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1.
The relationships between egg production (spawning behavior), larval growth and survival, and environmental conditions that larvae encounter were investigated in the Patuxent River tributary of Chesapeake Bay in 1991. Striped, bass (Morone saxatilis) eggs and larvae occurred predominantly above the salt front where conductivity was ≤800 μmhos cm?1. There were three prominent peaks in egg production, each coinciding with increasing temperatures. Estimated growth rates of 6-d, otolith-aged cohorts, which ranged from 0.15 mm d?1 to 0.22 mm d?1 (mean=0.17 mm d?1), were not demonstrated to differ significantly from each other. Observed zooplankton densities and temperature did not significantly affect growth rates. Stage-specific cumulative mortalities of combined cohorts were calculated for eggs (Zstage=0.20=18.1%), yolk-sac larvae (Zstage=5.80=99.7%), and first-feeding larvae (Zstage=2.95=94.8%). The very high mortality of yolk-sac larvae suggests that dynamic during this stage may have had a major impact on subsquent recruitment. Cohort-specific mortality rates of larvae were variable, ranging from Z=0.045 d?1 to 0.719 d?1, and were strongly temperature-dependent. Cohorts that experiented average temperature <15°C or >20°C during the first 25 d after hatching had significantly higher mortality rates than those which experienced intermediate temperatures. Estimated hatch-date frequencies of larvae ≥8 mm SL indicated goo, very good, and very low potential recruitments for cohorst spawned during early-season (April 2–11), mid-season (April 12–24) and late-season (April 25–May 5), respectively. Because seasonal temperature trends and fluctuations are unpredictable, striped bass females cannot select a spawning time that guarantees their offspring will be exposed to optimum temperatures. Consequently, selection may have occured for spawning over a broad range of temperatures and dates, a behavior insuring that some larval cohorts will encounter favorable temperatures. 相似文献
2.
Oxygen consumption rates were measured individually for mixed groups of male, female, and immature striped bass,Morone saxatilis, in filtered Patuxent River, Maryland, water and in filtered water containing suspensions of either fuller’s earth or Patuxent River sediment. Oxygen consumption was determined at fixed swimming speeds at two temperatures, 15 and 22.5°C. Oxygen consumption of striped bass in filtered 15°C water increased as swimming speed increased. At 22.5°C, the same range of swimming speeds had no effect on rates of oxygen consumption. Similar data were obtained with fish swimming at the same speeds in water containing 0.79 g per liter fuller’s earth particles (15°C), and among those swimming at 31.7 and 49.0 cm per s in water containing 1.32 g per 1 Patuxent River sediment (22.5°C). Male and female striped bass respiration rates were similar under all test conditions. At 15°C, striped bass oxygen consumption rates during exposure to fuller’s earth while swimming at 8.6 and 31.7 cm per s did not differ from rates of fish swimming at the same speeds in filtered water. At 49.0 cm per s, rates were significantly depressed. Respiration rates of fish exposed to Patuxent River sediment at 22.5°C while swimming at 31.7 and 49.0 cm per s were significantly lower than those of fish in filtered water. Respiratory response of striped bass to suspended particle stress was manifested by depressed oxygen consumption. This is considered a short-term response to an acute stress. This response and the potential for hematological response to chronic suspended particle stress are discussed. 相似文献
3.
Day of hatch tidewater silversides, Menidia peninsulae, were stocked at 5 fish per liter in 3 1 of seawater at 30‰ and raised for 16 days at 20°, 25° and 30 °C. Food organisms (Brachionus sp. or Artemia nauplii) were maintained at 500, 1,000, 5,000 or 10,000 organisms per 1. The influence of food density on growth of larval M. peninsulae was temperature dependent. At 20 °C, there was no difference in final size of fish based on food densities. But at 25° and 30 °C there was an increase in final body size as food density increased. There were no significant differences in survival among food densities in tests at 20°, 25° or 30 °C. However, for any given temperature and food density, the number of survivors in a replicate affected the final size attained. Optimal culture condition for larval M. peninsulae, considering both survival and growth was determined to be 5,000 food organisms per 1 at 25 °C. 相似文献
4.
Each winter, populations of striped bass (Morone saxatilis) migrate north from the coastal mid-Atlantic region of the US to the coastal waters of New England. During this migration, striped bass spend significant time in estuaries and saltmarshes, presumably to forage. However, the extent to which saltmarsh productivity supports striped bass remains unresolved. We used a three-isotope Bayesian mixing model to determine the relative contribution of three primary producers [C4 saltmarsh cordgrass (Spartina spp.), phytoplankton, and benthic diatoms] to striped bass tissue. Phytoplankton (51 % contribution) and Spartina-derived sources (44 % contribution) are the primary sources of production to striped bass, while benthic diatoms made a relatively small contribution (5 %). Our results highlight the importance of saltmarshes to striped bass by showing that primary producers unique to saltmarsh ecosystems support a large proportion of striped bass production. 相似文献
5.
Large, recreationally or commercially important populations of Atlantic sturgeon (Acipenser oxyrinchus), American shad (Alosa sapidissima), and striped bass (Morone saxatilis) occur in the Hudson River. Members of the Hudson River populations of these fishes also occur over a broad range along the Atlantic coast where they mix with conspecifics from other anadromous populations. For management purposes, it is imperative to be able to discriminate among individual stocks so that weak stocks may be protected and harvest may be allocated equitably. Because of their sensitivity and resistance to environmentally-induced temporal variation, molecular approaches have been increasingly employed in stock identification studies. However, post-Pleistocene recolonization of the Hudson River must have occurred less than 10,000 years ago—a relatively brief period for genetic divergence among populations. We tested whether various measures of DNA variation between Hudson River populations and adjacent populations of Atlantic sturgeon, American shad, and striped bass were sufficient to discriminate among their conspecific populations. American shad populations surveyed for mtDNA variation were highly diverse genotypically, but genotypic frequencies among the populations of the Connecticut, Hudson, and Delaware rivers were statistically homogenous (p>0.05). In contrast, Atlantic sturgeon (surveyed for mtDNA variation) and striped bass (surveyed for mtDNA and nuclear DNA variation) populations of the Hudson River were not genotypically diverse, but they were differentiated from northern and southern populations. Our results suggest higher gene flow (and lesser homing fidelity) among American shad populations in comparison with the two other species. 相似文献
6.
From conductance measurements, the negative logarithm of the dissociation constant of the CaHCO3+ ion pair, pK(CaHCO3+), is 0.7, 1.0 and 1.35 within ±0.05 units at 0, 25 and 60°C, respectively. A revaluation of published and unpublished data yields pK(CaCO30) ≈ 3.2 at 25°C. Use of these pK's to compute the dissociation constant of calcite (Kc) from published calcite solubility measurements in pure water gives pKc values which increase markedly with ionic strength. However, if the ion pairs are ignored, computed pKc values are nearly constant with ionic strength. All reasonable attempts to eliminate the trend in pKc by adjusting ion activity coefficients, and/or values of K(CaCO30) failed, so the dilemma remains. Kc values computed from the most reliable published calcite solubility data are in good agreement with such values based on solubility data measured in this study at 5, 15, 35 and 50°C. Study results ignoring ion pairs are accurately represented by the equation log Kc = 13.870 — (3059/T) ?0.04035T, and correspond to ?8.35, ?8.42, and ?8.635 at 0, 25 and 50°C, respectively. The logarithmic expression leads to ΔHro = ?2420 ± 300 cal/mol, ΔCp = ?110 ± 2 cal/deg mol, and ΔSro = ?46.6 ± 1.0 cal/deg mol for the calcite dissociation reaction at 25°C. The dependence of Kc on temperature when CaCO30 and CaHCO3+ are assumed, is described by log Kc = 13.543 ? (3000/T) ? 0.0401T which yields ?8.39, ?8.47, and -8.70 at 0, 25 and 50°C. This gives ΔHro = ?2585 ± 300 cal/mol, ΔCp = ?109 ± 2 cal/deg mol, and ΔSr0 = ?47.4 ± 1.0 cal/deg mol at 25°C. 相似文献
7.
The thermodynamic properties of monohydrocalcite, CaCO3 · H2O, have been obtained using a well-characterized natural specimen. Equilibration of the solid with water at 25°C under 0.97 atm CO2 led to an activity product [Ca2+][CO32?] = 10?7.60±0.03 and a free energy of formation ΔGfo = ?325,430 ± 270 calmol?. The enthalpy of solution of monohydrocalcite in 0.1 N HCl at 25°C led to a standard enthalpy of formation ΔHfo = ?358,100 ± 280 cal mol?1. Estimates of the variation of ΔGf with temperature and pressure showed monohydrocalcite to be metastable with respect to calcite and aragonite. 相似文献
8.
Chul-Min Chon Chul-Kyoo Lee Yungoo Song Sin Ae Kim 《Physics and Chemistry of Minerals》2006,33(5):289-299
The thermal response of the natural ferroan phlogopite-1M, K2(Mg4.46Fe0.83Al0. 34Ti0.22)(Si5.51Al2. 49)O20[OH3.59F0.41] from Quebec, Canada, was studied with an in situ neutron powder diffraction. The in situ temperature conditions were set up at ?263, 25, 100°C and thereafter at a 100°C intervals up to 900°C. The crystal structure was refined by the Rietveld method (R p=2.35–2.78%, R wp=3.01–3.52%). The orientation of the O–H vector of the sample was determined by the refinement of the diffraction pattern. With increasing temperature, the angle of the OH bond to the (001) plane decreased from 87.3 to 72.5°. At room temperature, a = 5.13 Å, b = 9.20 Å, c = 10.21 Å, β = 100.06° and V(volume) = 491.69 Å3. The expansion rate of the unit cell dimensions varied discontinuously with a break at 500°C. The shape of the M-octahedron underwent some significant changes such as flattening at 500°C. At temperatures above 500°C, the octahedral thickness and mean distance was decreased, while the octahedral flattening angle increased. Those results were attributed to the Fe oxidation and dehydroxylation processes. The dehydroxylation mechanism of the ferroan phlogopite was studied by the Fourier transform infrared spectroscopy (FTIR) after heated at temperatures ranging from 25 to 800°C with an electric furnace in a vacuum. In the OH stretching region, the intensity of the OH band associated with Fe2+(N B-band) begun to decrease outstandingly at 500°C. The changes of the IR spectra confirmed that dehydroxylation was closely related to the oxidation in the vacuum of the ferrous iron in the M-octahedron. The decrease in the angle of the OH bond to the (001) plane, with increasing temperature, might be related to the imbalance of charge in the M-octahedra due to Fe oxidation. 相似文献
9.
The temperature tolerance and resistance times of postlarval (<25 mm SL) and small juvenile spot,Leiostomus xanthurus, from the Cape Fear Estuary, North Carolina were tested in the laboratory. Critical thermal maximum techniques were used to determine first equilibrium loss (FEL) and critical thermal maximum (CTM) end points and thermal shock methods were used to determine 96-h upper incipient lethal temperatures (LT50). Acclimation temperatures ranged from 10 to 35°C and acclimation salinities were 10, 20 and 30‰. A quadratics model was fit to the CTM and FEL data; r2 values were 0.924 and 0.928 respectively. Acclimation salinity, estimated weight, acclimation salinity by acclimation temperature interaction and acclimation temperature by estimated weight interaction were the significant components of the CTM model. Predicted CTM values ranged from 30°C at 10 °C and 30‰ acclimation to just over 40°C at 30 °C and 30‰ acclimation. Acclimation temperature, acclimation temperature squared, estimated weight and acclimation temperatures by estimated weight interaction were the significant components of the FEL model. Predicted FEL values ranged from around 28°C at 10°C and 10‰ acclimation to about 39°C at 30°C and 30‰ acclimation. The 96-h LT50 values of spot acclimated to 20‰ increased linearly with acclimation temperature to 25°C. From about 25 to 35°C, LT50 values increased very little with acclimation temperature. The ultimate upper incipient lethal temperature of postlarval and small juvenile spot was estimated at 35.2°C. Increased salinity increased resistance time but decreased LT50 estimates. Thermal shock tests were better for predicting the effects of thermal addition than were CTM tests. 相似文献
10.
M. O Olorunfemi A. A Adepelumi D. E Falebita O. A Alao 《Arabian Journal of Geosciences》2013,6(5):1657-1667
Spectral analysis method was applied to aeromagnetic data obtained for Ikogosi warm spring (IWS) area of southwestern Nigeria. This was done with the objective of determining the bottom of the magnetized crust called Curie point depth (CDP) and understand the nature and extent of the local geothermal system at depth beneath IWS. The depth to the centroid, Z o, of the deepest distribution of the magnetic dipoles was obtained by computing least-squares fit to the lowest-frequency segment of the azimuthally averaged log power spectrum. The average depth to the top of the deepest crustal block was computed as the depth to the top, Z t, of the second lowest-frequency segment of the spectrum. The depth to the bottom of the deepest magnetic dipoles, the inferred Curie point depth, was then calculated from Z b?=?2Z o???Z t. The Curie depth estimates for IWS range between 4.68 and 11.38 km (below sea level). We also estimate the heat flow and Curie temperature using a one-dimensional conductive heat transport model. The average heat flow, 42 mW m?2, and geothermal gradient, 32°C/km, obtained suggest a low enthalpy thermal regime. The Curie temperature for the region varies between 153°C and 350°C. Also, an inverse linear relationship between heat flow and Curie depths was determined. Good agreement between the Curie point depths derived from heat flow data and magnetic data suggests that the Curie point depth analysis is useful to estimate the regional thermal structure and the tectonic settings. 相似文献
11.
Raman spectra of Ni2SiO4 spinel (O h 7 Z=8) have been measured in the temperature range from 20 to 600 °C and the Raman active vibrations (A 1g +E g +3F 2g ) have been assigned. A calculation of the optically active lattice vibrations of this spinel has been made, assuming a potential function which combines general valence and short range force constants. The values of the force constants at 20 and 500 °C have been calculated from the vibrational frequencies of the observed Raman spectra and infrared (IR) spectral data. The Ni spinel at 20 °C has a prominently small Si-O bond stretching force constant of K(SiO)=2.356 ～ 2.680 md/Å and a large Ni-O bond stretching constant of K(NiO)=0.843 ～ 1.062 md/Å and these force constants at 500 °C decrease to K(SiO)=2.327 ～ 2.494 md/Å and K(NiO)=0.861 ～ 0.990 md/Å. The Si-O bond is noticeably weakened at high temperatures, despite the small thermal expantion from 1.657 Å (20 °C) to 1.660 Å (500 °C). These changes of the interatomic force constants of the spinel at high temperatures are in accord with the thermal structure changes observed by X-ray diffraction study. The weakened Si-O bond is consistent with the fact that Si atoms in the spinel lattice can diffuse at significant rates at elevated temperature. 相似文献
12.
The tetrahedral-site order-disorder transformation in gallium albite (NaGaSi3O8) has been investigated using Rietveld structure refinement. Study of gallium-substituted albite (in contrast to pure albite [NaAlSi3O8]) is facilitated by a relatively rapid order-disorder transformation and the large difference in X-ray scattering efficiencies of gallium and silicon. High albite-structure NaGaSi3O8, grown in a Na2WO4 flux, was ordered by hydrothermal annealing below 820° C and dry annealing above 820° C, to avoid melting, using a load pressure of approximately 1 kbar. Equilibration of the order-disorder reaction has been verified by three independent reversals of ordering. The transformation between low gallium albite and high gallium albite occurs over the temperature range 890° C 970° C. The gallium content of the T 1o site increases continuously with decreasing temperature. The gallium contents of the T 1m and T 2m sites decrease smoothly with increasing ordering while the gallium content of the T 2o site decreases, then increases and then decreases again with decreasing temperature. Unit-cell parameters and the triclinic obliquity vary throughout the order-disorder transformation and undergo abrupt changes at 913±3° C and 937±3° C. These abrupt changes correlate with changes in the gallium content of the T 2o site, the X and Z ordering parameters and the configurational entropy. The order-disorder transformation in gallium-aluminum albite (NaGa0.5Al0.5Si3O8) occurs in the temperature range 765° C-850° C, at a temperature intermediate to the transformation in albite (50% order at about 680±20° C) and gallium albite. 相似文献
13.
Prey availability and feeding success affect survival of larval striped bass (Morone saxatilis) in Chesapeake Bay and contribute to the >30-fold interannual recruitment variability. Gut contents and stable isotope analyses (δ15N and δ13C) were conducted on striped bass larvae to evaluate sources of nutrition in 2007 and 2008, years of high and poor recruitment, respectively. Ichthyoplankton and zooplankton were surveyed in the upper Chesapeake Bay, in proximity to the estuarine turbidity maximum and associated salt front. Feeding incidence and numbers of prey per gut were similar in both years and varied in relation to the salt front. The primary prey in each year was the estuarine copepod Eurytemora affinis. Substantial consumption of the freshwater cladoceran Bosmina spp. also occurred, especially up-estuary of the salt front in 2007, demonstrating that secondary prey are important to larval diets in some years. Stable isotope analysis of yolk sac and feeding-stage larvae of striped bass revealed an ontogenetic shift from maternal stable isotope signatures to those indicative of prey source. Feeding-stage larvae from up-estuary locations had the most negative δ13C values, indicating a relatively high terrestrial carbon source in prey. Spatio-temporal variability in δ15N signatures of larvae followed similar trends of δ15N variability in zooplankton prey with the highest δ15N values up-estuary of the salt front and estuarine turbidity maximum. A stable isotope analysis on archived striped bass larvae collected in 1998 and 2003, years of moderate and high recruitment, respectively, expanded the documented range of isotope signatures but did not clearly distinguish effects of nutritional sources on recruitment. 相似文献
14.
Thermodynamic simulation of the system living matter (algae, zooplankton, or green plants) + mineral matter (25% carbonates + 75% clay minerals) + standard seawater at temperatures and pressure corresponding to diagenesis indicates that kerogen can be synthesized, together with hydrocarbons and carbon dioxide, in the reaction mix. The removal of CO2(g) and N2(g) from the system is favorable for the reaction Δ1C292H288O12 (s; H/C = 0.99, O/C = 0.041) → Δ2C128H68O7 (s; H/C = 0.53, O/C = 0.055) + xСH4(aq) + yCO2(aq) + zH2O, whose constant and stoichiometric coefficients were calculated based on the simulation results. It is demonstrated that a pressure increase is favorable, while a temperature increase is not, for the procedure of this reaction at P-T parameters of diagenesis: log K =–567 (20°C, 35 bar), 1170 (20°C, 200 bar),–1530 (20°C, 60 bar), and +1030 (20°C, 600 bar). 相似文献
15.
Three sets of pyrolysis experiments were performed on extracted coal (Ro% 0.39), coal (initial bitumen 13.5 mg/g coal) and bitumen enriched coal (total bitumen 80.9 mg/g coal) at two heating rates of 2 °C/h and 20 °C/h in confined systems (gold capsules). For all three experiments, the yields of bitumen, Σn-C8+, aromatic components and ΣC2–5 at first increase and then decrease with increasing EASY%Ro and reach the highest values within the EASY%Ro ranges of 0.67–1.08, 1.07–1.19, 1.46–1.79 and 1.46–1.68, respectively. In contrast, C1/ΣC1–5 ratio at first decreases and then increases with EASY%Ro and reaches a minimum value in EASY%Ro range of 0.86–1.08, closely corresponding to the maximum values of the yields of bitumen and Σn-C8+. Methane yields increase consistently with EASY%Ro. Nearly half of the maximum yield of methane from kerogen was generated at EASY%Ro > 2.2. The differences in methane yields among the three experiments at the same thermal stress are relatively minor at EASY%Ro < 2.2, but are greater with thermal stress at EASY%Ro > 2.2. This demonstrates that the kerogen always retained relatively more hydrogen and hydrocarbon generative potential at the postmature stage of bitumen rich coal than the extracted coal or coal.The maximum yield of ethane is 20–25% higher in the bitumen rich coal experiment than the extracted coal or coal, while the maximum yields of C3, C4 and C5 in the former are double to triple those in the latter. This result demonstrates that the added bitumen in bitumen rich coal substantially increased the generation of these wet gases. However, the averaged values of activation energies (with the same frequency factors) for both the generation and cracking of individual wet gases are similar and do not show consistent trends among the three experiments. For all three experiments, activation energies for the generation and cracking of wet gases are significantly lower than those in previously published oil pyrolysis experiments with same frequency factors (Pan et al., 2012; Organic Geochemistry 45, 29–47). Methane δ13C values at the maximum temperature or EASY%Ro are close to those of initial wet gases, especially C3, implying that the major part of methane shared a common initial precursor with wet gases, i.e., free and bound liquid alkanes. 相似文献
16.
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
17.
The thermal phase transition of K2SO4 has been investigated by high temperature polarized light microscopy. K2SO4 undergoes a first-order transition at 587° C where the orthorhombic low temperature form (Pmcn) transforms into a hexagonal high temperature modification (P63/mmc). Prior to the beginning of the phase transition, K2SO4 shows an anomalous optical behavior. The crystal apparently becomes optically uniaxial twice at 338° and 425° C, respectively, and truly optically uniaxial at 587° C. The phase transition propagates through an intermediate temperature form, which is sandwiched between the low and the high temperature forms and moves in a definite direction, 〈130〉 (orthorhombic indices), in the vicinity of the phase transition. Passing through the phase transition point on cooling, dark belts crossing each other are observed which are a result of the transformation twins parallel to {110} and {130}. 相似文献
18.
Gillnet surveys from 1990 to 1992 and from 1996 to 1999 indicated a two-fold decrease in native striped bass (Morone saxatilis) populations and a concomitant two-fold increase in hybrid striped bass (Morone saxatilis × M. americana) in the Cape Fear River estuary, North Carolina. Gut content analysis indicated high diet overlap, and tagrecapture data
suggested that hybrid striped bass participate in spawning migrations. These data provide circumstantial evidence that hybrid
striped bass compete with striped bass for food and that they may compete for mates or habitat on the spawning grounds. Increasing
abundance of adult hybrid striped bass in this system elevates the likelihood of hybrid introgression. We recommend that stocking
of hybrid striped bass be terminated to preserve native striped bass populations. 相似文献
19.
Based on potentiometric data and gypsum solubility in mixed salt solutions, respectively, the activity coefficients of MgCOo3 and CaSOo4 ion pairs decrease with ionic strength (I) at 25°C. Computed γ's for the ion pairs fit the empirical equation log γi = ? BI. B coefficients of 0.63 ±0.10 for MgCOo3 and 0.45 ± 0.15 for CaSOo4 are obtained from linear regression of log γi values vs I between 0.04 and 0.6 molal. Assumptions that the activity coefficients of these neutral ion pairs equal unity or are approximated by the Setchenow expression (log γi = kI) are therefore invalid at moderate ionic strengths. Log γi = ? BI is the same general form as the equation of Kirkwood (Chem. Rev.24, 233–251, 1939) for neutral dipoles. 相似文献
20.
Peter W. Mirwald 《Physics and Chemistry of Minerals》1979,4(4):291-297
The electrical conductivity of calcite cleavage fragments was measured using direct current. Five temperature intervals, characterized by different activation energies of conduction, were established — T 1: (300°)–500° C, T 2: 500–725° C, T 3: 725°–800° C, T 4: 800°–985° C and T 5: 985°–(1,200)° C. The data above 600° C indicate various intrinsic conduction mechanisms which are likely to be related to disorder in the CO3-sublattice of calcite. The transitions between the temperature intervals T 2-T 3-T 4 and T 4-T 5 are probably correlated with high-temperature transitions of calcite at 800° and 985° C. Measurement of the thermoelectric voltage indicates a conductivity dominated by negatively charged carriers. 相似文献