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Lourdes López-Merino Antonio Martínez Cortizas José Antonio López-Sáez 《Quaternary Science Reviews》2011,30(19-20):2745-2754
Wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles. Knowledge of their long-term ecology is essential for a proper understanding of these valuable ecosystems. We present the application of multi-proxy analyses to a 115 cm-thick core from La Molina mire (Alto de la Espina) located in NW Iberia, with a chronology spanning since ～500 BC. The mire is located in an area intensively mined for gold during the Roman period, and close to a water-canalization system used for mining operations at that time. Our aim was to get insights into the development of the wetland by combining palynological records of hydro-hygrophytes, non-pollen palynomorphs and geochemical analyses, supported by 14C datings and multivariate statistics. The results indicate a complex pattern of ecological succession. During the local Iron Age the wetland was minerotrophic. Since ～20 AD it was subjected to dramatic hydrological changes due to a rise of the water-table, fluctuating between the presence of open water and phases of drawdown. Finally, by ～745 AD, the wetland experienced a rapid evolution towards ombrotrophic conditions. High grazing pressure was detected for the last decades. The significant change occurred during Early Roman Empire seems to have been the consequence of the direct use of the wetland as a water-reservoir of the canalisation system used for gold-mining. Thus, the current nature of the mire may be the result of human impact, although multiple human- and climate-induced causes were potentially linked to the detected shifts. However, the system seems to have been resilient, successfully buffering the changes without substantial alterations of its functioning. Our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems, their long-term ecology and the role of human-induced changes. 相似文献
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Carmen Lourdes Yupanqui Zaa Joan E. McLean R. Ryan Dupont Jeanette M. Norton Darwin L. Sorensen 《Ground Water Monitoring & Remediation》2010,30(1):46-57
Dehalorespiration bioremediation has been considered for chlorinated compound removal from two trichloroethene contaminated groundwater plumes in the OU 5 area of Hill Air Force Base, Utah. The distributions and population densities of the 16S rRNA genes of Bacteria, Dehalococcoides ethenogenes, Desulfuromonas michiganensis, Geobacter spp. and Rhodoferax ferrireducens -like bacteria, as well as the functional genes trichloroethene reductive dehalogenase ( tce A) and vinyl chloride reductase ( vcr A) were determined in contaminated aquifer material samples. The influence of aquifer physical and chemical properties, including iron availability, on these distributions was evaluated. Twenty aquifer cores were collected. DNA was extracted and analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) to quantify the gene densities. Dehalococcoides population densities were low and unevenly distributed. D. michiganensis was found in 12 cores while Geobacter spp. were found in 8 cores. Rhodoferax ferrireducens -like bacteria were widely distributed. The vcr A gene distribution was relatively uniform and broad but the tce A gene was detectable in only 2 cores. Gene distribution was not related to core clusters derived from physical/chemical characteristics. 相似文献
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José I. Castillo-Manzano Mercedes Castro-Nuño Fernando González Laxe Lourdes López-Valpuesta M. Teresa Arévalo-Quijada 《Marine Policy》2009
Spanish Port Authorities currently face a wide range of complexities in their decision-making processes, as they have to satisfy several port management objectives that may conflict with one another. This paper examines these circumstances by using decision theory methodology with multiple objectives, which, through the Promethee method, makes the design of an index possible. This index combines different decision factors that shape the competitiveness of a port to rank the Spanish Port Authorities. This ranking serves as an alternative to the traditional ranking system by easily providing more information about port traffic. 相似文献
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Is there an active subduction beneath the Gibraltar orogenic arc? Constraints from Pliocene to present-day stress field 总被引：1，自引：0，他引：1
A. Pedrera A. Ruiz-Constán J. Galindo-Zaldívar A. Chalouan C. Sanz de Galdeano C. Marín-Lechado P. Ruano M. Benmakhlouf M. Akil A.C. López-Garrido A. Chabli M. Ahmamou Lourdes González-Castillo 《Journal of Geodynamics》2011
We present a new set of brittle microtectonic measurements carried out in the Pliocene and Quaternary rocks outcropping in several key sectors of the western Betic and Rif orogen, the so-called Gibraltar orogenic arc. This data set, along with available earthquake focal mechanisms and borehole breakouts, allowed us to compile the Pliocene and Quaternary stress map of this area. This map provides new constraints for tectonic models and the present-day tectonic activity of the proposed active eastward subduction of oceanic lithosphere beneath the Gibraltar Arc and roll-back. The horizontal maximum compressive stress (SHmax) is NW-SE in the Betic Orogen and N-S/NNW-SSE in the southern Rif Cordillera. There is a significant consistency between SHmax and the displacement field deduced from GPS measurements with respect to the African plate: both appear to reflect the NW-SE convergence between the African and the European plates that is perturbed in the Rif. We propose that part of the eastern Rif behaves as a quasi-rigid block welded to the stable African plate. This block is bounded by important faults that localized most of the deformation disturbing the stress and surface displacement field. Pliocene to Quaternary N-S to NW-SE Africa-Europe plate convergence seem to be associated to the reorganization of the remnant Early Miocene subduction system in a continental–continental collision framework. Three-dimensional reconstruction of available seismic tomography plotted against the intermediate seismicity shows that only part of the old subduction system, whose orientation ranges from N20°E to N100°E, remains active: the portion ranging from N30°E to N40°E, orthogonal to the regional convergence. 相似文献
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María Lourdes Jaubet María de los Ángeles Sánchez María Silvia Rivero Griselda Valeria Garaffo Eduardo Alberto Vallarino Rodolfo Elías 《Marine Ecology》2011,32(2):188-197
The rocky intertidal zone around the city of Mar del Plata (SW Atlantic, 38° S–57° W) is characterized by dense mussel beds of Brachidontes rodriguezii. This intertidal community develops on natural and artificial hard substrates, including abrasion platforms in sewage‐impacted areas. A monitoring program, designed to assess the effect of sewage discharge on intertidal macrobenthic communities, has been conducted since 1997. During the spring season of 2008, a new spionid polychaete (Boccardia proboscidea) was found near the sewage outfall, forming large biogenic reefs. This is the first report of biogenic reefs being built by a non reef‐forming spionid polychaete in areas organically impacted by sewage discharges. The aim of this work was to evaluate the spatial–temporal dynamics (% cover and density of B. proboscidea) of these reefs. These biogenic reefs covered almost the entire impacted site, reaching a density of 650,000 ind·m?2. This phenomenon is unique in that there is no other record available worldwide of any other biogenic polychaete reefs that could be sewage‐induced. The presence and stability of these biogenic reefs is discussed in relation to increased organic contamination as a structuring factor. 相似文献
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Liberto de Pablo-Galán Mari´a Lourdes Chávez-Garci´a Alfonso Huanosta Tera 《Physics and Chemistry of Minerals》1997,24(2):90-101
The electrical properties of opal-CT are validated at temperatures from 600 to 840 °C and frequencies from 5 Hz to 10 MHz.
The opals are hydrothermal, containing less than 11270 ppm total of Al, Fe, Ca, Na, and K, and from 1.17 to 17.63 wt% H2O interstitial and structural. Opal-CT shows fine crystallites, measuring from 19.4 to 22.7 μm, of an ordered tridymite-M
stratification with high-cristobalite, embedded in a non-crystalline matrix. When heated to 600 °C, the non-crystalline phase
devitrifies to the same stacked high-cristobalite-tridymite-M crystals. Opals containing less than 2070 ppm of cationic impurities
are characterized by one single high-frequency complex impedance arc corresponding to the bulk polarization of the crystalline
phase, of capacitances between 25 and 30×10−12 F and resistances from 132 to 890 ohm. Opals having over 6300 ppm of cationic impurities show two superimposed high- and
low-frequency complex impedance arcs. The high-frequency arc corresponds to the bulk polarization of the crystalline phase,
of capacitance between 8 and 15.7×10−12 F and resistance from 14 to 236 ohm, less than the capacitance of 0.25 to 0.53×10−9 F and resistance from 26 to 360 ohm of the non-crystalline minor intergranular material represented by the low-frequency
impedance arc. The electric module shows one single vertex, ascribed to the bulk polarization of the crystalline phase. The
conductivities are from 10−7 to 10−4 ohm−1cm−1, in the range of poor ionic conductors, essentially constant below 1.8 kHz, rapidly increasing at higher frequencies, due
to ionic and electronic charge carriers. The activation energy changes between 0.905 and 1.003 eV for the conduction mechanism
in the crystalline phase and from 0.924 to 1.087 eV in the non-crystaline phase. X-ray diffraction and impedance spectroscopy
confirm that opal-CT is a crystalline stacked sequence of tridymite-M and cristobalite-high, in a non-crystalline matrix.
Received October 20, 1995/Revised, accepted June 15, 1996 相似文献
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Antonio Martínez Cortizas Lourdes López-Merino Richard Bindler Timothy Mighall Malin Kylander 《Journal of Paleolimnology》2013,50(1):71-86
Extensive mining took place in Spain during the Iron Age and Roman times, although a detailed chronology is still lacking due to the inherent difficulties in dating mining structures. In this study we sampled and analyzed a core from La Molina mire in the Asturias region, northern Spain. Because more than 100 Roman mines have thus far been found within 20 km of the mire, our aim was to shed light on local mining history, which we can then compare to the wider narrative of early mining pollution in Spain. We focus on the section from ~500 BC to AD ~600, which has a high temporal resolution of 6–15 year per sample. Geochemical analyses included the determination of major, minor and trace lithogenic elements (Si, Al, Fe, Ti, Ga, Rb, Y, Zr, Th) as markers of mineral content of the peat, and trace metals/metalloids (Mn, Cu, Ni, As, Pb) as well stable Pb isotopes, as potential markers of atmospheric metal pollution. The use of principal components analysis enabled the identification of a dominant geogenic component and a secondary pollution component. The earliest pollution signal of the covered period was recorded by ~300 BC, coinciding with the late local Iron Age. Average 206Pb/207Pb ratios of samples with ages older than this date was 1.204 ± 0.002, while all samples with a younger age had a less radiogenic ratio. Based on the metal pollution component four phases were identified: I, ~500 to 300 BC; II, ~300 to 20 BC; III, ~20 BC–AD 480; IV, AD ~480 to 600. The lowest isotopic ratio and highest proportion of pollution Pb (206Pb/207Pb ratio of 1.157 and 89 % of total accumulated Pb) was reached at peak Pb production during Roman times (AD ~180 to 340), indicating that this was the period of most intense metal contamination in the area over the studied period. It is remarkable that the La Molina record shows a more extended period (two centuries) of active mining in comparison with other areas in Iberia, and a pattern of repeated shifts in Pb pollution of short duration, which is likely related to the local history of exploitation and exhaustion of mines within the area. 相似文献