Platinum group metals in common plants of northern forests: developments in analytical methods, and the application of biogeochemistry to exploration strategies

All platinum-group metals (PGM) in ashed plant tissues, from an area of platinum mineralization in Saskatchewan, have been measured by neutron activation analysis of a NiS fire assay bead. Concentrations of up to 1350 ppb (ng/g) Pd, 880 ppb Pt, 49 ppb Rh, 37 ppb Ru, 24 ppb Ir, and 15 ppb Os occur in ashed twigs of black spruce (Picea mariana), indicating that the ratios of PGM uptake are about the same as those occurring in the bedrock. Plants growing on drift-covered diabase, known to have about 100 ppb PGM, contain up to 77 ppb Pt in ash, demonstrating the potential value of biogeochemical methods in helping to delineate platiniferous zones. Twigs of black spruce, jack pine, and labrador tea appear to be the optimum sample media in this environment.A rapid multi-element neutron activation analysis by direct irradiation of tissue permits measurement of 0.05 ppb Ir in dry material, or 2 ppb Ir in ashed samples. In view of the normally very low concentrations of Ir in plants, any detectable Ir probably indicates enrichment of PGM in the substrate.Comparison of several wet-chemical analytical methods indicates that the optimum (cost-effective) technique for detecting 1–2 ppb Pt, Pd, or Rh in 2-g samples of ash is by Te co-precipitation (following fusion and dissolution), and analysis by ICP-MS with sample introduction by electrothermal vaporization. However, care must be taken to ensure complete dissolution of all PGMs in the ash.     

Graphical diagnostics for logistic oil exploration models

This paper demonstrates how some recently developed graphical diagnostic techniques can be used to explore and improve the specification of logistic oil exploration models. Techniques are applied to information on 124 hydrocarbon exploration wells drilled between 1948 and 1963 into the B Division of the Mississippian (Osage Series) in a 13 by 13 square mile area of Stafford County, south-central Kansas.     

Council Approaches to Implementing Sustainability: a case of rearranging deck chairs on the Titanic?

Local government has a key role to play in implementing sustainability. Yet even councils attempting to address the issue of sustainability are often unacceptably slow and ineffective in their endeavours. This study investigates the approaches that councils currently take in implementing sustainability, as this may shed additional light on the slow progress of councils towards sustainability. The approaches of three New South Wales councils were examined and assessed using a model developed for the study that utilised the Ecological Footprint as the primary assessment tool. The model assessed three key aspects of council approaches to implementing sustainability: (1) the issues councils target for change; (2) the methods councils use to change behaviours; and (3) the clarity and holistic nature of their approaches. All three council approaches scored poorly against the model mainly as a result of the councils' failure to target the behaviours of their residents that are causing the greatest ecological harm. The major implication is that councils need to reconsider, and possibly overhaul, their approaches to implementing sustainability as these approaches are unlikely ever to achieve sustainability.     

Using lumped conceptual rainfall-runoff models to simulate daily isotope variability with fractionation in a nested mesoscale catchment

This paper presents 19 months of stable isotope (δ²H and δ¹⁸O) data to enhance understanding of water and solute transport at two spatial scales (2.3 km² and 122 km²) in the agricultural Lunan catchment, Scotland. Daily precipitation and stream isotope data, weekly lake and spring isotope data and monthly groundwater isotope data revealed important insights into flow pathways and mixing of water at both scales. In particular, a deeper groundwater flow path significantly contributes to total streamflow (25-50%). Upstream lake isotope dynamics, susceptible to evaporative fractionation, also appeared to have an important influence on the downstream isotope composition. This unique tracer data set facilitated the conceptualization of a lumped catchment-scale flow-tracer model. The incorporation of hydrological, mixing and fractionation processes based on these data improved simulations of the stream δ²H isotope response at the catchment outlet from 0.37 to 0.56 for the Nash-Sutcliffe statistic. The stable isotope data successfully aided model conceptualization and calibration in the quest for a simple water and solute transport model with improved representation of process dynamics.     

Keck and VLT AO observations and models of the uranian rings during the 2007 ring plane crossings

We present observations of the uranian ring system at a wavelength of 2.2 μm, taken between 2003 and 2008 with NIRC2 on the W.M. Keck telescope in Hawaii, and on 15–17 August 2007 with NaCo on the Very Large Telescope (VLT) in Chile. Of particular interest are the data taken around the time of the uranian ring plane crossing with Earth on 16 August 2007, and with the Sun (equinox) on 7 December 2007. We model the data at the different viewing aspects with a Monte Carlo model to determine: (1) the normal optical depth τ₀, the location, and the radial extent of the main rings, and (2) the parameter Aτ₀ (A is the particle geometric albedo), the location, and the radial plus vertical extent of the dusty rings. Our main conclusions are: (i) The brightness of the ? ring is significantly enhanced at small phase and ring inclination angles; we suggest this extreme opposition effect to probably be dominated by a reduction in interparticle shadowing. (ii) A broad sheet of dust particles extends inwards from the λ ring almost to the planet itself. This dust sheet has a vertical extent of ∼140 km, and Aτ₀ = 2.2 × 10⁻⁶. (iii) The dusty rings between ring 4 and the α ring and between the α and β rings are vertically extended with a thickness of ∼300 km. (iv) The ζ ring extends from ∼41,350 km almost all the way inwards to the planet. The main ζ ring, centered at ∼39,500 km from the planet, is characterized by Aτ₀ = 3.7 × 10⁻⁶; this parameter decreases closer to the planet. The ζ ring has a full vertical extent of order 800–900 km, with a pronounced density enhancement in the mid-plane. (v) The η_c ring is optically thin and less than several tens of km in the vertical direction. This ring may be composed of macroscopic material, surrounded by clumps of dust.     

Intensity determination by continuous thermal cycling

The advent of cryogenic magnetometers with which remanence can be measured at high sensitivity statically permits continuous thermal demagnetization and, in principle, a continuous version of the classic stepwise method of intensity determination. In the technique we have initially tried a field is trapped in the superconducting shield of the magnetometer throughout the experiment. The sample is then thermally cycled over progressively higher temperature ranges so that the incremental acquisition of partial thermoremanence (PTRM) and loss of the natural remanence (NRM) of the sample can be compared. In control experiments we have found that bad intensity estimates arise because the presence of the field causes difficulty in reliable separation of remanent and induced moments. A better approach is to heat and cool the sample in the required fields outside of the magnetometer and to insert it into the magnetometer only for the measurement of remanence. In this way it will be possible to cycle the sample to progressively higher temperatures and measure at elevated temperatures without cooling to room temperature, but one will measure remanence directly in zero field.     

Die Ladungsbilanz für eine verfeinerte Kristallstruktur von Stranskiit,Zn2 Cu(AsO4)2

Zusammenfassung Die Kristallstruktur des Stranskiits wurde mit neuen Meßdaten, die an einer aus Tsumeb stammenden Probe gewonnen worden waren, bis zuR=0,034 für 1239 unabhängige beobachtete Reflexe verfeinert. Von der verfeinerten Struktur wurde die Ladungsbilanz aufgestellt und besonders im Hinblick auf die Ladungsdeformation des Cu²⁺ diskutiert. Eine Mikrosondenanalyse derselben Probe ergab, daß die tatsächliche Zusammensetzung der angegebenen Formel entspricht.

---

Charge balance of a refined crystal structure of stranskiite, Zn₂Cu (AsO₄)₂

Summary The crystal structure of stranskiite was refined with new intensity data obtained from a specimen from Tsumeb toR=0.034 for 1234 observed independent reflections. The charge balance was calculated and discussed particularly with respect of the charge deformation of Cu²⁺. An electron probe microanalysis gave the result that the actual composition of the specimen corresponds to the given formula.

     

GIS in Participatory Research: Assessing the Impact of Landmines on Communities in North-west Cambodia

The view of GIS, adopted by many, as an undemocratic and divisive technology is perhaps most poignant in settings where financial and skills‐based resources are limited, notably in lower‐income countries. Where those countries are also recovering from a period of military conflict there would at first sight seem to be little opportunity for employing GIS as part of a socially‐sensitive approach to ‘development’. This paper explores the potential for using GIS in participatory approaches to gathering and analysing geographical information on human‐environment interactions in post‐conflict settings. We discuss empirical work from northwest Cambodia where GIS and participatory methods have been integrated to assess risk to local communities from landmines and to develop priorities for landmine clearance. In juxtaposing ‘official’, spatially‐referenced data with indigenous geographical knowledge in this study we seek to privilege meaningful geographical understandings over conventional notions of spatial ‘accuracy’. In so doing we carry out a Participatory Mine Impact Assessment (PMIA) to explore spatial activities among local populations in mine‐contaminated communities and to help identify improved strategies for returning refugees in re‐establishing livelihoods.     

Air and water entrapment in the vicinity of the water table

A laboratory tank was used to study entrapment of water in coarse sand lenses above the water table and of air in coarse sand lenses below the water table. Monitoring of these experiments involved a combination of visual inspection, measurement of moisture content, and measurement of air/water pressure. The medium consisted of coarse sand lenses with various degrees of vertical connectivity embedded within a fine sand matrix. Experiments were performed under conditions of both drainage (from a fully saturated medium) and imbibition. Observations during drainage included: (1) water was trapped in the coarse sand zones above the water table at heights significantly greater than anticipated from consideration of capillary rise in the coarse sand; (2) rapid drainage of these same coarse zones occurred when air penetrated into these zones through the surrounding fine sands; and (3) prior to the time of penetration of the coarse sand by air, water pressure in the coarse zone dropped significantly below atmospheric pressure. Observations during imbibition included: (1) entrapment of air within coarse sands below the water table, (2) the pore fluids in these zones varied spatially from predominantly air to predominantly water, and (3) pressure in the trapped air phase was significantly greater than pressure in the water phase in the surrounding fine sand. Overall, these results demonstrated significant sensitivity to the geometry of the coarse sand inclusions, particularly the vertical connectivity of the coarse sand lens.