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1.
Five different methods for assessing intrinsic aquifer vulnerability were tested in a case study and their results compared. The test area was a slightly karstified district in the Condroz region of Belgium. The basin covers about 65 km2 and the karst aquifer provides a water-supply of about 28,000 m3d-1. The methods tested were: EPIK (Doerfliger et al. 1999), DRASTIC (Aller et al. 1987), 'German method' (von Hoyer and Söfner 1998), GOD (Foster 1987) and ISIS (Civita and De Regibus 1995). The results are compared and critically examined. From the analysis, it seems that reducing the number of parameters is unsatisfactory, due to the variety of geological conditions. The various methods produce very different results at any given site. As only physically-based methods can be checked for their reliability, it is clear that future vulnerability mapping techniques must incorporate such methods. 相似文献
2.
Application of groundwater sustainability indicators to the carbonate aquifer of the Sierra de Becerrero (Southern Spain) 总被引:3,自引:1,他引:2
L. J. Lambán S. Martos M. Rodríguez-Rodríguez J. C. Rubio 《Environmental Earth Sciences》2011,64(7):1835-1848
The objective of this study was to test the applicability of groundwater sustainability indicators defined by UNESCO, together
with the International Academy of Environmental Sciences (IAES), the International Association of Hydrogeology (IAH) Group
on Groundwater Indicators and the Geological Survey of Spain (IGME), to the aquifer scale. We selected four main indicators
based on their relevance in the field of groundwater sustainability and because they proved to be the most reliable, based
on the data collection and methodology utilized. These indicators were applied to a small—26 km2 of permeable outcrops—carbonate aquifer situated in the province of Seville (southern Spain), which has semi-arid climate
conditions (500 mm/year). The integral application of all these indicators in this particular groundwater body leads us to
conclude that, at present, the aquifer is undergoing intensive use. Therefore, the exploitation of its water resources is
surpassing the threshold of sustainability when both the quantity and the quality of the groundwater are taken into consideration.
The continued increase in exploitation generates a descending trend in the evolution of the piezometric levels, a consequence
of adaptation to the new hydrodynamic situation, and also results in exhaustion of the springs that drain the aquifer in undisturbed
conditions. At the same time, there is a trend of increasing salinity in the groundwater and a risk of contamination by nitrate
which, according to the EU Water Framework Directive and the Groundwater Daughter Directive (EU Official Journal of the European
Communities L327, 2000; EU Official Journal of the European Communities L372/19, 2006), should be controlled and reduced. In the future, application of the methodology described here may prove useful for the
evaluation of similar systems, either in southern Spain or in other countries with semi-arid climates. 相似文献
3.
James M. D. Day Colin G. Macpherson David Lowry D. Graham Pearson 《Contributions to Mineralogy and Petrology》2012,164(1):177-183
Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) report laser-assisted fluorination (LF) and secondary ionization mass spectrometry (SIMS) 18O/16O datasets for olivine grains from the Canary Islands of Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro. As with prior studies of oxygen isotopes in Canary Island lavas (e.g. Thirlwall et al. Chem Geol 135:233–262, 1997; Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010), these authors find variations in δ18Ool (~4.6–6.0 ‰) beyond that measured for mantle peridotite olivine (Mattey et al. Earth Planet Sci Lett 128:231–241, 1994) and interpret this variation to reflect contributions from pyroxenite-peridotite mantle sources. Furthermore, Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) speculate that δ18Ool values for La Palma olivine grains measured by LF (Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) may be biased to low values due to the presence of altered silicate, possibly serpentine. The range in δ18Ool values for Canary Island lavas are of importance for constraining their origin. Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) took a subset (39 SIMS analyses from 13 grains from a single El Hierro lava; EH4) of a more extensive dataset (321 SIMS analyses from 110 grains from 16 Canary Island lavas) to suggest that δ18Ool is weakly correlated (R 2 = 0.291) with the parameter used by Gurenko et al. (Earth Planet Sci Lett 277:514–524, 2009) to describe the estimated weight fraction of pyroxenite-derived melt (Xpx). With this relationship, end-member δ18O values for HIMU-peridotite (δ18O = 5.3 ± 0.3 ‰) and depleted pyroxenite (δ18O = 5.9 ± 0.3 ‰) were defined. Although the model proposed by Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) implicates similar pyroxenite-peridotite mantle sources to those proposed by Day et al. (Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) and Day and Hilton (Earth Planet Sci Lett 305:226–234, 2011), there are significant differences in the predicted δ18O values of end member components in the two models. In particular, Day et al. (Geochim Cosmochim Acta 74:6565–6589, 2010) proposed a mantle source for La Palma lavas with low-δ18O (<5 ‰), rather than higher-δ18O (c.f. the HIMU-peridotite composition of Gurenko et al. in Contrib Mineral Petrol 162:349–363, 2011). Here we question the approach of using weakly correlated variations in δ18Ool and the Xpx parameter to define mantle source oxygen isotope compositions, and provide examples of why this approach appears flawed. We also provide reasons why the LF datasets previously published for Canary Island lavas remain robust and discuss why LF and SIMS data may provide complementary information on oxygen isotope variations in ocean island basalts (OIB), despite unresolved small-scale uncertainties associated with both techniques. 相似文献
4.
Victor Kress 《Contributions to Mineralogy and Petrology》2007,154(2):191-204
Experiments were performed in the system O–S–Fe–Ni designed to extend our understanding of the chemistry of sulfide liquids.
Results indicate that adding nickel to Fe-rich sulfide liquids in equilibrium with silicate liquids extends their stability
field to much higher oxygen fugacities and lower sulfur fugacities. Increasing Ni/Fe at a given temperature and sulfur and
oxygen fugacity is accompanied by a significant decrease in the oxygen content of the sulfide liquid. Results of these experiments
are combined with data from the literature to calibrate an associated regular solution model for O–S–Fe–Ni liquids. This model
represents a complete refit of the associated regular solution model of Kress (Contrib Mineral Petrol 139:316–325, 2000). The resulting model is combined with the olivine solution model of Hirschmann (Am Mineral 76:1232–1248, 1991) to explore the effect of variations in oxygen and sulfur fugacities on the distribution of Fe and Ni between olivine and
sulfide liquid. Predicted olivine–sulfide distribution trends parallel those observed by Gaetani and Grove (Geochim Cosmochim
Acta 61:1829–1846, 1997), Gaetani and Grove (Earth Planet Sci Lett 169:147–163, 1999), Brenan and Caciagli (Geochim Cosmochim Acta 64:307–320, 2000) and Brenan (Geochim Cosmochim Acta 67:2663–2681, 2003), but are systematically offset toward lower predicted Ni in the sulfide. Nevertheless our results are consistent with the
assertion that low K
D
os
values in magmatic ore deposits such as the J-M Reef reflect high iron contents in the sulfides combined with relatively
high oxygen fugacities.
相似文献
Victor KressEmail: |
5.
Zr-in-rutile thermometry in HP/UHP eclogites from Western China 总被引:5,自引:0,他引:5
Guibin Zhang David J. Ellis Andrew G. Christy Lifei Zhang Shuguang Song 《Contributions to Mineralogy and Petrology》2010,160(3):427-439
Four Zr-in-rutile thermometry calibrations are applied to eclogites from Western China. Here, we show that if rutile grows
in equilibrium with Qtz and Zrn, and is isolated inside garnet, it preserves its Zr composition and does not undergo compositional
change due to cation exchange with the host garnet. It thus preserves the composition for the P–T conditions of its formation and the growth zoning of the host garnet. For the HP/UHP metamorphic temperature, the Tomkins
et al. (J Metamorph Geol 25:703–713, 2007) calibration yields temperatures that agree well with previous studies, whereas the other three calibrations (Zack et al.
in Contrib Mineral Petrol 148:471–488, 2004; Watson et al. in Contrib Mineral Petrol 151:413–433, 2006; Ferry and Watson in Contrib Mineral Petrol in 154:429–437, 2007), which do not include a pressure correction, give systematically lower temperatures. Zr contents of rutile inclusions within
garnet show systematic decrease from garnet core to rim. The rutile inclusions in garnet rims contain the lowest Zr content,
similar to that in the matrix. Analyses confirm that the pressure plays a significant role in modifying the primary temperature
dependence of the Zr content of rutile. Rutiles trapped in garnets are unable to re-equilibrate easily during retrogression,
but those in the matrix can do so, providing retrograde P–T path information. 相似文献
6.
T. W. Sisson J.-I. Kimura M. L. Coombs 《Contributions to Mineralogy and Petrology》2009,158(6):803-829
A basanite–nephelinite glass suite from early submarine Kilauea defines a continuous compositional array marked by increasing
concentrations of incompatible components with decreasing SiO2, MgO, and Al2O3. Like peripheral and post-shield strongly alkalic Hawaiian localities (Clague et al. in J Volcanol Geotherm Res 151:279–307,
2006; Dixon et al. in J Pet 38:911–939, 1997), the early Kilauea basanite–nephelinite glasses are interpreted as olivine fractionation products from primary magnesian
alkalic liquids. For early Kilauea, these were saturated with a garnet–phlogopite–sulfide peridotite assemblage, with elevated
dissolved CO2 contents responsible for the liquids’ distinctly low-SiO2 concentrations. Reconstructed primitive liquids for early Kilauea and other Hawaiian strongly alkalic localities are similar
to experimental 3 GPa low-degree melts of moderately carbonated garnet lherzolite, and estimated parent magma temperatures
of 1,350–1,400°C (olivine–liquid geothermometry) match the ambient upper mantle geotherm shortly beneath the base of the lithosphere.
The ~3 GPa source regions were too hot for stable crystalline carbonate and may have consisted of ambient upper mantle peridotite
containing interstitial carbonate–silicate or carbonatitic liquid, possibly (Dixon et al. in Geochem Geophys Geosyst 9(9):Q09005,
2008), although not necessarily, from the Hawaiian mantle plume. Carbonate-enriched domains were particularly susceptible to further
melting upon modest decompression during upward lithospheric flexure beneath the advancing Hawaiian Arch, or by conductive
heating or upward drag by the Hawaiian mantle plume. The early Kilauea basanite–nephelinite suite has a HIMU-influenced isotopic
character unlike other Hawaiian magmas (Shimizu et al. in EOS Tran Amer Geophys Union 82(47): abstr V12B-0962, 2001; Shimizu et al. in Geochim Cosmochim Acta 66(15A):710, 2002) but consistent with oceanic carbonatite involvement (Hoernle et al. in Contrib Mineral Petrol 142:520–542, 2002). It may represent the melting products of a fertile domain in the ambient upper mantle impinged upon and perturbed by the
sustained plume source that feeds later shield-stage magmatism. 相似文献
7.
Swastika Chatterjee Sirshendu Bhattacharyya Surajit Sengupta Tanusri Saha-Dasgupta 《Physics and Chemistry of Minerals》2011,38(4):259-265
We report studies based on a combination of ab initio electronic structure and Monte Carlo (MC) technique on the problem of
cation partitioning among inequivalent octahedral sites, M1 and M2 in mixed olivines containing Mg2+ and Fe2+ ions. Our MC scheme uses interactions derived out of ab initio, density functional calculations carried out on measured crystal
structure data. Our results show that there is no reversal of the preference of Fe for M1 over M2 as a function of temperature.
Our findings do not agree with the experimental findings of Redfern et al. (Phys Chem Miner 27:630–637, 2000), but are in agreement with those of Heinemann et al. (Eur J Mineral 18:673–689, 2006) and Morozov et al. (Eur J Mineral 17:495–500, 2005). 相似文献
8.
Perception of flood risk in Danube Delta,Romania 总被引:1,自引:1,他引:0
For exposed and vulnerable communities, the perception of natural risk is an essential link in the analysis of man–environment
coping relationship and also an important parameter in the quantification of complex vulnerability as a central predictive
variable in the risk equation. The topic of flood risk in related perception is of considerable interest, as some recently
published papers have proven (Messner and Meyer 2005, 2006; Raaijmakers et al. 2008). The aim of the current study is to reveal the conscious and unconscious attitudes towards the flood risk for the inhabitants
of the Danube Delta/Romania. These attitudes, defined by different degrees of psychological vulnerability, represent the background
for a series of psycho-behavioural patterns that generate certain adjustment mechanisms and strategies. Application of a specially
designed questionnaire and the statistical analysis of the results revealed two psychological factors as essential in establishing
the psychosocial vulnerability degree of the interviewed subjects: (i) an internal control factor and (ii) an external control
factor. The persons characterized by inner control have a significantly reduced general anxiety level in comparison to individuals
with the control factor placed externally. As confidence diminishes, it increases the tendency of the individual to rely on
the external factors for support and security. The lack of resources (indicating lower resilience) and mistrust in the support
given emphasizes non-adaptive behaviours.
相似文献
Iuliana ArmaşEmail: |
9.
Environmental hazards posed by the Los Angeles Basin urban oilfields: an historical perspective of lessons learned 总被引:1,自引:0,他引:1
Urban encroachment into areas historically reserved for oil and gas field operations is an ever-present problem within the Los Angeles Basin. The recent frenzy in real estate development has only intensified what can be characterized as a conflict in land usage. Subsurface mineral rights are severed from surface ownership, often resulting in developments being approved without adequate consideration of the underlying oil and gas field consequences. Also, surface operations are frequently co-located within residential areas without consideration of the health and safety consequences of emissions of toxics to air. This paper presents a review of the environmental, health and safety hazards posed by urban oilfield operations, with an emphasis upon the lessons learned from the L.A. Basin: Original Urban Oilfield Legend (see Castle and Yerkes 1976; Denton and others 2001; Endres and others 2002; Kouznetsov and others 1994; Katz and others 1994; Schumacher and Abrams 1994; and Schoell 1983). The Los Angeles Basin has provided the authors with one of the largest natural laboratories in the world for studying the consequences of these issues. The results presented are part of a long-term research program based upon the application of geoscience and petroleum engineering principles in obtaining a fundamental understanding of the root causes of the environmental hazards posed. Topics addressed include: (1) vertical migration of gas to the surface along faults and improperly completed or abandoned wellbores (e.g., due to poor cementing practices), (2) subsidence caused by the fluid production and declining reservoir pressures, (3) soil and groundwater contamination resulting from historic oil and gas field operations, and (4) air toxics resulting from surface operations. A number of case histories are discussed that illustrate the seriousness of the problem. A clear case is made for the urgent need for closer coordination and education by the petroleum industry of the local government planning departments. These departments have the principal role in determining land use policies, acting as the lead agency in performing environmental site assessments (e.g., under the California Environmental Quality Act), and in establishing mitigation measures for dealing with the long-term environmental hazards. This paper establishes prudent practices on the part of oilfield operators for the monitoring and mitigation of these hazards. 相似文献
10.
In situ unpolarized and polarized Fourier transform infrared spectra of a natural orthopyroxene at varying temperatures were
obtained using a heating stage attached on an Infrared microscope. The three main bands (3,595, 3,520 and 3,410 cm−1) at room temperature are ascribed to OH fundamental stretching bands. With increasing temperature from room temperature to
500 °C, the 3,595 cm−1 band shifts 20 cm−1 to lower frequency. The total integral absorbance decreases with increasing temperature. These changes are reversible. Excluding
the influences of dehydration, proton migration, thermal expansion, and changes in OH dipole direction, the change of integral
absorbance with temperature reflects the temperature dependence of absorption coefficient due to the anharmonicity of OH vibration.
Based on the integral absorption coefficient at room temperature (14.84 ppm−1 cm−2) from Bell et al. (Am Mineral 80:463–474, 1995), the integral absorption coefficients at other temperatures are calculated. The variation of integral absorption coefficient
between room temperature and 500 °C obtained in this study is about 18.5 % and may be greater at higher temperature according
to the proposed linear relationship. 相似文献
11.
Mingbin Huang D. G. Fredlund M. D. Fredlund 《Geotechnical and Geological Engineering》2010,28(2):105-117
There are significant advantages in using indirect pedo-transfer functions, (PTFs) for the estimation of unsaturated soil
properties. The pedo-transfer functions can be used for the estimation of the soil–water characteristic curve (SWCC) which
in turn is used for the estimation of other unsaturated soil properties. The accuracy of the indirect pedo-transfer function
method for the estimation of the SWCC depends on the PTF and the equation used to best-fit the particle-size distribution
(PSD) data. The objectives of this study are to: (1) evaluate the performance of the Fredlund et al. (Can Geotech J 37:817–827,
2000) equation for best-fitting the particle-size distribution, (PSD) data, and, (2) compare the predictions made by two of the
commonly used PTFs; namely, Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) and Fredlund et al. (Can Geotech J 39:1103–1117, 2002), for estimating the SWCC from the PSD. The authors used 258 measured PSDs and SWCC datasets from the Loess Plateau, China,
for this study. The dataset consisted of 187 silt–loam soils, 41 loam soils, 11 silt–clay–loam soils, 10 sand–loam soils,
6 silt–clay soils, and 3 loam–sand soils. The SWCC and PSD datasets were measured using a Pressure Plate apparatus and the
pipette method, respectively. The comparison between the estimated and measured particle-size distribution curves showed that
the Fredlund et al. (Can Geotech J 37:817–827, 2000) equation closely prepresented the PSD for all soils in the Loess Plateau, with a lower root mean square error (RMSE) of
0.869%. The comparison between the estimated and measured water contents at the same suction showed that the Fredlund et al.
(Can Geotech J 39:1103–1117, 2002) PTF performed somewhat better than the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) function. The Fredlund et al. method had RMSE value of 0.039 cm3 cm−3 as opposed to 0.046 cm3 cm−3 for the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) method. The Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF produced the closest predictions for sand–loam, loam–sand, and loam soils, with a lower RMSE for gravimetric water content
ranging from 0.006 to 0.036 cm3 cm−3. There were consistent over-estimations observed for silt–loam, silt–clay–loam, and slit–clay soils with RMSE values for
gravimetric water content ranging from 0.037 to 0.043 cm3 cm−3. The measured and estimated air-entry values were closest when using the Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF. The measured and estimated maximum slopes on the SWCC were closest when using the Arya and Paris (Soil Sci Soc Am J
45:1023–1030, 1981) PTF. 相似文献
12.
The conventional Cornell’s source-based approach of probabilistic seismic-hazard assessment (PSHA) has been employed all around
the world, whilst many studies often rely on the use of computer packages such as FRISK (McGuire FRISK—a computer program
for seismic risk analysis. Open-File Report 78-1007, United States Geological Survey, Department of Interior, Washington 1978) and SEISRISK III (Bender and Perkins SEISRISK III—a computer program for seismic hazard estimation, Bulletin 1772. United
States Geological Survey, Department of Interior, Washington 1987). A “black-box” syndrome may be resulted if the user of the software does not have another simple and robust PSHA method
that can be used to make comparisons. An alternative method for PSHA, namely direct amplitude-based (DAB) approach, has been
developed as a heuristic and efficient method enabling users to undertake their own sanity checks on outputs from computer
packages. This paper experiments the application of the DAB approach for three cities in China, Iran, and India, respectively,
and compares with documented results computed by the source-based approach. Several insights regarding the procedure of conducting
PSHA have also been obtained, which could be useful for future seismic-hazard studies. 相似文献
13.
Analysis of existing data and models on point defects in pure (Fe,Mg)-olivine (Phys Chem Miner 10:27–37,1983; Phys Chem Miner 29:680–694, 2002) shows that it is necessary to consider thermodynamic non-ideality of mixing to adequately describe the concentration of
point defects over the range of measurement. In spite of different sources of uncertainties, the concentrations of vacancies
in octahedral sites in (Fe,Mg)-olivine are on the order of 10−4 per atomic formula unit at 1,000–1,200 °C according to both the studies. We provide the first explicit plots of vacancy concentrations
in olivine as a function of temperature and oxygen fugacity according to the two models. It is found that in contrast to absolute
concentrations at ∼1,100 °C and dependence on fO2, there is considerable uncertainty in our knowledge of temperature dependence of vacancy concentrations. This needs to be
considered in discussing the transport properties such as diffusion coefficients. Moreover, these defect models in pure (Fe,Mg)-olivine
need to be extended by considering aliovalent impurities such as Al, Cr to describe the behavior of natural olivine. We have
developed such a formulation, and used it to analyze the considerable database of diffusion coefficients in olivine from Dohmen
et al. (Phys Chem Miner this volume, 2007) (Part - I) and older data in the literature. The analysis documents unequivocally for the first time a change of diffusion
mechanism in a silicate mineral—from the transition metal extrinsic (TaMED) to the purely extrinsic (PED) domain, at fO2 below 10−10 Pa, and consequently, temperatures below 900 °C. The change of diffusion mechanism manifests itself in a change in fO2 dependence of diffusivity and a slight change in activation energy of diffusion—the activation energy increases at lower temperatures. These are consistent with the predictions of Chakraborty (J Geophys Res 102(B6):12317–12331, 1997). Defect formation enthalpies in the TaMED regime (distinct from intrinsic defect formation) lie between −66 and + 15 kJ/mol
and migration energies of octahedral cations in olivine are most likely ∼ 260 kJ/mol, consistent with previous inferences
(Phys Chem 207:147–162, 1998). Plots are shown for diffusion at various constant fO2 as well as along fO2 buffers, to highlight the difference in behavior between the two. Considering all the diffusion data and constraints from
the point defect models, (Fe–Mg) diffusion in olivine along [001] is best described by the Master equations: (1) At oxygen
fugacities greater than 10−10 Pa:
where T is in Kelvin, P and fO2 is in Pascals, X
Fe is the mole fraction of the fayalite component and R is the gas constant in J/mol/K. (2) At oxygen fugacities less than 10−10 Pa:
These equations reproduce all of the 113 experimental data points within half an order of magnitude. (3) Alternately, a global
equation averaging out the change of mechanism may be used, with somewhat larger errors in reproducing the measured diffusion
data. It underestimates data at higher temperatures, and overestimates them at lower temperatures on the average. Note that
fO2 is not explicitly considered here, leading to additional sources of error:
To obtain diffusion coefficients along [100] and [010], log 6 needs to be subtracted from each of the above equations.
An erratum to this article can be found at 相似文献
14.
The origin of chromitites and related PGE mineralization in the Bushveld Complex: new mineralogical and petrological constraints 总被引:2,自引:0,他引:2
Naldrett A. J. Wilson Allan Kinnaird Judith Yudovskaya Marina Chunnett Gordon 《Mineralium Deposita》2012,47(3):209-232
This article reports a study of chromitites from the LG-1 to the UG-2/3 from the Bushveld Complex. Chromite from massive chromitite
follows two compositional trends on the basis of cation ratios: trend A—decreasing Mg/(Mg + Fe) with increasing Cr/(Cr + Al);
trend B—decreasing Mg/(Mg + Fe) with decreasing Cr/(Cr + Al). The chromitites are divided into five stages on the basis of
which trend they follow and the data of Eales et al. (Chemical Geology 88:261–278, 1990) on the behaviour of the Mg/Fe ratio of the pyroxene and whole rock Sr isotope composition of the environment in which they
occur. Following Eales et al. (Chemical Geology 88:261–278, 1990), the different characteristics of the stages are attributed to the rate at which new magma entered the chamber and the effect
of this on aAl2O3 and, in the case of stage 5, the appearance of cumulus plagioclase buffering the aAl2O3. The similarity of PGE profiles across the MG-3 and MG-4 chromitites that are separated laterally by up to 300 km and the
variation in V in the UG-2 argue that the chromitites have largely developed in situ. Modelling using the programme MELTS
shows that increase in pressure, mixing of primitive and fractionated magma, felsic contamination of primitive magma or addition
of H2O do not promote crystallization of spinel before orthopyroxene (in general they hinder it) and that the Cr2O3 content of the magma was of the order of 0.25 wt.%. Less than 20% of the chromite in the magma is removed before orthopyroxene
joins chromite, which implies a >13-km thickness of magma for the Critical Zone. It is suggested that the large excess of
magma has escaped up marginal structures such as the Platreef. The PGE profile of chromitites depends on whether sulphide
accumulated or not along with chromite. Modelling shows that contamination of Critical Zone magma with a felsic melt will
induce sulphide immiscibility, although not chromite precipitation. The LG-1 to LG-4 chromitites developed without sulphide,
whilst those from the LG-5 upwards had associated liquid sulphide. Much of the sulphide originally in the LG-5 and above has
been destroyed as a result of reaction with the chromite. 相似文献
15.
The standard thermodynamic properties at 25°C, 1 bar (ΔG
fo, ΔH
fo, S
o, C
Po, V
o, ω) and the coefficients of the revised Helgeson–Kirkham–Flowers equations of state were evaluated for several aqueous complexes
formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta
52:2009–2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359–1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate
the log K of the destruction reactions of these metal–arsenate and metal–arsenite aqueous complexes at pressures and temperatures required
by the EQ3/6 software package, version 7.2b. Apart from the AlAsO4o and FeAsO4o complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally
for the Ca–dihydroarsenate and Ca–hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)–hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79–94, 2006), whereas the disagreement with the log K measured for the Ca–arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and
arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous
solutions deriving from mixing of acid mine waters and surface waters.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
16.
Sarah Wolf 《Natural Hazards》2012,61(3):1099-1113
The concepts vulnerability and risk are of great importance in the fields of climate change and natural hazards. Confusion
is asserted in the terminology used by the respective communities, and a large conceptual literature has not solved this problem.
This affects the communication within and between the two communities and the comparison of results from vulnerability and
risk assessments. This paper argues that the main difference between methods to assess vulnerability and risk in the climate
and the disaster communities is not a conceptual one, but rather different terminologies are used. This point is made using
a formal framework of vulnerability to climate change that makes the structure of vulnerability and risk assessments explicit.
The framework distinguishes three assessment approaches in the field of vulnerability to climate change, which recur—under
different labels—in the risk assessment approaches analysed. While within each community, the same terms are ambiguously used
to refer to more than one assessment approach, the confusion is enhanced between the two communities by using different labels
for very similar approaches. As an application of the results, similarities and differences between two assessment tools are
analysed: the Dynamic Interactive Vulnerability Assessment model (DIVA) for the case of vulnerability to climate change and
the CATastrophe SIMulation model (CatSim) for risk of natural hazards. 相似文献
17.
Laurent Chauvaud Julien Thébault Jacques Clavier Anne Lorrain Øivind Strand 《Estuaries and Coasts》2011,34(2):211-220
Mollusk shells contain geochemical information about environmental conditions that prevailed at the time of formation. We
investigated ontogenetic and seasonal variations of δ13C in calcitic shells of Pecten maximus. Ontogenetic variations of δ13Cshell in three large specimens collected in Norway, France, and Spain exhibited a similar linear decrease with increasing shell
height. We removed this linear drift (detrending). These three residual time series displayed variations that could be linked
to environmental fluctuations. To check it, we reanalyzed the isotopic datasets of Lorrain et al. (Journal of Experimental
Marine Biology and Ecology 275:47–61, 2002, Geochimica et Cosmochimica Acta 68:3509–3519, 2004), who worked on three scallops harvested in 2000 in the bay of Brest (France), a well-monitored ecosystem. Lowest values
of δ13Cshell detrended were recorded in all shells in late spring–early summer, most likely reflecting corresponding variations in food availability.
Our results indicate that ontogenetic and seasonal variations of δ13Cshell cannot be used as a proxy for past δ13CDIC variations but should be considered as promising tools for ecophysiological studies. 相似文献
18.
Numerical models of atmosphere–ocean circulation are widely used to understand past climate and to project future climate change. Although the same laws of physics, chemistry, and fluid dynamics govern any general circulation model, each model’s formulations and parameterizations are different, yielding different projections. Notwithstanding, models within an ensemble will have varying degrees of similarity for different outputs of interest. Multi-model ensembles have been used to increase forecast skill by using simple or weighted averages where weights have been obtained by considering factors such as estimated model bias and consensus with other models (Giorgi and Mearns, J. Clim. 15:1141–1158, 2002, Geophys. Res. Lett. 30:1629–1632, 2003; Tebaldi et al., Geophys. Res. Lett. 31:L24213, 2004, J. Clim. 18:1524–1540, 2005). This paper considers an alternative view of multi-model ensembles. For use with the North American Regional Climate Change Assessment Program (NARCCAP), multivariate statistical models are employed to characterize modes of similarity within the members of an ensemble. Specifically, we propose a spatially-correlated latent variable model which facilitates the exploration of when, where, and how regional climate models are similar, and what factors best predict observed locations of model convergence. 相似文献
19.
The role of fluid injection on the occurrence and migration path for the aftershocks of 2004 Sumatra earthquake (Mw 9.3) and
January 2005 Andaman earthquake swarm within the aftershock sequence is investigated here from the viewpoint of pore fluid
diffusion process. The Sumatra earthquake created a regionally extensive crustal rupture plane exceeding 1,200 km length below
the Andaman Sea. The r–t plots (Shapiro et al. 1997) are constructed for these aftershocks in order to examine the role of poroelastic effects as rupturing progressed with time.
Their main results are as follows: the r–t plot corresponding to first 3 h of aftershock activity (when only 44 events of mb ≥ 4.5 originated) reveals that 95% of the
data points occurred below the modelled parabola with relatively high D value of 20 m2/s, whereas a significantly low D value of 3.5 m2/s characterises the aftershock activity for the first 24 h (when 420 events of mb ≥ 4.0 occurred). Here, the Coulomb stress
was transferred from the main shock with a rapid imposition of normal stress, thus inducing the pore-pressure change that
started diminishing almost immediately by fluid diffusion, at a rate, defined by the diminishing D value. The modelling results for fault seismicity at far off distances from the main epicentre are interpreted here as potential
indicators for large-scale sub-seabed rupturing—consequent to stress changes induced by bending of the Indian Ocean plate.
Bathymetric slopes under the Andaman subduction zone are particularly amenable to sub-marine slides where crustal E–W hinge
faults inferred seismically cut across the N–S trending regional thrust and strike-slip faults. Seabed rupturing appears to
allow deep-slab hydration in these areas, producing pressure gradients along the normal faults. These features are important
since they can herald marine geohazards in the Andaman region. 相似文献
20.
Brent Doberstein 《Natural Hazards》2009,50(2):361-377
This article explores whether past exposure to debris flow disasters with a human dimension (e.g. caused in part by deforestation)
results in adaptive hazard mitigation and improved environmental and resource management practices in affected areas. When
guiding hazard mitigation practice, the ‘adaptive hazard mitigation’ approach views mitigation as a multi-dimensional experiment,
with the associated need for post-experiment monitoring, evaluation, learning and adjustment, and attention paid to multiple
scales (Bogardi 2004). This article explores how the concept of ‘adaptive hazard mitigation’ has emerged, linking this ‘adaptive management’ used
increasingly in resource and environmental management. Two case studies of disasters linked to human-induced environmental
change are examined, and the mitigation responses of local communities, NGOs and Government agencies are documented. Data
sources include secondary data (journal articles, web-based disaster reports and grey literature) on each disaster, key informant
interviews (n = 8) and direct observation over the 2005–2006 period of post-disaster mitigation actions implemented after each disaster.
The research indicates that in both case studies, a limited range of hazard mitigation actions was employed, including both
structural and non-structural approaches. However, the research also found that causal factors involving human-induced environmental
change (e.g. deforestation) were not addressed, and overall, the hazard mitigation strategies adopted lacked monitoring, learning
and adjustment. In both case studies, responses to disaster were judged to be examples of ‘trial and error’ adaptation, rather
than either ‘passive’ or ‘active’ adaptation.
相似文献
Brent DobersteinEmail: |