Contaminant dispersion at the rehabilitated Mary Kathleen uranium mine, Australia

This study reports on the transfer of contaminants from waste rock dumps and mineralised ground into soils, sediments, waters and plants at the rehabilitated Mary Kathleen uranium mine in semi-arid northwest Queensland. Numerous waste rock dumps were partly covered with benign soil and the open pit mine was allowed to flood. The mineralised and waste calc-silicate rock in the open pit and dumps has major (>1 wt%) Ca, Fe and Mg, minor (>1,000 ppm) Ce, La, Mn, P and S, subminor (>100 ppm) Ba, Cu, Th and U, and trace (<100 ppm) As, Ni, Pb, Y and Zn values. Consequently, chemical and physical weathering processes have acted on waste rock and on rock faces within the open pit, mobilising many elements and leading to their dispersion into soils, stream sediments, pit water and several plant species. Chemical dispersion is initiated by sulfide mineral breakdown, generation of sulfuric acid and formation of several soluble, transient sulfate minerals as evaporative efflorescent precipitates. Radiation doses associated with the open pit average 5.65 mSv year⁻¹; waste dumps commonly have lower values, especially where soil-covered. Surface pit water is slightly acid, with high sulfate values accompanied by levels of U, Cu and Ni close to or above Australian water guideline values for livestock. Dispersion of U and related elements into soils and stream sediments occurs by physical (erosional) processes and from chemical precipitation. Plants growing in the mine void, on waste dumps and contaminated soil display evidence of biological uptake of U, LREE, Cu and Th and to a lesser degree of As, Ni, Pb, Y and Zn, with values being up to 1–2 orders of magnitude above background sites for the same species. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical and chemical mobility, including transfer into plants.     

Attaining m s<Superscript>−1</Superscript> level intrinsic Doppler precision with RHEA,a low-cost single-mode spectrograph

We present RHEA, a compact and inexpensive single-mode spectrograph which is built to exploit the capabilities of modest-sized telescopes in an economic way. The instrument is fed by up to seven optical waveguides with the aim of achieving an efficient and modal-noise-free unit, suitable for attaining extreme Doppler precision. The cross-dispersed layout features a wavelength coverage from 430–650 nm, with spectral resolution of R ～75,000. When coupled to small telescopes using fast tip/tilt control, our instrument is well-suited to sensitive spectroscopy. Example science cases are accurate radial velocity studies of low to intermediate-mass giant stars with the purpose of searching for giant plants and using asteroseismology to simultaneously measure the host star parameters. In this paper we describe the final instrument design and present first results from testing the internal stability.     

A spring and wooded habitat at FLK Zinj and their relevance to origins of human behavior

The 1959 discovery of the hominin fossil Zinjanthropus boisei brought the world's attention to the rich records at Olduvai Gorge, Tanzania. Subsequent excavations of archaeological level 22 (FLK Zinj) Bed I uncovered remains of Homo habilis and a high-density collection of fossils and Oldowan stone tools. The occurrence of this unusual collection of bones and tools at this specific location has been controversial for decades. We present paleoecological data that provide new insights into the origin of FLK Zinj. Our recent excavations 200 m north of the site uncovered a 0.5-m-thick tufa mound draped by Tuff IC, in the same stratigraphic horizon as level 22. Stable isotope analyses indicate that the carbonates were deposited by a freshwater spring. Phytolith analysis of the waxy clay under Tuff IC revealed abundant woody dicotyledon and palm phytoliths, indicating that the site was wooded to densely wooded. The time equivalency and close physical proximity of the two environments indicate the two are related. This study has provided the first documented evidence of springs in Bed I and these data have important implications for the interpretation of hominin behavior in meat acquisition and the ongoing debate on scavenging versus hunting.     

Eclogite-facies fluid infiltration: constraints from δ18O zoning in garnet

In situ analysis reveals that eclogite-facies garnets are zoned in δ¹⁸O with lower values in the core and rims that are ~1.5 to 2.5 ‰ higher. This pattern is present in 9 out of 12 garnets analyzed by SIMS from four orogenic eclogite terranes, and correlates with an increase in the mole fraction of pyrope and Mg/Fe ratio from core to rim, indicating prograde garnet growth. At the maximum temperatures and the time-scales experienced by these garnets, calculated intragranular diffusion distances for oxygen are small (<5 μm), indicating that δ¹⁸O records primary growth zoning and not diffusive exchange. The oxygen isotope gradients are larger than could form due to temperature changes during closed-system mineral growth. Thus, gradients reflect the compositions of fluids infiltrating during prograde metamorphism. Values of δ¹⁸O in garnet cores range from ?1 to 15 ‰, likely preserving the composition of the eclogite protoliths. Two garnet cores from the Almenningen eclogite in the Western Gneiss Region, Norway, have δ¹⁸O ~?1 ‰ and are the first negative δ¹⁸O eclogites identified in the region. In contrast with orogenic eclogites, seven high δ¹⁸O garnets (>5 ‰) from two kimberlites are homogeneous in δ¹⁸O, possibly due to diffusive exchange, which is possible for prolonged periods at higher mantle temperatures. Homogeneity of δ¹⁸O in garnets outside the normal mantle range (5–6 ‰) may be common in kimberlitic samples.     

Two occurrences of ultramafic hornfels in the Biggenden Beds,southeastern Queensland

Ultramafic hornfelses containing the assemblages hornblende + olivine + spinel + magnetite, and clinopyroxene + olivine + spinel + magnetite, are reported from two localities in the Biggenden Beds in southeastern Queensland. They are associated with mafic hornfelses in the contact metamorphic aureoles of the Mungore Adamellite and the Wateranga Gabbro. Chemical composition and minerology of the olivine + amphibole + spinel + magnetite hornfelses suggest that they represent metamorphosed picritic rocks, or possibly, altered serpentinites (blackwall rocks), whereas the clinopyroxene + olivine + spinel + magnetite hornfelses are interpreted as metamorphosed altered clinopyroxene‐rich picritic rocks. Cr‐Fe spinel relations in the hornfelses indicate partial homogenisation of primary chromian spinel with secondary magnetite ± ferrichromite during contact metamorphism.     

Infiltration of fine sediment into a coarse mobile bed: a phenomenological study

Experiments were undertaken to study the nature of granular interaction in running water by examining the influence of fine grain inputs to a coarser sediment bed with a mobile surface. Video recordings of grain sorting by both kinetic sieving and spontaneous percolation are used to diagnose the critical processes controlling the overall bed response. Kinetic sieving takes place in the mobile bed surface, with the finer sediment moving to the bottom of the bedload transport layer at the interface with the underlying quasi‐static coarse bed. We show that the behavior at this interface dictates how a channel responds to a fine sediment input. If, by spontaneous percolation, the fine sediment is able to infiltrate into the underlying quasi‐static bed, the total transport increases and the channel degrades. However, if the fine sediment input rate exceeds the transport capacity or is geometrically unable to infiltrate into the underlying bed, it forms a quasi‐static layer underneath the transport layer that inhibits entrainment from the underlying bed, resulting in aggradation and an increase in bed slope. Copyright © 2016 John Wiley & Sons, Ltd.     

A Numerical Case Study of the Implications of Secondary Circulations to the Interpretation of Eddy-Covariance Measurements Over Small Lakes

The CASES-99 experimental data are used to analyze turbulence behaviour under a range of stable conditions using an adaptive method based on Hilbert spectral analysis. The characteristic scales of intrinsic mode functions vary between different stratifications. The second-order Hilbert marginal spectra display clear separation between fine-scale turbulence and large-scale motions. After removing the large-scale motions, the statistical characteristics of the reconstructed signals confirm the distinction of different stratifications in the fine-scale range. The correlation coefficient analyses reveal that the Hilbert spectral analysis method separates turbulence from large-scale motions in the stable boundary layer.     

Adaptive Delta Management for flood risk and resilience in Dordrecht,The Netherlands

Many countries across the world are experiencing strict austerity measures due to the economic crisis. As a consequence, public financing for stand-alone adaptation to flooding and drought will become scarcer in the (near) future, and this hampers the pursuit of resilience (i.e. the ability to remain functioning under a range of hazard magnitudes). In such times, key challenges for adaptation are further complicated by weaker investment dynamics and an increased tendency to ‘work in silos’. These are: to minimise regret with respect to maladaptation, which results from over- or under-investment in water hazard management; to exploit the opportunities for mainstreaming adaptation to flooding and drought into other investment agendas; and to deliver multiple benefits for society and the economy, such as increased biodiversity, liveability and competitiveness. These common challenges drive the best way in which to adapt to uncertain climate and socio-economic changes. In the Netherlands, the Delta Programme has developed and applied a structured and well-defined approach (called Adaptive Delta Management) for including and acting upon uncertainty around these future changes. This approach allows for greater transparency to decision-makers and stakeholders, because it adheres to four specific steps for strategy development. This paper presents the current understanding of Adaptive Delta Management and an illustration of the approach for the management of flood risk and resilience in Dordrecht. It examines the added value and limitations of Adaptive Delta Management concerning its application in the context of the Delta Programme, with a specific emphasis on the lessons learned from Dordrecht.     

Comparing catchment hydrologic response to a regional storm using specific conductivity sensors

A better understanding of stormwater generation and solute sources is needed to improve the protection of aquatic ecosystems, infrastructure, and human health from large runoff events. Much of our understanding of water and solutes produced during stormflow comes from studies of individual, small headwater catchments. This study compared many different types of catchments during a single large event to help isolate landscape controls on streamwater and solute generation, including human‐impacted land cover. We used a distributed network of specific electrical conductivity sensors to trace storm response during the post‐tropical cyclone Sandy event of October 2012 at 29 catchments across the state of New Hampshire. A citizen science sensor network, Lotic Volunteer for Temperature, Electrical Conductivity, and Stage, provided a unique opportunity to investigate high‐temporal resolution stream behavior at a broad spatial scale. Three storm response metrics were analyzed in this study: (a) fraction of new water contributing to the hydrograph; (b) presence of first flush (mobilization of solutes during the beginning of the rain event); and (c) magnitude of first flush. We compared new water and first flush to 64 predictor attributes related to land cover, soil, topography, and precipitation. The new water fraction was positively correlated with low and medium intensity development in the catchment and riparian buffers and with the precipitation from a rain event 9 days prior to Sandy. The presence of first flush was most closely related (positively) to soil organic matter. Magnitude of first flush was not strongly related to any of the catchment variables. Our results highlight the potentially important role of human landscape modification in runoff generation at multiple spatial scales and the lack of a clear role in solute flushing. Further development of regional‐scale in situ sensor networks will provide better understanding of stormflow and solute generation across a wide range of landscape conditions.     

Catchment scale geostatistical simulation and uncertainty of soil erodibility using sequential Gaussian simulation

Soil erodibility (K) affects sediment delivery to streams and needs to be appropriately quantified and interpolated as a fundamental geographic variable for implementing suitable catchment management and conservation practices. The spatial distribution of K for erosion modelling at non-sampling grid locations has traditionally been estimated using interpolation algorithms such as kriging which do not adequately represent the uncertainty of estimates. These methods cause smoothing effects through overestimating the low values and underestimating the large values. In this study observed values were used to implement a sequential Gaussian simulation (SGS) procedure to evaluate the certainty of modelled data. Soil erodibility values were computed using 41 soil samples taken from the top 10 cm soil layer regularly distributed across four catchments, 367–770 ha in area, within Kangaroo River State forest, New South Wales (NSW). One hundred realisations were applied in the simulation process to provide spatial uncertainty and error estimates of soil erodibility. The results indicated that values simulated by the SGS algorithm produced similar K values for the neighbouring cells. At the pixel level, the SGS approach generated a reliable estimation of soil erodibility in most areas. Spatial variation of the K factor in this study was strongly related to soil landscape differences across the catchments; within catchments slope gradient did not have a substantial impact on the numerical values of the K factor using pixel-by-pixel comparisons of raster grid maps.