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1 IntroductionIncorporation of potentially toxic metals ( e.g.Cd, Cu, Cr, Pb, Hg, As, Se, Zn, Ni) into soils ei-ther through sewage-sludge irrigation or some othersources of pollution (e.g. atmospheric deposition, ap-plication of agri-chemicals) has posed… 相似文献
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《Journal of Geochemical Exploration》1997,59(2):123-146
The Forum of European Geological Surveys (FOREGS) includes representatives from 33 European countries and is responsible for co-ordinating Geological Survey activities in Europe. The FOREGS Geochemistry Task Group was established in 1994 to develop a strategy for the preparation of European geochemical maps following the recommendations of the International Geological Correlation Programme (IGCP) Project 259 ‘International Geochemical Mapping’ (now the International Union of Geological Sciences (IUGS) /International Association of Geochemistry and Cosmochemistry (IAGC) Working Group on Global Geochemical Baselines).The FOREGS geochemistry programme is aimed at preparing a standardised European geochemical baseline to IGCP-259 standards. The principal aims of this dataset will be for environmental purposes, as a baseline for the assessment of the extent and distribution of contaminated land in the context of variations in the natural geochemical background, but it will also have applications in resource assessment and for the development of policy for the sustainable management of metalliferous mineral and other resources.The first phase of the programme was the compilation of an inventory of geochemical data based on the results of a questionnaire completed by Geological Surveys and related organisations throughout the FOREGS community. The results show that the sample types which have been used most extensively are stream sediment (26% coverage), surface water (19% coverage) and soil (11% coverage). Stream sediments have been collected using a narrow range of mesh sizes (< 150–< 200 μm), but soil samples have been collected according to two different conventions: some surveys used a similar mesh size range to that used for stream sediments while others employed the < 1000 or < 2000 μm fractions traditionally used by soil surveys. Sample densities range from 1 sample per 0.5 km2 to 1 per 3500 km2. Various analytical methods have been used, but most of the available data have been calibrated using international reference materials, and data for the most important of the potentially harmful elements (PHEs) are available for most datasets. Systematic radiometric data are available for only a small proportion of Europe, a situation which compares very unfavourably with that in Australia, North America, the former Soviet Union and many developing countries.Recommendations are made for increasing the compatibility of geochemical methods between national geochemical surveys as a basis for the preparation of a series of European geochemical maps. The next stage of the FOREGS Geochemistry Task Group will be the collection of the Global Reference Network of samples against which to standardise national datasets according to the methods recommended in the final report of the IGCP 259 programme. 相似文献
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Thorsten Beitter Thomas Wagner Gregor Markl 《Contributions to Mineralogy and Petrology》2008,156(6):689-707
In this study, we have investigated the formation of quartz–kyanite veins of the Alpe Sponda, Central Alps, Switzerland. We
have integrated field observations, fluid inclusion and stable isotope data and combined this with numerical geochemical modeling
to constrain the chemical processes of aluminum transport and deposition. The estimated P–T conditions of the quartz–kyanite
veins, based on conventional geothermometry (garnet–biotite, white mica solvus and quartz–kyanite oxygen isotope thermometry)
and fluid inclusion data, are 550 ± 30°C at 5.0 ± 0.5 kbar. Geochemical modeling involved construction of aqueous species
predominance diagrams, calculation of kyanite and quartz solubility, and reaction–path simulations. The results of the modeling
demonstrate that (1) for the given chemical composition of the vein-forming fluids mixed Al–Si aqueous species are dominant
in transporting Al, and that (2) fluid cooling along a small temperature gradient coupled with a pH decrease is able to explain
the precipitation of the quartz–kyanite assemblages in the proportions that are observed in the Alpe Sponda veins. We conclude
that sufficient amounts of Al can be transported in typical medium- to high-grade regional metamorphic fluids and that immobile
behavior of Al is not very likely in advection–dominanted fluid–rock systems in the upper and middle crust. 相似文献
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Friedrich Lucassen Gerhard Franz Dieter Rhede 《Contributions to Mineralogy and Petrology》2012,164(6):987-997
Trace element distribution in titanite overgrowths on rutile has been investigated experimentally at 600?°C, 400?MPa and fO2 near NiNiO buffer. Compositionally homogenous Cr- or Nb-doped synthetic rutile single crystals or Nb-containing natural rutile crystals were the source of Cr, Nb and Ti to synthesize titanite using the double-capsule technique. All element exchange with the source of Si, Ca and Al occurred via a NaCl–H2O fluid. Titanite forms quickly and exclusively around the rutile crystals. The titanite overgrowth separates rutile from the bulk fluid, and all elements from rutile dissolution have to pass through the titanite rim. Trace element concentrations in titanite show a considerable scatter in experiments with and without Al, although the average concentrations of Cr or Nb of titanite around compositionally homogeneous synthetic rutile approach the expected values for closed system conditions. Variability of Al with Cr or Nb in the titanite is not correlated. The Al zoning is irregular and patchy, and also the distribution of trace elements does not show systematic trends in the spatial distribution. In experiments using zoned natural rutile, the concentrations of Nb in titanite are related to the Nb zoning in rutile, but the contents also vary unsystematically. Under the controlled conditions of the experiment, the explanation for the strongly irregular spatial distribution is most likely due to variations in elemental concentrations during transport from the rutile along the titanite grain boundaries. The transport pathway is complex because grain boundary migration is important during titanite growth. Such irregular element distribution is also found in a natural sample of titanite overgrowth on rutile from an eclogite with retrograde overprint in the amphibolite facies. Transport of Ti and trace elements was focused on grain boundaries and shielded from the rutile as a source of these elements. We conclude that this type of zoning is not related to changes in P–T or composition in an open system, but solely controlled by transport in and through the titanite rim. 相似文献
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Sarah Lambart Didier Laporte Pierre Schiano 《Contributions to Mineralogy and Petrology》2009,157(4):429-451
We performed experiments in a piston-cylinder apparatus to determine the effects of focused magma transport into highly permeable
channels beneath mid-ocean ridges on: (1) the chemical composition of the ascending basalt; and (2) the proportions and compositions
of solid phases in the surrounding mantle. In our experiments, magma focusing was supposed to occur instantaneously at a pressure
of 1.25 GPa. We first determined the equilibrium melt composition of a fertile mantle (FM) at 1.25 GPa-1,310°C; this composition
was then synthesised as a gel and added in various proportions to peridotite FM to simulate focusing factors Ω equal to 3
and 6 (Ω = 3 means that the total mass of liquid in the system increased by a factor of 3 due to focusing). Peridotite FM
and the two basalt-enriched compositions were equilibrated at 1 GPa-1,290°C; 0.75 GPa-1,270°C; 0.5 GPa-1,250°C, to monitor
the evolution of phase proportions and compositions during adiabatic decompression melting. Our main results may be summarised
as follows: (1) magma focusing induces major changes of the coefficients of the decompression melting reaction, in particular,
a major increase of the rate of opx consumption, which lead to complete exhaustion of orthopyroxene (and clinopyroxene) and
the formation of a dunitic residue. A focusing factor of ≈4—that is, a magma/rock ratios equal to ≈0.26—is sufficient to produce
a dunite at 0.5 GPa. (2) Liquids in equilibrium with olivine (±spinel) at low pressure (0.5 GPa) have lower SiO2 concentrations, and higher concentrations in MgO, FeO, and incompatible elements (Na2O, K2O, TiO2) than liquids produced by decompression melting of the fertile mantle, and plot in the primitive MORB field in the olivine–silica–diopside–plagioclase
tetrahedron. Our study confirms that there is a genetic relationship between focused magma transport, dunite bodies in the
upper mantle, and the generation of primitive MORBs. 相似文献
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《Applied Geochemistry》2000,15(1):35-49
A comparative assessment of two reactive-transport models, PHREEQC and HYDROGEOCHEM (HGC), was done to determine the suitability of each for simulating the movement of acidic contamination in alluvium. For simulations that accounted for aqueous complexation, precipitation and dissolution, the breakthrough and rinseout curves generated by each model were similar. The differences in simulated equilibrium concentrations between models were minor and were related to (1) different units in model output, (2) different activity coefficients, and (3) ionic-strength calculations. When adsorption processes were added to the models, the rinseout pH simulated by PHREEQC using the diffuse double-layer adsorption model rose to a pH of 6 after pore volume 15, about 1 pore volume later than the pH simulated by HGC using the constant-capacitance model.In PHREEQC simulation of a laboratory column experiment, the inability of the model to match measured outflow concentrations of selected constituents was related to the evident lack of local geochemical equilibrium in the column. The difference in timing and size of measured and simulated breakthrough of selected constituents indicated that the redox and adsorption reactions in the column occurred slowly when compared with the modeled reactions. MINTEQA2 and PHREEQC simulations of the column experiment indicated that the number of surface sites that took part in adsorption reactions was less than that estimated from the measured concentration of Fe hydroxide in the alluvium. 相似文献
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Stochastic continuum modeling of flow and transport in a crystalline rock mass: Fanay-Augères,France, revisited 总被引：1，自引：0，他引：1
A stochastic discrete-fracture model was used by Cacas et al.a,b to interpret flow measurements and transport experiments in a fractured crystalline rock mass at Fanay-Augères. They considered continuum models to be incapable of properly interpreting small-scale measurements or tracer tests in fractured systems, which, in their view, require three-dimensional modeling of numerous discrete channels; in their opinion, continuum modeling applies only to average flow on a relatively large scale. Cacas et al. considered their discrete fracture model to have been validated by its demonstrated ability to reproduce selected experimental results. In this paper, flow and transport at Fanay-Augères are modeled by viewing the fractured rock as a stochastic continuum in a manner originally proposed by Neumanc,d. The stochastic continuum approach obviates the need for detailed information about fracture geometry or assumptions about how individual fractures control flow and transport. All it requires is the delineation of a few dominant features, which can be embedded into the stochastic continuum model as heterogeneous porous slabs. Though a fault zone has been identified at the Fanay-Augères experimental site, it has been modeled neither by Cacas et al. nor in this paper. In fact, in this paper, a larger selection of experimental results than those considered by Cacas et al. are reproduced merely by modeling the rock as a statistically homogeneous continuum in two dimensions. These results demonstrate that a continuum approach may be well suited for the analysis of flow and transport in fractured rock. This does not constitute a validation of the continuum approach, just as the results of Cacas et al. fall short of validating the discrete fracture approach. Instead, the two sets of results illustrate jointly the well-established principle that an open system, especially one as complex as fractured hydrogeologic environments tend to be, cannot be described uniquely on the basis of sparse data and need not be described in great detail to capture its salient behavior by a model.a Cacas MC, Ledoux E, de Marsily G, Barbreau A, Calmels P, Gaillard B, Margritta R (1990a) Modelling fracture flow with a stochastic discrete fracture network: calibration and validation. 1. The flow model. Water Resour Res 26(3):479–489b Cacas MC, Ledoux E, de Marsily G, Barbreau A, Calmels P, Gaillard B, Margritta R (1990b) Modelling fracture flow with a stochastic discrete fracture network: calibration and validation. 2. The transport model. Water Resour Res 26(3):491–500c Neuman SP (1987) Stochastic continuum representation of fractured rock permeability as an alternative to the REV and fracture network concepts, in Rock Mechanics. In: Farmer IW, Daemen JJK, Desai CS, Glass CE, Neuman SP (eds) Proceedings of the 28th U.S. Symposium, Tucson, Arizona. Balkema, Rotterdam, pp 533–561d Neuman SP (1988) A proposed conceptual framework and methodology for investigating flow and transport in Swedish crystalline rocks. SKB Swedish Nuclear Fuel and Waste Management Co., Stockholm, September, Arbetsrapport 88–37, 39 pp 相似文献
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The past 15 years has been characterized by a high density of record-breaking weather extremes in Europe. These include the extratropical cyclones Lothar, Kyrill and Xynthia across western and mid Europe; the major floods in the UK, Germany and eastern Europe; the heat waves in 2003 and 2007 and, after a long period of mild winters, the heavy winter seasons in 2009/2010 and 2010/2011. Inspired by the rising trends in weather-related damages worldwide and the studies on the topic carried out in overseas, the EC funded the sister projects such as Weather Extremes-Assessing the Impacts on Transport and Hazards for European Regions (WEATHER), EWENT and ECCONET to determine the magnitude of current and future risks to the European transport sector and to assess suitable adaptation strategies. This paper presents the assessment framework of the WEATHER project and the results of weather-inflicted damage costs now and in 2040–2050. Total annual damages are found to be around €2.5 billion, which largely attribute to road traffic. However, broken down to passenger and ton kilometers the highest risk is borne by rail traffic due to its expensive infrastructures and its comparably complex operating structure. This indication even amplifies when looking four decades ahead: while average road transport costs will only raise by 7 % due to milder winters, rail traffic costs may increase by up to 80 % due to more floods and less predictable winter periods. A comparison with the results of the EWENT study uncovers a high range of uncertainty concerning methodological approaches and data treatment. Thus, the final figures might even be much higher. 相似文献
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K. Niranjan V. Sreekanth B. L. Madhavan T. Anjana Devi B. Spandana 《Journal of Earth System Science》2008,117(1):421-427
Realizing the importance of aerosol physical properties at the adjoining continental and coastal locations in the airmass pathways onto the oceanic region, extensive measurements of aerosol physical properties were made at Visakhapatnam (17.7°N, 83.3°E), an eastern coastal location in peninsular India during the ICARB period. The temporal variations of aerosol optical depth, near surface aerosol mass size distributions and BC mass concentrations show significantly higher aerosol optical depth and near surface mass concentrations during the first and last weeks of April 2007. The mean BC mass fraction in the fine mode aerosol was around 11%. The aerosol back scatter profiles derived from Micro Pulse Lidar indicate a clear airmass subsidence on the days with higher aerosol optical depths and near surface mass fraction. A comparison of the temporal variation of the aerosol properties at Visakhapatnam with the MODIS derived aerosol optical depth along the cruise locations indicates a resemblance in the temporal variation suggesting that the aerosol transport from the eastern coastal regions of peninsular India could significantly affect the aerosol optical properties at the near coastal oceanic regions and that the affect significantly reduced at the farther regions. 相似文献
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Emin Ciftci Cem B. Avci Osman S. Borekci A. Ufuk Sahin 《Environmental Earth Sciences》2012,67(8):2399-2409
Groundwater solute transport phenomena typically occur in water-bearing zones with heterogeneous solute dispersive characteristics and/or media hydraulic properties. A radial basis function collocation method (RBFCM)-based numerical method was developed in order to investigate the ability of RBFCM to accurately portray solute transport phenomena under heterogeneous conditions. Simulations were performed for 1-D and 2-D transport scenarios in which scale-dependent dispersivity fields were taken into consideration and compared with available analytical solutions. Different radial basis functions (RBFs) were employed for assessing the sensitivity of the present method on the selected RBFs. The simulation results were also compared with the results of MT3DMS which is a modular three-dimensional transport model with alternative solution schemes including the method of characteristics, the implicit central finite difference and the third order total variation diminishing finite volume. The proposed model was also used to simulate a real case condition where solute transport through a two-layer soil medium had been investigated experimentally. The results showed that RBFCM represented a powerful tool for predicting the solute transport occurrence under heterogeneous conditions with high accuracy. 相似文献
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Silicon and sediment transport of the Changjiang River (Yangtze River): could the Three Gorges Reservoir be a filter? 总被引：3，自引：0，他引：3
Ran Xiangbin Yu Zhigang Chen Hongtao Zhang Xinquan Guo Hongbo 《Environmental Earth Sciences》2013,70(4):1881-1893
Water samples were collected from the Changjiang River (Yangtze River) in May 2005, after the impoundment of the Three Gorges Reservoir (TGR), to examine the influence of the TGR and large lakes on material delivery to the estuary of the Changjiang River. The concentrations of suspended particle material (SPM), dissolved silica (DSi) and biogenic silica (BSi) in the main stream were analyzed. The concentrations of DSi and BSi in the main channel of the Changjiang varied between 73 and 100 and 1.1–15 μmol/l, with a distance weighted average of 81 and 8.0 μmol/l, respectively. A calculation shows that live diatom comprises only an average value of 5.2 % of the BSi in the Changjiang River, and most of BSi may come from drainage basin. The concentrations of BSi and the ratios of BSi/SPM were relatively low in the Changjiang River compared to other rivers throughout the world, but the BSi carried in suspension by the Changjiang River was an important component of the rivers silicon load (i.e. ~13 %). SPM, DSi and BSi concentrations as observed in the Changjiang River tend to decrease from the upper sections of the river to the Three Gorges Dam (TGD), reflecting sedimentation associated with BSi trapping and DSi retention in the TGR in the normal-water period. SPM and BSi retention are more strongly influenced by the TGD compared to DSi. About 98 % of SPM, 72 % of BSi and 16 % of DSi were retained within the TGR in May 2005. The fluxes variations of DSi, BSi and SPM suggested that the large lakes and dams had a coupled effect on the transportation of DSi, BSi and SPM in the normal-water period. Such a change in silicon (DSi and BSi) balances of the Changjiang River will affect the ecological environment of the Changjiang estuary and its adjacent sea to some extent. 相似文献
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The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the
salinity of stream-flows and agriculture land. This salinization is a serious environmental hazard particularly in semi-arid
and arid lands. In order to estimate the magnitude of the hazard posed by salinity, it is important to understand and identify
the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows.
In the present study, Malaprabha sub-basin (up to dam site) has been selected which has two distinct climatic zones, sub-humid
(upstream of Khanapur) and semi-arid region (downstream of Khanapur). In the upstream, both surface and ground waters are
used for irrigation, whereas in the downstream mostly groundwater is used. Both soils and ground waters are more saline in
downstream parts of the study area. In this study we characterized the soil salinity and groundwater quality in both areas.
An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation
conditions using the SWIM (Soil-Water Infiltration and Movement) model. Fair agreement was obtained between predicted and
measured results indicating the applicability of the model. 相似文献
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《中国地球化学学报》2006,(Z1)
For nuclear waste management, an important mechanism by which radioactive waste components are isolated from returning to the human environment, the biosphere, is by the geological barrier in which the effectiveness of the barrier is characterized by in-s… 相似文献