North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.     

Sunspot nests

For the period August 1959–December 1964 the Greenwich Photoheliographic Results were searched for sunspot nests. Such a nest is a sequence of sunspot groups that appear within a small area on the solar surface and that last for several months. The search procedure is described and data for 41 probable sunspot nests are given. At least three quarters of these nests appear to be real, and not chance clusters.The nests are the same type of activity sequences as the Fleckenherde discovered by Becker (1955) and the complexes of activity pointed out by Gaizauskas et al. (1983). The complexes of activity as defined by Bumba and Howard (1965) are different patterns, however; the relation between complexes and the nests is shown.Some properties of the nests are: (i) many nests appear as double structures; (ii) single nests and components of double nests are quite compact: the effective areas are comparable to those of medium-large sunspot groups; (iii) each nest rotates at its own steady rate about the Sun; (iv) the intrinsic scatter in the rotation rates is much larger than the trend in the differential rotation; (v) displacements in latitude are less than a few meters per second; (vi) many nests live for 6 to 15 Carrington rotation periods, the minimum lifetime is not yet determined; (vii) the fraction of the sunspot groups that are members of nests is large (at least 30%).     

Surface complexation effects on phosphate adsorption to ferric iron oxyhydroxides along pH and salinity gradients in estuaries and coastal aquifers

Non-conservative behavior of dissolved inorganic phosphate (DIP) in estuaries is generally ascribed to desorption from iron and aluminum (hydr)oxides with increasing salinity. Here, we assess this hypothesis by simulating the reversible adsorption of phosphate onto a model oxide (goethite) along physico-chemical gradients representative of surface and subsurface estuaries. The simulations are carried out using a surface complexation model (SCM), which represents the main aqueous speciation and adsorption reactions of DIP, plus the ionic strength-dependent coulombic interactions in solution and at the mineral-solution interface. According to the model calculations, variations in pH and salinity alone are unlikely to explain the often reported production of DIP in surface estuaries. In particular, increased aqueous complexation of phosphate by Mg²⁺ and Ca²⁺ ions with increasing salinity is offset by the formation of ternary Mg-phosphate surface complexes and the drop in electrical potential at the mineral-water interface. However, when taking into account the downstream decrease in the abundance of sorption sites, the model correctly simulates the observed release of DIP in the Scheldt estuary. The sharp increase in pH accompanying the admixing of seawater to fresh groundwater should also cause desorption of phosphate from iron oxyhydroxides during seawater intrusion in coastal aquifers. As for surface estuaries, the model calculations indicate that significant DIP release additionally requires a reduction in the phosphate sorption site density. In anoxic aquifers, this can result from the supply of seawater sulfate and the subsequent reductive dissolution of iron oxyhydroxides coupled to microbial sulfate reduction.     

Leaching mechanisms of oxyanionic metalloid and metal species in alkaline solid wastes: A review

An overview is presented on possible mechanisms that control the leaching behaviour of the oxyanion forming elements As, Cr, Mo, Sb, Se, V and W in cementituous systems and alkaline solid wastes, such as municipal solid waste incinerator bottom ash, fly ash and air pollution control residues, coal fly ash and metallurgical slags. Although the leachability of these elements generally depends on their redox state, speciation measurements are not common. Therefore, experimental observations available in the literature are combined with a summary of the thermal behaviour of these elements to assess possible redox states in freshly produced alkaline wastes, given their origin at high temperature. Possible redox reactions occurring at room temperature, on the other hand, are reviewed because these may alter the initial redox state in alkaline wastes and their leachates. In many cases, precipitation of oxyanions as a pure metalate cannot provide a satisfactory explanation for their leaching behaviour. It is therefore highly likely that adsorption and solid solution formation with common minerals in alkaline waste and cement reduce the leachate concentration of oxyanions below pure-phase solubility.     

A correcting “prism” for underwater viewpoints

The angular field observable in water by an observer in air depends on the configuration of the air-water interface. When the interface is a plane, the absolute limit to observable field is about from the normal to the interface. A practical limit, because of lateral chromatic aberration is considerably less, approximately 30°. A conventionally used configuration in research submersibles, is a polymethyl methacrylate port with inner and outer surfaces parallel. This has the same optical limitations as the plane air-water interface. It is shown that if the inner and outer surfaces are not required to be parallel to each other, there are solutions which permit extending the observable field to nearly a full hemisphere with acceptably small distortion and lateral chromatic aberration.     

A Yohkoh search for “black-light flares”

Calculations which predict that a phenomenon analogous to stellar negative pre-flares could also exist on the Sun were published by Hénouxet al. (1990), and Aboudarhamet al., (1990), who showed that at the beginning of a solar white-light flare (WLF) event an electron beam can cause a transient darkening before the WLF emission starts, under certain conditions. They named this event a black light flare (BLF). Such a BLF event should appear as diffuse dark patches lasting for about 20 seconds preceding the WLF emission, which would coincide with intense and impulsive hard X-ray bursts. The BLF location would be at (or in the vicinity of) the forthcoming bright patches. Their predicted contrast depends on the position of the flare on the solar disc and on the wavelength band of the observation.TheYohkoh satellite provided white-light data from the aspect camera of the SXT instrument (Tsunetaet al., 1991), at 431 nm and with a typical image interval of 10–12 s. We have studied nine white-light flares observed with this instrument, with X-ray class larger than M6. We have found a few interesting episodes, but no unambiguous example of the predicted BLF event. This study, although the best survey to date, was not ideal from the observational point of view. We therefore encourage further searches. Successful observations of this phenomenon on the Sun would greatly strengthen our knowledge of the lower solar atmosphere and its effects on solar luminosity variations.     

Palomar prime-focus infrared camera (PFIRCAM)

In a joint effort between engineers and scientists at the Jet Propulsion Laboratory and the California Institute of Technology, a near-infrared (0.8–2.6 m) direct imaging system has been developed and integrated into the Caltech Palomar Observatory detector series. The camera system has been tested and operated in a science mode at the prime-focus (f/3.3) of the Hale 5-m Telescope. This paper outlines the system components and performance, including discussion of the detector linearity.     

A verification of some methods to determine the fluxes of momentum,sensible heat,and water vapour using standard deviation and structure parameter of scalar meteorological quantities

A set of micro-meteorological data collected over a horizontal, uniform terrain (the plain of La Crau, France) in June 1987 is analysed. Conditions were predominantly sunny and arid, while due to the Mistral the wind speed could exceed 10 m/s. Verification of several methods to evaluate surface fluxes of heat, momentum and water vapour from the standard deviation of temperature, wind and specific humidity is presented. Also, a similar approach using the structure parameter of temperature is considered. These methods are all based on Monin-Obukhov (M-O) similarity theory. It is found that the standard deviation of temperature, vertical and horizontal wind speed as well as the structure parameter for temperature behave according to M-O similarity. It is shown that the sensible heat flux and friction velocity can be determined from a fast response thermometer and a cup anemometer. Also, it appears that the analytic solution of the set of governing equations as derived by the first author yields good results. M-O theory does not appear to work for the standard deviation of specific humidity. This may be due to the relative importance of large eddies.