Dioxin compounds in the deep-sea rose shrimp Aristeus antennatus (Risso, 1816) throughout the Mediterranean Sea   总被引：1，自引：0，他引：1  

Guiomar Rotllant  Esteban Abad  Francisco Sard  Manuela balos  Joan B. Company  Josep Rivera 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1895-1906

Polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) are among the more toxic anthropogenic contaminants. They are fat-soluble and accumulate in animal tissues. Exposure to PCDD/Fs can cause several endocrine, reproductive and developmental problems in animals, including human beings. Several studies have demonstrated that fish and invertebrates living in association with sediments are exposed to and accumulate contaminants, but to date there have been no studies of PCDD/Fs contamination in deep-sea regions. Specimens of Aristeus antennatus (Risso, 1816) were collected from depths of 600–2500 m at different points in the Mediterranean Sea, from the western basin off the coast of Barcelona to the central basin off the Peloponnesian Peninsula, with otter trawl gear. Amounts of PCDD/Fs were measured in different animal tissues by high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC–HRMS). This is the first study to report the presence of PCDD/Fs in deep-sea organisms dwelling at depths below 600 m. A. antennatus presented levels of PCDD/Fs of the same order of magnitude, or slightly higher, as those found in shallow-water species (Melicertus kerathurus) with respect to land-generated contamination. This highlights the widespread distribution of these pollutants and the potential threat posed to the biodiversity of fragile and vulnerable ecosystems such as the deep-sea. PCDD/F levels detected in the edible parts (muscle) of the commercial shrimp A. antennatus were clearly below the toxic limit value established by European legislation. Levels followed the trend muscle<ovary<hepatopancreas, according to the lipid content of the organs in question. The specific profile of toxic PCDD/F congeners in the studied Penaeid shrimp specimens was characterized mainly by octachlorodibenzo-p-dioxin (OCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) congeners. Moreover, non 2,3,7,8-substituted congeners bioaccumulated in this species, as observed in shallow-water crustaceans. PCDD/Fs were found in the shrimp A. antennatus throughout the Mediterranean Sea. Total PCDD/Fs burdens were higher in shrimps caught in the western Mediterranean than in those caught at eastern Mediterranean sites. There was a tendency for higher levels of PCDD/F contamination in samples obtained from deeper (2500 m) than from shallower sites (600 m).  相似文献   

Contrasts in genetic structure and historical demography of marine and riverine populations of Atherina at similar geographical scales     

Sara M. Francisco  Henrique Cabral  Maria Natividade Vieira  Vítor C. Almada 《Estuarine, Coastal and Shelf Science》2006,69(3-4):655

In this paper, we compare the genetic structure and the historical demography of two populations of the sand smelt Atherina boyeri from the rivers Tagus and Mondego (Portugal) with two groups of samples of the closely related marine Atherina presbyter collected on the shore at comparable latitudes. A. presbyter is a pelagic marine inshore fish, while A. boyeri is typically found in coastal lagoons, estuaries and freshwaters bodies. Analysis of mtDNA control region sequences showed that the marine A. presbyter did not display signs of genetic differentiation between sites some hundreds of kilometers apart. On the contrary, A. boyeri showed clear differences between populations. The populations of A. boyeri showed a much lower genetic diversity and younger coalescence times when compared with A. presbyter. We suggest that these differences reflect the interplay between differences in ecology between the two species and the historical impact of the glaciations. While A. presbyter likely moved to the south evading the cold periods, A. boyeri probably went extinct and its populations in Western Europe are recent recolonizations from western Mediterranean refugia.  相似文献   

Influence of mesh size and tooth spacing on the proportion of damaged organisms in the catches of the Portuguese clam dredge fishery     

Gaspar  Miguel B.; Leitao  Francisco; Santos  Miguel N.; Sobral  Manuel; Chicharo  Luis; Chicharo  Alexandra; Monteiro  Carlos C. 《ICES Journal of Marine Science》2002,59(6):1228-1236

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Fluid Inclusion Microthermometry and Implications for the Mechanisms of Ore-Grade Gold Mineralization in Epithermal System, Lalab Orebody, Sibutad, Zamboanga del Norte, Philippines     

Francisco A. Jimenez  Jr  Graciano P. Yumul  Jr Victor B. Maglambayan 《Resource Geology》2007,57(2):170-179

The Sibutad gold deposit has gold associated in quartz veins. The most important of these is the Lalab orebody, which contains ore‐grade gold, predominantly, in milky quartz veins and veinlets. Here, alteration quartz and fine‐grained crystalline clear and milky quartz were formed from hydrothermal fluids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II fine‐grained alteration quartz and stage III milky quartz ± barite veins and veinlets. Homogenization temperatures (T_H) are >248°C in stage I, 214–232°C in stage II and 186–239°C in stage III. These fluid inclusions have salinity between 1 and 2 wt% NaCl equivalent. In terms of gold assay, stage I drill‐core samples have gold grades 0.53–0.76 g/ton Au, stage II samples have 1.12–3.70 g/ton Au and stage III samples have 9.06–23.88 g/ton Au. This correlation suggests that gold was precipitated from the stage II and III fluids.  相似文献   

Evidence of rainfall variations in Southern Brazil from trace element ratios (Mg/Ca and Sr/Ca) in a Late Pleistocene stalagmite   总被引：1，自引：0，他引：1  

Francisco W. Cruz Jr.  Stephen J. Burns  Ivo Karmann  Mathias Vuille 《Geochimica et cosmochimica acta》2007,71(9):2250-2263

Trace element ratios in the Bt2 stalagmite from Botuverá cave, Southern Brazil, are explored as a proxy for changes in the local rainfall recharge during the last 116 ky. BP Mg/Ca and Sr/Ca ratios, measured with an electron microprobe, are significantly positively correlated with one another throughout the entire record, and vary in a way that is very consistent with variations of δ¹⁸O in the same speleothem during the last glacial period. We suggest that prior calcite precipitation in the vadose zone of the cave system is the main factor affecting the incorporation of Mg and Sr into calcite of the stalagmite. This interpretation is supported by trace element correlation patterns and by results from a hydrochemistry study performed in a cave located in the same region and in a similar environmental setting. Therefore, we conclude that higher (lower) Mg/Ca and Sr/Ca values are associated with lower (higher) levels of recharge into the karstic aquifer, as such conditions lead to an increase (decrease) in the volume of calcite precipitated in the unsaturated zone above the cave during dry (wet) climate periods.Trace element variations point to generally dryer (wetter) conditions during lower (high) phases of summer insolation in the southern hemisphere. These periods coincide with decreased (increased) activity of the South American summer monsoon, as revealed by δ¹⁸O stalagmite records. In addition trace element variations show that rather wet conditions persisted throughout most of the last glacial period from approximately 70 to 17 ky BP. We suggest that during this period the glacial boundary conditions, especially ice volume buildup in the northern hemisphere, played an important role for monsoon rainfall intensification in the region.  相似文献   

Global Positioning System measurements of strain accumulation and slip transfer through the restraining bend along the Dead Sea fault system in Lebanon   总被引：1，自引：0，他引：1  

Francisco Gomez  Gebran Karam  Mohamad Khawlie  Simon McClusky  Philippe Vernant  Robert Reilinger  Rani Jaafar  Charles Tabet  Kamal Khair  Muawia Barazangi 《Geophysical Journal International》2007,168(3):1021-1028

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Advanced DInSAR analysis on mining areas: La Union case study (Murcia, SE Spain)   总被引：5，自引：0，他引：5  

G. Herrera  R. Toms  J.M. Lopez-Sanchez  J. Delgado  J.J. Mallorqui  S. Duque  J. Mulas 《Engineering Geology》2007,90(3-4):148-159

The town of La Union (SE, Spain) is located within a metal mining area that has been exploited since the Roman period. This historic exploitation has left behind a high concentration of abandoned underground mining galleries. Currently, an industrial area is subsiding due to the collapse of one of these galleries in May 1998. In this paper, an advanced Differential Interferometry SAR (DInSAR) method called the Coherent Pixels Technique (CPT) has been used to study the subsidence phenomena for two time intervals, from January 1998 to December 2000, and from March 2003 to December 2004. DInSAR-derived deformation maps have enabled the detection and monitoring of different deformation processes that affect several locations within the study area. By comparing these results with the underground mining galleries map, a clear relationship between their presence and the subsidence has been proved. Deformation values retrieved with DInSAR between April 2003 and December 2004 have been compared with the topographical leveling network measurements performed in this same period, providing an absolute average difference of 0.7 cm with a standard deviation of 0.5 cm. Results obtained in the city of La Union have shown that the advanced DInSAR technique is able to provide very useful spatial and temporal deformation data for the measurement of small scale subsidence throughout short time periods. This technique has enabled the temporal evolution of the phenomena in the city of La Unión to be studied and understanding of subsidence to be expanded beyond the limits of a deployed topographical control network, in a more cost effective way than classical methods.  相似文献   

Anomalous Diffuse CO2 Emission prior to the January 2002 Short-term Unrest at San Miguel Volcano, El Salvador, Central America     

Nemesio M. Pérez  Pedro A. Hernández  Eleazar Padrón  Rafael Cartagena  Rodolfo Olmos  Francisco Barahona  Gladys Melián  Pedro Salazar  Dina L. López 《Pure and Applied Geophysics》2006,163(4):883-896

On January 16, 2002, short-term unrest occurred at San Miguel volcano. A gas-and-steamash plume rose a few hundred meters above the summit crater. An anomalous microseismicity pattern, about 75 events between 7:30 and 10:30 hours, was also observed. Continuous monitoring of CO₂ efflux on the volcano started on November 24, 2001, in the attempt to provide a multidisciplinary approach for its volcanic surveillance. The background mean of the diffuse CO₂ emission is about 16 g m^-2 d^-1, but a 17- fold increase, up to 270 g m^-2 d^-1, was detected on January 7, nine days before the January 2002 short-term unrest at San Miguel volcano. These observed anomalous changes on diffuse CO₂ degassing could be related to either a sharp increase of CO₂ pressure within the volcanic-hydrothermal system or degassing from an uprising fresh gas-rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse CO₂ emission.  相似文献   

Paleosubsidence and active subsidence due to evaporite dissolution in the Zaragoza area (Huerva River valley, NE Spain): processes, spatial distribution and protection measures for transport routes     

Jesús Guerrero  Francisco Gutirrez  Pedro Lucha 《Engineering Geology》2004,72(3-4):309-329

The lowest 17-km long reach of the Huerva River valley, down to its confluence with the Ebro River in Zaragoza city, flows across salt-bearing evaporites of the Ebro Tertiary Basin (NE Spain). Upstream, the horizontally lying Miocene evaporites are interfingered with non-soluble distal alluvial fan facies (shales and sandstones). The proportion of soluble facies in the Huerva River valley increases in a downstream direction towards the basin depocenter. On the basis of the type and magnitude of the paleosubsidence features, the valley has been divided into four reaches. Along reach I, undeformed terrace deposits less than 4 m thick rest on insoluble detrital bedrock. In reaches II and III, dissolution at the alluvium–bedrock boundary has generated local thickening, deformation and paleocollapse structures, which only affect the alluvial mantle. In reach IV, terrace deposits thicken to over 60 m resulting from a large-scale synsedimentary subsidence. In this sector, subsidence locally affects to both the alluvium and the underlying bedrock. This indicates that dissolution acts at the rockhead beneath the alluvial cover (alluvial karst) and within the evaporitic substratum (interstratal karst). The development of an intraevaporitic karst in reach IV is attributed to gypsum and salt dissolution. Irregular terrace gravel bodies (gravel pockets) embedded in a fine-grained matrix associated with paleocollapse structures have been interpreted as liquefaction–fluidization structures resulting from ground acceleration and suction induced by catastrophic collapses. Subsidence is currently active in the region affecting areas with a thin alluvial cover in reaches III and IV. The low subsidence activity in most of Zaragoza city is explained by the presence of thickened (around 50 m) and indurated alluvial deposits. In the surrounding area, numerous buildings in Cadrete and Santa Fe villages have been severely damaged by subsidence. Natural and human-induced subsidence favours the development of slope movements in the gypsum scarp overlooking Cadrete village. Several transport routes including the Imperial Canal (irrigation canal) and the recently completed Madrid–Barcelona high-speed railway are affected by human-induced sinkholes. The paleocollapse structures exposed in the trenches of this railway and a ring road under construction point to hazardous locations underlain by cavities and collapse structures where special protection measures should be applied. Rigid structures are recommended beneath the high-speed railway with sufficient strength to span the larger sinkholes with no deformation. Electronic monitoring devices linked to a warning system can detect subtle subsidence-induced deformations in carriageways or railways. This research demonstrates that the study of the paleokarst helps to understand the processes involved in the present-day subsidence phenomena and their general spatial distribution.  相似文献   

Internal structure of a collapsed terrain: The Lújar syncline and its significance for the fold- and sheet-structure of the Alborán Domain (Betic Cordilleras, Spain)     

Miguel Orozco  Antonio M lvarez-Valero  Francisco M Alonso-Chaves  John P Platt 《Tectonophysics》2004,385(1-4):85-104

Detailed structural analysis of the Sierra de Lújar in the western Alpujarras region (Betic Cordilleras, S Spain), a very representative area of the terrain known as the Alborán Domain, has revealed the existence of a very large N-vergent recumbent syncline which involves the whole mountain massif and neighbouring areas. The Lújar syncline and, probably, the associated recumbent anticline which crops out southeast of Sierra de Lújar show a great variation in the orientation of the hinge line. Although having a curved shape, the hinge line is contained in a plane whose attitude coincides with the main attitude of the axial-plane crenulation foliation (Sc), suggesting that it is a sheath fold.The strongly deformed overturned limb of the syncline is cut by two low-angle normal faults displacing towards the north. Similarity in the kinematics between the faults and the fold, and the association between the faults and the high-strain zone in the overturned limb of the fold, suggest that they are related. Regional constraints on the age of the crenulation cleavage and the low-angle normal faults indicate that they formed during the early Miocene late-orogenic extensional event in the Alborán Domain.We propose an alternate explanation for the structure of the Alpujarras region in which the Lújar syncline forms part of a recumbent syncline–anticline pair that extends along much of the Alpujarride outcrop in the southern Betic Cordillera. In several places, the fold is disrupted by low-angle normal faults, and it is overlain by an upper Alpujárride extensional sheet mainly composed of medium- to high-grade metamorphic rocks. We suggest that all these structures arose from the extensional deformation under decreasing temperature conditions of a previously thickened and metamorphosed orogenic crust.  相似文献