Historical analysis of heavy metal pollution in three estuaries on the north coast of Galicia (NW Spain)     

F. Lorenzo  A. Alonso  M. J. Pellicer  J. L. Pagés  M. Pérez-Arlucea 《Environmental Geology》2007,52(4):789-802

This research focuses on the development of metal pollution in sediment cores from three estuaries in Northwest Spain: Viveiro, Ortigueira and Barqueiro. Pb, Cu, Co, Cr, Cd and Zn and total organic carbon were assessed using principal component analysis (PCA) in order to obtain background values, measure pollution levels and identify pollution sources. Results were interpreted by considering the local industrial history, grain size and C/N relationship. The pollution levels obtained bear a strong resemblance to those documented for of a moderately industrialised area. PCA identifies factors that reflect mainly temporal associations with metals. Sedimentation rates between 0.9 and 1.1 cm/year were determined. In Viveiro core levels of Cr pollution are associated with tanneries. In Ortigueira, high core levels of Cu and Co are linked to mining, and Cr levels to adjacent ultramafic rocks. Erosion of Holocene sediment causes high values of Co and Cr in the Barqueiro core. Cu increase in the three estuaries is related to fungicide use since 1910. Sea level rise appears to be affecting the marine characteristics of the sediments in Barqueiro. In Viveiro, the nature of the sediment reflects engineering work and land reclamation.  相似文献   

Hydrogeochemical processes,mixing and isotope tracing in hard rock aquifers and surface waters from the Subarnarekha River Basin, (east Singhbhum District,Jharkhand State,India)   总被引：1，自引：2，他引：1  

Ph. Négrel  B. Lemière  H. Machard de Grammont  P. Billaud  B. Sengupta 《Hydrogeology Journal》2007,15(8):1535-1552

Geochemical observations, including major ion and trace element analysis, and isotopic tracing have been carried out in the Subarnarekha River system (northeastern India) during a surface-water- and groundwater-monitoring program aimed at evaluating impacts of mining. The aquifer is of fracture type. Groundwater flow conditions and pollutant transfer were observed through a network of 69 wells. δ¹⁸O and δ²H results suggest that transfer from rainfall towards groundwater storage through soils and the unsaturated zone is fast, without any major transformation like evaporation. The scatter of ⁸⁷Sr/⁸⁶Sr signatures in surface water and groundwater are explained by three end-members. One is compatible with rainwater inputs. The most mineralised end-member represents anthropogenic inputs (agricultural practices and ore processing). The third end-member, characterised by a high ⁸⁷Sr/⁸⁶Sr signature, is believed to be controlled by natural geochemical processes, although affected by human activities (e.g. drainage of mine waste). Potential flow paths, investigated north of the area, reveal that all groundwater types seem to evolve more in pockets than along a flow path. The limited extent of transfer and the predominance of natural phenomena help to explain the moderate level of groundwater contamination and the characteristics of surface water contamination by mining and the metallurgy industry.  相似文献   

Oxygen isotope systematics of gem corundum deposits in Madagascar: relevance for their geological origin   总被引：1，自引：1，他引：1  

Gaston Giuliani  Anthony Fallick  Michel Rakotondrazafy  Daniel Ohnenstetter  Alfred Andriamamonjy  Théogène Ralantoarison  Saholy Rakotosamizanany  Marie Razanatseheno  Yohann Offant  Virginie Garnier  Christian Dunaigre  Dietmar Schwarz  Alain Mercier  Voahangy Ratrimo  Bruno Ralison 《Mineralium Deposita》2007,42(3):251-270

The oxygen isotopic composition of gem corundum was measured from 22 deposits and occurrences in Madagascar to provide a gemstone geological identification and characterization. Primary corundum deposits in Madagascar are hosted in magmatic (syenite and alkali basalt) and metamorphic rocks (gneiss, cordieritite, mafic and ultramafic rocks, marble, and calc-silicate rocks). In both domains the circulation of fluids, especially along shear zones for metamorphic deposits, provoked in situ transformation of the corundum host rocks with the formation of metasomatites such as phlogopite, sakenite, and corundumite. Secondary deposits (placers) are the most important economically and are contained in detrital basins and karsts. The oxygen isotopic ratios (¹⁸O/¹⁶O) of ruby and sapphire from primary deposits are a good indicator of their geological origin and reveal a wide range of δ¹⁸O (Vienna Standard Mean Ocean Water) between 1.3 and 15.6‰. Metamorphic rubies are defined by two groups of δ¹⁸O values in the range of 1.7 to 2.9‰ (cordieritite) and 3.8 to 6.1‰ (amphibolite). “Magmatic” rubies from pyroxenitic xenoliths contained in the alkali basalt of Soamiakatra have δ¹⁸O values ranging between 1.3 and 4.7‰. Sapphires are classified into two main groups with δ¹⁸O in the range of 4.7 to 9.0‰ (pyroxenite and feldspathic gneiss) and 10.7 to 15.6‰ (skarn in marble from Andranondambo). The δ¹⁸O values for gem corundum from secondary deposits have a wide spread between −0.3 and 16.5‰. The ruby and sapphire found in placers linked to alkali basalt environments in the northern and central regions of Madagascar have consistent δ¹⁸O values between 3.5 and 6.9‰. Ruby from the placers of Vatomandry and Andilamena has δ¹⁸O values of 5.9‰, and between 0.5 and 4.0‰, respectively. The placers of the Ilakaka area are characterized by a huge variety of colored sapphires and rubies, with δ¹⁸O values between −0.3 and 16.5‰, and their origin is debated. A comparison with oxygen isotope data obtained on gem corundum from Eastern Africa, India, and Sri Lanka is presented. Giant placer deposits from Sri Lanka, Madagascar, and Tanzania have a large variety of colored sapphires and rubies with a large variation in δ¹⁸O due to mingling of corundum of different origin: mafic and ultramafic rocks for ruby, desilicated pegmatites for blue sapphire, syenite for yellow, green, and blue sapphire, and skarn in marbles for blue sapphire.  相似文献   

Sulphur and carbon isotopic composition of power supply coals in the Pannonian Basin, Hungary     

Mria Hmor-Vid  Tams Hmor 《International Journal of Coal Geology》2007,71(4):179

The present work is an attempt to establish the stable isotope database for Mesozoic to Tertiary coals from the Pannonian Basin, Hungary. Maceral composition, proximate analysis, sulphur form, sulphur isotopes (organic and pyritic), and carbon isotopes were determined. This database supports the assessment of the environmental risks associated with energy generation, the characterization of the formation and the distribution of sulphur in the coals used.The maceral composition, the sulphur composition, the C, S isotopic signatures, and some of the geological evidences published earlier show that the majority of these coals were deposited in freshwater and brackish water environments, despite the relatively high average sulphur content. However, the Upper Cretaceous, Eocene, and Lower Miocene formations also contain coal seams of marine origin, as indicated by their maceral composition and sulphur and carbon chemistry.The majority of the sulphur in these coals occurs in the organic form. All studied sulphur phases are relatively rich in ³⁴S isotopes (δ³⁴S_organic = + 12.74‰, δ³⁴S_pyrite = + 10.06‰, on average). This indicates that marine bacterial sulphate reduction played a minor role in their formation, in the sense that isotopic fractionation was limited. It seems that the interstitial spaces of the peat closed rapidly during early diagenesis due to a regime of high depositional rate, leading to a relative enrichment of the heavy sulphur isotopes.  相似文献   

Cementation of kerogen-rich marls by alkaline fluids released during weathering of thermally metamorphosed marly sediments. Part I: Isotopic (C,O) study of the Khushaym Matruk natural analogue (central Jordan)     

Serge Fourcade  Laurent Trotignon  Philippe Boulvais  Isabelle Techer  Marcel Elie  Didier Vandamme  Elias Salameh  Hani Khoury 《Applied Geochemistry》2007

The Khushaym Matruk site in central Jordan may represent a natural analogue depicting the interaction of alkaline solutions with a clayey sedimentary formation or with clay-rich confining barriers at the interface with concrete structures in waste disposal sites. In this locality, past spontaneous combustion of organic matter in a clayey biomicritic formation produced a ca. 60 m-thick layer of cement-marble containing some of the high-temperature phases usually found in industrial cements (e.g., spurrite, brucite, and Ca-aluminate). A vertical cross-section of the underlying sediments was used in order to study the interaction between cement-marbles and neighbouring clayey limestones under weathering conditions. A thermodynamic approach of the alteration parageneses (calcite–jennite–afwillite–brucite and CSH phases) in the cement-marbles constrains the interacting solutions to have had pH-values between 10.5 and 12. Over 3 m, the sediments located beneath the metamorphic unit were compacted and underwent carbonation. They display large C and O isotopic variations with respect to “pristine” sediments from the bottom of the section. Low δ¹³C-values down to −31.4‰/PDB show the contribution of CO₂ derived from the oxidization of organic matter and from the atmosphere to the intense carbonation process affecting that particular sedimentary level. The size of the C isotopic anomalies, their geometrical extent and their coincidence with the variations of other markers like the Zn content, the structure of organic matter, the mineralogical composition, all argue that the carbonation process was induced by the percolation of high pH solutions which derived from the alteration of cement-marbles. The temperature of the carbonation process remains conjectural and some post-formation O isotopic reequilibration likely affected the newly-formed carbonate. Carbonation induced a considerable porosity reduction, both in fractures and matrixes. The Khushaym Matruk site may have some bearing to the early life of a repository site, when water saturation of the geological formations hosting the concrete structures is incomplete, enabling simultaneous diffusion of alkaline waters and gaseous CO₂ in the near field.  相似文献   

Cementation of kerogen-rich marls by alkaline fluids released during weathering of thermally metamorphosed marly sediments. Part II: Organic matter evolution,magnetic susceptibility and metals (Ti,Cr, Fe) at the Khushaym Matruk natural analogue (Central Jordan)     

Marcel Elie  Isabelle Techer  Laurent Trotignon  Hani Khoury  Elias Salameh  Didier Vandamme  Philippe Boulvais  Serge Fourcade 《Applied Geochemistry》2007

Spontaneous combustion, less than 1 Ma ago, affected a 60-m thick sediment pile of biomicrite at the Khushaym Matruck site (Jordan). The present study shows that three retrograde alteration stages occurred: weathering, thermal stress and oxidative alkaline perturbation. μ-FT-i.r. spectra of isolated kerogens and oxygen index of whole rocks indicate that oxidation of organic matter occurred down to ∼10 m beneath the metamorphosed zone at Khushaym Matruck. The occurrence of the oxidative weathering bacterially mediated, as suggested by the mass chromatograms of saturated hydrocarbons, can explain high Rock-Eval T_max values and low petroliferous potential measured along the sedimentary pile. On the other hand, the thermal extent of combustion events was limited to the first 2 m from the contact. The mean reflectance of 0.20–0.24% and porosity of ca. 50% of the grey clayey biomicrites indicate that organic matter was very immature and sediments were unconsolidated at the time of the combustion event. Using mineralogy, microscopic analyses of vegetable debris and magnetic susceptibility, a suite of characteristic points corresponding to the thermal imprint can be assessed: (i) x = 0m, T ∼ 1000 °C, (ii) x = 1 m, T ∼ 350 °C, (iii) x = 2 m, T ∼ 150 °C and (iv) x > ∼ 8 m, T ∼ 30 °C. Paleocirculation of meteoric groundwater in the ‘cement-marbles’ generated high-pH fluids that have circulated via fractures and through the matrix porosity of the underlying biomicrites but have also induced alkaline hydrolysis and oxidative attack of the organic matter. The polysaccharide/lignin ratio derived from μ-FT-i.r. analyses shows that the delignification of vegetable debris and degradation of polysaccharides progressively decline in the indurated zone, which indicates a decrease in the pH of migrating solutions. The latter also severely oxidized organic matter at 2.10 and 3.05 m as revealed by the oxygen index and induced the generation of bitumen. The spatial correlation between the oxidation levels of organic matter and the metal contents (Fe, Ti and Cr) suggests that redox reactions were responsible for the immobilization of metals in the indurated biomicrites. The intensity of these reactions is attributed to changes in the fluid flow regime within the sedimentary column.  相似文献   

GPS/GNSS current bibliography     

Tomás Soler 《GPS Solutions》2007,11(3):223-226

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Diffuse Emission of Hydrogen from Poás Volcano,Costa Rica,America Central     

Gladys V. Melián  Inés Galindo  Nemesio M. Pérez  Pedro A. Hernández  Mario Fernández  Carlos Ramírez  Raúl Mora  Guillermo E. Alvarado 《Pure and Applied Geophysics》2007,164(12):2465-2487

We report the results of four soil H₂ surveys carried out in 2000–2003 at Poás volcano, Costa Rica, to investigate the soil H₂ distribution and evaluate the diffuse H₂ emission as a potential surveillance tool for Poás volcano. Soil gas H₂ contents showed a wide range of concentration from 0.2 to 7,059 ppmV during the four surveys. Maps of soil gas H₂ based on Sequential Gaussian Simulation showed low H₂ concentration values in the soil atmosphere (<0.7 ppmV) for most of the study area, whereas high soil gas H₂ values were observed inside the active crater of Poás. A significant increase in soil gas H₂ concentration was observed inside the active crater during 2001 and 2002 with respect to year 2000, followed by a decrease in 2003. The observed spatial and temporal variations of soil H₂ concentration have been well correlated with seismicity, microgravimetry and fumarolic chemistry changes which occurred during this study. These observations evidence changes in the shallow magmatic-hydrothermal system of Poás, and it might be related to a potential magmatic intrusion during the period 1998–2004. Therefore, monitoring diffuse H₂ emission of Poás has become an important geochemical tool for the monitoring of its volcanic activity.  相似文献   

Embryo dune development on a large,actively accreting macrotidal beach: Calais,North Sea coast of France     

Edward J. Anthony  Stéphane Vanhée  Marie‐Hélène Ruz 《地球表面变化过程与地形》2007,32(4):631-636

Sediment budget data from an 18‐month topographic survey were analysed with data from brief experiments on wind parameters, beach moisture contents, bedforms and sand mobilization in order to monitor conditions and patterns of embryo dune development over a flat 150–1000 m wide accreting upper beach. The surface conditions over the upper beach locally affect aeolian transport, but net dune development over time depends on sustained strong winds and their orientation. Incoming marine sand supplied by storms and onshore winds is reorganized by the dominant offshore to longshore winds into elongated embryo dunes over this upper beach, imprinting a regional morphology of long‐term longshore dune ridge development. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Badland dynamics in the Central Pyrenees: temporal and spatial patterns of weathering processes     

E. Nadal‐Romero  D. Regüés  C. Martí‐Bono  P. Serrano‐Muela 《地球表面变化过程与地形》2007,32(6):888-904

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