Spatial distribution of sedimentary linear alkylbenzenes and faecal steroids of Santos Bay and adjoining continental shelf, SW Atlantic, Brazil: origin and fate of sewage contamination in the shallow coastal environment   总被引：1，自引：0，他引：1  

Martins CC  Ferreira JA  Taniguchi S  Mahiques MM  Bícego MC  Montone RC 《Marine pollution bulletin》2008,56(7):1359-1363

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Walking through volcanic mud: the 2,100-year-old Acahualinca footprints (Nicaragua)     

Hans-Ulrich Schmincke  Steffen Kutterolf  Wendy Perez  Juanita Rausch  Armin Freundt  Wilfried Strauch 《Bulletin of Volcanology》2009,71(5):479-493

We present the stratigraphy, lithology, volcanology, and age of the Acahualinca section in Managua, including a famous footprint layer exposed in two museum pits. The ca. 4-m-high walls of the main northern pit (Pit I) expose excellent cross sections of Late Holocene volcaniclastic deposits in northern Managua. We have subdivided the section into six lithostratigraphic units, some of which we correlate to Late Holocene eruptions. Unit I (1.2 m thick), chiefly of hydroclastic origin, begins with the footprint layer. The bulk is dominated by mostly massive basaltic-andesitic tephra layers, interpreted to represent separate pulses of a basically phreatomagmatic eruptive episode. We correlate these deposits based on compositional and stratigraphic evidence to the Masaya Triple Layer erupted at Masaya volcano ca. 2,120 ± 120 a B.P.. The eruption occurred during the dry season. A major erosional channel unconformity up to 1 m deep in the western half of Pit I separates Units II and I. Unit II begins with basal dacitic pumice lapilli up to 10 cm thick overlain by a massive to bedded fine-grained dacitic tuff including a layer of accretionary lapilli and pockets of well-rounded pumice lapilli. Angular nonvesicular glass shards are interpreted to represent hydroclastic fragmentation. The dacitic tephra is correlated unequivocally with the ca. 1.9-ka-Plinian dacitic Chiltepe eruption. Unit III, a lithified basaltic-andesitic deposit up to 50 cm thick and extremely rich in branch molds and excellent leaf impressions, is correlated with the Masaya Tuff erupted ca. 1.8 ka ago. Unit IV, a reworked massive basaltic-andesitic deposit, rich in brown tuff clasts and well bedded and cross bedded in the northwestern corner of Pit I, cuts erosionally down as far as Unit I. A poorly defined, pale brown mass flow deposit up to 1 m thick (Unit V) is overlain by 1–1.5 m of dominantly reworked, chiefly basaltic tephra topped by soil (Unit VI). A major erosional channel carved chiefly between deposition of Units II and I may have existed as a shallow drainage channel even prior to deposition of the footprint layer. The swath of the footprints is oriented NNW, roughly parallel to, and just east of, the axis of the channel. The interpretation of the footprint layer as the initial product of a powerful eruption at Masaya volcano followed without erosional breaks by additional layers of the same eruptive phase is strong evidence that the group of 15 or 16 people tried to escape from an eruption.  相似文献   

Climatic Warming in the Spanish Mediterranean: Natural Trend or Urban Effect     

J. Quereda Sala  A. Gil Olcina  A. Perez Cuevas  J. Olcina Cantos  A. Rico Amoros  E. Montón Chiva 《Climatic change》2000,46(4):473-483

The evolution of the mean annual temperatures recordedin the major historical network of SpanishMediterranean observatories(36°N–45°/60°W–4°E)exhibits a significant warming trend. Analysis of thetrend is difficult and could be biased by non-climaticprocesses such as the urban effect and weather stationrelocation, which also need to be taken intoaccount.The present work examines the effects of non-climaticprocesses and shows that most of the temperature risecould be due to an urban effect. On correcting for theurban effect, the actual rise was found to be zero ornegligible. The assumption of temperature stability inthe Spanish Mediterranean should thereforenot be rejected.  相似文献   

Shock deformation confirms the impact origin for the Cerro do Jarau,Rio Grande do Sul,Brazil, structure     

Wolf Uwe Reimold  Alvaro Penteado Crsta  Maximilian Hasch  Astrid Kowitz  Natalia Hauser  Joana Paula Sanchez  Luiz Sergio Amarante Simes  Grace Juliana de Oliveira  Patrice T. Zaag 《Meteoritics & planetary science》2019,54(10):2384-2397

Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30^o12′S and 56^o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks.  相似文献   

Quantum Instability of Magnetized Stellar Objects     

R. González Felipe  H. J. Mosquera Cuesta  A. Pérez Martínez  H. Pérez Rojas 《中国天文和天体物理学报》2005,5(4):399-411

The equations of state for degenerate electron and neutron gases are studied in the presence of magnetic fields. After including quantum effects in the investigation of the structural properties of these systems, it is found that some hypermagnetized stars can be unstable according to the criterion of stability of pressures. Highly magnetized white dwarfs should collapse producing a supernova type Ia, while superstrong magnetized neutron stars cannot stand their own magnetic field and must implode, too. A comparison of our results with a set of the available observational data of some compact stars is also presented, and the agreement between this theory and observations is verified.  相似文献   

TPH and PAH concentrations in the subsoil of polyduct segments, oil pipeline pumping stations, and right-of-way pipelines from Central Mexico     

Rosario Iturbe  Alejandrina Castro  Guillermina Perez  Carlos Flores  Luis G. Torres 《Environmental Geology》2008,55(8):1785-1795

For the year 1996, 366 incidents related with clandestine poaching of oil-products were reported in Mexico, 159 in 1997, and 240 in 1998. For the year 2003 (the most recently reported figure), there were 136 events. Petroleos Mexicanos (PEMEX), very concerned with the environmental agenda, has developed programs oriented to diminish contamination levels in all of its oil facilities. This work was aimed at characterizing zones around polyduct segments, pipelines, pumping stations, and right-of-way pipelines located in the center of Mexico. The TPH contaminated sites were, in decreasing order, polyduct km 39 + 150 > polyduct km 25 + 020 > Zoquital > Tepetitlan > Catalina > Venta Prieta > Ceiba. Most of the sampled points showed the presence of more than one of the 16 PAHs considered by USEPA as priority pollutants. Except point TEPE 2A, where no PAHs were detected, all the sampled points showed values from low to medium concentrations; however, values found at the sites did not exceed the limits according to the Mexican or the American legislation. The place with the largest contaminated area corresponded to the polyduct km 39 + 150, with 130 m² and 260 m³ to be treated. The least contaminated area was that around the JUAN 4 point at Juandho station, with 20 m² and 22 m³ of contaminated soil. The total area to be treated is about 230 m² and 497 m³.  相似文献   

Fertilization Changes Seagrass Community Structure but not Blue Carbon Storage: Results from a 30-Year Field Experiment     

Jason L. Howard  Alex Perez  Christian C. Lopes  James W. Fourqurean 《Estuaries and Coasts》2016,39(5):1422-1434

Seagrass ecosystems are attracting attention as potentially important tools for carbon (C) sequestration, comparable to those terrestrial and aquatic ecosystems already incorporated into climate change mitigation frameworks. Despite the relatively low C stocks in living biomass, the soil organic carbon pools beneath seagrass meadows can be substantial. We tested the relationship between soil C storage and seagrass community biomass, productivity, and species composition by revisiting meadows experimentally altered by 30 years of consistent nutrient fertilization provided by roosting birds. While the benthos beneath experimental perches has maintained dense, Halodule wrightii-dominated communities compared to the sparse Thalassia testudinum-dominated communities at control sites, there were no significant differences in soil organic carbon stocks in the top 15 cm. Although there were differences in δ¹³C of the dominant seagrass species at control and treatment sites, there was no difference in soil δ¹³C between treatments. Averages for soil organic carbon content (2.57?±?0.08 %) and δ¹³C (?12.0?±?0.3?‰) were comparable to global averages for seagrass ecosystems; however, our findings question the relevance of local-scale seagrass species composition or density to soil organic carbon pools in some environmental contexts.  相似文献   

Decomposition and analysis by atomic absorption photospectrometry of silicate rocks     

J. Saavedra  A.Garcia Sanchez  S.Rodriguez Perez 《Chemical Geology》1974,13(2):135-139

A rapid and simple method of analysis of silicate rocks using gold crucibles and fluoroboric acid as a solvent of the disintegrated material has been developed. The main elements are determined in a single treatment. The results obtained are comparable to the values recommended for samples of eleven standard rocks.  相似文献   

Volcanic particles in agriculture and gardening          下载免费PDF全文

Valentin R. Troll  Juan Carlos Carracedo  Beatrice Jägerup  Michael Streng  Abigail K. Barker  Frances M. Deegan  Francisco Perez‐Torrado  Alejandro Rodriguez‐Gonzalez  Harri Geiger 《Geology Today》2017,33(4):148-154

Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro‐bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe.  相似文献   

Reply to Discussion “Geopolymers Based on Recycled Glass Powder for Soil Stabilization” Jair de Jesús Arrieta Baldovino,Ronaldo Luis dos Santos Izzo,Juliana Lundgren Rose,and Mônica Angélica Avanci     

de Jesús Arrieta Baldovino  Jair  dos Santos Izzo  Ronaldo Luis  Rose  Juliana Lundgren  Avanci  Mônica Angélica 《Geotechnical and Geological Engineering》2021,39(6):4655-4657

Geotechnical and Geological Engineering -  相似文献