Chemical evolution of the Mt. Hekla,Iceland, groundwaters: A natural analogue for CO₂ sequestration in basaltic rocks     

Therese K. Flaathen  Sigurður R. Gislason  Eric H. Oelkers  Árný E. Sveinbjörnsdóttir 《Applied Geochemistry》2009

A detailed study of the chemical composition of the groundwater surrounding the Mt. Hekla volcano in south Iceland was performed to assess fluid evolution and toxic metal mobility during CO₂-rich fluid basalt interaction. These fluids provide a natural analogue for evaluating the consequences of CO₂ sequestration in basalt. The concentration of dissolved inorganic C in these groundwaters decreases from 3.88 to 0.746 mmol/kg with increasing basalt dissolution while the pH increases from 6.9 to 9.2. This observation provides direct evidence of the potential for basalt dissolution to sequester CO₂. Reaction path calculations suggest that dolomite and calcite precipitation is largely responsible for this drop in groundwater dissolved C concentration. The concentrations of toxic metal(loid)s in the waters are low, for example the maximum measured concentrations of Cd, As and Pb were 0.09, 22.8 and 0.06 nmol/kg, respectively. Reaction path modelling indicates that although many toxic metals may be initially liberated by the dissolution of basalt by acidic CO₂-rich solutions, these metals are reincorporated into solid phases as the groundwaters are neutralized by continued basalt dissolution. The identity of the secondary toxic metal bearing phases depends on the metal. For example, calculations suggest that Sr and Ba are incorporated into carbonates, while Pb, Zn and Cd are incorporated into Fe (oxy)hydroxide phases.  相似文献   

Fortress Australia? (In)security and private governance in a gated residential estate     

Therese Kenna 《The Australian geographer》2010,41(4):431-446

Part of a broader trend towards all-inclusive master planned developments, gated residential estates are an intensely private form of residential development with a degree of securitisation. Gated residential estates have been the topic of intense debate in urban planning and policy circles and the target of fierce criticism for potential exclusionary outcomes as fearful residents lock themselves away from the ills of wider urban society. Crime, a fear of crime and the need for security dominate discussions and understandings of gated residential developments in Australia without much empirical validation. This paper poses two key research questions: does fear of crime and need for increased security drive residents towards gated estates; and what are the lived experiences of security, gates and crime once residing within a gated estate? Based on in-depth research in Macquarie Links (one of Sydney's largest gated estates) this paper offers insights into the lived dimensions of gated estates. The paper explores the attractions and realities of security services and infrastructure, private control over the residential environment and the importance placed by the residents on the ability to protect the nature of their neighbourhood and to protect themselves from any ‘unwanted’ activities or groups. The discussion in this paper demonstrates that for the residents in the study, residing in a secure residential neighbourhood is less about the role and place of physical security and security services, and more to do with protection afforded by the private governance structure of the neighbourhood.  相似文献   

Hydrochemical studies of Cross River Basin (southeastern Nigeria) river systems using cross plots, statistics and water quality index   总被引：2，自引：1，他引：1  

Aniekan Edet  Aniediobong Ukpong  Therese Nganje 《Environmental Earth Sciences》2013,70(7):3043-3056

Water quality assessment study of the three major rivers within the Cross River Basin have been carried out using cross plots, ionic ratio, correlation analysis, factor analysis and water quality index (WQI) based on the World Health Organization and world average data guidelines. The primary aim was to determine their suitability for domestic and irrigation uses, while the secondary aim was to determine the sources of the ions in the river water. The results showed that the water samples from the Cross River estuary generally had elevated values of dissolved ions as compared to the Calabar and Great Kwa Rivers. Cross plots, ionic ratios, correlation and factor analyses showed tidal influence, silicate weathering, nitrate pollution and dissolution of carbonate minerals from soil CO₂ as the origin of the variables. Chemical indices including sodium adsorption ratio and residual sodium carbonate indicate that the river water of the study area are suitable for domestic and irrigation, while sodium percentage (Na %) indicate unsuitability for irrigation applications. The WQI values on the average indicate water of very poor to excellent quality. Generally in terms of quality for the different rivers, the Great Kwa River is best as compared to the Calabar River and Cross River estuary for domestic and irrigation purposes.  相似文献   

Evolution des hydrocarbures et des populations bactériennes et microphytiques dans les sédiments des marais maritimes de l'ile grande pollués par l'Amoco cadiz: 2—Evolution des peuplements microphytiques     

Therese le Campion-Alsumard  Marie-Reine Plante-Cuny  Eveline Vacelet  Gilbert Mille 《Marine environmental research》1984,11(4):275-303

In this work we attempt to estimate the short- and long-term effects of the Amoco Cadiz oil spill on benthic microalgal populations (cyanophytes and diatoms) which, under natural conditions, live on upper layers of ‘schorres’ soils or of ‘slikke’ muds in the Ile Grande salt marsh system (Côtes du Nord, France). These populations were completely destroyed in 1978 in the oil-affected sites. Ubiquitous species settled fairly rapidly on intertidal polluted muds (tidal flat). The chlorophyll a content values reached 100 μg g⁻¹ dry sediment, i.e. 1000 mg m⁻² in 1980. Conversely, the salt marsh soils are still much less densely repopulated 3 years after the Amoco Cadiz grounding—especially when they are infrequently flooded (3 to 40 μg Chl.a g⁻¹, i.e. 40 to 270 mg m⁻²). Some of these soils remain ten times less populated than reference stations.  相似文献   

Minor constituents in the Martian atmosphere from the ISM/Phobos experiment     

Rosenqvist J  Drossart P  Combes M  Encrenaz T  Lellouch E  Bibring JP  Erard S  Langevin Y  Chassefiere E 《Icarus》1992,98(2):254-270

Global Martian atmospheric results derived from the infrared imaging spectrometer ISM flown aboard the Phobos 2 Soviet spacecraft are presented. Over low altitude regions the expected CO mixing ratio of (8 +/- 3) x 10(-4) is measured. Variations of the 2.35-micrometers feature are inconsistent with this value over the Great Martian Volcanoes. If the 2.35-micrometers band is entirely attributable to carbon monoxide, the CO mixing ratio is typically depleted by a factor of 3 over these high altitude areas. Orography should play a major role in the existence of this CO "hole." If, however, these spectral variations at 2.35 micrometers are due to the surface composition, the fraction of the surface covered by the responsible mineral must smoothly decrease as the surface elevation decreases. This phenomenon implies a strong interaction between the surface and the atmosphere for the Great Martian Volcanoes. Diurnal behavior and latitudinal variations of water vapor are globally consistent with Viking measurements. During the Phobos observations, the water vapor amounts over the bright equatorial regions range around 11 pr-micrometers during the day. These amounts are slightly larger than those inferred from 1976 to 1979. The lack of global dust storms during 1988-1989 could explain the enhancement of H2O in the atmosphere.  相似文献   

Water and related chemistry in the solar system. A guaranteed time key programme for Herschel     

P. Hartogh  E. Lellouch  M. Banaszkiewicz  E.A. Bergin  N. Biver  M.I. Blecka  D. Bockelée-Morvan  J. Cernicharo  G. Davis  P. Encrenaz  A. González  T. de Graauw  D. Hutsemékers  E. Jehin  M. Kidger  A. de Lange  D.C. Lis  J. Manfroid  R. Moreno  G. Orton  M. Rengel  M. Sánchez-Portal  S. Sidher  B. Swinyard  N. Thomas  B. Vandenbussche  C. Waelkens 《Planetary and Space Science》2009,57(13):1596-1606

“Water and related chemistry in the Solar System” is a Herschel Space Observatory Guaranteed-Time Key Programme. This project, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the outer planets, Titan, Enceladus and the comets. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in giant planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Mars’ atmosphere evolution, will be accurately measured in H₂O and CO. The role of water vapor in Mars’ atmospheric chemistry will be studied by monitoring vertical profiles of H₂O and HDO and by searching for several other species (and CO and H₂O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the outer planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches will enhance our knowledge of the composition of planetary and cometary atmospheres.  相似文献   

Comparison of Prominences in Hα and He  II 304 Å     

Haimin Wang  Jongchul Chae  Joseph B. Gurman  Therese A. Kucera 《Solar physics》1998,183(1):91-96

In this letter, we bring attention to prominences which show different morphology in H and Heii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two kinds of anomaly: (1) prominences showing strong H emissions in the lower part and strong Heii emissions in the upper part, and (2) erupting prominences showing extensive Heii emission, but nothing in H. Our results indicate that a part or the whole of a prominence may be too hot to emit H radiation, possibly due to heating or thermal instability. Please note that these are not just two isolated cases, many other prominences show the similar differences in H and Heii 304 Å.  相似文献   

The chemical atmospheric composition of the giant planets     

T. Encrenaz 《Earth, Moon, and Planets》1994,67(1-3):77-87

For a long time it was believed that the atmospheres of the giant planets, dominated by molecular hydrogen and helium, were similar in composition to the primordial nebula from which they formed. However, this image has strongly evolved over the past twenty years, due to new developments of ground-based infrared spectroscopy, coupled with the success of the Voyager space mission.Significant differences were measured in the abundances of helium, deuterium and carbon of the four giant planets. The variations in the C/H and D/H ratios have given support to the "nucleation" formation scenario, in which the four giant planets first accreted a nucleus of about ten terrestrial masses, big enough to bind gravitationally the surrounding gaseous nebula; the helium depletion in Saturn has been interpreted as a differentiation effect in Saturn's interior; the apparent helium excess in Neptune, coupled with the recent unexpected detection of CO and HCN in this planet, might imply the presence of molecular nitrogen. In the case of Jupiter and Saturn, disequilibrium species have been detected (CO, PH₃, GeH₄, AsH₃), which are tracers of vertical dynamical motions.In the future, significant progress in our knowledge of the Jovian composition, including the noble gases, should be obtained with the mass spectrometer of the Galileo probe. The ISO mission is expected to provide new far-infrared spectroscopic data which should lead to the detection of new minor species and a better determination of the D/H ratio.  相似文献   

The rotational temperature and column density of H₃ in Uranus     

Th. Encrenaz  P. Drossart  G. Orton  H. Feuchtgruber  E. Lellouch  S. K. Atreya 《Planetary and Space Science》2003,51(14-15):1013

H₃⁺ emission from Uranus has been observed repeatedly for over a decade. However, the details of the emission mechanisms are still poorly understood. In this paper, we discuss our findings from the observations we made in September 2000 and September 2001. The spectrum of Uranus was recorded at the NASA Infrared Telescope Facility using the SpeX instrument between 3 and 5 μm, with a resolving power of 1000. The 3.4–4.1 μm range permits a determination of both the H₃⁺ column density and its rotational temperature. The H₃⁺ emission, measured at 3.986 μm in the 0.8×3.7 arcsec aperture, was 0.031 Jy in September 2000 and 0.053 Jy in September 2001. The rotational temperature was found to be 560±40 K and 640±40 K in 2000 and 2001 respectively, with corresponding column densities of 5.1 (+3.2,−1.4) 10¹¹ and 4.0 (+1.8,−1.0) 10¹¹ cm⁻². These results extend the baseline for the variability study of the H₃⁺ emission (Astrophys. J. 524 (1999) 1059). Previous observations between 1992 and 1998 seemed to indicate a correlation between the H₃⁺ intensity and the solar cycle. The current data for 2000 and 2001 appear to be consistent with this general tendency.  相似文献   

Airborne interferometric measurement of the infrared spectrum of Jupiter from 6 to 14 μm     

Th. Encrenaz  D. Gautier  G. Michel  Y. Zeau  J. Lecacheux  L. Vapillon  M. Combes 《Icarus》1976,29(2):311-314

A new spectrum of Jupiter from 700 to 1600 cm^?1 was obtained with an interferometric experiment using the 91.5 cm telescope of the NASA Airborne Infrared Observatory. The spectral resolution is 10 cm^?1 and the signal-to-noise ratio is 30 at 900 cm^?1. NH₃ absorption lines are observed between 820 and 1020 cm^?1. The 1306 cm^?1ν₄CH₄ band strongly appears in emission at a temperature of at least 145° K. The Jovian brightness temperature between 1400 and 1600 cm^?1, according to our measurement, is lower than 170° K.  相似文献