Two Experimental Methods to Determine the Speciation of Cadmium in Sediment from the River Neckar

The binding forms of Cd to an anaerobic sediment of low sulfide content from Lauffen reservoir (River Neckar, Germany) were studied using two different approaches, i. e. sequential extraction (modified from published protocols) and titrimetric study of the pH-dependent Cd release. Thermodynamic equilibrium calculations were applied to calculate both the release pattern of Cd during the titrations and the speciation of Cd within the single fractions of the extraction protocol. The calculations were based on measured sediment parameters such as hydrous ferric oxide (HFO), acid volatile sulfide, carbonate content and total Cd content, and the extractants (oxalate, acid etc.) used. The results of the two independent approaches coincided well in that they both assigned more than two thirds of the total Cd content to be adsorbed to organic matter. Cd bound as CdS is of little importance. Sequential extraction after a 3-month oxidation period at pH 7 revealed a shift of Cd from being mainly bound in stronger surface complexes with organic matter to being mainly bound in weaker surface complexes with organic matter and HFO, and thus becoming more bioavailable. This study suggests that the use of sequential extraction although being frequently criticized due to its operational character can be used to determine binding forms of metal ions if they are accompanied by 1) careful supporting experiments, 2) analysis of important sediment parameters, and 3) the use of thermodynamic equlibrium models which can help to understand Cd speciation within the extraction fractions.     

High-speed photography of the bubble generated by an airgun1

High-speed photography has been used visually to study the shape, surface, turbulence and behaviour of an underwater oscillating bubble generated by an airgun. The source was a BOLT airgun with a chamber volume of 1.6cu.in., placed in a 0.85m³ tank at 0.5m depth. Near-field signatures were also recorded in order to compare the instant photographs of the oscillating bubble with the pressure field recorded about 25 cm from the gun. Estimations of the bubble-wall velocity and bubble radius estimated from high-speed film sequences are also presented, and are compared with modelled results. The deviation between the modelled and measured bubble radii was at most 9%. In order to check the capacity for transmission of light through the bubble, a concentrated laser beam was used as illumination. We found that the air bubble is a strong scattering medium of laser light, hence the bubble is opaque.     

The Operational Geography of Great Britain*

This article examines the operational geography of Great Britain in terms of six components: domestic context; student quality, preparation, and training; professional work environment; publications and productivity; conveniences and facilities; and employment. The goal of operational geography is to provide the basis for blending the strengths of different systems of geography which have much to offer one another. This article uses personal experiences and survey data to examine the strengths and weaknesses in Britain as compared to the United States. It finds that Britain has strong national support, a greater emphasis on geographic education, high-quality but narrowly trained undergraduates, and a productive academic faculty. The United States enjoys a more effective graduate curriculum, better funding, and more opportunity for personal advancement.     

Controls on Quaternary coastal evolution of the east-northeastern coast of Brazil: roles of sea-level history, trade winds and climate

East-northeastern Brazil has a wave-dominated, micro- to meso-tidal coast, lying entirely within the southern Atlantic trade wind belt. Integration of geologic mapping, radiocarbon dating and vibracoring data shows that the Quaternary coastal evolution of this area was controlled by three major factors: (1) sea-level history; (2) trade winds; and (3) climate change.

Sea-level history. Along the east-northeastern coast of Brazil, relative sea level has fallen approximately 5 m during the last 5000 y. Correlation of this sea-level history with the evolution of beach-ridge, lagoonal and coastal plain deposits shows that: (1) sea-level rise favours the formation of barrier island—lagoonal systems and the construction of intralagoonal deltas; (2) sea-level lowering is not conductive to barrier island formation. Rather, lagoons and bays become emergent and beach-ridge plains rapidly prograde.

Trade winds. Sediment dispersal systems along the coastal zone of east-northeastern Brazil have been highly persistent since Pleistocene time, as deduced from beach-ridge orientation. This persistence results from the fact that sediment dispersal in wave-dominated settings is ultimately controlled by atmospheric circulation which, for the east-northeastern coast of Brazil is associated with the South Atlantic high-pressure cell. The remarkable stability of this cell through time, has allowed the accumulation of extensive beach-ridge plains at the longshore drift sinks located along the coast.

Climate change. Effects of Quaternary climate changes on coastal sedimentation are twofold. Climate changes may affect rainfall patterns, thus exerting an important control on coastal dune development. Along the coast of northeastern Brazil, active coastal dunes are only present in those areas in which at least four consecutive dry months occur during the year. Mapping of these areas has shown that dune development during the Holocene has been episodic, these episodes being probably controlled by variations in rainfall patterns associated with climate changes. Secondly, despite its overall stability, the position of the high-pressure cell has experienced small shifts in position during the Holocene in response to climate changes. Changes in wind direction associated with these shifts have induced modifications in the coastal dispersion system, which are recorded in the strandplains as small truncations in the beach-ridge alignments.

These results have important implications in understanding accumulation of ancient sandstone shoreline sequences.     

The geography of defence — developing themes of study

Greater access to information after the Post-Cold War period gives researchers new opportunities to study the environmental, economic and social impacts of military defence. Changing political and economic circumstances are influencing the distribution of military facilities and defence industries in developed countries. The paper illustrates these developments and looks at the contribution to change made by pressure groups end at examples from the UK defence sector. Defence forces are reacting to criticism about negative impacts through a variety of measures including environmental training, site remediation and the use of simulation technology. A framework for further research is presented and many references cited.     

Die ostpazifische ‚'Wärmewelle“ von 1957/1958

Zusammenfassung Nach einer längeren kalten Periode des Oberflächenwassers vor der Westküste Nordamerikas trat dort 1957/58 eine ausgeprägte Wassererwärmung auf. Ihr ging eine Erhöhung des Meeresspiegels an der pazifischen Küste von Kalifornien bis Alaska parallel. Die ozeanische 'Wärmewelle zeigte sich auch an der Küste Perus (Puerto Chicama) und im freien Seegebiet südlich des Alaska-Golfs (Ozean-Wetterstation 'Papa). Die Hauptursache scheint eine Anomalie der atmosphärischen Zirkulation zu sein. Infolge Abschwächung der subtropischen Hochdruckgebiete im Ostpazifik ergab sich eine Verminderung der äquatorwärts gerichteten Windkomponenten in den Gebieten kalten Auftriebwassers.

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The warm water period of 1957/1958 in the eastern Pacific Ocean

Summary Following a longer period of cold surface waters off the west coast of North America, the ocean in this area showed a pronounced rise in temperature in 1957/1958 which was accompanied by a rise in sea level along the Pacific coast extending from California to Alaska. The oceanic warm water wave likewise occurred along the Peruvian coast (Puerto Chicama) and in the offing south of the Gulf of Alaska (Ocean Weather Station Papa). Its main cause seems to be an anomaly of the atmospheric circulation. A weakening of the subtropical high pressure system over the eastern part of the Pacific Ocean caused the wind components, directed towards the equator, to decrease over the areas of cold upwelling waters.

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La période «d'échauffement» de 1957 à 1958 en océan Pacifique oriental

Résumé Au bout d'une longue période d'eau froide de surface qui se manifestait devant la côte occidentale de l'Amérique du Nord, il se produisit en 1957/1958 dans ces parages un échauffement prononcé des eaux qui était accompagné d'une élévation du niveau de la mer le long de la côte Pacifique à partir de la Californie jusqu'à l'Alaska. La «période d'échauffement» océanique se manifestait également sur la côte de Pérou (Puerto Chicama) et au large au sud du golfe de l'Alaska (station météorologique océanique «Papa»). Il semble que la cause principale en est une anomalie de la circulation atmosphérique. Par suite d'un affaiblissement du système subtropical des hautes pressions dans la partie orientale du Pacifique, les composantes des vents orientées vers l'équateur subissaient un affaiblissement au-dessus de la région de la remontée des eaux froides.

     

Das Debye-Scherrer-Diagramm des rhombischen Schwefels

Ohne Zusammenfassung     

Anmerkungen zu „Geochemische Untersuchungen an Sedimenten des Persischen Golfs“

Ohne Zusammenfassung     

Composition and origin of lithic fragments and glasses in apollo 11 samples

Approximately 100 glasses and 52 lithic fragments from Apollo 11 lunar fines and microbreccias were analyzed with the electron microprobe. Ranges in bulk composition of lithic fragments are considerably outside the precision (<±1%) and accuracy (±2–5%) of the broad electron beam technique. Results of this study may be summarized as follows: i) A large variety of rock types different from the hand specimens (basalt) were found among the lithic fragments, namely anorthosites, troctolitic and noritic anorthosites, troctolites, and norites (different from Apollo 12 norites). ii) In analogy to the hand specimens, the basaltic lithic fragments may be subdivided into low-K and high-K groups, both of which extend considerably in composition beyond the hand specimens. iii) Glasses were divided into 6 groups: Group 1 are the compositional analogs of the anorthositic-troctolitic lithic fragments and were apparently formed in single-stage impact events directly from parent anorthosites and troctolites. iv) Group 2 glasses are identical in composition to Apollo 12 KREEP glass and noritic lithic fragments, but have no counterparts in our Apollo 11 lithic fragment suite. Occurrence of KREEP in Apollo 11,12, and 14 samples is indicative of its relatively high abundance and suggests that the lunar crust is less depleted in elements that are common in KREEP (e.g. K, rare earths, P) than was originally thought on the basis of Apollo 11 basalt studies. v) Group 3 glasses are the compositional analogs of the basaltic lithic fragments, but low-K and high-K glasses cannot be distinguished because of loss of K (and Na, P) by volatilization in the vitrification process. vi) Group 4 glasses have no compositional analogs among the lithic fragments and were probably derived from as yet unknown Fe-rich, moderately Ti-rich, Mg-poor basalts. vii) Group 5 (low Ti-high Mg peridotite equivalent) and 6 (ilmenite peridotite equivalent) glasses have no counterparts among the Apollo 11 lithic fragments, but rock equivalents to group 5 glasses were found in Apollo 12 samples. Group 6 glasses are abundant, have narrow compositional ranges, and are thought to be the products of impact melting of an as yet unrecognized ultramafic rock type. iix) The great variety of igneous rocks (e.g. anorthosites, troctolites, norites, basalts, peridotites) suggests that large scale melting or partial melting to considerable depth must have occurred on the moon.