Experimental constraints on Pt, Pd and Au partitioning and fractionation in silicate melt–sulfide–oxide–aqueous fluid systems at 800 °C, 150 MPa and variable sulfur fugacity

We have performed experiments to constrain the effect of sulfur fugacity (fS₂) and sulfide saturation on the fractionation and partitioning behavior of Pt, Pd and Au in a silicate melt–sulfide crystal/melt–oxide–supercritical aqueous fluid phase–Pt–Pd–Au system. Experiments were performed at 800 °C, 150 MPa, with oxygen fugacity (fO₂) fixed at approximately the nickel–nickel oxide buffer (NNO). Sulfur fugacity in the experiments was varied five orders of magnitude from approximately log fS₂ = 0 to log fS₂ = −5 by using two different sulfide phase assemblages. Assemblage one consisted initially of chalcopyrite plus pyrrhotite and assemblage two was loaded with chalcopyrite plus bornite. At run conditions pyrrhotite transformed compositionally to monosulfide solid solution (mss), chalcopyrite to intermediate solid solution (iss), and in assemblage two chalcopyrite and bornite formed a sulfide melt. Run-product silicate glass (i.e., quenched silicate melt) and crystalline materials were analyzed by using both electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry. The measured concentrations of Pt, Pd and Au in quenched silicate melt in runs with log fS₂ values ranging from approximately 0.0 to −5.0 do not exhibit any apparent dependence on fS₂. The measured Pt, Pd and Au concentrations in mss do vary as a function of fS₂. The measured Pt, Pd and Au concentrations in iss do not appear dependent on fS₂. The data suggest that fS₂, working in concert with fO₂, via the determinant role that these variables play in controlling the magmatic sulfide phase assemblage and the solubility of Pt, Pd and Au as lattice bound components in magmatic sulfide phases, is a controlling factor on the budgets of Pt, Pd and Au during the evolution of magmatic systems.     

Remote Sensing of Biologically Reworked Sediments: A Laboratory Experiment

The present study aims to test the application of remote sensing to address the impact of bioturbation on physical sediment properties. Therefore, a laboratory experiment was developed, using microcosms mimicking a marine intertidal water–sediment interface to test the influence of Corophium volutator densities on sediment properties. Three main variables (water content, clay content, and mean grain size) were measured in three treatments (no Corophium, 5,000 Corophium per square meter, and 20,000 Corophium per square meter) after 16 days of bioturbation. Results obtained with conventional—destructive—techniques showed a significant increase of water content and a significant, but small decrease of clay content in the presence of Corophium. The remote sensing technique detected the impact of Corophium on water content as an increase in absorption at 1,450 nm, but was not able to detect the animal impact on clay content. This study demonstrates that remote sensing data could be significantly modified by bioturbation activities and that remote sensing can be applied in the laboratory to address the impact of bioturbation on sediment properties. This possibly opens new perspectives for long-term experiments concerning the role of bioturbation on sedimentary processes.     

Computational validation of static and dynamic plate load testing

In this paper, the static load plate test and the dynamic load plate test by means of the light falling weight device are assessed utilizing numerical simulations. Simplified computational models of the tested subsoil and of the testing devices are developed, which capture the main effects of both the static and the dynamic load plate test. In extensive parametric studies, the impact of various subsoil conditions on the test results and several sources of error are evaluated and discussed. Computational test results of the static load plate test and of the dynamic load plate test are set in contrast to an effort to demonstrate the differences and the common features of the outcomes.     

Trends in heat-related mortality in the United States, 1975–2004

This study addresses the long-term trends in heat-related mortality across 29 US metropolitan areas from 1975 to 2004 to discern the spatial patterns and temporal trends in heat vulnerability. Mortality data have been standardized to account for population trends, and seasonal and interannual variability. On days when a city experienced an “oppressive” air mass, mean anomalous mortality was calculated, along with the likelihood that oppressive days led to a mortality response at least one standard deviation above the baseline value. Results show a general decline in heat-related mortality from the 1970s to 1990s, after which the decline seems to have abated. The likelihood of oppressive days leading to significant increases in mortality has shown less of a decline. The number of oppressive days has stayed the same or increased at most metropolitan areas. With US homes near saturation in terms of air-conditioning availability, an aging population is still significantly vulnerable to heat events.     

Correlates of vulnerability to climate-induced distribution changes in European avifauna: habitat, migration and endemism

Accelerated climatic change will alter species’ distributions substantially by the end of the 21st Century and studies modeling distribution change using Climatic Envelope Modeling (CEM) are increasingly crucial for understanding long-term biotic implications of climate change. However, most CEM studies generate either all-species means, which are of limited practical use, or copious species-specific predictions that make it hard to draw general conclusions about those groups most vulnerable. Intermediate analyses that are half way between these two extremes are necessary to establish the relative vulnerability of species to change based on factors that can be related directly to policy and practice, including habitat associations and ecological traits such as endemism and migration status. Here we use species-specific CEM data to analyse changes in geographical distribution, range size, and overlap between current and potential ranges, for all 431 bird species breeding regularly in Europe. Future range sizes are predicted to be 80 % of current range sizes, with an average overlap of 39 %. However, we show that change varies significantly according to habitat, current range size, and endemism status, with no differences according to migration status. Coastal, wetland and upland birds will be significantly worse off under CEM scenarios than birds associated with woodland, farmland and heathland, while urban birds and those using multiple habitats doing best. Birds with small ranges show more severe, and spatially more complex, distribution shifts. The identification of species groups most vulnerable to climate change means that CEM predictions can now be used to inform policy and management, especially where initiatives are based on species grouped according to such variables or where habitat-specific policies are in place.     

Mapping Cropping Practices Using MODIS Time Series: Harnessing the Data Explosion

The MODIS (Moderate Resolution Imaging Spectroradiometer) 250m EVI dataset provides a valuable ongoing means of characterising and monitoring changes in land use and resource condition. However the multiple factors that influence a time series of greenness data make the data difficult to analyse and interpret. Without prior knowledge, underlying models for time series in a given remote sensing image are often heterogeneous. So while conventional time series analysis methods such as wavelet transform and Fourier analysis may work well for part of the image, these models are either invalid or must be substantially re-parameterised for other parts of the image. To overcome these challenges we propose a new approach to distil information from earth observation time series data. The characteristics of a remote sensing time series are represented by a set of statistics (which we call coefficients) selected to correspond to the dynamics of a natural system. To ensure the coefficients are robust and generic, statistics are calculated independently by applying statistical models with less complexity on shorter segments within the time series. An International Standards Organization (ISO) Land Cover classification (Jansen 2000) was generated for cropping regions in the Gwydir and Namoi catchments, in Australia. Areas identified in the classification as irrigated and rain fed cropping were analysed using a tailored time series analysis tool. The crop analysis tool identifies time series features such as the number and duration of fallow periods, crop timing, presence/absence of a crop during a year for a specific growing season. This information is combined with paddock boundaries derived from Landsat imagery to provide detailed year-by-year insight into cropping practices in the Gwydir and Namoi catchments.     

Temporal distributions of anthropogenic Al, Zn and Pb in Hong Kong Porites coral during the last two centuries

A 182-year long record of trace metal concentrations of aluminum, zinc and lead was reconstructed from a massive Porites coral skeleton from southeastern Hong Kong to evaluate the impacts of anthropogenic activity on the marine environment. Zn/Ca and Pb/Ca ratios fluctuate synchronously from the early 19th century to the present, indicating that the marine environment has been anthropogenically influenced since industrialization. Additionally, land reclamation, mining, and ship building activities are recorded by elevated Al/Ca ratios from 1900 to 1950. The coral record indicates that high levels of Zn, Pb and Al occur coincidentally with local wars, and may have contributed to partial colony mortality. Pb/Ca does not correlate well with hemispheric proxy records after 1950, indicating that coastal corals may be recording local rather than hemispheric contamination. Pb/Ca levels in Hong Kong, Guangdong and Hainan corals imply a continuous supply of Pb-based contamination to southern China not reflected in hemispheric signals.     

Influences of subsurface heterogeneity and vegetation cover on soil moisture, surface temperature and evapotranspiration at hillslope scales

Physical processes are at the root of determining hydrologic response at all scales. Here, the physical mechanisms linking (1) subsurface heterogeneities to soil moisture and (2) resulting land-surface energy feedbacks to the atmosphere, are examined at the hillslope scale using a fully coupled surface-subsurface-land-surface model, ParFlow. A hillslope with a heterogeneous subsurface and uniform topography was modeled numerically using summer atmospheric conditions and a single precipitation event under controlled boundary conditions in order to isolate the contribution of hydraulic conductivity to land-surface hydrological processes and energy interactions. Patterns of subsurface hydraulic conductivity are shown to govern soil-moisture distribution at the hillslope scale following precipitation. This variability in soil moisture is closely linked to the variability in land-surface energy feedbacks. The role that vegetation plays in subsurface soil moisture and land energy communications is also examined. Results show that hillslope soil moisture variation is first established by patterns in vertical hydraulic conductivity, while later on in the dry-down period, vegetation exerts greater control on the land-surface energy fluxes and controls the rate of hillslope dry down. Furthermore, as compared to bare-soil simulations, grass-cover simulations show an increase in near-surface soil moisture despite water up-take along the rooting depth.     

Measuring Earth orientation with the global positioning system

Summary A globally distributed network of high-precision receivers which obtain data from the full Global Positioning System (GPS) configuration of 18 or more satellites may soon become an efficient and economical method for the rapid determination of short-term variations in Earth orientation. A covariance analysis has been performed to evaluate the errors associated with GPS monitoring of Earth orientation. Earth orientation parameters were modeled either as constants over observing windows of various lengths, or as stochastic process-noise variables. The sensitivity of Earth orientation estimates to systematic errors in selected model parameters was also examined. GPS measurements appear to be highly competitive with those from other techniques, and have the potential to generate nearly continuous centimeter-level Earth orientation information to aid both spacecraft navigation and the study of high-frequency Earth orientation-related processes.