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761.
Drew T. Shindell 《Journal of Atmospheric Chemistry》1997,26(3):323-335
The inability to explain the observedoxygen suppression of chlorine photosensitized ozoneloss remains a gap in our understanding of thephotochemistry responsible for depletion of thestratospheric ozone layer. It has been suggested thatthe presence of a weakly bound ClO·O2complexcould explain this effect. The existence of thiscomplex would alter the chlorine budget of thestratosphere, perhaps reducing the chlorine availablefor catalytic ozone destruction. On the other hand,the chemistry of ClO·O2 provides two newpathwaysfor ClO dimer formation, which could increase the rateof catalytic ozone loss. In this paper, we constrainthe kinetic rate system of ClO·O2 tomatch themeasured Cly budget. It is shown thatClO·O2cannot be both fairly stable and rapidly form the ClOdimer, or the resulting partitioning of chlorinebecomes incompatible with observations of both ClO andtotal available chlorine. These constraints allow thateither: (1) the ClO·O2 is fairly stable,but doesnot significantly enhance ClO dimer formation andtherefore has a negligible effect on ozone loss rates,or (2) the ClO·O2 complex is only veryweaklystable, but does rapidly form the ClO dimer, andtherefore can influence stratospheric ozone depletion.Even at the ClO·O2 mixing ratios allowedunderthe assumption of weak stability, 0.1 to 0.2 ppbv,significant ozone loss rate enhancements werecalculated. Of course, the chlorine budget constraintalso allows for a thirdpossibility; that ClO·O2 is neither verystablenor forms Cl2O2 very rapidly. Measuredlimits on the reaction rates for ClO·O2to form the ClO dimer would greatly aid the resolution of thisissue. Since the uncertainties aboutClO·O2chemistry are so large, a potential role forClO·O2 in stratospheric ozone loss cannotbe ruled out at this time. 相似文献
762.
Accumulation of total CO2 (CT) was investigated in the sub-halocline deep water of the Gotland Sea (Baltic Sea) during a period of stagnation from 1995 to 1999. Depth profiles for CT, nitrate, phosphate, and oxygen were measured during seven cruises in a grid consisting of 26 stations. The mean CT increased by more than 60 μmol/kg from October 1995 to July 1999 corresponding to a mean accumulation rate of 1.1 mol/m2 year. Taking into account vertical mixing, the vertical distribution of the CT accumulation was used to determine mineralization rates at different depths. High rates immediately below the halocline indicated the existence of a fraction of organic matter, which is rapidly mineralized during sinking through the water column. A second fraction is more refractive and accumulates at the sediment surface in the deep center of the basin where it is slowly mineralized and partly buried. Phosphate release rates in anoxic waters and especially at the redoxcline were substantially higher than those estimated on the basis of the carbon mineralization and the Redfield C/P ratio. This is attributed to non-Redfield mineralization ratios and the dissolution of iron oxide/phosphate associates. The formation of nitrate by mineralization under oxic conditions was almost completely compensated by denitrification. Using the carbon mineralization rates and a C/N ratio of 8.4, a denitrification rate of 280 mmol/m2 year was obtained, which approximately balances the input of nitrate/ammonia into the surface water. Relating the apparent oxygen utilization (AOU) to the CT fraction that was generated by mineralization yielded a carbon mineralization/O2 consumption ratio of 0.83. 相似文献
763.
河流碳通量与陆地侵蚀研究 总被引:29,自引:2,他引:29
河流碳通量系陆地侵蚀产物,它构成全球碳循环的一个重要环节。河流碳通量在数量上远小于全球碳循环的其他环节,但由于与陆地生态系统联系密切,故对它的研究尤为重要。全球每年河流碳通量约为1GtC(109t碳),其中约60%为无机碳、40%为有机碳。溶解态有机碳和颗粒状有机碳主要来源于土壤侵蚀,另有一部分有机碳来源于河湖中的浮游植物;溶解态无机碳主要源于大气中CO2和碳酸盐;颗粒无机碳主要指未溶解的碳酸盐。亚洲季风区河流对全球河流碳通量具有较大贡献,而对其研究程度较低。河流碳通量研究既可为流域治理提供基础资料,也是进一步了解人为CO2“未知汇”的途径之一。 相似文献
764.
Zafer Ekinci Enes ŞayanAyşe Vildan Beşe Osman Nuri Ata 《International Journal of Mineral Processing》2007
In this study, the boric acid extraction from colemanite ore in aqueous media saturated by CO2 and SO2 gases was studied and the effects of relevant parameters, namely; reaction temperature, solid-to-liquid ratio, mean particle size, stirring speed and reaction time have been investigated on the boric acid extraction from colemanite ore by using the fractional factorial design and central composite design methods. The chosen experimental parameter levels were as follows: reaction temperature, 11.4–58.6 °C; solid-to-liquid ratio, 0.0685–0.1315 g/mL; mean particle size, 0.2835–3 mm; stirring speed, 107–893 rpm; reaction time, 7.125–22.875 min. A model has been developed between the boric acid extraction efficiency from colemanite ore and relevant parameters by means of variance analysis by using the matlab computer software and the obtained model was used to determine optimum conditions. The optimum conditions were found to be as follows: reaction temperature, 41 °C; solid-to-liquid ratio, 0.0685 g/mL; mean particle size, 0.2835 mm; stirring speed, 266 rpm; reaction time, 7 min. The calculated boric acid extraction efficiency from colemanite ore was approximately 99.9% under the optimum conditions. 相似文献
765.
Copper–gold mineralization at the world‐class Batu Hijau porphyry deposit, Sumbawa Island, Indonesia, is closely related to the emplacement of multiple stages of tonalite porphyries. Petrographic examination indicates that at least two texturally distinct types of tonalite porphyries are currently recognized in the deposit, which are designated as “intermediate tonalite” and “young tonalite”. They are mineralogically identical, consisting of phenocrysts of plagioclase, hornblende, quartz, biotite and magnetite ± ilmenite, which are set in a medium‐coarse grained groundmass of plagioclase and quartz. The chemical composition of the rock‐forming minerals, including plagioclase, hornblende, biotite, magnetite and ilmenite in the tonalite porphyries was systematically analyzed by electron microprobe. The chemical data of these minerals were used to constrain the crystallization conditions and fluorine–chlorine fugacity of the corresponding tonalitic magma during its emplacement and crystallization. The crystallization conditions, including temperature (T), pressure (P) and oxygen fugacity (fO2), were calculated by applying the hornblende–plagioclase and magnetite–ilmenite thermometers and the Al‐in‐hornblende barometer. The thermobarometric data indicate that the tonalite porphyries were emplaced at 764 ± 22°C and 1.5 ± 0.3 × 105 kPa. If the pressure is assumed to be lithostatic, it is interpreted that the rim of hornblende and plagioclase phenocrysts crystallized at depths of approximately 5.5 km. As estimated from magnetite–ilmenite thermometry, the subsolidus conditions of the tonalite intrusion occurred at temperatures of 540–590°C and log fO2 ranging from ?20 to ?15 (between Ni‐NiO and hematite–magnetite buffers). This occurred at relatively high fO2 (oxidizing) condition. The fluorine–chlorine fugacity in the magma during crystallization was determined on the basis of the chemical composition of magmatic biotite. The calculation indicates that the fluorine–chlorine fugacity, represented by log (fH2O)/(fHF) and (fH2O)/(fHCl) in the corresponding tonalitic magma range from 4.31 to 4.63 and 3.62 to 3.79, respectively. The chlorine fugacity (HCl) to water (H2O) is relatively higher than the fluorine fugacity (HF to water), reflecting a high activity of chlorine in the tonalitic magma during crystallization. The relatively higher activity of chlorine (rather than fluorine) may indicate the significant role of chloride complexes (CuCl2? and AuCl2?) in transporting and precipitating copper and gold at the Batu Hijau deposit. 相似文献
766.
Linda T. Elkins-Tanton David S. Draper Carl B. Agee Jessica Jewell Andrew Thorpe P. C. Hess 《Contributions to Mineralogy and Petrology》2007,153(2):191-209
The final lavas of the Siberian flood basalts are a ∼1,000 m thick section of meimechites, high-alkali, high-titanium, hydrous
lavas that contrast sharply with the tholeiites that precede them. This paper presents a phase equilibrium study indicating
that a candidate primary meimechite magma with 1 wt% water originated at ∼5.5 GPa and 1,700°C, both hotter and shallower than
other estimates for melting beneath continental lithosphere. The experiments also suggest that a higher volatile content was
involved in meimechite source genesis. Both the absence of orthopyroxene in any experiment and the close field association
with carbonatites suggest that the meimechite source region may have been metasomatized with a CO2-rich fluid. A small additional quantity of CO2 and water would move magma origination to ∼1,550–1,600°C. 相似文献
767.
A theoretical model for gas adsorption-induced coal swelling 总被引:6,自引:2,他引:6
Swelling and shrinkage (volumetric change) of coal during adsorption and desorption of gas is a well-known phenomenon. For coalbed methane recovery and carbon sequestration in deep, unminable coal beds, adsorption-induced coal volumetric change may cause significant reservoir permeability change. In this work, a theoretical model is derived to describe adsorption-induced coal swelling at adsorption and strain equilibrium. This model applies an energy balance approach, which assumes that the surface energy change caused by adsorption is equal to the elastic energy change of the coal solid. The elastic modulus of the coal, gas adsorption isotherm, and other measurable parameters, including coal density and porosity, are required in this model. Results from the model agree well with experimental observations of swelling. It is shown that the model is able to describe the differences in swelling behaviour with respect to gas species and at very high gas pressures, where the coal swelling ratio reaches a maximum then decreases. Furthermore, this model can be used to describe mixed-gas adsorption induced-coal swelling, and can thus be applied to CO2-enhanced coalbed methane recovery. 相似文献
768.
Fluid inclusions have recorded the history of degassing in basalt. Some fluid inclusions in olivine and pyroxene phenocrysts of basalt were analyzed by micro-thermometry and Raman spectroscopy in this paper. The experimental results showed that many inclusions are present almost in a pure CO2 system. The densities of some CO2 inclusions were computed in terms of Raman spectroscopic characteristics of CO2 Fermi resonance at room temperature. Their densities change over a wide range, but mainly between 0.044 g/cm3 and 0.289 g/cm3. Their micro-thermometric measurements showed that the CO2 inclusions examined reached homogenization between 1145.5℃ and 1265℃ . The mean value of homogenization temperatures of CO2 inclusions in basalts is near 1210℃. The trap pressures (depths) of inclusions were computed with the equation of state and computer program. Distribution of the trap depths makes it know that the degassing of magma can happen over a wide pressure (depth) range, but mainly at the depth of 0.48 km to 3.85 km. This implicates that basalt magma experienced intensive degassing and the CO2 gas reservoir from the basalt magma also may be formed in this range of depths. The results of this study showed that the depth of basalt magma degassing can be forecasted from CO2 fluid inclusions, and it is meaningful for understanding the process of magma degassing and constraining the inorganogenic CO2 gas reservoir. 相似文献
769.
用氢氧化钠-过氧化钠混合熔剂分解样品,酸提取后加入亚硫酸钠水浴加热消除过氧化氢和大量钛的干扰,硅钼蓝分光光度法快速测定钛铁矿中二氧化硅的含量。经国家一级标准物质分析验证,结果与标准值相符,相对标准偏差(RSD,n=7)为0.34%~2.24%。 相似文献
770.
Nemesio M. Pérez Pedro A. Hernández Eleazar Padrón Rafael Cartagena Rodolfo Olmos Francisco Barahona Gladys Melián Pedro Salazar Dina L. López 《Pure and Applied Geophysics》2006,163(4):883-896
On January 16, 2002, short-term unrest occurred at San Miguel volcano. A gas-and-steamash plume rose a few hundred meters
above the summit crater. An anomalous microseismicity pattern, about 75 events between 7:30 and 10:30 hours, was also observed.
Continuous monitoring of CO2 efflux on the volcano started on November 24, 2001, in the attempt to provide a multidisciplinary approach for its volcanic
surveillance. The background mean of the diffuse CO2 emission is about 16 g m-2 d-1, but a 17- fold increase, up to 270 g m-2 d-1, was detected on January 7, nine days before the January 2002 short-term unrest at San Miguel volcano. These observed anomalous
changes on diffuse CO2 degassing could be related to either a sharp increase of CO2 pressure within the volcanic-hydrothermal system or degassing from an uprising fresh gas-rich magma within the shallow plumbing
system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse CO2 emission. 相似文献