Calculation of the thermodynamic and geochemical consequences of nonideal mixing in the system H₂O-CO₂-NaCl on phase relations in geologic systems: Equation of state for H₂O-CO₂-NaCl fluids at high pressures and temperatures   总被引：1，自引：0，他引：1  

Teresa Suter Bowers  Harold C. Helgeson 《Geochimica et cosmochimica acta》1983,47(7):1247-1275

Fluid inclusion analyses leave little doubt that solutions containing large concentrations of H₂O, CO₂, and electrolytes are involved in a wide range of geologic processes. Although the miscibility gap in the system H₂O-CO₂ occurs only at low temperatures, experimental data reported by Takenouchi and Kennedy (1965) and Gehrig (1980) indicate that the addition of 6 weight percent NaCl relative to H₂O + Nacl extends the region of immiscibility in the system H₂O-CO₂-NaC] to ≥700°C at 500 bars and mole fractions of CO₂ (X_CO2) ? 0.1. In contrast, addition of 20 weight percent NaCl relative to H₂O + NaCl at 700°C and 500 bars expands the miscibility gap to X_CO2 ? 0.2. At 2000 bars, addition of 20 and 35 weight percent NaCl relative to H₂O + NaCl causes the miscibility gap to extend to ~500° and ~700°C, respectively, at . The existence of the immiscible region in this high-pressure/temperature environment has a profound effect on temperatures of equilibration for metamorphic mineral assemblages (Bowers and Helgeson, 1983). To determine the extent to which nonideality in the ternary system affects these equilibria, the modified Redlich-Kwong (MRK.) equation of state was fit to pressure-volume-temperature data taken from Gehrig (1980) along pseudobinaries for which is constant. Fugacity coefficients of the components were then generated from the fugacity coefficient analog of the MRK equation of state and these coefficients were used together with solubility data to determine the compositions of the coexisting immiscible phases. The tie lines connecting the coexisting phases shift in orientation from nearly parallel to the H₂O-CO₂ binary at low temperatures to almost perpendicular to this binary at high temperatures.  相似文献   

Biomonitoring with benthic macroalgae and direct assay of heavy metals in seawater of the Oporto coast (northwest Portugal)   总被引：2，自引：0，他引：2  

M.C.Fernanda Leal  M.Teresa Vasconcelos  Isabel Sousa-pinto  João P.S. Cabral 《Marine pollution bulletin》1997,34(12):1006-1015

The concentrations of dissolved Cd, Cu, Hg and Pb in seawater and algae (Enteromorpha spp. and Porphyra spp.) were determined in parallel on three beaches located in the Oporto coast (Portugal), during 8 successive months, comprising periods of low and high biological productivity. The concentrations of dissolved metals in seawater varied markedly during the sampling period and exhibited seasonality. The concentrations of Cd were high in autumn and winter, but low in spring. The concentrations of Cu and Hg were high in autumn, low in winter and peaked in May. The concentrations of Pb were low in autumn and winter, and also peaked in May. It is likely that biological activity was, at least partially, responsible for the observed seasonal changes. The mean concentrations of dissolved metals in seawater were similar to those reported for polluted and industrialized european coastal areas. Metal concentration factors, calculated month-to-month for each alga, metal and site, varied markedly during the sampling period, indicating that concentration factors based on single or few determinations could be misleading. On the contrary, mean concentration factors (calculated by dividing the mean metal concentration in the algae by the mean metal concentration in seawater) were relatively constant at all three sites, indicating that in the Oporto coast, Enteromorpha spp. can be used to estimate the mean concentration of dissolved Cd, Cu and Hg in seawater, and Porphyra spp., the mean concentration of Cd, Cu and Pb. However, considering that future estimates of the concentrations of these metals in seawater should be based on determinations of the metal contents in Enteromorpha spp. and Porphyra spp. carried out on several occasions spanning a considerable period of time, the use of these algae as monitors of heavy metal pollution can have limited practical advantages over the direct assay of the metals in seawater.  相似文献   

Paleoseismic indications along ‘aseismic’ fault segments in the guadalentín depression (SE Spain)     

Pablo G. Silva  JosL. Goy  Cari Zazo  Javier Lario  Teresa Bardají 《Journal of Geodynamics》1997,24(1-4)

The Guadalentín Depression, located in SE Spain (Murcia Region), is bounded by two of the main NE-SW master faults of the Eastern Betics Cordilleras: The Lorca-Alhama and the Palomares left-lateral strike-slip faults. Available earthquake data indicate that, in the last 600 years, some sectors of the Lorca-Alhama Fault and the entire sector of the Palomares Fault have not been associated with significant historical seismicity. However, they show a wide range of diagnostic features of earthquake surface displacements on late Pleistocene and Holocene alluvial and colluvial surfaces. Aside from the left-lateral offsets recorded along 045–050 ° master fault strands of the Lorca-Alhama Fault, major paleoseismic surface displacements show different kinematics in relation to the broad orientation of the fault strands: (1) vertical normal displacements along 010–020 ° trending faults mainly preserved as degraded fault scarps of 2.5-1.8 m high (Aljibejo site); and (2) vertical reverse displacements, with average offsets of 0.2 – 1 m, along 065–080 ° subsidiary faults. In this last group, the younger one (Carraclaca Baths site) remains as a fault scarp of 0.8 m height affecting a cascade tufa which was active until the Spanish Roman Period (2nd Century B.C. to 6th Century A.D.). In other cases, reverse offsets resulted in smaller displacements (0.26 m) of paleosols, but show a recurrent behaviour (La Escarihuela site). The strongest earthquakes recorded in the study area did not exceed more than Mb 4.5 or MSK Intensity VIII (historical) with no evidence of coseismic rupture. Therefore, the preliminary data presented here seem to indicate that the paleoseismic activity on both faults is capable of producing coseismic surface displacements, probably reaching magnitudes of at least 6.5. These data show that paleoseismic studies based on geomorphological analyses are a useful tool in the assessment of the relative degree of activity of apparently ‘aseismic’ fault traces.  相似文献   

High resolution distribution of magnesium and strontium and the evaluation of Mg/Ca thermometry in Recent brachiopod shells     

Alberto Pérez-Huerta  Maggie Cusack  Teresa E. Jeffries  C. Terry Williams 《Chemical Geology》2008,247(1-2):229-241

High resolution distribution of magnesium and strontium determined by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) are presented in this study for Recent brachiopod shells. The concentration of magnesium and strontium decreases in a similar fashion from the outer to inner regions of shells of rhynchonelliform species but remains unaltered in craniid brachiopods. In rhynchonelliform brachiopods with low-magnesium shells, there is a characteristic chemical profile with an abrupt decrease in magnesium concentration from the primary layer towards the secondary layer until it reaches a region in which the values are almost constant. In addition, there is a proportional relationship in magnesium concentration between primary and secondary layers. Both findings demonstrate the biological control in magnesium incorporation in rhynchonelliform brachiopods confirming previously reported findings. Calculated Mg/Ca ratios based on magnesium concentrations within the innermost region of the secondary layer show that rhynchonelliform brachiopods can record seawater temperature. This finding opens up the possibility of using Mg/Ca (palaeo) thermometry even within the context of biological control and the potential application of Mg/Ca ratios as a seawater temperature proxy in fossil brachiopods.  相似文献   

The Vegetation Resilience After Fire (VRAF) index: Development,implementation and an illustration from central Italy     

Marina Bisson  Alessandro FornaciaiAlessandro Coli  Francesco MazzariniMaria Teresa Pareschi 《International Journal of Applied Earth Observation and Geoinformation》2008

A suitable index is proposed to evaluate the natural short–medium-term recovery capability of vegetation in burnt areas. The study area covers 2450 km² in western Tuscany (Province of Pisa, Italy). This region is characterized by a typical Mediterranean climate and is subject to fire damage during the dry summer season. Damage is mitigated where a natural rapid regrowth of vegetation prevents soil erosion, supporting the return to a natural pre-fire state.  相似文献   

Turning Contention into Collaboration: Engaging Power,Trust, and Learning in Collaborative Networks     

Vanessa R. Levesque  Aram J. K. Calhoun  Kathleen P. Bell  Teresa R. Johnson 《社会与自然资源》2017,30(2):245-260

Given the complexity and multiplicity of goals in natural resource governance, it is not surprising that policy debates are often characterized by contention and competition. Yet at times adversaries join together to collaborate to find creative solutions not easily achieved in polarizing forums. We employed qualitative interviews and a quantitative network analysis to investigate a collaborative network that formed to develop a resolution to a challenging natural resource management problem, the conservation of vernal pools. We found that power had become distributed among members, trust had formed across core interests, and social learning had resulted in shared understanding and joint solutions. Furthermore, institutions such as who and when new members joined, norms of inclusion and openness, and the use of small working groups helped create the observed patterns of power, trust, and learning.  相似文献   

The Signatures of Structured Winds in T Tauri Stars     

Maria Teresa V.T. Lago  Jorge F. Gameiro  Vitor M. Costa  Leandro Machado  António Pedrosa 《Astrophysics and Space Science》1998,261(1-4):107-116

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Variation in the Sizes of Chthamalid ­Barnacle Post-Settlement Cyprids on European Shores     

Ruth M. O'Riordan  Jane Delany    David McGrath    Alan A. Myers  Anne Marie Power    Neil F. Ramsay  Damaso Alvarez  Teresa Cruz  Federica G. Pannacciulli    Pedro Range  & Giulio Relini 《Marine Ecology》2001,22(4):307-322

Abstract. As part of a wider study on the settlement and recruitment of Chthamalus spp. in Europe, this study investigated whether chthamalid cyprids can be separated by length on a European scale. Variation in cyprid length with latitude and temporal variation at selected localities were also examined. The lengths of cyprids collected between 1996 – 1999 on nine rocky shores in Europe are reported. Elminius modestus cyprids were found only at Roscoff, NW France and could be distinguished due to their carapace shape and length. They showed a unimodal length distribution, measuring between 450 and 625 µm, with no variation in length between the two sampling dates (1997 and 1998). Based on carapace shape and length, the remaining cyprids in the collections were identified as one of three chthamalid species, Chthamalus montagui, Chthamalus stellatus or Euraphia depressa. Bimodal length distributions of chthamalid cyprids were seen on some shores, while others had a single small‐sized modal group (representing C. montagui on Atlantic shores and/or E. depressa in the Mediterranean) separated from a few distinctly larger cyprids (C. stellatus). Metamorphs collected simultaneously with cyprid collections were identified as C. stellatus or C. montagui, except at Roscoff, where E. modestus were also found. In southern Portugal, where all metamorphs collected were C. montagui and adult C. montagui were the dominant barnacles, most cyprids measured between 350 and 550 µm long and this size distribution coincides with the distribution expected for C. montagui. Cyprids collected on these four more southerly Portuguese shores had the same modal length class (475 µm) and this remained constant between successive years at Luz and Albufeira, Algarve. The smallest (350 µm long) wild chthamalid cyprids found were from southern Portugal and Italy. In Spain, France and Ireland the smallest chthamalid cyprid was 425 µm long. The results from the present study support the hypothesis that on Atlantic shores cyprids of C. montagui can be separated from those of C. stellatus based on size, although there is some variation in cyprid length with latitude as well as temporal variation at selected localities.  相似文献   

Taxonomic versus trophic structure of mesozooplankton: a seasonal study of species succession and stable carbon and nitrogen isotopes in a coastal upwelling ecosystem   总被引：2，自引：0，他引：2  

Bode  Antonio; Alvarez-Ossorio  Maria Teresa 《ICES Journal of Marine Science》2004,61(4):563-571

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Contribution of consensus methods to resolve sources of uncertainty in suitability maps modeling: application in the Zahrez El Gharbi,Steppe of Algeria     

Boudjema Sehl  Mohamed Said Guettouche  Hocine Ait Mouheb  María Teresa Camacho Olmedo 《Arabian Journal of Geosciences》2018,11(7):143

Modeling techniques have the power to predict land use change. Our research had three main aims: firstly, to compare and contrast the predictive performance of individual models versus consensus methods; secondly, to compare the different consensus methods; and finally, to compare their predictive performance for generalized and marginal land uses in the environment in the study area. Seven individual models were used to generate the suitability maps for each type of land use in Zahrez El Gharbi (Algeria), characterized by the suitability values for their occurrence. Seven consensus methods were created by combining the individual models. The predictive performance of the individual models and of the consensus methods was assessed by calculating the area under the curve (AUC). For each type of land use, the predictive quality of the consensus methods was considerably better than that of the individual models. The weighted averages method (WA) proved the most efficient of the seven consensus methods. The types of land use have a significant influence on the predictive quality, in that the AUC values increase in line with increases in the marginality of the particular type of land use. The improvements in predictive quality achieved by consensus methods in general and the weighted averages method (WA) in particular would substantially resolve the different sources of uncertainties resulting from the use of individual models and from the environmental characteristics of the different types of land use.  相似文献