and Applied Geophysics》2008,165(8):1683-1706
Convective removal and mantle delamination are geodynamical mechanisms proposed to explain the presence of extension in the
Alboran Sea within a regional context of compression. Using a new thermo-mechanical algorithm, we present here a quantitative
evaluation and comparison of conceptual models based on these geodynamical mechanisms. In contrast to the in situ convective removal process, the laterally propagating delamination mechanism is shown here to be consistent with first-order
features of the Alboran Sea such as the thinning/thickening distribution, intermediate-depth seismicity and upper mantle structure
imaged by seismic tomography. The lower crust is predicted to reach depths of 100–150 km in some areas, due to mechanically-driven
viscous drag of the downwelling mantle. 相似文献
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As-Fe-Cu-Pb-Zn-Ag-Sb sulphides and sulphosalts, with native gold as a frequent accessory (locally concentrated with high values) are the ore minerals of a deposit occurring in a Silurian volcanosedimentary sequence, either as concordant bedded orebodies, or as discordant veins and split fillings at the contact between shales and lamprophyres of the late Hercynian magmatism. Scheelite, mainly bound to acid metavolcanics, is occasionally scattered as isolated grains in the sulphides. The local geological setting together with correlations with other deposits occurring along the same regionally distributed Lower Paleozoic sequence, permit the proposal of the following scheme for the origin and evolution of the Baccu Locci Au-bearing mineral deposit: (1) Base-metal sulphide deposition, with gold, in the Silurian volcanosedimentary sequence: protore. (2) Hercynian tectonometamorphic activity, accompanied by multiphase ore mobilization and concentration processes, stratabound. (3) Hercynian magmatism, locally represented by lamprophyre dikes and by the effects of multiphase hydrothermal activity: ore mobilization and redeposition. 相似文献
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R. A. Burenin R. A. Sunyaev M. N. Pavlinsky D. V. Denisenko O. V. Terekhov A. Yu. Tkachenko Z. Aslan I. Khamitov K. Uluch M. A. Alpar U. Kiziloglu A. Baikal I. F. Bikmaev N. R. Sakhibullin V. F. Suleymanov 《Astronomy Letters》2003,29(9):573-578
We describe the first results of our observations of the exceptionally bright optical afterglow from the cosmic gamma-ray burst (GRB) of March 29, 2003 (030329), with the 1.5-m Russian-Turkish telescope (RTT150) installed at the TUBITAK National Observatory (Turkey) at Mount Bakyrlytepe. RTT150 was one of the first medium-class telescopes pointed at the afterglow. The observations began as early as about six hours after the GRB. During the first five hours of our observations, the BV RI flux fell off exactly as a power law with the same slope ?1.19±0.01. Subsequently, in all of the BV RI bands, we observed the same increase in the power-law slope of the light curve to a value that was later recorded during the observations at observatories in the western hemisphere. The break in the power-law light curve occurs at t ? t 0 ≈ 0.57 days (13.5 h) and lasts for about 0.2 days. Apart from this smooth decrease in the flux, the afterglow exhibited no flux variability. The upper limits on the variability are 10–1% on time scales of 0.1–1000 s, respectively. The BV RI spectral flux distribution during the first night of our observations closely corresponds to a power-law spectrum with a spectral index α=0.66±0.01. The change in the power-law slope of the light curve at the end of our observations is probably attributable to the deceleration of the ultrarelativistic jet to a gamma factor when its structural features begin to show up in the light curve. The radio, optical, and X-ray broadband spectrum is consistent with the assumption about the synchrotron radiation of the ultrarelativistic jet. This unique object continues to be observed with RTT150. 相似文献
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Studies on breeding parameters in peripheral populations have been centred on species with stable or regressive ranges. However, the studies on peripheral expanding populations are few, probably due to the scarcity of suitable models. On the other hand, islands are a sort of peripheral populations with their own rules. By using an arid-land passerine, the Trumpeter Finch, we compare the clutch size between two peripheral populations, one in expansion located in south-eastern Iberian Peninsula, another located in Fuerteventura, Canary Islands, with the clutch size of their presumably source population, Northwest Africa. We did not find differences in clutch size between continental peripheral population nor island one compared with North African one. We also present other breeding parameters including incubation period, hatching rate, nestling period, fledgling rate and productivity in both peripheral populations. 相似文献
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D. Cicchella S. Albanese B. De Vivo E. Dinelli L. Giaccio A. Lima P. Valera 《Journal of Geochemical Exploration》2010
Microbiological studies have always had an important role in the evaluation of drinking water quality. However, since geological processes are the most important factors controlling the source and distribution of chemical elements in natural waters, the importance of geochemical data must not be underestimated. This study presents data on pH, conductivity and concentrations of 69 elements and ions (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, Zr, Br−, HCO3−, Cl−, F−, NH4+, NO2−, NO3−, PO43−, SO42−, SiO2) from 186 bottled mineral waters of 158 different Italian name brands. Analyses show a large range in concentrations for most of these elements, with variations up to four orders of magnitude. Our data demonstrate that some elements (such as Be), generally considered unlikely to occur, can instead reach surprisingly high levels in drinking water, and also how packaging can release some trace elements to the bottled water. Data analysis shows that the implementation of an international database of bottled water geochemistry and of potential toxicological effects is of paramount importance to provide a robust data set which would be useful to set international action levels and guidelines to secure bottled water quality, whose consumption has steadily increased in the recent years. A new formula to calculate nitrate and nitrite tolerable concentration levels in waters intended for human consumption is proposed, to take into account that about 5% of dietary nitrate in humans is converted to nitrite. 相似文献