The yield and isotopic composition of radiolytic H2, a potential energy source for the deep subsurface biosphere

The production rate and isotopic composition of H₂ derived from radiolytic reactions in H₂O were measured to assess the importance of radiolytic H₂ in subsurface environments and to determine whether its isotopic signature can be used as a diagnostic tool. Saline and pure, aerobic and anaerobic water samples with pH values of 4, 7, and 10 were irradiated in sealed vials at room temperature with an artificial γ source, and the H₂ abundance in the headspace and its isotopic composition were measured. The H₂ concentrations were observed to increase linearly with dosage at a rate of 0.40 ± 0.04 molecules (100 eV)⁻¹ within the dosage range of 900 to 3500 Gray (Gy; Gy = 1 J Kg⁻¹) with no indication of a maximum limit on H₂ concentration. At ∼2000 Gy, the H₂ concentration varied only by 16% across the experimental range of pH, salinity, and O₂. Based upon this measured yield and H₂ yields for α and β particles, a radiolytic H₂ production rate of 10⁻⁹ to 10⁻⁴ nM s⁻¹ was estimated for the range of radioactive element concentrations and porosities typical of crustal rocks. The δD of H₂ was independent of the dosage, pH (except for pH 4), salinity, and O₂ and yielded an αD_H2O-H2 of 2.05 ± 0.07 (αD_H2O-H2 = (D/H)_H2O to (D/H)_H2), slightly less than predicted radiolytic models. Although this radiolytic fractionation value is significantly heavier than that of equilibrium isotopic exchange between H₂ and H₂O, the isotopic exchange rate between H₂ and H₂O will erase the heavy δD of radiolytic H₂ if the age of the groundwater is greater than ∼10³ to 10⁴ yr. The millimolar concentrations of H₂ observed in the groundwater of several Precambrian Shields are consistent with radiolysis of water that has resided in the subsurface for a few million years. These concentrations are well above those required to support H₂-utilizing microorganisms and to inhibit H₂-producing, fermentative microorganisms.     

青海五龙沟地区1:5万遥感信息找矿勘查与靶区预测研究

在青海五龙沟地区开展15万遥感信息找矿勘查与靶区预测研究,是以矿化蚀变的遥感异常提取为主线,结合成矿源场、成矿位场遥感信息的解译,通过遥感与地质、矿产、化探等多源信息的空间集成和综合分析,进行15万遥感岩石地层-构造-蚀变岩填编图与遥感找矿预测,优选出了13处新的找矿靶区.经有关地勘单位野外实地检查,取得了很好的应用效果,并证明了该方法的有效性.     

地质体三维可视化建模的技术方法研究

地质体三维可视化模型具有形象、直观、动态、准确、信息丰富等特点,在指导地质找矿和矿山开发等方面具有很大的优势及实用价值。文章对地质体三维可视化建模的整个技术方法流程作了总结性阐述,并分析其技术关键,同时还进一步探讨了模型的分类及其应用。     

Orographic effects on a conditionally unstable flow over an idealized three-dimensional mesoscale mountain

Summary Idealized numerical simulations using the Weather and Research Forecast (WRF) model indicate that three flow regimes, based on the moist Froude number, can be identified for a conditionally unstable, rotational, horizontally homogeneous, uniformly stratified flow over an idealized, three-dimensional, mesoscale mountain stretched spanwise to the impinging flow: (I) a quasi-stationary upslope convective system and an upstream-propagating convective system, (II) a quasi-stationary upslope convective system, and (III) a stationary upslope convective system and a quasi-stationary downstream convective system. Several major differences from a similar type of flow with no rotation over a two-dimensional mountain range are found. One important finding is that relatively strong mean flow produces a quasi-stationary mesoscale convective system (MCS) and maximum rainfall on the windward slope (upslope rain), instead of on the mountain peak or over the lee side.We found that the Coriolis force helps produce heavy upslope rainfall by making transition from flow-around the eastern part of the upslope to flow-over the western part of the upslope (transits to a higher flow regime) by deflecting the incident southerly flow to become east–southeasterly barrier winds. We found that the addition of the western flank of the arc-shaped mountain helps slow down the barrier wind from east and causes the maximum rainfall to move east of the windward slope. A lower-Froude number flow tends to produce a rainfall maximum near the concave region.Several other important facts can also be found in this study. The ratio of the maximum grid scale rainfall to the sub-grid scale rainfall increases when the moist Froude number increases. When the CAPE decreases, it is found that the upstream moist flow tends to shift to a higher Froude-number regime. Therefore, the Froude number cannot solely be used to define a moist flow regime when different CAPEs are considered. In another word, other parameters, such as CAPE, might play an important role in determining moist flow regimes.     

Improvement on the second-order solution of artificial satellite orbits

Three methods are proposed in this paper to lessen the complexity in the derivation and the resulting expressions of second-order analytical solutions of artificial satellite orbits while retaining the advantages of analytical solutions. Of the three, the one combining the theories of elliptical perturbation and of intermediate orbits is noteworthy for its simplicity. It can also be used with advantage in first-order and third- or higher order solutions.     

The solar particle event of July 16–19, 1966 and its possible association with a flare on the invisible solar hemisphere

An energetic solar proton and electron event was observed by particle detectors aboard Explorer 33 (AIMP-1) and OGO-3 during the period July 16–19, 1966. Optical and radio observations of the sun suggest that these particles were produced by a flare which may have occurred on July 16 near the central meridian of the invisible hemisphere. The active region to which the flare is assigned is known to have produced the energetic particle events of July 7 and 28, 1966. The propagation of the particles in the July 16–19 event over the 180° extent of solar longitude from the flare to the earth is discussed, and it is concluded that there must exist a means of rapidly distributing energetic particles over a large area of the sun. Several possible mechanisms are suggested.     

Interplanetary scattering of fast solar electrons deduced from type III bursts observed at low frequencies

Observations of low frequency solar type III radio bursts and the associated fast solar electrons show that the total path length traveled by the particles between the Sun and the Earth is significantly greater than the length of the smooth Archimedean spiral trajectory followed by the centroid of the type III exciter (Alvarez et al., 1975). Here we assume that the ratio of electron path length and the spiral length increases approximately as r ⁿ, where r is heliocentric distance, and then compute the radio bursts arrival time at 1 AU for different values of n. A comparison with the radio observations indicates that the best fit occurs for n = 1.5 ± 1.0. We interpret these results in terms of the variation of electron scattering with heliocentric distance.     

Precision IR and visible solar photometry

A precision Solar Photometric Telescope (SPT) was constructed to study the large-scale thermal structure of the solar photosphere. This instrument does full-disk, broad-band (10 nm FWHM), two-color (500 and 650 nm) imaging of the solar photosphere. Data obtained by the SPT reveals network structures correlated with the supergranulation velocity field, and the CaK network of the chromosphere. Infrared array photometry extends these measurements to 1.6 and 2.2 micron. The observed correlation of the network brightness signal with the CaK network is positive at visible wavelengths. The correlation between the network at the opacity minimum (1.6 micron) and in the higher photosphere (2.2 micron) is positive also. The root-mean-square (r.m.s.) amplitude of the contrast at disk center is (2.34 ± 0.38) × 10^-3, (1.83 ± 0.51) × 10^-3, (1.02 ± 0.21) × 10^-3, and (1.11 ± 0.21) × 10^-3 for the green, red, H, and K band, respectively. It is consistent with a brightness temperature modulation of 2.9 K. The r.m.s. amplitude of the contrast of active region network shows a large increase toward the limb, and the quiet region network shows little center-to-limb variation (CLV). Power-spectrum analysis shows that the bright facular points in the active regions appear in the form of enhanced network.     

P-wave velocities in rocks at high pressure and temperature and the constitution of the central California crust

Summary. Velocities of compressional waves are determined for central California rocks at pressures up to 0.7 GPa (7 kb) and temperatures up to 450°C. These data are used to interpret the seismic velocity structure of the crust in the California Coast Ranges. The seismic data on both sides of the San Andreas fault are consistent with the following model; besides some patches of surface sediments the upper 10—15 km of the crust on the northeast side consists predominantly of sedimentary and metasedimentary rocks of the Franciscan assemblage; the lower crust, of a thickness of 15—20 km, may be composed of gabbroic or other mafic rocks. Across the fault on the south-west side, the entire crustal section is probably a granitic complex similar to that exposed on the surface. The proposed model is shown to be consistent with the observed gravity anomaly.     

Fast solar electrons,interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft

IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons.