Characteristics, development and utilization of geothermal resources- a Nordic perspective

Geothermal energy is classified as a renewable energy source and it utilizes the heat generated in the earth primarily from the natural radioactive decay of isotopes of uranium, thorium and potassium. Heat is extracted from the earth to generate geothermal energy via a carrier, usually water occurring either in the liquid or steam phase. In the late 19th century and the early 20th century, the first developments of geothermal resources for power generation and household heating got underway successfully. Many of these geothermal fields are still being utilized today, proving their sustainability. Today geothermal energy is being utilized in more than 72 countries around the world and of the Nordic countries Iceland and Sweden have been in the forefront in each of their respective fields. While geothermal heat pumps are widely used for space heating in Sweden, geothermal energy covers 55% of the primary energy consumption in Iceland where it is used for space heating, power generation and industrial purposes. Future developments aim at expanding the range of viable geothermal resources by improving the capabilities to generate electricity from geothermal resources at temperatures as low as 100℃, as well as developing geothermal resources where water needs to be introduced, so-called hot dry rock resources. But the biggest expansion is expected to continue to be in the installations of geothermal heat pumps.     

Clear‐sky closure studies of lower tropospheric aerosol and water vapor during ACE‐2 using airborne sunphotometer, airborne in‐situ, space‐borne, and ground‐based measurements

We report on clear‐sky column closure experiments (CLEARCOLUMN) performed in the Canary Islands during the second Aerosol Characterization Experiment (ACE‐2) in June/July 1997. We present CLEARCOLUMN results obtained by combining airborne sunphotometer and in‐situ (optical particle counter, nephelometer, and absorption photometer) measurements taken aboard the Pelican aircraft, space‐borne NOAA/AVHRR data and ground‐based lidar and sunphotometer measurements. During both days discussed here, vertical profiles flown in cloud‐free air masses revealed 3 distinctly different layers: a marine boundary layer (MBL) with varying pollution levels, an elevated dust layer, and a very clean layer between the MBL and the dust layer. A key result of this study is the achievement of closure between extinction or layer aerosol optical depth (AOD) computed from continuous in‐situ aerosol size‐distributions and composition and those measured with the airborne sunphotometer. In the dust, the agreement in layer AOD (λ=380–1060 nm) is 3–8%. In the MBL there is a tendency for the in‐situ results to be slightly lower than the sunphotometer measurements (10–17% at λ=525 nm), but these differences are within the combined error bars of the measurements and computations.     

Mineralogical alteration of artificial meteorites during atmospheric entry. The STONE-5 experiment

The generic concept of the artificial meteorite experiment STONE is to fix rock samples bearing microorganisms on the heat shield of a recoverable space capsule and to study their modifications during atmospheric re-entry. The STONE-5 experiment was performed mainly to answer astrobiological questions. The rock samples mounted on the heat shield were used (i) as a carrier for microorganisms and (ii) as internal control to verify whether physical conditions during atmospheric re-entry were comparable to those experienced by “real” meteorites. Samples of dolerite (an igneous rock), sandstone (a sedimentary rock), and gneiss impactite from Haughton Crater carrying endolithic cyanobacteria were fixed to the heat shield of the unmanned recoverable capsule FOTON-M2. Holes drilled on the back side of each rock sample were loaded with bacterial and fungal spores and with dried vegetative cryptoendoliths. The front of the gneissic sample was also soaked with cryptoendoliths.

The mineralogical differences between pre- and post-flight samples are detailed. Despite intense ablation resulting in deeply eroded samples, all rocks in part survived atmospheric re-entry. Temperatures attained during re-entry were high enough to melt dolerite, silica, and the gneiss impactite sample. The formation of fusion crusts in STONE-5 was a real novelty and strengthens the link with real meteorites. The exposed part of the dolerite is covered by a fusion crust consisting of silicate glass formed from the rock sample with an admixture of holder material (silica). Compositionally, the fusion crust varies from silica-rich areas (undissolved silica fibres of the holder material) to areas whose composition is “basaltic”. Likewise, the fusion crust on the exposed gneiss surface was formed from gneiss with an admixture of holder material. The corresponding composition of the fusion crust varies from silica-rich areas to areas with “gneiss” composition (main component potassium-rich feldspar). The sandstone sample was retrieved intact and did not develop a fusion crust. Thermal decomposition of the calcite matrix followed by disintegration and liberation of the silicate grains prevented the formation of a melt.

Furthermore, the non-exposed surface of all samples experienced strong thermal alterations. Hot gases released during ablation pervaded the empty space between sample and sample holder leading to intense local heating. The intense heating below the protective sample holder led to surface melting of the dolerite rock and to the formation of calcium-silicate rims on quartz grains in the sandstone sample.     

Analysis of ordinary chondrites using powder X‐ray diffraction: 2. Applications to ordinary chondrite parent‐body processes

Abstract– We evaluate the chemical and physical conditions of metamorphism in ordinary chondrite parent bodies using X‐ray diffraction (XRD)‐measured modal mineral abundances and geochemical analyses of 48 type 4–6 ordinary chondrites. Several observations indicate that oxidation may have occurred during progressive metamorphism of equilibrated chondrites, including systematic changes with petrologic type in XRD‐derived olivine and low‐Ca pyroxene abundances, increasing ratios of MgO/(MgO+FeO) in olivine and pyroxene, mean Ni/Fe and Co/Fe ratios in bulk metal with increasing metamorphic grade, and linear Fe addition trends in molar Fe/Mn and Fe/Mg plots. An aqueous fluid, likely incorporated as hydrous silicates and distributed homogeneously throughout the parent body, was responsible for oxidation. Based on mass balance calculations, a minimum of 0.3–0.4 wt% H₂O reacted with metal to produce oxidized Fe. Prior to oxidation the parent body underwent a period of reduction, as evidenced by the unequilibrated chondrites. Unlike olivine and pyroxene, average plagioclase abundances do not show any systematic changes with increasing petrologic type. Based on this observation and a comparison of modal and normative plagioclase abundances, we suggest that plagioclase completely crystallized from glass by type 4 temperature conditions in the H and L chondrites and by type 5 in the LL chondrites. Because the validity of using the plagioclase thermometer to determine peak temperatures rests on the assumption that plagioclase continued to crystallize through type 6 conditions, we suggest that temperatures calculated using pyroxene goethermometry provide more accurate estimates of the peak temperatures reached in ordinary chondrite parent bodies.     

Where Have We Been? Where Are We Going?

“Heavier-than-air flying machines are impossible” Lord Kelvin ca. 1895, British Mathematician and Physicist²“But what ... is it good for?” Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.³     

Book reviews

VANCOUVER'S CHINATOWN: racial discourse in Canada 1875–1980 by K. J. Anderson. 16 × 24 cm, 323 pages. McGill‐Queen's University Press, Montreal, 1991. (ISBN 07735 0844 9) $C34.95 (hard).

GEOGRAPHIC INFORMATION SYSTEMS: developments and applications edited by L. Worrall. 15 × 23 cm, 251 pages. Belhaven, London, 1990. (ISBN 1 85293 140 X) £45.00 (hard).

SAVANNA ECOLOGY AND MANAGEMENT: Australian perspectives and intercontinental comparisons edited by P. A. Werner. 22 × 27 cm, xii and 221 pages. Blackwell Scientific, Oxford, 1991. (ISBN 0 632 03199 9) $A89.00 (soft).

GLOBAL CHANGE AND CHALLENGE: geography for the 1990s edited by R. J. Bennett and R. Estall. 14 × 22 cm, xii and 264 pages. Routledge, London, 1991. (ISBN 0 415 00143 9) $A29.95 (soft).

PLAINS OF PROMISE RIVERS OF DESTINY: water management and the development of Queensland 1824–1990 by J. M. Powell. 17 × 24 cm, xvii and 395 pages. Boolarong Publications, Brisbane, 1991. (ISBN 0 7242 4470 0) $A40.00 (hard).

A SHARED HARVEST: The Australian Wheat Industry, 1939–1989 by G. Whitwell and D. Sydenham. 17 × 25 cm, xi and 324 pages. Macmillan, Melbourne, 1991. (ISBN 0 7329 0584 2) $A29.95 (hard).

TAMING THE GREAT SOUTH LAND: a history of the conquest of nature in Australia by W. J. Lines. 16 × 23cm, xx and 337 pages. Allen & Unwin, Sydney, 1991. (ISBN 1 86373 017 6) $A34.95 (hard).

PLAINS OF PROMISE RIVERS OF DESTINY: water management and the development of Queensland 1824–1990 by J. M. Powell. 17 × 24 cm, xvii and 395 pages. Boolarong Publications, Brisbane, 1991. (ISBN 0 7242 4470 0) $A40.00 (hard).

THE HUMANITIES AND THE AUSTRALIAN ENVIRONMENT: Papers from the Australian Academy of the Humanities Symposium edited by D. J. Mulvaney. 24 × 17 cm, xiii and 123 pages. Australian Academy of the Humanities, Canberra, 1991. (ISBN 0 909897 22 0) $A18.50 posted (soft).

GROWTH (Vol. 167, Sage Library of Social Research) by H. Teune. 141 pages. Sage Publications, Newbury Park, CA, 1988. (ISBN 0 8039 3183 2) US$46.00 (hard); (ISBN 0 8039 3190 5) US$22.95 (soft).

BEYOND GROWTH: elements of sustainable development by U.E. Simonis. 151 pages. Edition Sigma Bohn, Berlin, 1990. (ISBN 3 924859 56 6) DM24.80 (soft).

BEYOND BEEF: the rise and fall of the cattle culture by J. Rifkin. 16 × 24 cm, xi and 353 pages. Viking O'Neil, Melbourne, 1992. (ISBN 0 670 84844 1) $35.00 (hard).

A QUESTION OF PLACE: exploring the practice of human geography by R.J. Johnston. 15 × 23 cm, ix and 280 pages. Blackwell, Oxford, 1991. (ISBN 0 631 18207 1) $39.95 (soft).

GEOGRAPHY IN SOCIETY edited by R. Gerber. 21 × 29 cm, 92 pages. Royal Geographical Society of Queensland, Brisbane, [1992]. (ISBN 0 949286 02 8) $8.00 (soft).     

Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria

Minerals formed by bio-oxidation of ferrous iron (Fe(II)) at neutral pH, their association with bacterial ultrastructures as well as their impact on the metabolism of iron-oxidizing bacteria remain poorly understood. Here, we investigated iron biomineralization by the anaerobic nitrate-dependent iron-oxidizing bacterium Acidovorax sp. strain BoFeN1 in the presence of dissolved Fe(II) using electron microscopy and Scanning Transmission X-ray Microscopy (STXM). All detected minerals consisted mainly of amorphous iron phosphates, but based on their morphology and localization, three types of precipitates could be discriminated: (1) mineralized filaments at distance from the cells, (2) globules of 100 ± 25 nm in diameter, at the cell surface and (3) a 40-nm thick mineralized layer within the periplasm. All of those phases were shown to be intimately associated with organic molecules. Periplasmic encrustation was accompanied by an accumulation of protein moieties. In the same way, exopolysaccharides were associated with the extracellular mineralized filaments. The evolution of cell encrustation was followed by TEM over the time course of a culture: cell encrustation proceeded progressively, with rapid precipitation in the periplasm (in a few tens of minutes), followed by the formation of surface-bound globules. Moreover, we frequently observed an asymmetric mineral thickening at the cell poles. In parallel, the evolution of iron oxidation was quantified by STXM: iron both contained in the bacteria and in the extracellular precipitates reached complete oxidation within 6 days. While a progressive oxidation of Fe in the bacteria and in the medium could be observed, spatial redox (oxido-reduction state) heterogeneities were detected at the cell poles and in the extracellular precipitates after 1 day. All these findings provide new information to further the understanding of molecular processes involved in iron biomineralization by anaerobic iron-oxidizing bacteria and offer potential signatures of those metabolisms that can be looked for in the geological record.     

An evaluation of glass prisms in boat docks to reduce shading of submerged aquatic vegetation in the lower St. Johns River,Florida

The effectiveness of glass prisms in boat docks was assessed to determine if shading impacts to submerged aquatic vegetation (SAV), primarilyVallisneria americana, were reduced. Six experimental docks, three with prisms and three without prisms, were constructed in the lower St. Johns River, Florida. SAV percent cover and photosynthetically active radiation (PAR) were monitored under each dock and in an adjacent control area with no experimental docks. Subsurface PAR during the growing season of the first year of the study was not significantly greater beneath docks having prisms than beneath docks without prisms. Postconstruction SAV monitoring (February 2000 to May 2002) revealed no significant differences in SAV percent cover between dock treatments, although coverage declined in both dock treatments and the control area. Declining water quality conditions at the study site clearly impacted the health of the SAV habitat as indicated by the decline in SAV coverage in the control area initially in the study. Given the subsequent resurgence of SAV in the control area, the additional light transmitted through the prisms did not appear to be biologically significant or adequate to counteract effects from larger-scale environmental stressors.     

Adsorption mechanisms of trivalent gold on iron- and aluminum-(oxy)hydroxides. Part 1: X-ray absorption and Raman scattering spectroscopic studies of Au(III) adsorbed on ferrihydrite, goethite, and boehmite

Gold adsorption products on powdered ferrihydrite, goethite, and boehmite samples, prepared by reacting Au(III)-Cl solutions ([Au] = 4.2 × 10⁻⁵-9.0 × 10⁻³ M; [Cl] = 0.017-0.6 M) with these adsorbents at pH values of 4 to 9 and Au adsorption densities ranging from 0.046 to 1.53 μmol/m² were characterized using Au-L_III XAFS spectroscopy. The solutions (before and after uptake) were investigated by Raman scattering to determine speciation and by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) to determine solution composition. We present an analysis of several effects that are observed in the Au L_III-edge XAFS spectra, including X-ray beam-induced photo-reduction, multi-electronic excitations, disorder effects, and multiple scattering, that would complicate interpretation of the spectra if not accounted for. A combination of methods (spectral deconvolution, principal component analysis, spectral inversion, and wavelet analysis) was used to identify and quantify these effects, to characterize the nature of mixed ligands around gold, and to distinguish between multiple-scattering features and features due to next-nearest neighbors in the XAFS spectra.Analysis of the Au-L_III XAFS spectra showed that Au(III) is present as square-planar Au(III)(O,Cl)₄ complexes in the aqueous solutions and on the surfaces of the Al/Fe-(oxy)hydroxide adsorption samples with dominantly O ligands at pH > 6 and mixed O/Cl ligands at lower pH values. The EXAFS-derived Au-O and Au-Cl distances are 2.00(2) and 2.28(2) Å, respectively, and the magnitudes of the Debye-Waller factors and third cumulants from anharmonic analyses indicate very little thermal or positional disorder around Au(III) in the adsorption samples. Iron second neighbors are present around Au in the Au(III)/ferrihydrite and Au(III)/goethite adsorption samples, with Au-Fe distances of 3.1(1) and 3.3(1) Å. In boehmite, two sets of Au-Al distances were detected at 3.0(1) and 3.2(1) Å. A reverse Monte Carlo study of the XAFS spectroscopic data suggests the presence of a continuum of edge-shared AuO₄-FeO₆ distances, which cannot be described correctly by a classical model of these data in which only a mean distance (although severely under-estimated) is derived.     

Geologische Grundzüge der Dinariden

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