Sun Q.,Peking University |
Qin C.,Chinese Academy of science
Chemical Geology | Year: 2011
Raman spectroscopy is an efficient method which has been widely employed in many research fields. However, this method is more commonly associated with qualitative study than with quantitative analysis. In this work, a quantitative measurement using Raman spectroscopy is provided. According to the theoretical analysis of Raman intensity, Raman quantitative measurement should be based on the intensity ratio, which can be classified into external and internal standards. This allows the influence from measurement conditions to be eliminated. For aqueous solutions, it is reasonable to treat the Raman OH stretching band of water as an internal standard. In this study, the intensity ratio ICO32-/IW is used to determine carbonate concentrations in solutions, where ICO32- is the intensity of the carbonate band, and IW is the sum of intensities of the two used OH stretching sub-bands. © 2011 Elsevier B.V.
Hu R.-Z.,Chinese Academy of science |
Zhou M.-F.,University of Hong Kong
Mineralium Deposita | Year: 2012
Mesozoic mineral deposits in South China include world-class deposits of W, Sn and Sb and those that provide the major sources of Ta, Cu, Hg, As, Tl, Pb, Zn, Au and Ag for the entire country. These deposits can be classified into polymetallic hydrothermal systems closely related to felsic intrusive rocks (Sn-W -Mo granites, Cu porphyries, polymetallic and Fe skarns, and polymetallic vein deposits) and low-temperature hydrothermal systems with no direct connection to igneous activities (MVT deposits, epithermal Au and Sb deposits). Recent studies have shown that they formed in the Triassic (Indosinian), Jurassic-Cretaceous (Early Yanshanian), and Cretaceous (Late Yanshanian) stages. Indosinian deposits include major MVT (Pb-Zn-Ag) deposits and granite-related W-Sn deposits. Early Yanshanian deposits are low-temperature Sb-Au and high-temperature W-Sn and Cu porphyry types. Many Late Yanshanian deposits are low-temperature Au-As-Sb-Hg and U deposits, and also include high-temperature W-Sn polymetallic deposits. The formation of these deposits is linked with a specific tectonothermal evolution and igneous activities. This special issue brings together some of the latest information in eight papers that deal with the origins and tectonic environments of mineral deposits formed in these stages. We anticipate that this issue will stimulate more interests in these ore deposits in South China. © 2012 Springer-Verlag.
Xu H.,CAS Institute of Earth Environment |
Hong Y.,Chinese Academy of science |
Hong B.,Chinese Academy of science
Climate Dynamics | Year: 2012
The trend of the Indian summer monsoon (ISM) intensity and its nature during the past 100 and 200 years still remain unclear. In this study we reconstructed the ISM intensity during the past 270 years from tree ring δ18O at Hongyuan, eastern edge of the Tibet Plateau. The monsoon failures inferred from δ18Otree ring correlate well with those recorded in ice cores, speleothem, and historical literature sources. 22.6, 59.0, and 110.9-years frequency components in the Hongyuan δ18Otree ring series, which may be the responses to solar activities, synchronize well with those recorded in other ISM indices. A notable feature of the reconstructed ISM intensity is the gradually decreasing trend from about 1860 to the present, which is inversely related to the increasing temperature trend contemporaneously. Such "decreasing ISM intensity-increasing temperature" tendency can also be supported by ice core records and meteorological records over a wide geographic extension. The decrease in sea surface temperature gradient between tropical and north Indian Ocean, and the decrease in land-sea thermal contrast between tropical Indian Ocean and "Indian sub-continent-western Himalaya" are possibly responsible for the observed decreasing ISM trend. © 2012 Springer-Verlag.
Cao X.,Chinese Academy of science |
Liu Y.,Chinese Academy of science
Geochimica et Cosmochimica Acta | Year: 2011
With a growing interest in small 17O-anomaly, there is a pressing need for the precise ratio, ln17α/ln18α, for a particular mass-dependent fractionation process (MDFP) (e.g., for an equilibrium isotope exchange reaction). This ratio (also denoted as "θ") can be determined experimentally, however, such efforts suffer from the demand of well-defined process or a set of processes in addition to high precision analytical capabilities. Here, we present a theoretical approach from which high-precision ratios for MDFPs can be obtained. This approach will complement and serve as a benchmark for experimental studies. We use oxygen isotope exchanges in equilibrium processes as an example. We propose that the ratio at equilibrium, where 18βb is the fractionation factor between a compound "b" and the mono-atomic ideal reference material "O", 18αa-b is the fractionation factor between a and b and it equals to 18βa/18βb and κ is a new concept defined in this study as κ≡ln17β/ln18β. The relationship between θ and κ is similar to that between α and β. The advantages of using κ include the convenience in documenting a large number of θ values for MDFPs and in estimating any θ values using a small data set due to the fact that κ values are similar among O-bearing compounds with similar chemical groups. Frequency scaling factor, anharmonic corrections and clumped isotope effects are found insignificant to the κ value calculation. However, the employment of the rule of geometric mean (RGM) can significantly affect the κ value. There are only small differences in κ values among carbonates and the structural effect is smaller than that of chemical compositions. We provide κ values for most O-bearing compounds, and we argue that κ values for Mg-bearing and S-bearing compounds should be close to their high temperature limitation (i.e., 0.5210 for Mg and 0.5159 for S). We also provide θ values for CO2(g)-water, quartz-water and calcite-water oxygen isotope exchange reactions at temperature from 0 to 100°C. © 2011 Elsevier Ltd.
Li X.,Chinese Academy of science |
Liu Y.,Chinese Academy of science
Earth and Planetary Science Letters | Year: 2011
Several important equilibrium Se isotope fractionation parameters are investigated by first-principles calculations, involving dominant inorganic and organic Se-bearing species in gaseous, aqueous and condensed phases. Because anharmonic effects are found to be negligible for Se isotope fractionation calculation, the Bigeleisen-Mayer equation method is used without corrections beyond harmonic approximation. All calculations are made at B3LYP/6-311. +. G(d,p) level, with a frequency scaling factor of 1.05. Solvation effects are carefully evaluated by the explicit solvent model (i.e. the "water droplet" method). A number of conformers are used for aqueous complexes in order to reduce the possible error coming from different configurations. Redox state is found to be an important factor controlling equilibrium Se isotope fractionations. Our results suggest a trend of heavy Se isotopes enrichment as SeO4 2->SeO3 2->HSeO3 ->SeO2>selenoamino acids>alkylselenides>Se(0) or H2Se>HSe-. The Se(-II) species regardless of organic and inorganic forms can enrich extremely light Se isotopes comparing with other species. Equilibrium Se isotope fractionation factors provided in this study suggest Se isotopes can be used as a tracer of redox conditions and also useful to study Se cycling. © 2011 Elsevier B.V.
Cao X.,Chinese Academy of science |
Liu Y.,Chinese Academy of science
Geochimica et Cosmochimica Acta | Year: 2012
Clumped (or multiply substituted) isotope geochemistry, as an emerging field, has displayed an array of unique and effective geological and atmospheric applications. In this study, we introduce a new method to facilitate the calculation of concentrations of multiply substituted isotopologues at equilibrium conditions, especially for the calculation of Δ i (" i" refers to a specific isotopologue) and Δ mass (" mass" refers to isotopologues with the same mass number). The proposed exact method has equivalent accuracy and can be solved by similar level of effort compared to that of Wang et al. (2004). However, the approximate method proposed here can handle molecules with isotopomers (e.g., 14N 15N 16O vs. 15N 14N 16O) and can estimate Δ mass of any kind of molecule, whether the Δ i values of singly-substituted isotopologues are small or large. The accuracy and convenience of the proposed method are illustrated through several examples (i.e., CO 2, N 2O and CH 4).Higher-order anharmonic corrections to Δ i have been studied carefully. Our results suggest that such corrections are significant, especially for isotopologues involving hydrogen atoms. To obtain the most precise Δ i or Δ mass value, including those higher-order anharmonic corrections into the calculation is recommended. Such corrections to Δ i are on the order of percent and are similar to anharmonic corrections for the β factor. The difference is that higher-order anharmonic corrections usually reduce β values, but would either reduce or increase Δ i values. For example, the corrections can reduce Δ13CDH3 by five percent but increase Δ18O13C16O by two percent at 300K. The choice of the frequency scaling factor in the Δ i calculation is also found similar to the calculation of β factors. The scaled Δ i value will approximately equal the un-scaled Δ i times the scaling factor, suggesting that the uncertainty in the frequency scaling factor (usually on the order of percent) could possibly cause large errors in the calculation of Δ i. The best way to reduce such errors is to use high-level theoretical methods to reduce the uncertainty of the scaling factor, or to choose frequency scaling factors carefully.Using the method proposed, the equilibrium Δ 47 of CO 2 is found to be roughly independent of δ 13C and δ 18O for most geologic samples, suggesting the effects of bulk isotope compositions on Δ 47 are negligible. We find that the sum of Δ i for all of the singly substituted isotopologues will be equal to zero approximately, enabling us to determine the stochastic concentrations of isotopologues from experiments. © 2011 Elsevier Ltd.
Dai L.,Yale University |
Dai L.,Chinese Academy of science |
Karato S.-I.,Yale University
Earth and Planetary Science Letters | Year: 2014
Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T<. 900K), whereas at higher temperatures (T>. 1000K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere. © 2014 Elsevier B.V.
Ni J.,Chinese Academy of science
Climatic Change | Year: 2013
China is an important region for the global study of carbon because of its vast territory with various climate regimes, diverse ecosystems, and long-term human disturbances and land-use history. Carbon storage in ecosystems in China has been estimated using inventory and modeling methods in the past two decades. However, different methods may result in varied magnitudes and forms of carbon storage. In this study, the current status of carbon storage in terrestrial ecosystems in China, including the impacts of land use, is summarized in the national, regional, and biome scales. Significant differences in data have existed among studies. Such differences are mainly attributed to variations in estimation methods, data availability, and periods. According to available national-scale information on Chinese terrestrial ecosystems, vegetation carbon in China is 6.1 Pg C to 76.2 Pg C (mean 36.98 Pg C) and soil carbon is 43.6 Pg C to 185.7 Pg C (mean 100.75 Pg C). The forest sector has vegetation carbon of 3.26 Pg C to 9.11 Pg C (mean 5.49 Pg C), whereas the grassland sector has 0.13 Pg C to 3.06 Pg C (mean 1.41 Pg C). Soil carbon in the forest and grassland sectors exhibits more significant regional variations. Further studies need a comprehensive methodology, which combines national inventory, field measurement, eddy covariance technique, remote sensing, and model simulation in a single framework, as well as all available data at different temporal and spatial scales, to fully account for the carbon budget in China. © 2013 Springer Science+Business Media Dordrecht.
Zhang B.,Chinese Academy of science |
Zhang B.,Okayama University
AIP Advances | Year: 2014
On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and Éphases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered. © 2014 Author(s).
Chinese Academy Of Science | Date: 2012-09-12
The present invention relates to a novel phosphate based composite anode material, preparation method and uses thereof. Specifically disclosed is a phosphate based composite cell anode material, the material having monoclinic and orthorhombic crystal lattice structures with the chemical formula of A_(3-x)V_(2-y)M_(Y)(PO_(4))_(3), wherein A is Li^(+), Na^(+) or the mixture thereof, M is Mg, Al, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn or Nb, 0x3.0, 0y2.0, and C is the carbon layer. Also disclosed are a preparation method and uses of the composite material. Unlike simple physical mixing, the composite material of the present invention has the advantages of an adjustable electric potential plateau, high reversible capacity, good cycle stability, power consumption early warning and the like.