Selenium in volcanic environments: A review   总被引：1，自引：0，他引：1  

Geerke H. Floor  Gabriela Román-Ross 《Applied Geochemistry》2012

Selenium is a chemical element with major environmental implications, due to the extremely narrow range between essential and toxic concentrations. Volcanoes emit significant amounts of Se, which has an enormous impact on the Se cycle and potentially human and animal health. This paper presents a broad overview of the current state of knowledge of major aspects of volcanic derived Se, focussing on the processes in soils and aquifers.  相似文献   

Transtensional fault-termination basins: an important basin type illustrated by the Pliocene San Jose Island basin and related basins in the southern Gulf of California, Mexico     

Paul J. Umhoefer  Tobias Schwennicke†  Maya T. Del Margo  Gabriela Ruiz-Geraldo†  James C. Ingle Jr.  ‡  William McIntosh§ 《Basin Research》2007,19(2):297-322

Transtensional basins are sparsely described in the literature compared with other basin types. The oblique‐divergent plate boundary in the southern Gulf of California has many transtensional basins: we have studied those on San Jose island and two other transtensional basins in the region. One major type of transtensional basin common in the southern Gulf of California region is a fault‐termination basin formed where normal faults splay off of strike‐slip faults. These basins suggest a model for transtensional fault‐termination basins that includes traits that show a hybrid nature between classic rift and strike‐slip (pull‐apart) basins. The traits include combinations of oblique, strike‐slip and normal faults with common steps and bends, buttress unconformities between the fault steps and beyond the ends of faults, a common facies pattern of terrestrial strata changing upward and away from the faults into marine strata, small fault blocks within the basin that result in complex lateral facies relations, common Gilbert deltas, dramatic termination of the margin of the basin by means of fault reorganization and boundary faults dying and an overall short basin history (few million years). Similar transtensional fault‐termination basins are present in Death Valley and other parts of the Eastern California shear zone of the western United States, northern Aegean Sea and along ancient strike‐slip faults.  相似文献   

Disrupting biogeochemical cycles - Consequences of damming   总被引：12，自引：0，他引：12  

Gabriela Friedl  Alfred Wüest 《Aquatic Sciences - Research Across Boundaries》2002,64(1):55-65

  相似文献   

Sedimentary facies,depositional processes and climatic controls in a Triassic Lake,Tanzhuang Formation,western Henan Province,China     

María Gabriela Mángano  Luis Alberto Buatois  Xiantao Wu  Junmin Sun  Guocheng Zhang 《Journal of Paleolimnology》1994,11(1):41-65

The Middle to Upper Triassic Tanzhuang Formation represents part of the infill of the early Mesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition within prevailing shallow lake conditions. Well-developed sequences crop out near Jiyuan, western Henan Province, central China. Six sedimentary facies clustered into two facies assemblages were recognized in the lacustrine section. Facies assemblage 1 consists of stacked coarsening-upward sequences composed, from base to top, of organic-rich shales (facies E, type I), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemblage 1 record progradation of small mouth-bar deltas within a perennial open lacustrine system under temperate and humid conditions. Facies assemblage 2 lacks a clear vertical pattern and consists of interbedded fine-grained carbonates and siltstones (facies C); deformed and wave-reworked sandstones (facies D); organic-rich shales (facies E, type II) and clayey mudstones (facies F). The assemblage also represents a perennial, hydrologically-open, shallow lacustrine system, but characterized by strong seasonal climatic control. Water stratification probably occurred in several periods of the lake history. Pangaean megamonsoonal influence is envisaged to explain the strong seasonality imprint evidenced toward the upper part of the Tanzhuang lacustrine column.This is the fourth paper in a series of papers published in this issue on Climatic and Tectonic Rhythms in Lake Deposits.  相似文献   

The impact of heat waves on surface urban heat island and local economy in Cluj-Napoca city,Romania     

Ioana?Herbel  Adina-Eliza?CroitoruEmail author  Adina?Viorica?Rus  Cristina?Florina?Ro?ca  Gabriela?Victoria?Harpa  Antoniu-Flavius?Ciupertea  Ionu??Rus 《Theoretical and Applied Climatology》2018,133(3-4):681-695

The association between heat waves and the urban heat island effect can increase the impact on environment and society inducing biophysical hazards. Heat stress and their associated public health problems are among the most frequent. This paper explores the heat waves impact on surface urban heat island and on the local economy loss during three heat periods in Cluj-Napoca city in the summer of 2015. The heat wave events were identified based on daily maximum temperature, and they were divided into three classes considering the intensity threshold: moderate heat waves (daily maximum temperature exceeding the 90th percentile), severe heat waves (daily maximum temperature over the 95th percentile), and extremely severe heat waves (daily maximum temperature exceeding the 98th percentile). The minimum length of an event was of minimum three consecutive days. The surface urban heat island was detected based on land surface temperature derived from Landsat 8 thermal infrared data, while the economic impact was estimated based on data on work force structure and work productivity in Cluj-Napoca derived from the data released by Eurostat, National Bank of Romania, and National Institute of Statistics. The results indicate that the intensity and spatial extension of surface urban heat island could be governed by the magnitude of the heat wave event, but due to the low number of satellite images available, we should consider this information only as preliminary results. Thermal infrared remote sensing has proven to be a very efficient method to study surface urban heat island, due to the fact that the synoptic conditions associated with heat wave events usually favor cloud free image. The resolution of the OLI_TIRS sensor provided good results for a mid-extension city, but the low revisiting time is still a drawback. The potential economic loss was calculated for the working days during heat waves and the estimated loss reached more than 2.5 mil. EUR for each heat wave day at city scale, cumulating more than 38 mil. EUR for the three cases considered.  相似文献   

Impacts of river impoundment on dissolved heavy metals in floodplain soils of the Lahn River (Germany)     

Jens Hahn  Christian Opp  Nina Zitzer  Gabriela Laufenberg 《Environmental Earth Sciences》2016,75(15):1141

  相似文献   

Present Limnological Conditions and Recent (ca. 340 yr) Palaeolimnology of a Tropical Lake in the Sierra de Los Tuxtlas, Eastern Mexico     

Margarita Caballero  Gabriela Vázquez  Socorro Lozano-García  Alejandro Rodríguez  Susana Sosa-Nájera  Ana Carolina Ruiz-Fernández  Beatriz Ortega 《Journal of Paleolimnology》2006,35(1):83-97

The Sierra de Los Tuxtlas is a recently active volcanic field, with eruptions in 1664 and 1792. It holds one of the reserves of tropical evergreen forest in Mexico, as well as several maar lakes. One of them, Lago Verde, was chosen for a three-fold study (1) on its present limnological conditions, (2) on the algal community living in the water column and preserved in the surface sediments; and (3) on its recent history (ca. 340 yr). The palaeolimnological study was based on multiproxy analyses on core material dated by ²¹⁰Pb, ¹³⁷Cs and ¹⁴C. Lago Verde is a small, shallow lake with dilute, slightly alkaline water (CO₃²⁻ + HCO₃⁻ > Cl⁻ > SO₄²⁻, Na⁺ + K⁺ > Ca²⁺ > Mg²⁺). It is turbid, eutrophic, with high phosphorus levels. It is a warm polymictic lake, with thermal and oxygen stratification establishing by midday during the warm months. The lake does not stratify in winter. Diatoms dominate the phytoplankton community in the cold ‘nortes’ season, Cyanobacteria in summer, and Chlorophyta in autumn. Cyanobacteria (Chroococcales) are not well preserved in the surface sediments while Chlorophyta are better preserved. Sedimentary diatoms are well preserved, dominated by the three most abundant species in the water column: Achnanthidium minutissimum, Fragilaria capucina and Aulacoseira granulata. The base of the studied sequences is constrained by the historic eruption of 1664. The period from 1664 to 1963 is characterised by a meso-eutrophic lake. Tropical Forest vegetation reaches maximum values between ca. 1800 and 1963. Between ca. 1785 and 1885 the lake was slightly shallower than in the rest of the 1664–1963 period, probably recording climatic variability. An early pulse of anthropogenic disturbance was recorded by ca. 1921 and after ca. 1963 intense forest clearance and high erosion rates led to a more turbid, more productive, nutrient-rich lake. The highest anthropogenic impact was reached by ca. 1988; afterwards the lake and its basin reached a new balance, with the establishment of the present modern conditions.  相似文献   

Textural evidence for recent co-seismic circulation of fluids in the Nojima fault zone, Awaji island, Japan     

Anne-Marie Boullier  Koichiro Fujimoto  Tomoyuki Ohtani  Gabriela Roman-Ross  ric Lewin  Hisao Ito  Philippe Pezard  Benoît Ildefonse 《Tectonophysics》2004,378(3-4):165

The Hirabayashi borehole (Awaji Island, Japan) was drilled by the Geological Survey of Japan (GSJ) 1 year after the Hyogo-ken Nanbu (Kobe) earthquake (1995, M_JMA=7.2). This has enabled scientists to study the complete sequence of deformation across the active Nojima fault, from undeformed granodiorite to the fault core. In the fault core, different types of gouge and fractures have been observed and can be interpreted in terms of a complex history of faulting and fluid circulation. Above the fault core and within the hanging wall, compacted cataclasites and gouge are cut by fractures which show high apparent porosity and are filled by 5–50 μm euhedral and zoned siderite and ankerite crystals. These carbonate-filled fractures have been observed within a 5.5-m-wide zone above the fault, but are especially abundant in the vicinity (1 m) of the fault. The log-normal crystal size distributions of the siderite and ankerite suggest that they originated by decaying-rate nucleation accompanied by surface-controlled growth in a fluid saturated with respect to these carbonates. These carbonate-filled fractures are interpreted as the result of co-seismic hydraulic fracturing and upward circulation of fluids in the hanging wall of the fault, with the fast nucleation of carbonates attributed to a sudden fluid or CO₂ partial pressure drop due to fracturing. The fractures cut almost all visible structures at a thin section scale, although in some places, the original idiomorphic shape of carbonates is modified by a pressure-solution mechanism or the carbonate-filled fractures are cut and brecciated by very thin gouge zones; these features are attributed to low and high strain-rate mechanisms, respectively. The composition of the present-day groundwater is at near equilibrium or slightly oversaturated with respect to the siderite, calcite, dolomite and rhodochrosite. Taken together, this suggests that these fractures formed very late in the evolution of the fault zone, and may be induced by co-seismic hydraulic fracturing and circulation of a fluid with a similar composition to the present-day groundwater. They are therefore potentially related to recent earthquake activity (<1.2 Ma) on the Nojima fault.  相似文献   

Analytic hierarchy process applied to landslide susceptibility mapping of the North Branch of Argentino Lake,Argentina     

Moragues  Silvana  Lenzano  María Gabriela  Lanfri  Mario  Moreiras  Stella  Lannutti  Esteban  Lenzano  Luis 《Natural Hazards》2021,105(1):915-941

Natural Hazards - In the present study, we achieved the susceptibility mapping to slope instability processes by the implementation of Analytic Hierarchy Process and Weighted Linear Combination...  相似文献   

Accelerating the solution of linear systems appearing in two-phase reservoir simulation by the use of POD-based deflation methods     

Diaz Cortés  Gabriela Berenice  Vuik  Cornelis  Jansen  Jan-Dirk 《Computational Geosciences》2021,25(5):1621-1645

We explore and develop a Proper Orthogonal Decomposition (POD)-based deflation method for the solution of ill-conditioned linear systems, appearing in simulations of two-phase flow through highly heterogeneous porous media. We accelerate the convergence of a Preconditioned Conjugate Gradient (PCG) method achieving speed-ups of factors up to five. The up-front extra computational cost of the proposed method depends on the number of deflation vectors. The POD-based deflation method is tested for a particular problem and linear solver; nevertheless, it can be applied to various transient problems, and combined with multiple solvers, e.g., Krylov subspace and multigrid methods.

  相似文献