Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine     

Marmolejo-Rodríguez AJ  Prego R  Meyer-Willerer A  Shumilin E  Cobelo-García A 《Marine pollution bulletin》2007,55(10-12):459-468

Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Pe?a Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (<4%). According with the total metal concentrations, background levels and normalised enrichment factors (NEF) of the metals studied, the impact of the Pe?a Colorada iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities.  相似文献   

Net Primary Productivity of <Emphasis Type="Italic">Spartina densiflora</Emphasis> Brong in an SW Atlantic Coastal Salt Marsh     

Gabriela González Trilla  Silvia De Marco  Jorge Marcovecchio  Ricardo Vicari  Patricia Kandus 《Estuaries and Coasts》2010,33(4):953-962

Coastal marshes are known as organic matter producers. The goal of this work is to study tiller demography, standing biomass, and net aerial primary productivity (NAPP) in a Spartina densiflora coastal wetland, using a method applied to permanent sample plots located at two sites differing in topographic location, a regularly flooded zone [relative low marsh (LM)] and an irregularly flooded one [relative high marsh (HM)]. Measurements were made every 2 months during the 2005–2007 period. The annual NAPP was estimated to be 2,599?±?705 gDW m^?2?year^?1 for the HM and 2,181?±?605 gDW m^?2?year^?1 and 602?±?154 gDW m^?2?year^?1 for the first and second period of the LM populations, respectively, showing a seasonal pattern reaching maximum values in summer. The reduced NAPP values of the LM sites in the second year was associated with an extremely high precipitation period related to the 2007–2008 El Niño event.  相似文献   

Constraints on the provenance of the uppermost allochthonous terrane of the NW Iberian Massif: inferences from detrital zircon U–Pb ages     

Javier Fernández-Suárez  Florentino Díaz García  Teresa E. Jeffries  Ricardo Arenas  Jacobo Abati 《地学学报》2003,15(3):138-144

ABSTRACT Insight into the origin and pre-orogenic palaeogeographical links of terranes involved in the assembly of collisional mountain belts is fundamental to the understanding of orogenic processes. Here we address the provenance and possible tectonic settings of the uppermost allochthonous terrane of the NW Iberian Variscan Belt through a 213-nm Laser Ablation ICP-MS study of U–Pb ages of detrital zircons. The age groups of zircons from greywackes in this terrane ( c . 480–610, 1900–2100, 2400–2500 Ma) and the lack of Mesoproterozoic zircons suggest an origin in a Neoproterozoic – Early Palaeozoic peri-Gondwanan realm along the periphery of the west African craton. It is further inferred that the greywackes were deposited in the periphery of a crustal unit that had been detached from the Gondwanan margin in relation to the opening of the Rheic ocean in Cambro-Ordovician times. This terrane was thrusted back upon the Gondwanan margin during the course of the Variscan collision and closure of the intervening ocean.  相似文献   

Imaging downward granitic magma transport in the Rogaland Igneous Complex, SW Norway     

OlivierBolle  Ricardo I. F. Trindade  JeanLuc Bouchez  & Jean-ClairDuchesne 《地学学报》2002,14(2):87-92

Combining geological mapping and petrological, structural and geophysical (gravity and seismic) data already available for the late Proterozoic Rogaland Igneous Complex of Norway allows the 3D shape of the Bjerkreim–Sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks. Using the latter data, along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber, evidence is presented to show that the granitic material was down-dragged through the sinking of its high-density mafic floor into lower density anorthosites and granulitic gneisses. This example illustrates that downward gravity-driven flows of rocks were active, in addition to upward flows, in the building of the early crust up to late-Proterozoic times, helping to explain the geochemical and structural complexities of the old crust.  相似文献   

Urban climate and clues of heat island events in the metropolitan area of Rio de Janeiro     

Andrews José de Lucena  Otto Corrêa Rotunno Filho  José Ricardo de Almeida França  Leonardo de Faria Peres  Luciano Nóbrega Rodrigues Xavier 《Theoretical and Applied Climatology》2013,111(3-4):497-511

This paper aims to map the thermal field in the metropolitan region of Rio de Janeiro (MARJ) considering the atmospheric characteristics and the land use that contribute to understanding the urban heat island. Three thermal maps are defined through the use of Landsat5-TM satellite images for three winter events chosen for the decades of 1980, 1990, and 2000, respectively. The results reveal a concentration of warmer cores in urban central areas as well as some local warmer areas in suburban region. Sites with lower temperatures correspond to vegetated areas which are away from the central part of the MARJ, including points of suburban areas. This work emphasizes the importance of the combined analysis of surface temperature with land use and atmospheric conditions, depicting a distinct pattern of heat islands for tropical climate.  相似文献   

A Hybrid Statistical-Dynamical Downscaling of Air Temperature over Scandinavia Using the WRF Model     

Jianfeng WANG  Ricardo M. FONSECA  Kendall RUTLEDGE  Javier MARTíN-TORRES  Jun YU 《大气科学进展》2020,37(1):57-74

An accurate simulation of air temperature at local scales is crucial for the vast majority of weather and climate applications.In this work,a hybrid statistical–dynamical downscaling method and a high-resolution dynamical-only downscaling method are applied to daily mean,minimum and maximum air temperatures to investigate the quality of localscale estimates produced by downscaling.These two downscaling approaches are evaluated using station observation data obtained from the Finnish Meteorological Institute over a near-coastal region of western Finland.The dynamical downscaling is performed with the Weather Research and Forecasting(WRF)model,and the statistical downscaling method implemented is the Cumulative Distribution Function-transform(CDF-t).The CDF-t is trained using 20 years of WRF-downscaled Climate Forecast System Reanalysis data over the region at a 3-km spatial resolution for the central month of each season.The performance of the two methods is assessed qualitatively,by inspection of quantile-quantile plots,and quantitatively,through the Cramer-von Mises,mean absolute error,and root-mean-square error diagnostics.The hybrid approach is found to provide significantly more skillful forecasts of the observed daily mean and maximum air temperatures than those of the dynamical-only downscaling(for all seasons).The hybrid method proves to be less computationally expensive,and also to give more skillful temperature forecasts(at least for the Finnish near-coastal region).  相似文献   

Reinterpretation of the Ordovician rotations in NW Argentina and Northern Chile: a consequence of the Precordillera collision?     

Cecilia M. Spagnuolo  Augusto E. Rapalini  Ricardo A. Astini 《International Journal of Earth Sciences》2011,100(2-3):603-618

Early Paleozoic paleomagnetic data from NW Argentina and Northern Chile have shown large systematic rotations within two domains: one composed of the Western Puna that yields very large (up to 80°) counter-clockwise rotations, and the other formed by the Famatina Ranges and the Eastern Puna that shows (~40°) clockwise rotations around vertical axes. In several locations, lack of significant rotations in younger rocks constrains this kinematic pattern to have occurred during the Paleozoic. Previous tectonic models have explained these rotations as indicative of rigid-body rotations of large para-autochthonous crustal blocks or terranes. A different but simple tectonic model that accounts for this pattern is presented in which rotations are associated to crustal shortening and tectonic escape due to the collision of the allochthonous terrane of Precordillera in the Late Ordovician. This collision should have generated dextral shear zones in the back arc region of the convergent SW Gondwana margin, where systematic domino-like clockwise rotations of small crustal blocks accommodate crustal shortening. The Western Puna block, bordering the Precordillera terrane to the north, might have rotated counterclockwise as an independent microplate due to tectonic escape processes, in a fashion similar to the present-day relationship between the Anatolia block and the Arabian microplate.  相似文献   

Generalized Bootstrap Method for Assessment of?Uncertainty in Semivariogram Inference   总被引：1，自引：0，他引：1  

Ricardo A. Olea  Eulogio Pardo-Ig??zquiza 《Mathematical Geosciences》2011,43(2):203-228

The semivariogram and its related function, the covariance, play a central role in classical geostatistics for modeling the average continuity of spatially correlated attributes. Whereas all methods are formulated in terms of the true semivariogram, in practice what can be used are estimated semivariograms and models based on samples. A generalized form of the bootstrap method to properly model spatially correlated data is used to advance knowledge about the reliability of empirical semivariograms and semivariogram models based on a single sample. Among several methods available to generate spatially correlated resamples, we selected a method based on the LU decomposition and used several examples to illustrate the approach. The first one is a synthetic, isotropic, exhaustive sample following a normal distribution, the second example is also a synthetic but following a non-Gaussian random field, and a third empirical sample consists of actual raingauge measurements. Results show wider confidence intervals than those found previously by others with inadequate application of the bootstrap. Also, even for the Gaussian example, distributions for estimated semivariogram values and model parameters are positively skewed. In this sense, bootstrap percentile confidence intervals, which are not centered around the empirical semivariogram and do not require distributional assumptions for its construction, provide an achieved coverage similar to the nominal coverage. The latter cannot be achieved by symmetrical confidence intervals based on the standard error, regardless if the standard error is estimated from a parametric equation or from bootstrap.  相似文献   

Hydrothermal faunal assemblages and habitat characterisation at the Eiffel Tower edifice (Lucky Strike,Mid‐Atlantic Ridge)     

Daphne Cuvelier  Pierre‐Marie Sarradin  Jozée Sarrazin  Ana Colaço  Jon T. Copley  Daniel Desbruyères  Adrian G. Glover  Ricardo Serrão Santos  Paul A. Tyler 《Marine Ecology》2011,32(2):243-255

The Eiffel Tower edifice is situated in the Lucky Strike hydrothermal vent field at a mean depth of 1690 m on the Mid‐Atlantic Ridge (MAR). At this 11‐m‐high hydrothermal structure, different faunal assemblages, varying in visibly dominant species (mussels and shrimp), in mussel size and in density of mussel coverage, were sampled biologically and chemically. Temperature and sulphide (∑S) were measured on the different types of mussel‐based assemblages and on a shrimp‐dominated assemblage. Temperature was used as a proxy for calculating total concentrations of CH₄. Based on the physico‐chemical measurements, two microhabitats were identified, corresponding to (i) a more variable habitat featuring the greatest fluctuations in environmental variables and (ii) a second, more stable, habitat. The highest temperature variability and the highest maximum recorded temperatures were found in the assemblages visibly inhabited by alvinocaridid shrimp and dense mussel beds of large Bathymodiolus azoricus, whereas the less variable habitats were inhabited by smaller‐sized mussels with increasing bare surface in between. Larger mussels appeared to consume more ∑S compared with smaller‐sized (<1 cm) individuals and thus had a greater influence on the local chemistry. In addition, the mussel size was shown to be significantly positively correlated to temperature and negatively to the richness of the associated macrofauna. The presence of microbial mats was not linked to specific environmental conditions, but had a negative effect on the presence and abundance of macro‐fauna, notably gastropods. Whereas some taxa or species are found in only one of the two microhabitats, others, such as polychaetes and Mirocaris shrimp, cross the different microhabitats. Temperature was proposed to be a more limiting factor in species distribution than ∑S.  相似文献   

Larval growth,size, stage duration and recruitment success of a temperate reef fish     

Jorge Fontes  Ricardo S. Santos  Pedro Afonso  Jennifer E. Caselle 《Journal of Sea Research》2011,65(1):1-7

Understanding the causes of variation in recruitment of marine fishes has been a central goal for marine ecologists, fishery scientists and resource managers over the last century. Although the idea that recruitment variability is linked to the pelagic environmental conditions that enhance larval growth, survival, and/or delivery is consensual, such relationship is poorly known for most species. In this study we analyzed patterns of recruitment and early life history of a temperate reef fish, Coris julis from the Azores archipelago to test the relationships between early life history and recruitment success over two consecutive years. Growth from hatch to larval age 30 d was the best predictor of recruitment, implying that fast growing larger-at-age larvae have a survival advantage and contribute more to high recruitment, supporting the “bigger-is-better” hypothesis. The “stage-duration” hypothesis and the predictions regarding the relationships between size at age (SAA), size at settlement (SAS) and recruit abundance were also partially supported. The results presented in this study highlight the importance of understanding the early life traits that determine recruitment and larval-survivorship patterns, especially early larval growth, as this may provide a basis for prediction of recruitment and thus management of resources.  相似文献