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1.
Activities of CoO in (Co,Mn)O solid solutions in contact with metallic Co have been determined on ten compositions ranging
from 0.12 to 0.84 XCoO in order to calibrate the divariant equilibrium between (Co,Mn)O oxide solutions and Co metal as an oxygen fugacity sensor
for application in experimental petrology. Experiments were conducted over the temperature range 900–1300 K at 1 bar, using
an electrochemical technique with oxygen-specific calcia-stabilized zirconia (CSZ) electrolytes. Co + CoO or Fe + FeO was
used as the reference electrode. Compositions of the (Co,Mn)O solid solutions were measured after each run by electron microprobe,
and these were checked for internal consistency by measuring the lattice parameter by X-ray diffraction. Activity–composition
relations were fitted to the Redlich–Kister formalism. (Co,Mn)O solid solutions exhibit slight positive deviations from ideality,
which are symmetrical (corresponding to a regular solution mixing model) across the entire composition range with A0
G = 3690(±47) Jmol−1. Excess entropies and enthalpies were also derived from the emf data and gave Sex=0.77(±0.08) JK−1 mol−1 and Hex=4558(±90) Jmol−1 respectively. The experimental data from this study have been used to formulate the (Co,Mn)O/Co oxygen fugacity sensor to
give an expression:
where μO2
CoCoO=−492,186 + 509.322 T − 53.284 T lnT + 0.02518 T2, taken from O'Neill and Pownceby (1993).
Received: 10 September 1999 / Accepted: 4 April 2000 相似文献
2.
The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization
of the bituminous limestone in thermal power stations and/or retorting processes. The laboratory tests have been selected
with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the
production of lightweight concrete block has revealed optimum results. The compressive strength of various ash–glass sand
mixes has ranged between 19 and 76 kg/cm2 at 28 days. The compressive strength of ash–tuff mixes has ranged between 54 and 63 kg/cm2 at 28 days. Ultra light mixtures using ash–polyester with a density of 0.88 kg/m3 and a compressive strength of 21 kg/cm2 at 28 days are produced at normal room curing temperature without the use of ordinary Portland cement. The high alkalinity
of El-Lajjun ash is considered a disadvantage when utilized in normal concrete mixes for structural purposes. Ash only can
be mixed with aggregates to produce lean concrete for blinding purposes for use in foundations. 相似文献
3.
Case study: a 3D resistivity and induced polarization imaging from downstream a waste disposal site in Brazil 总被引:2,自引:2,他引:0
Andréa Teixeira Ustra Vagner Roberto Elis Giulliana Mondelli Lázaro Valentin Zuquette Heraldo Luiz Giacheti 《Environmental Earth Sciences》2012,66(3):763-772
A contaminated site from a downstream municipal solid waste disposal site in Brazil was investigated by using a 3D resistivity and induced polarization (IP) imaging technique. This investigation purpose was to detect and delineate contamination plume produced by wastes. The area was selected based on previous geophysical investigations, and chemical analyses carried out in the site, indicating the presence of a contamination plume in the area. Resistivity model has successfully imaged waste presence (ρ < 20 Ωm), water table depth, and groundwater flow direction. A conductive anomaly (ρ < 20 Ωm) outside wastes placement was interpreted as a contamination plume. Chargeability model was also able to imaging waste presence (m > 31 mV/V), water table depth, and groundwater flow direction. A higher chargeability zone (m > 31 mV/V) outside wastes placement and following conductive anomaly was interpreted as a contamination plume. Normalized chargeability (MN = m/ρ) confirmed polarizable zone, which could be an effect of a salinity increase (contamination plume), and the clay presence in the environment. 相似文献
4.
The spinel solid solution was found to exist in the whole range between Fe3O4 and γ-Fe2SiO4 at over 10 GPa. The resistivity of Fe3−
x
Si
x
O4 (0.0<x<0.288) was measured in the temperature range of 80∼300 K by the AC impedance method. Electron hopping between Fe3+ and Fe2+ in the octahedral site of iron-rich phases gives a large electric conductivity at room temperature. The activation energy
of the electron hopping becomes larger with increasing γ-Fe2SiO4 component. A nonlinear change in electric conductivity is not simply caused by the statistical probability of Fe3+–Fe2+ electron hopping with increasing the total Si content. This is probably because a large number of Si4+ ions occupies the octahedral site and the adjacent Fe2+ keeping the local electric neutrality around Si4+ makes a cluster, which generates a local deformation by Si substitution.
The temperature dependence of the conductivity of solid solutions indicates the Verwey transition temperature, which decreases
from 124(±2) K at x=0 (Fe3O4) to 102(±5) K at x=0.288, and the electric conductivity gap at the transition temperature decreases with Si4+ substitution.
Received: 15 March 2000 / Accepted: 4 September 2000 相似文献
5.
Geophysical methods, when integrated with soil chemical and hydrogeological methods, can be used to investigate groundwater
contamination. Direct current (DC) resistivity geo-electrical sounding and very-low-frequency electromagnetic (VLF-EM) data
were collected at an open waste site used by the municipality of the city of Isparta, Turkey. The groundwater at shallow depths
in alluvium, which is composed of gravel, sand and clay, were expected to be hazardously contaminated under and around the
open waste-disposal site, in which both household and industrial wastes are known to be disposed of improperly. In this study,
we mapped the spread of groundwater contamination using a VLF-EM method, which allows fast and inexpensive data collection.
The method complements the results of geo-electrical sounding. There is a good correlation between the results of the VLF-EM
and the DC-resistivity methods employed for the investigation of subsurface structure of the site, where soil chemical and
previous hydrogeological surveys have indicated high levels of chemical concentrations.
Received: 17 January 2000 · Accepted: 12 August 2000 相似文献
6.
Irena Pluta 《Environmental Geology》2001,40(3):345-348
Waters discharged from coal mines in the Upper Silesia in Poland cause contamination of rivers and their sediments. Saline
waters discharged from coal mines of the southern region contain elevated barium and radium. The discharge of these elements
can be reduced by treating these waters with sulphates in mine workings. Sources of sulphate used in treatments include gypsum,
anhydrite and industrial wastes such as: fly ash, slags and flotation tailings. Gypsum and anhydrite are used in the coal
mine workings as components of the fire protection walls. Industrial wastes from power plants are stored in the mine workings
as fire- and methane-protection agents. Sulphates precipitate barium and radium from saline waters inflowing into the mine
workings. The waters can be treated by flowing them through old mine workings. In this case, the source of sulphates is the
natural oxidation of pyrite. Mining activities and the natural process of desulphurisation of the Carboniferous rocks reduce
the amount of barium and radium that is discharged in the southern region of Upper Silesia. The processes for reducing the
environmental impact of toxic discharges from the mines should be monitored.
Received: 3 July 1997 · Accepted: 27 March 2000 相似文献
7.
Enis Morkoc Legovic Tarzan Oya Okay Huseyin Tufekci Vildan Tufekci Leyla Tolun Fatma Karakoc 《Environmental Geology》2007,53(1):103-112
The Izmit Bay is an elongated semi-enclosed bay in the Marmara Sea. It is being increasingly polluted by both domestic and
industrial waste discharge since 1970’s. A monitoring program was conducted between 1999-2000 to document the state of pollution
in the bay. This includes the effect of Marmara (Izmit) earthquake (magnitude 7.4) that occurred in August 1999. A stable
two-layer ecosystem exists in the bay throughout the year due to continuous inflows of the saltier Mediterranean and brackish
Black Sea waters to the Marmara basin. Therefore, the principal biochemical characteristics of the bay are governed by the
two-layer flow system over the basin. Dissolved oxygen (DO) is generally at a saturated levels in the surface layer which
is 10 to 15 m thick, but it is depleted to 60–70 μM in the lower layer, exhibiting a steep gradient in the sharp halocline.
When the earthquake occurred, great loads of industrial wastes were released into the bay surface waters, which enhanced primary
production in the upper layer and thus large export of particulate organic matter to lower layer and eventually to the bottom.
Accordingly, DO was consumed and anoxic condition was established even in the upper layer/halocline interface, the halocline
and bottom waters of the eastern and central bay. In this period, concurrent increases were observed in phosphate and ammonia
contents at the halocline and in deep waters whilst the nitrate was almost consumed via denitrification processes in the anoxic
water. Recently, the industrial C, N and P loads increased by as much as 8 fold within five years (1995–2000) whilst domestic
inputs increased by 50%. Total organic matter discharged to the bay increased more than double within the last 15 years. Besides,
most factories in the region release toxic wastes into the bay after only partial treatment. 相似文献
8.
The volumes and enthalpies of mixing, ΔV Mix and ΔH
Mix, of binary solid-solution aluminosilicate garnets have been studied by computer simulation. The use of “average atoms” to
simulate solid solution was found to give results that are considerably different from those obtained by calculating and averaging
over many configurations of cations at a given composition. Although we expect mineral properties calculated from model calculations
to be correct only on a qualitative rather than a quantitative scale, fair agreement with experiment was obtained where carefully
tested potential parameters were used. The results show that mixing behaviour in these materials is controlled by local strain
and relaxation effects resulting from the atomic size mismatch of the mixing divalent cations. In particular, ΔV
Mix and ΔH
Mix are shown to scale quadratically with the volume difference between the end members, and to vary essentially symmetrically
with composition, with a moderate dependence on the degree and nature of cation order. We conclude that computer modelling
should be useful in providing detailed qualitative information about the mixing properties of solid solutions, which can help
to better constrain and interpret experimental results.
Received: 8 March 2000 / Accepted: 1 October 2000 相似文献
9.
The effect of Cr on the solubility of Al in orthopyroxene: experiments and thermodynamic modelling 总被引:1,自引:1,他引:0
The partitioning of chromium and aluminium between coexisting orthopyroxene and spinel in equilibrium with forsterite in
the system MgO–Al2O3–SiO2–Cr2O3 (MAS–Cr) has been experimentally determined as a function of temperature, pressure and Cr/(Cr + Al) ratio. Experiments were
conducted at temperatures between 1300 and 1500 °C and at pressures from 5 to 54 kbar. Previous experimental results on the
(Al, Cr)2O3 and Mg(Al, Cr)2O4 solid solutions have been combined with the present results plus relevant data from the CMAS system to derive a thermodynamic
model for Al–Cr-bearing orthopyroxenes, spinels and corundum–eskolaite solid solutions. The orthopyroxene solid solution can
be modelled within the accuracy of all experimental constraints as a ternary solid solution involving the components Mg2Si2O6 ( E), MgAl2SiO6 (M) and MgCr2SiO6 (C), in which the activities are related to composition through the equations:
The mole fractions are defined as
where n
Al and n
Cr are the number of Al and Cr cations per orthopyroxene formula unit of six oxygens. These expressions reduce to one-site mixing
for Mg2Si2O6–MgAl2SiO6 orthopyroxenes in the Cr-free system, but are equivalent to two-site mixing for the exchange of Al and Cr between orthopyroxene
and spinel, as required by the experimental data. We find W
opx
EM
=W
opx
EC
= 20 kJ mol−1 and W
opx
MC
=0.
Received: 9 August 1999 / Accepted: 18 February 2000 相似文献
10.
The Gabbro Akarem (Late Precambrian) intrusion is concentrically zoned with a dunite core surrounded by lherzolite–clinopyroxenite
enveloped by olivine–plagioclase hornblendite and plagioclase hornblendite. Cu–Ni–PGE mineralization is closely associated
with peridotite, especially in the inner, olivine-rich core (dunite pipes) where net-textured and massive sulfides (pyrrhotite,
pentlandite, chalcopyrite) are found in association with Al–Mg-rich spinel and Cr-magnetite. Primary magmatic textures are
well preserved; however, deformation and mobilization due to shearing are locally observed. Platinum-group minerals (PGM)
documented from the deposit are: merenskyite (PdTe2) and michenerite (PdTeBi), as well as palladian bismuthian melonite (Ni,Pd) (Te,Bi)2. These minerals occur in intimate association with hessite (Ag2Te) and electrum (Au0.65Ag0.31Bi0.04) in two distinct textural positions: (1) as inclusions in pyrrhotite, pentlandite, and rarely chalcopyrite and (2) at sulfide–silicate
grain boundaries and on microfractures in base-metal sulfides (BMS) and olivine associated with serpentine and secondary magnetite.
Textural features suggest that PGM were exsolved from monosulfide solid solution over a wide range of temperatures. Late-stage,
low-temperature hydrothermal solutions led to redistribution of PGE. Mineralized samples show Ni/Cu ratios ranging from 0.2
to 2 with an average of 1.0. The (Pt + Pd + Rh)/(Os + Ir + Ru) ratio is generally >6 in most samples, and Os, Ru, and Ir are
below the detection limit (2 ppb). The PGE contents show positive correlation with S only at low sulfur contents. The PGE
patterns of Gabbro Akarem are similar to those of Alaskan-type deposits. Compared with stratiform deposits, Gabbro Akarem
is depleted in PGE. The consistently low PGE contents of the mineralization and their uniform distribution in the ultramafic
rocks despite the high sulfur content of the rock is attributed to rapid crystallization of sulfides in a highly dynamic environment.
Received: 3 November 1999 / Accepted: 29 July 2000 相似文献
11.
Synchrotron radiation S K-edge XANES spectra and unit-cell parameters are used to investigate the local electronic structure
of non-stoichiometric binary and ternary Fe-Co-Ni monosulfide solid solution (mss; M0.923S, M = Fe, Co, Ni) quenched from 800 °C and low pressure. The prominent absorption edge feature of the XANES spectra represents
transition of S 1s core level electrons to unoccupied S 3p σ* antibonding orbitals hybridized with empty metal 3d(eg) orbitals. There is a progressive increase in area of the edge peak from Fe0.923S to Ni0.923S and Co0.923S, which correlates with progressive decrease in c and a parameters for the NiAs-type subcell and increase in metallic character, and reflects increase in the number and availability
of empty eg
β orbitals and covalence of metal-S bonds. More generally, the area of the edge peak exhibits an inverse linear correlation
with a, c and unit-cell volume of binary and ternary mss. This inverse linear correlation is attributed to progressive increase in
covalence and M-S-M bonding interaction in the c-axis direction, through metal-S [M 3d(eg) - S 3p (or 3d)] π bonding. However, the area of the edge peak does not correlate very well with the average number of 3d
electrons per metal atom in these solid solutions, showing that the absorption of synchrotron radiation reflects the local
electronic structure of individual absorber atoms (i.e. the SM6 cluster), and is not a group (crystal energy band) effect.
Received: 21 March 2000 / Accepted: 14 July 2000 相似文献
12.
Iron tracer diffusion experiments in diopside have been performed using natural and synthetic single crystals of diopside,
and stable iron tracers enriched in 54Fe, at temperatures in the range 950–1100 °C, total pressure 1 atm, for times up to 29 days. Iron isotope diffusion profiles
were determined with an ion microprobe. For experiments performed at log pO2 = −13, in directions parallel to the c axis and the b axis of two natural, low iron (Fe ∼ 1.8 at %) diopsides, the data obey
a single Arrhenius relationship of the form D = 6.22−5.9
+49.6×10−15 exp(−161.5 ± 35.0 kJ mol−1/RT) m2 s−1. A single datum for iron diffusion in iron-free, single-crystal diopside at 1050 °C, is approximately 1 order of magnitude
slower than in the natural crystals. The pO2 dependence of iron diffusion in natural crystals at 1050 °C (power exponent = 0.229 ± 0.036) indicates a vacancy mechanism;
this is consistent with the results of unpublished atomistic simulation studies. There is no evidence of anisotropy for iron
diffusion in diopside.
Received: 16 March 1999 / Accepted: 10 April 2000 相似文献
13.
The phase relations in the Fe2SiO4–Fe3O4 binary system have been determined between 900 and 1200 °C and from 2.0 to 9.0 GPa. At low to moderate pressures magnetite
can accommodate significant Si, reaching XFe2SiO4=0.1 and 0.2 at 3.0 and 5.0 GPa respectively, with temperature having only a secondary influence. At pressures below 3.5 GPa
at 900 °C and 2.6 GPa at 1100 °C magnetite-rich spinel coexists with pure fayalite. This assemblage becomes unstable at higher
pressures with respect to three intermediate phases that are spinelloid polytypes isostructural to spinelloids II, III and
V in the Ni-aluminosilicate system. The phase relations between the spinelloid phases are complex. At pressures above ≈8.0 GPa
at 1100 °C, the spinelloid phases give way to a complete spinel solid solution between Fe3O4 and Fe2SiO4. The presence of small amounts of Fe3+ stabilises the spinel structure to lower pressures compared to the Fe2SiO4 end member. This means that the fayalite–γ-spinel transition is generally unsuitable as a pressure calibration point for
experimental apparatuses. The molar volumes of the spinel solid solutions vary nearly linearly with composition, having a
small negative deviation from ideal behaviour described by Wv=−0.15(6) cm3. Extrapolation yields V°(298) = 41.981(14) cm3 for the Fe2SiO4-spinel end member. The cell parameters and molar volumes of the three spinelloid polytypes vary systematically with composition.
Cation disorder is an important factor in stabilising the spinelloid polytypes. Each polytype exhibits a particular solid
solution range that is directly influenced by the interplay between its structure and the cation distributions that are energetically
favourable. In the FeO–FeO1.5–SiO2 ternary system Fe7SiO10 (“iscorite”) coexists with the spinelloid phases at intermediate pressures on the SiO2-poor, or Fe3+-poor side of the Fe2SiO4–Fe3O4 join. On the SiO2 and Fe3+-rich side of the join, orthopyroxene or high-P clinopyroxene coexists with the spinelloids and spinel solid solutions. The
assemblage pyroxene+spinel+SiO2 is stable over a wide range of bulk composition. The stability of spinelloid III is of particular petrologic interest since
this phase has the same structure as (Mg,Fe)2SiO4–wadsleyite, indicating that Fe3+ can be easily incorporated in this important phase in the Earth's transition zone, in addition to silicate spinel. This has
important implications for the redox state of the Earth's transition zone and for the depth at which the olivine to spinel
transition occurs in the mantle, potentially leading to a shift in the “410 km” seismic discontinuity to shallower depths
depending on the prevailing redox state. In addition, a coupled tetrahedral substitution of Fe3++OH for Si+O could provide a further mechanism for the incorporation of H2O in wadsleyite.
Received: 10 January 2000 / Accepted: 12 May 2000 相似文献
14.
Andrea Orlando Yves Thibault Alan D. Edgar 《Contributions to Mineralogy and Petrology》2000,139(2):136-145
Experiments ranging from 2 to 3 GPa and 800 to 1300 °C and at 0.15 GPa and 770 °C were performed to investigate the stability
and mutual solubility of the K2ZrSi3O9 (wadeite) and K2TiSi3O9 cyclosilicates under upper mantle conditions. The K2ZrSi3O9–K2TiSi3O9 join exhibits complete miscibility in the P–T interval investigated. With increasing degree of melting the solid solution becomes progressively enriched in Zr, indicating
that K2ZrSi3O9 is the more refractory end member. At 2 GPa, in the more complex K2ZrSi3O9–K2TiSi3O9–K2Mg6Al2Si6O20(OH)4 system, the presence of phlogopite clearly limits the extent of solid solution of the cyclosilicate to more Zr-rich compositions
[Zr/(Zr + Ti) > 0.85], comparable to wadeite found in nature, with TiO2 partitioning strongly into the coexisting mica and/or liquid. However, at 1200 °C, with increasing pressure from 2 to 3 GPa,
the partitioning behaviour of TiO2 changes in favour of the cyclosilicate, with Zr/(Zr + Ti) of the K2(Zr,Ti)Si3O9 phase decreasing from ∼0.9 to ∼0.6. The variation in the Ti content of the coexisting phlogopite is related to its degree
of melting to forsterite and liquid, following the major substitution VITi+VI□=2VIMg.
Received: 26 January 1999 / Accepted: 10 January 2000 相似文献
15.
Weisse Elster River sediment from the Leipzig Lowlands region (Saxony, Germany) is anthropogenically polluted by heavy metals.
Sediment dredged from a trap to the south of Leipzig was characterized in detail. When freshly dredged sediment contacts air,
the material turns acidic because of oxidation processes, the heavy metals become soluble and the sediment poses an environmental
risk. We are therefore developing a sediment-treatment process based on heavy metal removal by bioleaching. Leaching experiments
were carried out in suspension and in the solid bed. The heavy metals were solubilized to nearly the same extent by H2SO4 dosage (pure chemical extraction) and addition of elemental sulphur (microbial oxidation of S0 to H2SO4). With increasing dosage of the leaching agent, Zn, Cd, Ni, Cu and Cr were more and more solubilized, whereas Pb was only
dissolved in small amounts. The addition of 2% S0 is considered an optimum dosage. When 5% S0 was added to the sediment, the pH dropped to 1.76 and large amounts of undesirable compounds such as Ca, Al and Fe were solubilized.
The higher the temperature, the faster the metals were solubilized in both suspension and the solid bed. The temperature optimum
for activating the indigenous S0-oxidizing microbes of the sediment lies between 30 and 40 °C. Conditioning of freshly dredged sediment with plants makes
it suitable for solid-bed leaching; the kinetics of heavy metal solubilization from sediment conditioned for 6 months with
Phragmites australis was the same as from long-term stored sediment.
Received: 26 November 1999 · Accepted: 5 May 2000 相似文献
16.
Arsenic and mercury contamination in 31 cores taken in 1965, St. Anna Trough, Kara Sea, Arctic Ocean
Several cores of 31 collected in 1965 in the St. Anna Trough, Kara Sea, have very high concentrations of Hg and As in surface/near-surface
samples. Mercury contents range from 94 to 3915 ppb with a mean of 444 ppb and a baseline value of 314 ppb. Arsenic contents
range from 5 to 710 ppm with a mean of 51 ppm and a baseline value of 23 ppm. The Hg and part of the As loading is likely
anthropogenic from industrial activities in Siberia via atmospheric emission and deposition onto catchments. This is followed
by mobilization into fluvial systems and is added to by industrial effluent discharge. Post-depositional diagenesis from depth
in the cores contributes to high As values. A north-flowing bottom current transports Hg- and As-bearing suspended material
from the Ob River sea discharge zone to depositional environments in the St. Anna Trough. Dumping of military materials and
other wastes into the Kara Sea from the late 1940s to 1991 has likely added to Hg and As loading in the trough sediments.
The bioavailability of mercury from suspended materials may be the reason why higher than normal levels of these potentially
toxic elements are found in European Arctic seabirds, ringed seal and polar bear.
Received: 12 December 1999 · Accepted: 23 May 2000 相似文献
17.
A new profile mass balance procedure is presented to calculate the chemical composition of solid precipitated during cooling and crystallization of many tholeiitic and alkaline magmas. It is a variant of the earlier interval method (MacLean 2000, Contrib Mineral Petrol 139:85–100), and is also based on chemical variation diagrams of lava sequences (liquid profiles) constructed with a quantitative monitor of fractionation derived from the residual enrichment of an incompatible trace high field-strength element (HFSE). In this new profile method, the concentration of a component in solid is shown by mass transfer considerations to be a function of its mass on a liquid fractionation path (profile) and on a path (profile) of perfect incompatible enrichment. The latter hypothetically contains all of the component, hence subtraction of the amount contained in liquid will yield its mass in the solid. The calculations are straightforward and adaptable to both equilibrium and fractional crystallization processes. Corrections to the fractionation monitor for measured
(solid/liquid distribution coefficient), estimates of "trapped liquid" in solid, and other variables, can be applied. The method is illustrated with chemical data for a suite of alkaline volcanic rocks from Mt. Erebus, Antarctica (Kyle et al. 1992, J Petrol 33:849–875). The lavas are silica-undersaturated, and range from nepheline-bearing basanite to phonolite. The solids correspond to those of ultrabasic rocks through most of fractionation, and are more SiO2-undersaturated than the lavas.Editorial responsibility: I. Parsons 相似文献
18.
U. Becker A. Fernández-González M. Prieto R. Harrison A. Putnis 《Physics and Chemistry of Minerals》2000,27(4):291-300
Thermodynamic properties of the barite–celestite solid solution were calculated using molecular principles. Cation–cation
(Ba–Ba, Sr–Sr, and Ba–Sr) interaction energies were derived from a number of random and ordered cation distributions which
were energy-optimized using force potentials as incorporated in the program package GULP. With these interaction energies,
diagrams for the enthalpy and free energy of mixing could be computed for the entire range of the solid solution between the
barite and celestite end members and for a number of annealing temperatures. These thermodynamic data show that the solid
solution is nonideal. The system has a tendency for Ba2+ and Sr2+ cations to order onto alternating layers ||(100). However, this ordering scheme is thermodynamically only relevant for annealing
temperatures below approximately 500 K and systems that are kinetically inhibited during crystal growth. For sufficiently
long annealing times at room temperature, the solid solution tends to exsolve with barite–celestite interfaces ||(100). The
cell parameters a and c were calculated to have almost linear behavior for the whole solid solution, suggesting close to ideal behavior according
to Vegard's law. In contrast, b tends to deviate positively from linearity, in agreement with experimental values.
Received: 6 April 1999 / Revised, accepted: 29 September 1999 相似文献
19.
J. S. Chinchón X. Querol J. L. Fernández-Turiel A. López-Soler 《Environmental Geology》1991,18(1):11-15
The mineral transformations undergone by high sulfur coal ash were studied. An X-ray diffraction (XRD) experiment was carried out to reproduce experimentally the mineral transformations produced during coal combustion in coal-fired power stations. We have verified that the anhydrite is the main crystalline phase that contains sulfur in the solid combustion waste from 500°C until its decomposition at 1060±10°C. Thus, this calcium sulfate is the main crystalline phase involved in the sulfur retention in the combustion wastes at high temperatures. Therefore, a considerable proportion of the sulfur would not be emitted into the atmosphere at temperatures lower than 1060°C. Taking as a reference the annual coal consumption of the Teruel Mining District (6 million tons), the mean sulfur content and the anhydrite content at 900°C, it was shown that the SO2 emissions could be reduced by approximately 13 percent (83,000 ton/yr) provided that the combustion temperature was 900°C. 相似文献
20.
M. R. Al-Agha 《Environmental Geology》2000,39(3-4):405-410
Investment in the coastal resources of Gaza City is vital to various developmental issues and projects. Access to the coast
and coastal erosion represent two major geo-environmental problems to the city. This paper describes local engineering works
developed by the municipality and local people to overcome such problems. A cliff of calcareous sandstone – Kurkar as it is
locally known – (up to 18 m high), is located at a distance of 20–50 m from the water–land contact. People who need to reach
the beach must cross this Kurkar cliff. The engineering works used to facilitate access to the beach are: old automobile tires,
white waste skeletons (refrigerators) and construction waste, where long stairs were designed using these materials. Meanwhile
the engineering works which were used as erosion control measures include: rock gabions, concrete wastes, construction waste,
concrete walls and shallow excavations. Such practices are commonly used in third world countries and are characterized by
inexpensive transportation and implementation costs. The performance of these methods was evaluated from an economic, environmental
and safety point of view. Suggestions were made to improve the performance of these practices in the future.
Received: 18 November 1998 · Accepted: 15 February 1999 相似文献