Thermal equation of state of magnesiowüstite (Mg0.6Fe0.4)O

Volume measurements for magnesiowüstite (Mg_0.6Fe_0.4)O, were carried out up to pressures of 10.1 GPa in the temperature range 300–1273 K, using energy-dispersive synchrotron X-ray diffraction. These data allow reliable determination of the temperature dependence of the bulk modulus and good constraint on the thermal expansitivity at ambient pressure which was previously not known for magnesiowüstite. From these data, thermal and elastic parameters were derived from various approaches based on the Birch–Murnaghan equation of state (EOS) and on the relevant thermodynamic relations. The results from three different equations of state are remarkably consistent. With (∂K_T/∂P)_T fixed at 4, we obtained K₀=158(2) GPa, (∂K_T/∂T)_P=−0.029(3) GPa K⁻¹, (∂K_T/∂T)_V=−3.9(±2.3)×10⁻³ GPa K⁻¹, and α_T=3.45(18)×10⁻⁵+1.14(28)×10⁻⁸T. The K₀, (∂K_T/∂T)_P, and (∂K_T/∂T)_V values are in agreement with those of Fei et al. (1992) and are similar to previously determined values for MgO. The zero pressure thermal expansitivity of (Mg_0.6Fe_0.4)O is found to be similar to that for MgO (Suzuki, 1975). These results indicate that, for the compositional range x=0–0.4 in (Mg_1−xFe_x)O, the thermal and elastic properties of magnesiowüstite exhibit a dependence on the iron content that is negligibly small, within uncertainties of the experiments. They are consequently insensitive to the Fe–Mg partitioning between (Mg, Fe)SiO₃ perovskite and magnesiowüstite when applied to compositional models of the lower mantle. With the assumption that (Mg_0.6Fe_0.4)O is a Debye-like solid, a modified equation of heat capacity at constant pressure is proposed and thermodynamic properties of geophysically importance are calculated and tabulated at high temperatures.     

Experimental study on supercritical phenomena of WO_3 solubility in NaCl-H_2O system

The singular behavior of supercritical fluids was found more than one hundred years ago. In 1879, English scientists Hannay and Hogarth[1] firstly studied the properties of supercritical fluids collectively and discovered that ethanol and carbon tetrachlo…     

RETRACTED: A theoretical study of the ligand-exchange reactions of Na+·X complexes (X=O,O2,N2,CO2 and H2O): implications for the upper atmosphere

This article has been retracted at the request of the editor.Reason: The publisher regrets that several errors appeared in this paper and that it therefore has been retracted. A correct version of the complete paper has been published in Volume 64, Issue 7, pages 863–870 of the Journal of Atmospheric and Solar-Terrestrial Physics.     

Variations of near-surface atmospheric CO_2 and H_2O concentrations during summer on Muztagata

1 Introduction As one of the most important greenhouse gases, atmospheric carbon dioxide (CO2) has increased in concentration rapidly since preindustrial times[1―4] and significantly contributes to the climate change[5] caused by anthropogenic emissions. Documentation of the global carbon cycle has been critical for under-standing the causative relationships between green-house gases and climate change. For example, the CO2 level in the atmosphere has been monitored at many sites worldwide …     

NaCl-H2O体系中WO3溶解度超临界现象实验探讨

以适量Na2WO4·2H2O, HCl, NaCl和H2O为原料, 从过饱和的角度对4.0% NaCl水溶液中WO3溶解度的超临界现象进行实验探讨. 压力恒定在34 Mpa, 接近临界压力31.4 Mpa, 温度变化于250～550℃之间, 在快速淬火高压釜中进行实验. 结果表明在临界区域内, WO3溶解度具有超临界现象, 溶解度对温度、密度的变化反应敏感. 本实验温、压条件与许多钨矿床成矿流体的温、压条件比较接近, 超临界地质流体可能有助于揭示钨矿床的形成机制.     

Asymmetry of the contours of the Fe X 6374-Å coronal line

The east-west asymmetry has been analyzed using the 1946–2000 corona observation data for the green line at the Kislovodsk station. A positive east-west asymmetry has been revealed throughout the entire observation period except for three years, 1994–1996. Time variations of the east-west asymmetry for certain periods coincide with those for flares. Seasonal variations of the east-west asymmetry revealed earlier by other authors are not confirmed. If seasonal variations of the east-west asymmetry in the corona exist, their amplitudes are smaller than or comparable to the instrumental errors, errors caused by atmospheric variations during the observation period and to differences between the corona-intensity measuring systems used at different observatories.     

High-pressure phase relations in the system CaAl4Si2O11–NaAl3Si3O11 with implication for Na-rich CAS phase in shocked Martian meteorites

High-pressure phase relations in the system NaAl₃Si₃O₁₁–CaAl₄Si₂O₁₁ were examined at 13–23 GPa and 1600–1900 °C, using a multianvil apparatus. A Ca-aluminosilicate with CaAl₄Si₂O₁₁ composition, designated CAS phase, is stable above about 13 GPa at 1600 °C. In the system NaAl₃Si₃O₁₁–CaAl₄Si₂O₁₁, the CAS phase dissolving NaAl₃Si₃O₁₁ component coexists with jadeite, corundum and stishovite below 22 GPa, above which the CAS phase coexists with Na-rich calcium ferrite, corundum and stishovite. At 1600 °C, the solubility of NaAl₃Si₃O₁₁ component in the CAS solid solution increases with increasing pressure up to about 50 mol% at about 22 GPa, above which the solubility decreases with pressure. The maximum solubility of NaAl₃Si₃O₁₁ component in the CAS phase increases with temperature up to around 70 mol% at 1900 °C at 22 GPa. The dissociation of NaAlSi₂O₆ jadeite to NaAlSiO₄ calcium ferrite plus stishovite occurs at about 22 GPa. Lattice parameters of the CAS phase with the hexagonal Ba-ferrite structure change with increase of the NaAl₃Si₃O₁₁ component: a-axis decreases and c-axis slightly increases, resulting in decrease of molar volume. Enthalpies of the CAS solid solutions were measured by high-temperature drop-solution calorimetry techniques. The results show that enthalpy of hypothetical NaAl₃Si₃O₁₁ CAS phase is much higher than the mixture of NaAlSi₂O₆ jadeite, corundum and stishovite and is close to that of the mixture of NaAlSiO₄ calcium ferrite, corundum and stishovite. When we adopt the Na:Ca ratio of 75:25 of the natural Na-rich CAS phase in a shocked Martian meteorite, Zagami, the phase relations determined above suggest that the natural CAS phase crystallized from melt at pressure around 22 GPa and temperature close to or higher than 2000–2200 °C. The inferred P, T conditions are consistent with those estimated using other high-pressure minerals in the shocked meteorite.     

反应HO2+O→OH+O2对OH夜气辉辐射的贡献

本文探讨了OH Meinel夜气辉辐射的光化学模式,给出OH(ν≤9)分子数密度分布的计算通式,重点研究了化学反应HO2 O→OH(ν≤6) O2对ν≤6各振动能级上OH分子数密度分布以及(ν′—ν″)(ν′≤6)振动带气辉辐射的影响.结果表明,该反应对数密度的贡献随振动能级的减小而增大,对(ν′—ν″)振动带辐射的贡献随着较高振动能级ν′的减小而增大,以春分时为例,它可使第1振动能级上的OH分子最大数密度和(1—0)带的最大辐射率增加约33%,第6振动能级上的最大数密度和(6—ν″)带的最大辐射率增加约7%,(1—0)带的辐射强度增加约30%,(6—ν″)带的强度增加约11%.该反应使各振动能级上分子数密度的高度分布剖面以及各振动带体辐射率的高度分布剖面变宽,最大数密度、最大发射率所处的高度下降1km左右.此外,该反应的影响程度随着原子氧密度的降低而增大,随着温度的升高而增大,并且在夏至时最大,在冬至时最小.     

含Fe3+的硅酸盐尖晶石γ-Fe2SiO4的M(o)ssbauer效应研究

对3个合成的含Fe3+的铁硅酸盐尖晶石γ-Fe2SiO4进行了电子探针分析, 并在298, 150和95 K的温度下对它们进行了M(o)ssbauer谱的测试. 每个温度下的M(o)ssbauer谱均由两个双峰组成. 这两个双峰分别被指派给八面体位置上的Fe2+和四面体位置上的Fe3+, 并且根据M(o)ssbauer吸收面积给出了占位. 结果表明, Fe3+和少量的Si4+分别占据在四面体和八面体位置上. 根据M(o)ssbauer分析所得到的占位, 使用经过修正的公式, 计算了八面体和四面体位置的平均键长. 在此基础上, 八面体和四面体的平均键长进而被用来计算含Fe3+的γ-Fe2SiO4的晶胞参数和氧参数. 此外, 使用次近邻效应解释了含Fe3+的γ-Fe2SiO4 M(o)ssbauer谱的Fe3+谱线的宽化现象.     

反应HO2+O→OH+O2对OH夜气辉辐射的贡献

本文探讨了OH Meinel夜气辉辐射的光化学模式，给出OH(ν≤9)分子数密度分布的计算通式，重点研究了化学反应HO\-2+O→OH(ν≤6)+O2对ν≤6各振动能级上OH分子数密度分布以及(ν′—ν″)(ν′≤6)振动带气辉辐射的影响.结果表明，该反应对数密度的贡献随振动能级的减小而增大，对(ν′—ν″)振动带辐射的贡献随着较高振动能级ν′的减小而增大，以春分时为例，它可使第1振动能级上的OH分子最大数密度和（1—0）带的最大辐射率增加约33%，第6振动能级上的最大数密度和（6—ν″）带的最大辐射率增加约7%，（1—0）带的辐射强度增加约30%，（6—ν″）带的强度增加约11%.该反应使各振动能级上分子数密度的高度分布剖面以及各振动带体辐射率的高度分布剖面变宽，最大数密度、最大发射率所处的高度下降1 km左右.此外，该反应的影响程度随着原子氧密度的降低而增大，随着温度的升高而增大，并且在夏至时最大，在冬至时最小.     

Singlet oxygen O2(b1Σ g + ) production at altitudes of the polar ionosphere

The relative rate constants of O₂(b¹Σ _g ⁺ , v= 1–4) production at an inelastic interaction between electronically excited N(²D) atoms and O₂(X³Σ _g ^? , v = 0) oxygen molecules have been calculated. It was shown that an increase in equilibrium distances between oxygen atoms in NO₂ quasi-molecule, produced during the interaction, substantially increases the calculated relative production rates of O₂(b¹Σ _g ⁺ , v > 1). The obtained coefficients are used to calculate the O₂(b¹Σ _g ⁺ , v= 1–4) relative populations at 110 km (T = 250 K) and 150 km (T = 500 K) altitudes of the polar ionosphere. The calculated populations have been compared with the results of the published measurements of the Atmospheric system band luminosity intensities, and satisfactory agreement has been obtained for low altitudes.     

Evidence for solar forcing of climate variation from δ18O of peat cellulose

There have been a number of investigations for examining the possible link between long-term climate variability and solar activity.A continuous δ18O record of peat cellulose covering the past 6000 years and the response of climate variation inferred from the proxy record to solar forcing are reported.Results show that during the past 5000 years the abrupt climate variations,including 17 warming and 17 cooling,and a serious of periodicities,such as 86,101,110,127,132,140,155,207,245,311,820 and 1050 years,are strikingly correlative to the changes of solar irradiation and periodicity.These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.     

Macrodynamics of α2 dynamos

Abstract

Two distributions of the α-effect in a sphere are considered. The inviscid limit is approached both by direct numerical solution and by solution of a simpler nonlinear eigenvalue problem deriving from asymptotic boundary layer analysis for the case of stress-free boundaries. The inviscid limit in both cases is dominated by the need to satisfy the Taylor constraint which states that the integral of the Lorentz force over cylindrical (geostrophic) contours in a homogeneous fluid must tend to zero. For a small supercritical range in α, this condition can only be met by magnetic fields which vanish as the viscosity goes to zero. In this range, the agreement of the two approaches is excellent. In a portion of this range, the method of finite amplitude perturbation expansion is useful, and serves as a guide for understanding the numerical results. For larger α, evidence from the nonlinear eigenvalue problem suggests both that the Taylor state exists, and that the transition from small to large amplitude can require a finite amplitude (oscillatory) instability in accord with the findings of Soward and Jones (1983). However, solutions of the full equations have not been found which are independent of viscosity at larger values of α.     

湖、库水体N2O排放研究进展

湖、库水体是重要的N₂O排放源,在全球氮素循环及全球气候变化中具有重要作用.本文综述了目前有关湖、库水体N₂O排放研究进展,重点介绍湖、库水体N₂O产生和排放的过程、不同时空尺度的排放特征、N₂O排放的影响因子框架及监测方法.湖、库水体N₂O不仅源于内部微生物硝化作用、反硝化作用、硝化-反硝化耦合作用、脱氮作用以及极少数底栖无脊椎动物代谢过程,同时流域上游河流汇入、地表径流输入、污水排放以及地下水排泄等构成湖、库水体N₂O的重要外源,但目前对内源/外源的相对贡献的定量化研究不足;湖、库水体N₂O排放方式包括扩散、植物传输及少量气泡排放,对水库而言,大坝下游水电涡轮机形成的脱气作用可能是N₂O排放的潜在途径.对文献综合分析表明,湖、库水体N₂O排放通常呈现明显的季节变化（夏季>冬季）和日变化,同时在全球（一般低纬度>高纬度）、区域及水体内部等不同尺度上表现出显著的空间变异性;这种时空变异特征主要受到湖、库自身理化因子（温度、营养盐、溶解氧、C/N、水文）、生物因子（水生植物、藻华）以及陆域人类活动（污水排放、农业活动以及城市化等）的影响;湖、库N₂O排放不同监测方法的差异也是潜在的影响因素,传统的漂浮箱法和薄边界层法均可能低估水体N₂O排放通量,未来需将传统的监测方法与新型的涡度相关法相结合,减小监测方法的不确定性.结合当前湖、库水体N₂O排放的研究不足,建议未来可以从湖、库N₂O产生的微生物机制,区域尺度上人类活动与湖、库群N₂O排放的耦合关系,水陆交错带的产、排过程,变化环境下的湖、库N₂O排放以及监测方法等方面深入研究.     

Observations of Pc 3–4 and Pi 2 geomagnetic pulsations in the low-latitude ionosphere

Day-time Pc 3–4 (≃5–60 mHz) and night-time Pi 2 (≃5–20 mHz) ULF waves propagating down through the ionosphere can cause oscillations in the Doppler shift of HF radio transmissions that are correlated with the magnetic pulsations recorded on the ground. In order to examine properties of these correlated signals, we conducted a joint HF Doppler/magnetometer experiment for two six-month intervals at a location near L = 1.8. The magnetic pulsations were best correlated with ionospheric oscillations from near the F region peak. The Doppler oscillations were in phase at two different altitudes, and their amplitude increased in proportion to the radio sounding frequency. The same results were obtained for the O- and X-mode radio signals. A surprising finding was a constant phase difference between the pulsations in the ionosphere and on the ground for all frequencies below the local field line resonance frequency, independent of season or local time. These observations have been compared with theoretical predictions of the amplitude and phase of ionospheric Doppler oscillations driven by downgoing Alfvén mode waves. Our results agree with these predictions at or very near the field line resonance frequency but not at other frequencies. We conclude that the majority of the observations, which are for pulsations below the resonant frequency, are associated with downgoing fast mode waves, and models of the wave-ionosphere interaction need to be modified accordingly.     

7^Be和210^Pb观测示踪研究瓦里关山近地面O3和CO2浓度变化

根据2002年10月～2004年1月在青海瓦里关山全球大气本底站（101.898°E,36.287°N,3810ma.s.l.）近地面空气7Be,210Pb,O3和CO2的周平均浓度数据,建立这4种组分相邻周浓度差（分别以Δ7Be,Δ210Pb,ΔO3和ΔCO2表示）数据序列,以此示踪研究高层大气向下输送和陆地地表排放这两个过程各自对瓦里关山近地面O3和CO2浓度变化的影响.结果表明,与使用直接周浓度数据的示踪结果相比,浓度差的引进降低了大气气溶胶季节性湿沉降对7Be和210Pb示踪信号的干扰,较清晰地揭示了瓦里关山站近地面O3和CO2各自浓度变化的物理机制.Δ7Be与ΔO3的关系表明瓦里关山近地面O3显著地受到高层大气向下输送影响;Δ210Pb与ΔCO2关系则表明陆地地表排放对近地面CO2浓度变化有着明显的贡献.Δ210Pb与ΔO3关系也反映出地表排放在冬、夏季对瓦里关山近地面O3浓度变化不同的影响,Δ7Be和ΔCO2关系则反映了来自高层大气向下输送在夏季（冬季）是增加（减低）瓦里关山近地面CO2的浓度.根据对7Be和O3的观测,本文推算月平均平流层输送到瓦里关山近地面O3浓度在4月和6～8月为（6.0～8.0）×10-9（体积混合比,下同）,而其余月份稳定在（2～4.0）×10-9;在瓦里关山近地面O3本底浓度的构成中,平流层贡献5～7月份为20×10-9左右,而在其余月份在（12～15）×10-9,总体上相对贡献率为35%～40%.     

Temporal variations of δ~(18)O of atmospheric water vapor at Delingha

Oxygen stable isotope of atmospheric water vapor is widely used to study the modern process of cli- mate. Atmospheric water vapor samples were collected at Dlingha, northeast of Tibetan Plateau during the period from July 2005 to February 2006. The variation of δ18O and the relationships between δ18O and both the temperature and specific humidity are analyzed in this paper. Results show that the sea- sonal variation of δ18O of atmospheric water vapor at Delingha is remarkable with higher δ18O in summer and lower δ18O in winter. The temporal variation of vapor δ18O shows obvious fluctuations, with magnitude of over 37‰. The daily variation of the δ18O is highly correlated with air temperature. The relationship between δ18O and atmospheric water vapor content is complex. Study shows that δ18O of atmospheric water vapor is positively correlated with specific humidity in winter in seasonal scale and inversely correlated with specific humidity in summer rainy period. The δ18O values of at- mospheric water vapor are lower than those of precipitation at Delingha, and the average difference is 10.7‰. Variations of δ18O of atmospheric water vapor is also found to be affected by precipitation events, The model results show that the precipitation effect could have caused the vapor δ18O in the raining season to lower by 7% in average in July and August.     

区域C-N-H_2O耦合循环过程及其驱动机制

区域C-N-H_2O耦合循环从分子到生态系统层面存在不同的耦合机制,其通过水文通量的物理化学和生物地球化学耦合过程将陆地和水生生态系统紧密链接,并影响着流域生态系统的生产力以及大气和下游水体的C、N交换过程.文章在综合分析区域生态系统尺度的C、N、H_2O循环动态过程相互制约关系的基础上,揭示区域生态系统C、N、H_2O循环动态过程偶联关系的生态学理论基础,阐明人类活动影响下区域生态系统C-N-H_2O耦合循环对气候与环境变化的响应与适应,为全面认识和调控不同尺度生态系统的C、N、H_2O循环相互作用关系及其耦合过程提供了理论基础.