Estimate of carbonate production by scleractinian corals at Luhuitou fringing reef, Sanya, China

Carbonate production by scleractinian corals not only maintains coral reef growth, but also represents an important source of atmospheric carbon dioxide. In this paper the carbonate production by scler-actinian corals at Luhuitou fringing reef, Sanya, Hainan Island, China, is investigated with an ecological census-based method. Averaged carbonate production is 1.16 ± 0.55 kg·m-2·a-1 and 3.52 ± 1.32 kg·m-2·a-1 on the reef flat and reef slope, respectively, depending on the composition and distribution of cor...     

Influence of wettability on flow characteristics of water through microtubes and cores

The flow characteristics of deionized water in hydrophilic and hydrophobic microtubes with diameters of 14.9, 5.03 and 2.05 μm are investigated experimentally. The results indicate that the flow characteristics of deionized water in microtubes with diameter of 14.9 μm are in agreement with the classical Hagen-Poiseuille （H-P） equation, but for hydrophilic and hydrophobic microtubes with smaller diameters, the results show significant departure from the prediction of conventional theory, and the discrepancies are influenced by wettability of the microtubes and increase as the Reynolds numbers decrease. Besides, flows of fluid in cores are the macroscopic reflection of flows in countless mi- cron-sized pore throats, the influence of wettability on microscale flow in pore throats will cause the change of seepage characteristic in cores. Therefore, flow experiments of brine through cores with different wettabilities are conducted. The results demonstrate that wettability exerts similar influence on water flows in cores and microtubes.     

低渗和特低渗油层CO2-N2复合驱研究

针对低渗-特低渗油层CO₂-N₂复合驱提高采收率,以大庆外围YS油田的特低渗透油层为背景,进行了数值模拟和物理模拟两方面的研究。利用CMG数值模拟软件GEM模块,建立了一维长细管、均质、非均质理想模型及五点法井网单元模型,分别对CO₂-N₂复合驱的驱油方式、影响因素、五点法井网单元模型下的段塞组成进行了模拟计算及分析。与此同时,在室内分别选用30 cm长的低渗透、特低渗透天然岩心,各进行了5种不同驱替方案的实验研究,确定了CO₂-N₂复合中CO₂合理段塞尺寸及驱油效果,并验证了数值模拟计算的可靠性。研究结果表明,低渗-特低渗透油层CO₂-N₂复合驱不宜采用CO₂与N₂混合驱方式,而应采用一次注入合理的CO₂段塞(约0.3PV)＋N₂的段塞组合驱方式,这样不仅可以减少CO₂用量,而且可以充分发挥CO₂与N₂各自的优势,获得优于全部注CO₂驱的驱油效果;且油层渗透率越低、渗透率级差越小或长厚比越大,越有利于提高CO₂-N₂复合驱采收率;厚度小于井距1%的油层也有利于CO₂-N₂复合驱提高采收率。     

Measurement of GaAs start duration in different solution concentration using infrared images

This paper proposes a new infrared method to measure the start duration of GaAs substrate in chemical etching. When etching starts, the temperature of liquid-film will change because of heat release in the chemical reaction. As a result, the start duration of GaAs can be tested by collecting real-time in-frared thermal images in the course of temperature variation. Both theoretical analysis and experi-mental results show that the line shape liquid film of a 2-mm width is a good monitoring subject. By making use of the grey distribution change of a certain cross section of the line shape liquid film, the start duration of reaction between GaAs and H2SO4-H202-H20 is obtained. The start durations of reac-tion between GaAs substrate and H2SO4： H202： H20 （=5：1：50 and 15：3：50） solution are about 0.2 s and 0.3-0.4 s, respectively. This result and relative method will impulse the research of wet chemical etching technology of GaAs and so on.     

Experimental investigation on flow characteristics of deionized water in microtubes

The flow characteristics of deionized water in microtubes with diameters ranging from 2 to 30 μm are investigated. The experimental results show that the flow characteristics in microtubes with diameters of 16 μm and larger ones are in agreement with the classical theory. However, as the diameters are de-creased to 5 and 2 μm, the nonlinear flow characteristics prevail and the results indicate significant departure of flow characteristics from the predictions of the conventional theory, and the smaller the diameters, the larger the departure. As the Reynolds number increases, the degree of nonlinear flow characteristics decrease gradually and the experimental results are approximately equal to the theo-retical expectation. The minimum Reynolds number in this study is only 2.46×10~(-5).     

Significance of native arsenic in the Baogutu gold deposit, western Junggar, Xinjiang, NW China

Native arsenic together with comb quartz and stibnite is found in the Baogutu gold deposit, western Junggar (Xinjiang), NW China. It is anhedral with various grain size (<0.001 to 2 mm), and contains 98 wt% to 98.7 wt% As. Micro-granular electrum, the main auriferous mineral in the Baogutu gold deposit, is commonly enclosed in or closely accompanied by native arsenic. Three ore-forming paragenetic stages could be identified. Native arsenic mainly formed at stage II which is also the major stage for gold deposition. Mineral assemblage formed at this stage is native arsenic-stibnite-electrum-arseno- pyrite-miargyrite-freibergite-pyrrhotite-pyrite. Based on native arsenic and its coexisting minerals, the temperature (230 to 170℃), oxygen fugacity (logfO₂ = −42―−56.5) and sulfur fugacity (logf S₂ = −13.3― −16.6) of stage II are estimated. From stage I to stage II, the temperature, sulfur fugacity and S²⁻ con-centration of hydrothermal fluid decrease obviously, whereas the As concentration increases. Coexis-tence with native arsenic of electrum and its contents of 0.5 wt%―1.3 wt% As suggest that As is im-portant to transport Au when S²⁻ concentration decrease in hydrothermal fluid. Crystallization of native arsenic induced the deposition of electrum and consequently the formation of the Baogutu gold deposit.     

A novel Pd/silicalite-1 composite membrane for hydrogen separation

A novel Pd/silicalite-1 composite membrane supported on the macroporous tubular stainless steel substrate was successfully fabricated by electroless plating at 303 K. The structure, morphology and gaseous permeability of the membrane were detected by X-ray diffractiometry （XRD）, scanning electron microscopy （SEM） and single-gas permeation test, respectively. Results confirm the formation of a thin, smooth, and continuous Pd/silicalite-1 composite membrane. The obtained composite membrane shows a high H2 permeance of 1.15×10^-6 mol. m^-2. s^-1. Pa^-1 with moderate H2 selectivity of 250 for H2/N2 at 773 K, at 0.1 MPa pressure drop, suggesting the potential application for H2 separation.     

The Siberian Traps and the End-Permian mass extinction: a critical review

The association between the Siberian Traps, the largest continental flood basalt province, and the largest-known mass extinction event at the end of the Permian period, has been strengthened by recently-published high-precision ⁴⁰Ar/³⁹Ar dates from widespread localities across the Siberian province^[1]. We argue that the impact of the volcanism was amplified by the prevailing late Permian environmental conditions―in particular, the hothouse climate, with sluggish oceanic circulation, that was leading to widespread oceanic anoxia. Volcanism released large masses of sulphate aerosols and carbon dioxide, the former triggering short-duration volcanic winters, the latter leading to long-term warming. Whilst the mass of CO₂ released from individual eruptions was small compared with the total mass of carbon in the atmosphere-ocean system, the long ‘mean lifetime’ of atmospheric CO₂, compared with the eruption flux and duration, meant that significant accumulation could occur over periods of 105 years. Compromise of the carbon sequestration systems (by curtailment of photosynthesis, destruction of biomass, and warming and acidification of the oceans) probably led to rapid atmospheric CO₂ build-up, warming, and shallow-water anoxia, leading ultimately to mass extinction.     

TiO2-based building materials: Above and beyond traditional applications

In the 1910s, TiO₂ began to be used in building materials as pigments and opacifier due to its excellent optical property. Since the photocatalytic property of TiO₂ was observed in 1972, its application field was expanded to air cleaning and sterilization. Thereafter, people added TiO₂ into building materials to develop novel and facile building materials. These materials were widely used for air cleaning, sterilization, self-cleaning, anti-fogging, decoration, and building cooling. The combination of building and other functions can serve simultaneously. Although TiO₂-based building materials have bright prospects, some aspects such as improving the stability and enhancing photoactive performance of the materials are of importance for future research. Supported by the National High Technology Research and Development Program (“863” Program) of China (Grant No. 2007AA061402), Chinese Key Technology Research and Development Program of the Eleventh Five-year Plan (Grant No. 2006BAJ02A08), Hangzhou Science & Technology Development Program (Grant No. 20061133B27) and Research Fund for the Doctoral Program of Higher Education (Grant No. 20070335197)     

炭气凝胶微球的物理活化与化学活化比较

以炭气凝胶微球为原料,分别采用CO2和KOH作为活化剂,研究物理活化和化学活化对炭气凝胶微球孔结构和电化学性能的影响差异,探讨CO2和KOH的活化机理。结果表明,CO2和KOH活化均能有效改善炭气凝胶微球的孔结构,比表面积最高可达1 320 m2/g;同时显著提高材料的电化学性能,活化后的比电容最高可为活化前的3倍。结果还表明两种方法的活化机理不同,CO2活化,有利于保持炭气凝胶微球的中孔,为电子进出提供大量的快速通道,提高传质速率;KOH活化,对炭气凝胶微球的微孔形成非常有利,可增大电化学活化表面,提高电化学性能。     

The uptake of ethyl iodide on black carbon surface

The importance of the iodine chemistry in the atmosphere has been demonstrated by recent obserations. The uptake of ethyl iodine on black carbon surface was inestigated at 298 K for the first time. Degussa FW2 （an amorphous black carbon comprising medium oxides） was used as black carbon sample. Black carbon surface was found to be deactiated in reaction with C2H51, and the uptake coefficient （r） was dependent on the time of exposure. The alue of （2.3±0.9）×10^-2 was determined for the initial uptake coefficient （No）. The result suggests that the heterogeneous loss of C2H51 on carbonaceous aerosols may be important under the atmospheric conditions.     

Variation of δ13C in karst soil in Yaji Karst Experiment Site, Guilin

This study deals with δ₁₃ C variation in karst soil system of Yaji Karst Experiment Site, Guilin, a typical region of humid subtropical karst formations. Samples of near ground air, plant tissue, soil and water (soil solution and karst spring) were respectively collected on site in different seasons during 1996–1999. Considerable variation of δ₁₃ C values are not only found with different carbon pools of soil organic carbon, soil air CO₂ and soil water HCO₃⁻, but also with the soil depths and with different seasons during a year. The °₁₃ C values of CO₂ both of near ground air and soil air are lower in July than those in April by 1‰–4‰ PDB. Our results indicate that the δ₁₃ C values of carbon in the water and air are essentially dependent on interface carbon interaction of air-plant—soil-rock—water governed by soil organic carbon and soil CO₂ in the system.     

Density functional study on mechanism of CO oxidation with activated water on O/Au （1 1 1 ） surface

With density functional theory, the mechanism of water-enhanced CO oxidation on oxygen pre-covered Au （111） surface is theoretically studied. First, water is activated by the pre-covered oxygen atom and dissociates to OHads group. Then, OHads reacts with COads to form chemisorbed HOCOads, Finally, with the aid of water, HOCOads dissociates to CO2. The whole process can be described as 1/2H2Oads ＋ H2Oads ＋ 1/2Oads＋ COads→H3Osds ＋ CO2, gas. One CO2 is formed with only 1/2 pre-covered oxygen atom. That is why more CO2 is observed when water is present on oxygen pre-covered Au （111） surface. Activation energy of each elementary step is low enough to allow the reaction to proceed at low temperature.     

Diet control on carbon isotopic composition of land snail shell carbonate

Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ 13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ 13Ca values are closely correlated to the body δ 13Corg values, expressed as δ 13Ca = 1.021 δ 13Corg 14.38 (R = 0.965; N = 31). This relationship indicates that δ 13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3-in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity.     

Export and remineralization of POM in the Southern Ocean and the South China Sea estimated from 210Po/210Pb disequilibria

Disequilibria between ^210Po and ^210Pb in the upper water and their potential applications as a proxy of particle export and remineralization were examined in the Southern Ocean （station IV3） and the South China Sea （NS44）. ^210po was deficit in surface waters but excessive relative to ^210Pb in subsurface waters. Good positive correlation between ^210Po and particulate organic carbon （POC） indicated deficits and excess of ^210Po resulted from particulate organic matter （POM） export and remJneralization respectively, which was also supported by the decreased δ^13C and increased δ^15N downwards as a result of particle remineralization. On the basis of ^210Po/^210Pb box-model, POC export flux out of the surface waters were 1.2 mmol C. m^-2. d^-1 and 2.3 mmol C. m^-2. d^-1 for station NS44 and IV3, respectively. In the subsurface waters, remineralization fluxes of ^210Po were 0.062 Bq. m^-2.d^-1 and 0.566 Bq.m^-2.d^-1 for station NS44 and IV3 along with the recycle efficiency of 52±26% and 119±52%, respectively. Remineralized fluxes of POM derived from ^210Po and exported POC were 0.6 mmol C.m^-2.d^-1 and 2.7 mmol C. m^-2. d^-1 for NS44 and IV3. This study suggested that ^210Po was a powerful tracer of particle export and remineralization.     

A retrieval algorithm for TanSat XCO2 observation: Retrieval experiments using GOSAT data

This study developed a highly accurate retrieval algorithm for the column-averaged CO2 dry-air mixing ratio (XCO2) to be observed by TanSat, China’s carbon dioxide observation satellite that will be launched in 2015. The Greenhouse Gases Observing Satellite (GOSAT) L1B spectrum was applied in retrieval experiment, and the results were validated with ground-observed measurements from the Total Column Carbon Observing Network (TCCON). At mid-latitudes, most results fell in the 1% error region, which correspond to the performance of GOSAT algorithm. The results also showed seasonal variation in XCO2 in both hemispheres.     

Diurnal and monthly variations of carbon dioxide flux in an alpine shrub on the Qinghai-Tibet Plateau

Long-term flux observation is an efficient approachto collect CO2 emission or assimilation data in an ecosys-tem. In cooperation with a series of international coopera-tion programs including those sponsored by IGBP (Inter-national Geosphere-Biosphere Program), WCRP (WorldClimate Research Program), IHDP (International HumanDimension of Global Environment Change), GCTE(Global Change and Terrestrial Ecosystem) and LUCC(Land Use and Land Cover Change), a lot of researchwork conce…     

Crystallization dynamics of supersaturated NaClO4 aerosols studied by high-speed photography

Single supersaturated NaClO4 aerosol droplets on a quartz substrate were observed by a high-speed video camera for their morphologic changes with decreasing relative humidity （RH）. The supersaturated droplets were found to form anhydrous NaClO4 at -10% RH. Three stages were roughly observed in this process, i.e., the main stem appearance, primary and secondary branches growth, and the deep dehydration. The main stem grew steadily and finished in 120 ms. Affected by both crystal precipitation and water evaporation, primary branches grew for 1200 ms, accompanied by a slower growth of secondary branches. The deep dehydration was more complicated, and lasted for a longer time.     

State of water and its implications for supersaturated structures in Mg(NO3)2 aerosols

One technique based on the difference spectra was developed to study the state of water in supersaturated Mg(NO₃)₂ aerosols. The technique could be derived from the observation that the Raman scattering and infrared absorbance cross sections of molecular vibrations of interest remain practically constant from diluted solutions to supersaturated aerosols. The spectra of solvated water were obtained and primarily related to the first hydration layers of solute molecules in supersaturated Mg(NO₃)₂ aerosols. Based on this investigation, a chain structure was proposed to occur in the supersaturated Mg(NO₃)₂ aerosols at low relative humidities (RHs). Supported by National Natural Science Foundation of China (Grant Nos. 20673010 and 20640420450), “111” Project (Grant No. B07012), and China Postdoctoral Science Foundation (Grant No. 20070410466)     

Influence of O2/Ar ratio on the properties of transparent conductive niobium-doped ZnO films

Niobium-doped ZnO transparent conductive films are deposited on glass substrates by radio frequency sputtering at 300℃. The influence of O2/Ar ratio on the structural, electrical and optical properties of the as-deposited films is investigated by X-ray diffraction, Hall measurement and optical transmission spectroscopy. The lowest resistivity of 4.0×10^-4Ω· cm is obtained from the film deposited at the O2/Ar ratio of 1/12. The average optical transmittance of the films is over 90%.