Sorption of noble gases by solids,with reference to meteorites. I. Magnetite and carbon

To simulate trapping of meteoritic noble gases by solids, 18 samples of Fe₃O₄ were synthesized in a noble gas atmosphere at 350–720 K by the reactions: 3Fe + 4H₂O → Fe₃O₄ + 4H₂ (Ne, Ar, Kr, Xe) 3Fe + 4CO → Fe₃O₃ + 4C + carbides (Xe only) Phases were separated by selective solvents (HgCl₂, HCl). Noble gas contents were analyzed by mass spectrometry, or, in runs where 36 d Xe¹²⁷ tracer was used, by γ-counting. Surface areas, as measured by the BET method, ranged from 1 to 400 m²/g. Isotopic fractionations were below the detection limit of 0.5%/m.u.Sorption of Xe on Fe₃O₄ and C obeys Henry's Law between $\text{1 × 10}{}^{\mathrm{?8}}$ and $\text{4 × 10}{}^{\mathrm{?5}}$ atm, but shows only a slight temperature dependence between 650 and 720 K ($\text{ΔH}{}_{\mathrm{sol}}\text{= ?4 ± 2}\text{kcal/mole}$). The mean distribution coefficient K_Xe is $\text{0.28 ± 0.09}$ cc STP/g atm for Fe₃O₄ and only a factor of $\text{1.2 ± 0.4}$ greater for C; such similarity for two cogenetic phases was predicted by Lewis et al. (1977). Stepped heating and etching experiments show that 20–50% of the total Xe is physically adsorbed and about 20% is trapped in the solid. The rest is chemisorbed with $\text{ΔH}{}_{\mathrm{s}}\text{? ?13}\text{kcal/mole}$. The desorption or exchange half-time for the last two components is >10² yr at room temperature.Etching experiments showed a possible analogy to “Phase $\text{Q}$” in meteorites. A typical carbon + carbide sample, when etched with HNO₃, lost 47% of its Xe but only 0.9% of its mass, corresponding to a ~0.6 Å layer. Though this etchable, surficial gas component was more thermolabile than $\text{Q}$ (release $\text{T}$ below 1000°C, compared to 1200–1600°C), another experiment shows that the proportion of chemisorbed Xe increases upon moderate heating (1 hr at 450°C). Apparently adsorbed gases can become “fixed” to the crystal, by processes not involving volume diffusion (recrystallization, chemical reaction, migration to traps, etc.). Such mechanisms may have acted in the solar nebula, to strengthen the binding of adsorbed gases.Adsorbed atmospheric noble gases are present in all samples, and dominate whenever the noble gas partial pressure in the atmosphere is greater than that in the synthesis. Many of the results of Lancet and Anders (1973) seem to have been dominated by such an atmospheric component; others are suspect for other reasons, whereas still others seem reliable. When the doubtful samples of Lancet and Anders are eliminated or corrected, the fractionation pattern—as in our samples—no longer peaks at Ar, but rises monotonically from Ne to Xe. No clear evidence remains for the strong temperature dependence claimed by these authors.     

Water movement within lac du bonnet batholith as revealed by detailed thermal studies of three closely-spaced boreholes

Successive temperature logs have been obtained over a period of two years in three closely-spaced boreholes in the Lac du Bonnet batholith of the Superior Province of the Canadian Shield. Two of the boreholes, of depth 450 m and 830 m, intersect a dipping fracture zone at 435–450 m. In both holes water is flowing from near the surface to the fracture zone at approximately 1.5–1.9·10⁻⁵ m³ s⁻¹, the flow being inferred from analysis of the temperature logs. Below 25 m, temperatures in these two holes are 0.22–0.28 K lower than those in the third, 145 m, hole.The temperature data have been combined with over 200 thermal conductivity measurements on core samples to produce heat flow values. In the deepest hole heat flow above the fracture zone is 16% higher than that below the zone. This indicates that water is flowing up the fracture zone. The flow rate is approximately 0.3 g s⁻¹ m⁻¹, and the flow has existed for thousands of years.Observation of thermal effects of water flow in massive, relatively unfractured plutons in a region having little topographic relief causes one to be concerned about the reliability of heat flow values measured in similar environments.The regional heat flow is taken to be 50 mW m⁻² after correction for glaciation effects. The average value of 24 determinations of radioactive heat generation in granitic core samples is 5.23 ± 1.11 μW m⁻³, which is more than three times higher than expected for such a heat flow in the Superior Province. This implies that the layer of high radioactive heat generation is thin, being not more than 4 km and probably about 1.3 km thick.     

Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field,Kilauea volcano,Hawaii

Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10° C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. In general, the emissivity of the flows varied systematically with age but the relationship between age and emissivity was not unique. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows. Such incipient alteration may have been the cause for virtually all of the emissivity variations observed on the flow field, the spectral anomalies representing areas where the acid attack was most intense.     

The role of choke points in the ocean context

Choke points are narrow international waterways where three characteristics are present. The waterway should be narrow and capable of being closed off to both commercial and military snipping. There should be no readily available maritime route to utilize in the event of closure. Finally, the choke point should be of considerable significance to at least several States. This article identifies seven “primary” choke points which seem to satisfy these criteria. These are Gibraltar, Bab el Mandeb, Hormuz, the Danish and Turkish Straits, and the Suez and Panama Canals. It also identifies eleven “secondary” choke points, where at least one of the reouired characteristics is missing. The eleven include Dover, Bering and Magellan Straits, as well as Malacca-Singapore and a number of others in the Western Pacific. Turning to a consideration of the status of choke points in a Post-Cold War era, the article notes four basic assumptions: (1) the intense military rivalry between the United States and the Soviet Union will be reduced in coming years; (2) for many countries marine-related environmental concerns may be increasing considerably; (3) as the Cold War recedes, regional contests and confrontations will grow more intense; and (4) the overall densities of water-borne traffic will undergo change as the relative economic growth of regional centers changes. The article then considers the potential impact of these trends on the future role of choke points.     

Reducing global warming — The role of rice

Activities to provide energy for an expanding population are increasingly disrupting and changing the concentration of atmospheric gases that increase global temperature. Increased CO₂ and temperature have a clear effect on growth and production of rice as they are key factors in photosynthesis. Rice yields could be increased with increased levels of CO₂, however, the rise of CO₂ may be accompanied by an increase in global temperature. The effect of doubling CO₂ levels on rice production was predicted using rice crop models. They showed different effects of climate change in different countries. A simulation of the Southeast Asian region indicated that a doubling of CO₂ increases yield, whereas an increase in temperature decreases yield.Enhanced UV-B radiation resulting for stratographic ozone depletion has been demonstrated to significantly reduce plant height, leaf area and dry weight of two rice cultivars under glasshouse conditions. Data are still insufficient, however, for conclusive results on the effect of UV-B radiation on rice growth under field conditions.Rice production itself has a significant effect on global warming and atmospheric chemistry through methane emission from flooded ricefields. Water regime, soil properties and the rice plant are major factors controlling the flux of methane in ricefields. Global and regional estimates of methane emission rates are still highly uncertain and tentative. Integration of mechanistic modeling of methane fluxes with geographic information systems of factors controlling these processes are required to improve estimates and predictions.     

Isotopic composition of strontium in three basalt-andesite centers along the Lesser Antilles arc

Si⁸⁷/Sr⁸⁶ ratios have been determined for lavas and py lastic rocks from three basalt-andesite centers along the Lesser Antilles arc—Mt. Misery on the island of St. Kitts, Soufriere on the island of St. Vincent, and Carriacou, an island of The Grenadines. The average Si⁸⁷/Sr⁸⁶ content of these rocks is 0.7038 for Mt. Misery, 0.7041 for Soufriere, and 0.7053 for Carriacou. All the Sr⁸⁷/Sr⁸⁶ values from each center are the same within analytical uncertainty (±0.0002). The constancy of strontium isotopic data within each center supports the hypothesis that basalts and andesites for each specific center investigated are generated from the same source — in agreement with petrographic and major- and minor-element data. Strontium isotopic compositions and elemental concentrations, particularly of strontium and nickel, indicate that this source was mantle peridotite and that the relationship between the respective basalts and andesites is probably fractional crystallization.Publication authorized by the Director, U.S. Geological Survey.     

Morphology of HCN and CN in Comet Hale-Bopp (1995 O1)

We compare images of Comet Hale-Bopp (1995 O1) in HCN and CN taken near perihelion (April 1, 1997) to determine the origin of CN in comets. We imaged the J=1→0 transition of HCN at λ=3 mm with the BIMA Array. Data from two weeks around perihelion were summed within four phase bins based on the rotational period of the comet. This increases both the signal-to-noise ratio and the u-v coverage while decreasing the smearing of the spatial features. The similarly phased narrowband CN images were taken at Lowell Observatory within the same range of dates as the HCN images. We find that there is a better correlation between HCN and CN than between HCN and the optically dominant dust. If the CN in jets does have a dust source it would have to have a very low albedo and/or small particle size. The production rates are consistent with HCN being a primary parent of CN, although there are discrepancies between the HCN destruction scalelength and the CN production scalelength which we discuss.     

The Global Impact of Clouds on the Production of MODIS Bidirectional Reflectance Model-Based Composites for Terrestrial Monitoring

A global data set of cloud occurrence probability derived from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua gridded daily data is analyzed to investigate the probability of obtaining at least a minimum number of cloud-free observations within various compositing periods. The probabilities derived from Terra and Aqua, with morning and afternoon overpass times, respectively, are similar and increase with compositing period. Compositing both Terra and Aqua observations results in considerably higher probabilities of obtaining a sufficient number of observations for bidirectional reflectance model-based compositing. Given that the only alternative to obtaining sufficient samples is to extend the observation period, which can cause significant problems when the surface state changes, it is concluded that using data from the two MODIS sensors provides the most effective way of generating composited products. Findings with respect to the availability of cloud-free composites when n-day composites are generated on a temporally overlapping daily rolling basis, i.e., every day, rather than every n-days, are also discussed for regional and global applications     

Fate and groundwater impacts of produced water releases at OSPER “B” site,Osage County,Oklahoma

For the last 5 a, the authors have been investigating the transport, fate, natural attenuation and ecosystem impacts of inorganic and organic compounds in releases of produced water and associated hydrocarbons at the Osage-Skiatook Petroleum Environmental Research (OSPER) “A” and “B” sites, located in NE Oklahoma. Approximately 1.0 ha of land at OSPER “B”, located within the active Branstetter lease, is visibly affected by salt scarring, tree kills, soil salinization, and brine and petroleum contamination. Site “B” includes an active production tank battery and adjacent large brine pit, two injection well sites, one with an adjacent small pit, and an abandoned brine pit and tank battery site. Oil production in this lease started in 1938, and currently there are 10 wells that produce 0.2–0.5 m³/d (1–3 bbl/d) oil, and 8–16 m³/d (50–100 bbl/d) brine. Geochemical data from nearby oil wells show that the produced water source is a Na–Ca–Cl brine (∼150,000 mg/L TDS), with high Mg, but low SO₄ and dissolved organic concentrations. Groundwater impacts are being investigated by detailed chemical analyses of water from repeated sampling of 41 boreholes, 1–71 m deep. The most important results at OSPER “B” are: (1) significant amounts of produced water from the two active brine pits percolate into the surficial rocks and flow towards the adjacent Skiatook reservoir, but only minor amounts of liquid petroleum leave the brine pits; (2) produced-water brine and minor dissolved organics have penetrated the thick (3–7 m) shale and siltstone units resulting in the formation of three interconnected plumes of high-salinity water (5000–30,000 mg/L TDS) that extend towards the Skiatook reservoir from the two active and one abandoned brine pits; and (3) groundwater from the deep section of only one well, BR-01 located 330 m upslope and west of the site, appear not to be impacted by petroleum operations.