A radiation-driven disc wind model for massive young stellar objects

The generation of magnetic fields by a battery, operating in an ion–electron plasma around a Kerr black hole, is studied in the 3+1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms can less easily be quenched than the classical ones. In axisymmetry the battery can induce only toroidal magnetic fields. Once a toroidal magnetic field is present, however, the coupling of gravitomagnetic and electromagnetic fields generates a poloidal magnetic field even in axisymmetry. A rotating black hole, embedded in plasma, will therefore always generate toroidal and poloidal magnetic fields.     

Biogeochemistry of iron in an acidic lake

In this paper, the fate of iron in Lake Cristallina, an acidic lake in the Alps of Switzerland, is discussed. A simple conceptual model is developed in order to explain the observed diel variation in dissolved iron(II) concentration. Biotite weathering provides reduced iron that is oxidized and subsequently precipitated in the lake. The amorphous Fe(III)hydroxide (FeOOH xH₂O), found in the sediments of Lake Cristallina, is an Fe(II) oxidation product. This oxygenation reaction is most probably catalyzed by bacteria surfaces, as indicated by the relatively high estimated oxidation rate compared to the oxidation rate of the homogeneous oxidation of inorganic Fe(II) species at the ambient pH of Lake Cristallina (pH 5.4 at 4 °C) and by the scanning electron micrograph pictures. Under the influence of light, these amorphous iron(III)hydroxide phases are reductively dissolved. The net concentration of Fe(II) reflects the balance of the reductive dissolution and the oxidation/precipitation reactions and tends to parallel the light intensity, leading to a diurnal variation in the Fe(II) concentration. The rate of the photochemical reductive dissolution of Lake Cristallina iron(III)hydroxides is greatly enhanced in situ and in the laboratory by addition of oxalate to the lake water.     

Scalar fluxes from urban street canyons. Part I: Laboratory simulation

Flow over urban surfaces depends on surface morphology and interaction with the boundary layer above. However, the effect of the flow on scalar fluxes is hard to quantify. The naphthalene sublimation technique was used to quantify scalar vertical fluxes out of a street canyon under neutral conditions. For an array of eight canyons with aspect ratio H/W=0.75 (here, H is building height and W is the street width), increased flux was observed in the first two or three canyons for moderate and low roughness upstream. This is consistent with predictions of the length scale for initial adjustment of flow to an urban canopy. The flux was constant after the initial adjustment region and thus dependent only on local geometry. For a street canyon in the equilibrium part of the array, each facet of the street canyon was coated with naphthalene to simulate scalar release from street, walls and roof, to evaluate the effect of street canyon geometry on fluxes for H/W=0.25, 0.6, 1 and 2. Fluxes from the roof and downstream wall were considerably larger than fluxes from the street and upstream wall, and only the flux from the downstream wall exhibited a simple decrease with H/W. For each H/W there was a monotonic decrease between downstream wall, street and upstream wall transfer. This suggests that flow decelerates around the recirculation region in the lee of the upstream building, i.e. a recirculating jet rather than a symmetrical vortex. The addition of a second source within the street canyon resulted in reduced fluxes from each facet for H/W>0.25, due to increased concentration of naphthalene in the canyon air.     

Anthropogenic inputs of several heavy metals to nearshore basins off Los Angeles

Budgets of anthropogenically-derived Cr, Zn and Pb in the Santa Monica-San Pedro Basin and the Palos Verdes Shelf are estimated from profiles of these metals in a large number of sediment cores. Comparisons of inventories in the deep basin with combined emissions from the responsible sewage outfalls indicate that no more than 7% of the Cr, 2% of the Zn and 5% of the Pb derived from the sewage source are buried in the nearshore basin. A similar comparison of metal accumulation on the Palos Verdes Shelf with discharges from the nearby JWPCP outfall indicates that 12% of the Zn and 20% of the Cr and Pb are deposited locally. The annual percentages of sewage-derived Pb retained should be significantly lower, because surface runoff and atmospheric fallout are also important input pathways for anthropogenic Pb. Offshore variations in sediment metal composition suggest that Cr is most strongly attached to sewage particles while Zn and Pb are more labile. We conclude that the majority of anthropogenic metals are exported offshore beyond the inner basin.     

Ichthyoplankton abundance, distribution, and assemblage structure in the Gulf of Alaska during September 2000 and 2001

Autumn ichthyoplankton assemblage structure in the Gulf of Alaska (GOA) region has not previously been characterized. Ichthyoplankton data from September 2000 and 2001 survey collections were analyzed to describe assemblages in the western GOA, to examine interannual variation in assemblages, and to relate observations to oceanographic conditions. Taxa with the highest frequency of occurrence (2000/2001) included Osmeridae (94/87%), Hexagrammos lagocephalus (57/45%), Sebastes spp. (35/47%) and Bathymaster spp. (27/57%). Through the use of clustering techniques and ordination, three identifiable larval assemblages common to both years were identified. Slope assemblages appeared well defined in both years, while nearshore and mid-shelf assemblages tended to be more loosely associated and variable between years. Analyses of environmental variables (temperature, salinity, water depth, distance from shore, and water transport) suggest ichthyoplankton assemblage structure is affected primarily by bathymetry and circulation. We demonstrate that early autumn ichthyoplankton assemblage structure in the GOA is fundamentally linked to variations in macro- (slope vs. shelf) and meso-scale topography (on-shelf proximity to land masses), and suggest that these intrinsic associations may be modified by spatial and temporal variations in local hydrographic conditions.     

GGR Critical Review of Analytical Developments in 2006–2007

In 2005 the Geostandards and Geoanalytical Research editorial team, in the true spirit of scientific endeavour, embarked on an experiment of our own. We decided to trial a new kind of review, somewhat different from those more typically observed in journals, and one that would provide readers with a summary of analytical developments across a broad range of topics appropriate to the Earth sciences. The first contribution of this kind appeared in 2005, and reported on developments in 2003 (Hergt et al. 2005). The second, this time a biennial review, was published in 2006 and reported on highlights of the 2004 and 2005 literature (Hergt et al. 2006). Based on reprint requests, positive remarks at conferences and strong citations we consider the experiment a resounding success and proudly present here the third in this series. This comprises six individual review sections that cover the main analytical technologies and topical application fields in geoanalysis and geochemistry, including geological and environmental reference materials, ICP‐thermal and secondary ionisation‐mass spectrometry, as well as neutron activation analysis, X‐ray fluorescence and atomic absorption spectrometry.