Thermal equation of state of synthetic orthoferrosilite at lunar pressures and temperatures

Iron-rich orthopyroxene plays an important role in models of the thermal and magmatic evolution of the Moon, but its density at high pressure and high temperature is not well-constrained. We present in situ measurements of the unit-cell volume of a synthetic polycrystalline end-member orthoferrosilite (FeSiO₃, fs) at simultaneous high pressures (3.4–4.8 GPa) and high temperatures (1,148–1,448 K), to improve constraints on the density of orthopyroxene in the lunar interior. Unit-cell volumes were determined through in situ energy-dispersive synchrotron X-ray diffraction in a multi-anvil press, using MgO as a pressure marker. Our volume data were fitted to a high-temperature Birch–Murnaghan equation of state (EoS). Experimental data are reproduced accurately, with a  $\varDelta P$ Δ P  standard deviation of 0.20 GPa. The resulting thermoelastic parameters of fs are: V ₀ = 875.8 ± 1.4 Å³, K ₀ = 74.4 ± 5.3 GPa, and $\frac{{\text d}K}{{\text d}T} = -0.032 \pm 0.005\,\hbox{GPa K}^{-1}$ d K d T = - 0.032 ± 0.005 GPa K - 1 , assuming ${K}^{\prime}_{0} = 10 $ K 0 ′ = 10 . We also determined the thermal equation of state of a natural Fe-rich orthopyroxene from Hidra (Norway) to assess the effect of magnesium on the EoS of iron-rich orthopyroxene. Comparison between our two data sets and literature studies shows good agreement for room-temperature, room-pressure unit-cell volumes. Preliminary thermodynamic analyses of orthoferrosilite, FeSiO₃, and orthopyroxene solid solutions, (Mg_1?x Fe _x ) SiO₃, using vibrational models show that our volume measurements in pressure–temperature space are consistent with previous heat capacity and one-bar volume–temperature measurements. The isothermal bulk modulus at ambient conditions derived from our measurements is smaller than values presented in the literature. This new simultaneous high-pressure, high-temperature data are specifically useful for calculations of the orthopyroxene density in the Moon.     

Annual volcanic carbon dioxide emission: An estimate from eruption chronologies

Continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing anthropogenic production of CO₂. Volcanoes are also a major source of carbon dioxide, but their average input to the atmosphere is generally considered minor relative to anthropogenic input. This study examines eruption chronologies to determine a new estimate of the volcanic CO₂ input and to test if temporal fluctuations may be resolved. Employing representative average values of 2.7 g cm⁻³ as density of erupted material, 0.2 wt percent CO₂ in the original melt, 60 percent degassing during eruption, and an average volume of 0.1 km³ for each of the eruptions in the recently published eruption chronology of Hirschboeck (1980), a volcanic input of about 1.5 · 10¹¹ moles CO₂ yr⁻¹ was determined for the period 1800–1969. The period 1800–1899 had a somewhat lower input than 1900–1969, which could well be related more to completeness of observational data than to a real increase in volcanic CO₂. This input is well below man's current CO₂ production of 4–5 · 10¹⁴ moles CO₂ yr⁻¹. The average values above together with specific volumetric estimates were employed to calculate CO₂ input from individual historic eruptions, massive flood basalts, and ash-flow eruptions. Total CO₂ release from the largest of flood basalt and ash-flow sequences was 10¹⁵-10¹⁶ moles of CO₂. The impact of these sources on global atmospheric CO₂ and climate, however, will be limited by the duration and spacing of the major individual eruptive periods in the sequences.     

CO2地质处置研究进展

减少CO2向大气排放的一个主要的方法是将其隔离在地下深部,即CO2地质处置.CO2地质处置的方法主要包括:含水层处置,海洋处置,利用CO2开采油气以及煤层甲烷气体等.含水层处置有三种机制:(1)水力学方法;(2)溶解的方法;(3)矿物处置.CO2地质处置是可行的技术方法,在实际中已有了应用.在难以获得复杂的深部含水层环境的情况下,地球化学数值模拟方法在评价地质处置CO2可行性上具有重要的作用.     

An equation correlating the solubility of quartz in water from 25° to 900°C at pressures up to 10,000 bars

The solubility of quartz in water from 25° to 900°C at specific volume of the solvent ranging from about 1 to 10 and from 300° to 600°C at specific volume of the solvent ranging from about 10 to 100 is given by an empirically derived equation of the form: log m = A + B(log V) + C(log V)² where m is the molal silica concentration, V is the specific volume of pure water, and A = ?4.66206 + 0.0034063T + 2179.7T^?1 ? 1.1292 × 10⁶T^?2 + 1.3543 × 10⁸T^?3B = ?0.0014180T— 806.97T^?1C = 3.9465 × 10^?4T T is temperature in kelvins. The experimental data used in formulating the empirical relation ranged in pressure from 1 bar at 25°C to about 10,000 bars at 900°C, and the lowest pressure in the low-density steam region was about 30 bars. According to the above equation, the average difference in molality between 518 measured and calculated solubilities is ?0.016 m with a standard deviation of 0.089.     

An empirical Redlich-Kwong-type equation of state for water to 1,000 °C and 200 Kbar

An empirically derived Redlich-Kwong type of equation of state (ERK) is proposed for H₂O, expressing a, the term related to the attraction between the molecules, as a pressure-independent function of temperature, and b, the covolume, as a temperature-independent function of pressure. The coefficients of a(T) and b(P) were derived by least squares non-linear regression, using P-V-T data given by Burnham et al. (1969b) and Rice and Walsh (1957) in conjunction with more precise recent data obtained by Tanishita et al. (1976), Hilbert (1979) and Schmidt (1979): $$a(T) = 1.616 x 10^8 - 4.989 x 10^4 T - 7.358 x 10^9 T^{ - 1} $$ and $$ = \frac{{1 + 3.4505x 10^{--- 4} P + 3.8980x 10^{--- 9} P^2 - 2.7756x 10^{--- 15} P^3 }}{{6.3944x 10^{--- 2} + 2.3776x 10^{--- 5} + 4.5717x 10^{--- 10} P^2 }}$$ , where T is expressed in Kelvin and P in bars. The ERK works very well at upper mantle conditions, at least up to 200 kbar and 1,000 °C. At subcritical conditions and those somewhat above the critical point, it still reproduces the molar Gibbs energy, \(\tilde G_{{\text{H}}_{\text{2}} {\text{O}}} \) , with a maximum deviation of 400 joules. Thus, for the purpose of calculation of geologically interesting heterogeneous equilibria, it predicts the thermodynamic properties of H₂O well enough. The values of molar volume, \(\tilde V_{{\text{H}}_{\text{2}} {\text{O}}} \) , and \(\tilde G_{{\text{H}}_{\text{2}} {\text{O}}} \) are tabulated in the appendix over a considerable P-T range. A FORTRAN program generating these functions as well as a FORTRAN subroutine for calculating the fugacity values, \(f_{{\text{H}}_{\text{2}} {\text{O}}} \) for incorporation into existing programs, are available upon request.     

Emission of gaseous carbon dioxide from salt-marsh sediments and its relation to other carbon losses

Rates of CO₂ emission from bare salt-marsh sediments in areas of short and tall formSpartina alterniflora were measured monthly for 1 yr. Maximum emission rates, as high as 325 ml CO₂m^?2h^?1, were observed during summer months, while minimum rates, 10.2 ml CO₂ m^?2h^?1, were observed during the winter. An exponential function of inverse soil temperature explained most of the seasonal variability, but other factors are involved in regulating CO₂ emissions as demonstrated by rates that were higher in spring than in late summer at equivalent temperatures. Annual CO₂ emissions from bare sediments were 27.3 and 18.6 mol C m^?2 yr^?1 in communities of short and tallS. alterniflora, respectively. It was estimated that losses of dissolved inorganic carbon from the turnover of pore water, up to 14.6 mol C m^?2 yr^?1 at the creek bank (tall,S. alterniflora) site, and diffusion of CO₂ from the root system ofS. alterniflora through the culms, 12.3 to 16.2 mol C m^?2 yr^?1, could also be important pathways of carbon loss from marsh sediments. If the internal flux of CO₂ from the root system through the culm is refixed within the leaves, then the observed rate of 9.8 μI CO₂ min^?1 cm^?2 of culm cross sectional area appears to make a small but significant contribution to total photosynthesis.     

The hildebrand equation of state for minerals relevant to geophysics

The Hildebrand thermal equation of state (EOS) is revived and applied to minerals appropriate to the earth's interior. The chief virtue of this EOS is that it escapes the necessity of evaluating a Grüneisen parameter at high compression and high temperature. The classical Grüneisen parameter is replaced by the product of two experimentally measured parameters: α, the coefficient of thermal expansivity, and K _T , the isothermal bulk modulus. In order for the Hildebrand EOS to be useful in geophysical conditions it is necessary to show that α K _T is, to a large extent, independent of volume. This can be done directly by experiment, following Yagi, or indirectly using thermodynamic formulae where other measurements are used in place of α K _T . Four such tests are proposed, two of them following tests proposed by Swenson. The result indicates that most, if not all, of the close-packed minerals relevant to geophysics follow the rule that the value of α K _T is to a satisfactory extent independent of compression.     

HgO at high pressures: the transition to the NaCl structure (HgO-III) and the equation of state of tetragonal HgO-II

The high-pressure behavior of HgO-montroydite was investigated up to 36.5 GPa using angle-dispersive X-ray diffraction. The tetragonal phase of this material (HgO-II), a distortion of the NaCl structure, transforms into the cubic NaCl structure (HgO-III) above ~31.5 GPa. The transformation of mercury oxide from the orthorhombic Pnma (HgO-I) structure to a tetragonal I4/mmm structure (HgO-II) is confirmed to occur at 13.5 ± 1.5 GPa. Neither of the high-pressure phases, HgO-II nor HgO-III, is quenchable in pressure. The derived isothermal bulk modulus of HgO-II and its pressure derivative strongly depend on the assumed zero-pressure volume of this phase, but our elasticity results on HgO-II nevertheless lie significantly closer to theoretical calculations than prior experimental results, and the measured pressure of the phase transformation to the NaCl structure is also in agreement with recent theoretical results. The general accord with theory supports the existence of significant relativistic effects on the high-pressure phase transitions of HgO.     

Hydrostatic compression of γ-Mg2SiO4 to mantle pressures and 700 K: Thermal equation of state and related thermoelastic properties

P-V-T equations of state for the γ phase of Mg₂SiO₄ have been fitted to unit cell volumes measured under simultaneous high pressure (up 30 GPa) and high temperature (up to 700 K) conditions. The measurements were conducted in an externally heated diamond anvil cell using synchrotron x-ray diffraction. Neon was used as a pressure medium to provide a more hydrostatic pressure environment. The P-V-T data include 300 K-isothermal compression to 30 GPa, 700 K-compression to 25 GPa and some additional data in P-T space in the region 15 to 30 GPa and 300 to 700 K. The isothermal bulk modulus and its pressure derivative, determined from the isothermal compression data, are 182(3) GPa and 4.2(0.3) at T=300 K, and 171(4) GPa and 4.4(0.5) at T=700 K. Fitting all the P-V-T data to a high-temperature Murnaghan equation of state yields: K _TO=182(3.0) GPa, K _TO=4.0(0.3), ?K _T /?T)₀=?2.7(0.5)×10^?2 GPa/K and (?² K _T /?P?T)₀=5.5(5.2)×10^?4/K at the ambient condition.     

Solubility of carbon dioxide in aqueous fluids and mineral suspensions at 294 K and subcritical pressures

An experimental investigation has been carried on the solubility of CO₂ in water and 1 M NaCl between 0.3 and 4 MPa, in order to test the validity of the results given by various modelling codes. In addition to experiments with pure fluids, the effect of a range of likely reservoir minerals on CO₂–water interactions, including K-feldspar, kaolinite, calcite, Ca-montmorillonite and Na-montmorillonite were also investigated. In addition to measurements of CO₂ solubility, the pH of the CO₂-saturated suspensions was also measured directly at pressures of up to 1 MPa. The results demonstrate that predictions of CO₂ solubility made with PHREEQC and Geochemist’s Workbench agree to within 20% with the experimental value, provided corrections are first made off-line for the fugacity coefficient of CO₂, while predictions from standalone models are slightly more accurate. In the presence of mineral suspensions, PHREEQC and Geochemist’s Workbench give good results for calcite and kaolinite but underestimate the pH of montmorillonite-bearing assemblages while slightly overestimating the pH of K-feldspar suspensions. These results are significant because they indicate that CO₂-charged fluids reacted with clays may be less acidic than indicated by the models, which will impact predictions of the potential for dissolution of reservoir and cap rock minerals, as well as the potential for leaching of toxic metals.     

状态方程法在渗流-应力耦合场求解中的应用

提出了一种计算土体渗流-应力耦合场的状态方程法。按平面应变问题,将描述渗流-应力耦合的平面固结方程进行空间离散,并用状态方程表示了有限元控制方程。利用牛顿-柯特斯公式,导出了当前时间步节点位移向量与前一时间步位移向量之间关系的递推公式。算例表明：状态方程法解决土体渗流-应力耦合问题与传统差分法相比的优势在于用较少的机时即可得到较为精确的解。     

An equation of state for biologically active lake sediments and its implications for interpretations of sediment data

The aim of this work is to link physical sediment parameters to biological parameters by an equation of state, which describes how the given variables interact in biologically active deposits from accumulation areas, i.e. lake areas where fine material is being continuously deposited. In the model the following parameters are utilized: sediment depth, rate of deposition, degree of compaction, bulk density, water content, net biotransport, upward biotransport, downward biotransport, and substrate decomposition. The equation of state has been empirically tested with data from Lake Ekoln and Lake Vänern, Sweden. The model enables determinations of age frequency distributions for arbitrary sediment layers, and it has been shown that, for example, the sediment layer 12-13 cm in Lake Ekoln has a median age of 15.3 years and that the deposits from the median year only constitutes about 15% of the total amount of material in this particular sediment layer. The spread due to bioturbation is considerable and the range at this sediment layer is 22 years. A mechanism to explain secondary lamination is introduced and discussed in the light of the results from the model.     

Geochemical interactions resulting from carbon dioxide disposal on the seafloor

The storage of CO_2(liquid) on the seafloor has been proposed as a method of mitigating the accumulation of greenhouse gases in the Earth's atmosphere. Storage is possible below 3000 m water depth because the density of CO_2(liquid) exceeds that of seawater and, thus, injected CO_2(liquid) will remain as a stable, density stratified layer on the seafloor. The geochemical consequences of the storage of CO_2(liquid) on the seafloor have been investigated using calculations of chemical equilibrium among complex aqueous solutions, gases, and minerals. At 3000 m water depth and 4°C, the stable phases are CO_2(hydrate) and a brine. The hydrate composition is CO₂·6.3H₂O. The equilibrium composition of the brine is a 1.3 molal sodium-calcium-carbonate solution with pH ranging from 3.5 to 5.0. This acidified brine has a density of 1.04 g cm⁻³ and will displace normal seawater and react with underlying sediments. Seafloor sediment has an intrinsic capacity to neutralize the acid brine by dissolution of calcite and clay minerals and by incorporation of CO₂ into carbonates including magnesite and dawsonite. Large volumes of acidified brine, however, can deplete the sediments buffer capacity, resulting in growth of additional CO_2(hydrates) in the sediment. Volcanic sediments have the greatest buffer capacity whereas calcareous and siliceous oozes have the least capacity. The conditions that favor carbonate mineral stability and CO_2(hydrates) stability are, in general, mutually exclusive although the two phases may coexist under restricted conditions.The brine is likely to cause mortality in both plant and animal comunities: it is acidic, it does not resemble seawater in composition, and it will have reduced capacity to hold oxygen because of the high solute content. Lack of oxygen will, consequently, produce anoxic conditions, however, the reduction of CO₂ to CH₄ is slow and redox disequilibrium mixtures of CO₂ and CH₄ are likely. Seismic or volcanic activity may cause conversion of CO_2(liquid) to gas with potentially catastrophic release in a Lake Nyos-like event. The long term stability of the CO_2(hydrate) may be limited: once isolated from the CO_2(liquid) pool, either through burial or through depletion of the CO₂ pool, the hydrate will decopose, releasing CO₂ back into the sediment-water system.     

An approach for valid covariance estimation via the Fourier series

The use of kriging for construction of prediction or risk maps requires estimating the dependence structure of the random process, which can be addressed through the approximation of the covariance function. The nonparametric estimators used for the latter aim are not necessarily valid to solve the kriging system, since the positive-definiteness condition of the covariance estimator typically fails. The usage of a parametric covariance instead may be attractive at first because of its simplicity, although it may be affected by misspecification. An alternative is suggested in this paper to obtain a valid covariance from a nonparametric estimator through the Fourier series tool, which involves two issues: estimation of the Fourier coefficients and selection of the truncation point to determine the number of terms in the Fourier expansion. Numerical studies for simulated data have been conducted to illustrate the performance of this approach. In addition, an application to a real environmental data set is included, related to the presence of nitrate in groundwater in Beja District (Portugal), so that pollution maps of the region are generated by solving the kriging equations with the use of the Fourier series estimates of the covariance.     

P-V-T equation of state of lawsonite

A pressure-volume-temperature data set has been obtained for lawsonite [CaAl₂Si₂O₇(OH)₂.H₂O], using synchrotron X-ray diffraction and an externally heated diamond anvil cell. Unit-cell volumes were measured to 9.4 GPa and 767 K by angle dispersive X-ray diffraction using imaging plates. Phase changes were not observed within this pressure-temperature range, and lawsonite compressed almost isotropically at constant temperature. The P-V-T data have been analyzed using a Birch- Murnaghan equation of state and a linear equation of state expressed as β=–1/V₀ (∂V/∂P) _T . At room temperature, the derived equation of state parameters are: K ₀=124.1 (18) GPa K'₀ set to 4) and β^–1=142.0(24) GPa, respectively. Our results are intermediate between previously reported measurements. The high-temperature data show that the incompressibility of lawsonite decreases with increasing temperature to ∼500 K and then increases above. Hence, the second order temperature derivative of the bulk modulus is taken into account in the equation of state; a fit of the volume data yields K ₀=123.9(18) GPa, (∂K/∂T)_P=–0.111(3) GPa K^–1, (∂² K/∂T ²)_P=0.28(6) 10^–3 GPa K^–2, α₀=3.1(2) 10^–5 K^–1, assuming K'₀=4. Received: 2 June 1998 / Revised, accepted: 12 Ocotber 1998     

水环境同位素技术在二氧化碳地质储存中的应用之探讨

通过分析二氧化碳地质储存的地下空间和时间特征,并结合水环境同位素技术的特点,提出将其应用于碳储存方面可以从以下三方面入手:(1)利用水环境同位素技术判断二氧化碳规模化封存场地的水文地质条件的方法,评价典型二氧化碳规模化封存咸水层的安全持久性及储存二氧化碳的适宜性;（2）确定判断泄露二氧化碳“碳源”的同位素方法,研究泄露的“碳”源;（3）通过水环境同位素技术,研究二氧化碳地质封存与地下水循环、径流之间的关系,评价规模化封存二氧化碳潜在泄露对浅层含水层的影响。     

A study on carbon dioxide emissions from bituminous coal in Korea

Consumption of primary energy in Korea increased 5.25 % per year over a 10 years span starting in 1990. Korea ranked 8th in primary energy consumption in 2011; coal consumption increased 35 % from 87,827 million tons in 2006–119,321 tons in 2010. Heavy energy-consuming countries consistently conduct research to develop an emission factor of Tier 2 level, reflecting the characteristics of the fuel that they use. To calculate the emission factor of bituminous coal for fuel, this study developed emission factor and calculated emission amount by implementing fuel analysis on bituminous coal consumed in Korea between 2007 and 2009. CO₂ emission factor calculated by fuel analysis method is 95,315 kg/TJ, which is 0.75 % higher than the default value suggested by IPCC. The emission amount calculated by using the CO₂ emission factor in this study is 231.881 million tons, which has a difference of 1.739 million tons compared to the IPCC default value.