Polycyclic aromatic hydrocarbons in coastal sediments from the subtropical Mexican Pacific     

García-Ruelas C  Botello AV  Ponce-Vélez G  Díaz-González G 《Marine pollution bulletin》2004,49(5-6):514-519

  相似文献   

Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico   总被引：6，自引：0，他引：6  

Hernández-Romero AH  Tovilla-Hernández C  Malo EA  Bello-Mendoza R 《Marine pollution bulletin》2004,48(11-12):1130-1141

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.  相似文献   

The k -2 Rupture Model Parametric Study: Example of the 1999 Athens Earthquake     

Gallovič  F.  Brokešová  J. 《Studia Geophysica et Geodaetica》2004,48(3):589-613

We employ a realistic finite-extent k ^-2 stochastic source model with k-dependent rise time, introduced by Bernard et al. (1996) and extended by Gallovi and Brokeová (2004), to synthesize the strong ground motions in near source distances. For a given magnitude, this rupture model involves a number of free parameters (fault dimensions, slip roughness, maximum rise time, slip velocity function). We study their influence on the peak ground acceleration (PGA) maps (parametric study) for an example of the 1999 Athens earthquake of M _w = 5.9. The observed macroseismic intensities serve us as a rough constraint on the simulated PGA's to find a set of suitable k ^-2 models. These models agree with empirical source scaling relations.  相似文献   

Arsenic in contaminated soils and anthropogenic deposits at the Mokrsko,Roudný, and Kašperské Hory gold deposits,Bohemian Massif (CZ)     

Michal?FilippiEmail author  Viktor?Goliá?  Zdeněk?Pertold 《Environmental Geology》2004,45(5):716-730

Soil, mine tailing, and waste dump profiles above three mesothermal gold deposits in the Bohemian Massif with different anthropogenic histories have been studied. Their mineralogical, major element, and arsenic (As) contents and the contents of secondary arsenic minerals were analyzed. The As-bearing minerals were concentrated and determined using X-ray diffraction (XRD) analysis, the Debye-Scherrer powder method, scanning electron microscopy (SEM), and energy-dispersive microanalysis (EDAX). The amorphous hydrous ferric oxides (HFO), As-bearing goethite, K-Ba- or Ca-Fe- and Fe- arsenates pharmacosiderite, arseniosiderite, and scorodite, and sulfate-arsenate pitticite were determined as products of arsenopyrite or arsenian pyrite oxidation. The As behaviour in the profiles studied differs in dependence on the surface morphology, chemical and mineralogical composition of the soil, mine wastes or tailings, oxidation conditions, pH, presence of (or distance from) primary As mineralization in the bedrock, and duration of the weathering effect. Although the primary As mineralization and the bedrock chemical composition are roughly similar, there are distinct differences in the As behaviour amongst the Mokrsko, Roudný and Kaperské Hory deposits.  相似文献   

Investigation of natural and anthropogenic hydrocarbon inputs in sediments using geochemical markers. I. Santos, SP--Brazil   总被引：2，自引：0，他引：2  

Medeiros PM  Bícego MC 《Marine pollution bulletin》2004,49(9-10):761-769

A study on the inputs of organic matter to marine sediments of Santos Bay and Estuary, located in southeastern S?o Paulo State, Brazil, is presented here. The following geochemical markers were identified and quantified: aliphatic hydrocarbons (normal and isoprenoid alkanes), petroleum biomarkers, linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs). Sediment samples, collected at 15 sites in the bay and surrounding channels, were extracted and analyzed by gas chromatography with flame ionization and mass spectrometer detectors. Total concentrations varied from 0.17 to 107.80 microg g(-1) for aliphatics, from 47.2 to 2560.1 ng g(-1) for petroleum biomarkers, from 16.9 to 430.6 ng g(-1) for LABs and from 79.6 to 15389.1 ng g(-1) for PAHs. Anthropogenic contributions were apparent, indicating the influences of the Cubatao industrial complex, sewage outfalls along the area, the waste deposit of Santos city and storage facilities for petroleum and derivatives, based on the higher concentrations of geochemical markers detected.  相似文献   

Seasonal and photochemical changes of DOM in an acidified forest lake and its tributaries   总被引：1，自引：0，他引：1  

Petr?PorcalEmail author  Josef?Hejzlar  Ji?í?Kopá?ek 《Aquatic Sciences - Research Across Boundaries》2004,66(2):211-222

  相似文献   

Neoproterozoic–Cambrian synsedimentary magmatism in the Central Iberian Zone (Spain): geology,petrology and geodynamic significance     

M.?D.?Rodríguez-AlonsoEmail author  M.?Peinado  M.?López-Plaza  P.?Franco  A.?Carnicero  J.?C.?Gonzalo 《International Journal of Earth Sciences》2004,93(5):897-920

Petrographic, geochemical and field studies in low grade metamorphic areas (Ciudad Rodrigo-Hurdes-Sierra de Gata domain, CRHSG, central-western Spain) show that Neoproterozoic-Lowermost Cambrian series in the Central Iberian Zone (CIZ) record two kinds of provenance sources including: (1) detrital material derived from recycled orogens and (2) a Cadomian coeval juvenile contribution that governs their isotopic signature. Evidence of magmatism contemporaneous with Neoproterozoic-Cambrian sedimentation is provided by the presence of coherent, massive volcanic rocks (metabasalts, metaandesites, and metarhyolites), volcaniclastic shales, sandstones, conglomerates and breccias. The appearance of volcanogenic lithic fragments and crystals mixed in different proportions with siliciclastic constituents and also present within calcareous components in the sedimentary succession, reinforces this evidence. Although most of the selected volcanic and volcaniclastic samples appear to show tholeiitic affinity, some of them display calc-alkaline affinity. Different trace element ratios, such as Sm/Nd, Nb/Yb and Ta/Yb, suggest a magmatic evolution in the same tectonic setting. The geochemical results reported here support the existence of an active geodynamic setting as a direct contributor to the synsedimentary and magmatic content of the Neoproterozoic–Lowermost Cambrian successions in the CIZ. In particular, the relatively high Nd _(T) values and the high range of f ^Sm/Nd ratios are consistent with an active margin during the Neoproterozoic–Early Cambrian. The existence of tectonic activity is also confirmed by the presence of synsedimentary deformation and volcanic rocks. All of these traits favour a geodynamic model in which the Iberian Cadomian segment represented in the CIZ would have been part of an active northern margin of Gondwana, with an associated magmatic arc and related basins during Neoproterozoic–Lower Cambrian times. A proposed link between the Ossa Morena and the Central Iberian Zones might account for late Cadomian pull-apart basins developed on both sides of the magmatic arc, sharing the same scenario and involving similar magmatic activity during the Neoproterozoic–Cambrian transition.

M. D. Rodríguez-AlonsoEmail: Phone: +34-923-294498Fax: +34-923-294514

  相似文献   

Détermination indirecte des limites d'Atterberg par gravimétrie dynamique     

Chantal Proust  Agnès Jullien  Lydie Le Forestier 《Comptes Rendus Geoscience》2004,336(14):1233-1238

This study presents a new method for Atterberg limits measurements using dynamic drying. Indeed, for some polluted clays, or clay mixtures, classical methods cannot be used. The principle of liquid $(W_{\mathrm{L}})$ and plasticity $(W_{\mathrm{P}})$ limits determination by this method is presented. Experimental values for classical clays are close to those obtained with Casagrande's methods, allowing for larger physical mud characterisation. To cite this article: C. Proust et al., C. R. Geoscience 336 (2004).  相似文献   

On the Dynamic Disconnection of Rising Omega Loops     

László Tóth  Ottó Gerlei 《Solar physics》2004,220(1):43-59

The tilt-angle variation of solar bipolar magnetic regions (BMRs) in space and time is a probable indicator of large-scale properties of magnetic field distribution, the dynamo and other different processes affecting the rising of magnetic flux tubes. We analyze the tilt-angle distribution and evolution of clearly oriented BMRs using sunspot position and area measurements from the Greenwich Photo-Heliographic Results (GPHR) supplemented by high-quality full-disk sunspot drawings made in the Haynald Observatory in Hungary. Our work is made on the basis of the 14th sunspot cycle and we compare our results with present theories of magnetic flux evolution in the convective zone. Our results support the assumption that the scatter of tilt angles of BMRs around Joy`s law is determined by the convective turbulence. Furthermore, we find that regular BMRs grouped by age generally do not show the phenomenon of toroidal relaxation towards the east–west direction. We interpret this by the disconnection of -loops from the bottom of the convection zone.  相似文献   

A mechanism for anomalous decline in radon precursory to an earthquake     

Kuo MC  Fan K  Kuochen H  Chen W 《Ground water》2006,44(5):642-647

Mechanisms for interpreting anomalous decreases in radon in ground water prior to earthquakes are examined with the help of a case study to show that radon potentially is a sensitive tracer of strain changes in the crust preceding an earthquake. The 2003 Chengkung earthquake of magnitude (M) 6.8 on December 10, 2003, was the strongest earthquake near the Chengkung area in eastern Taiwan since 1951. The Antung radon-monitoring station was located 20 km from the epicenter. Approximately 65 d prior to the 2003 Chengkung earthquake, precursory changes in radon concentration in ground water were observed. Specifically, radon decreased from a background level of 780 pCi/L to a minimum of 330 pCi/L. The Antung hot spring is situated in a fractured block of tuffaceous sandstone surrounded by ductile mudstone. Given these geological conditions, we hypothesized that the dilation of brittle rock mass occurred at a rate faster than the recharge of pore water and gas saturation developed in newly created cracks preceding the earthquake. Radon partitioning into the gas phase may explain the anomalous decrease of radon precursory to the 2003 Chengkung earthquake. To support the hypothesis, vapor-liquid, two-phase radon-partitioning experiments were conducted at formation temperature (60 degrees C) using formation brine from the Antung hot spring. Experimental data indicated that the decrease in radon required a gas saturation of 10% developed in rock cracks. The observed decline in radon can be correlated with the increase in gas saturation and then with the volumetric strain change for a given fracture porosity.  相似文献