Spatially Explicit Analysis of Metal Transfer to Biota: Influence of Soil Contamination and Landscape

Concepts and developments for a new field in ecotoxicology, referred to as “landscape ecotoxicology,” were proposed in the 1990s; however, to date, few studies have been developed in this emergent field. In fact, there is a strong interest in developing this area, both for renewing the concepts and tools used in ecotoxicology as well as for responding to practical issues, such as risk assessment. The aim of this study was to investigate the spatial heterogeneity of metal bioaccumulation in animals in order to identify the role of spatially explicit factors, such as landscape as well as total and extractable metal concentrations in soils. Over a smelter-impacted area, we studied the accumulation of trace metals (TMs: Cd, Pb and Zn) in invertebrates (the grove snail Cepaea sp and the glass snail Oxychilus draparnaudi) and vertebrates (the bank vole Myodes glareolus and the greater white-toothed shrew Crocidura russula). Total and CaCl2-extractable concentrations of TMs were measured in soils from woody patches where the animals were captured. TM concentrations in animals exhibited a high spatial heterogeneity. They increased with soil pollution and were better explained by total rather than CaCl2-extractable TM concentrations, except in Cepaea sp. TM levels in animals and their variations along the pollution gradient were modulated by the landscape, and this influence was species and metal specific. Median soil metal concentrations (predicted by universal kriging) were calculated in buffers of increasing size and were related to bioaccumulation. The spatial scale at which TM concentrations in animals and soils showed the strongest correlations varied between metals, species and landscapes. The potential underlying mechanisms of landscape influence (community functioning, behaviour, etc.) are discussed. Present results highlight the need for the further development of landscape ecotoxicology and multi-scale approaches, which would enhance our understanding of pollutant transfer and effects in ecosystems

WEST full tungsten operation with an ITER grade divertor

The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation in a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with a focus on testing the ITER actively cooled W divertor in tokamak conditions. Following the successful completion of phase 1 (2016-2021), phase 2 started in December 2022 with the lower divertor made entirely of actively cooled ITER-grade tungsten mono-blocks. A boronization prior the first plasma attempt allowed for a smooth startup with the new divertor. Despite the reduced operating window due to tungsten, rapid progress has been made in long pulse operation, resulting in discharges with a pulse length of 100 s and an injected energy of around 300 MJ per discharge. Plasma startup studies were carried out with equatorial boron nitride limiters to compare them with tungsten limiters, while Ion Cyclotron Resonance Heating assisted startup was attempted. High fluence operation in attached regime, which was the main thrust of the first campaigns, already showed the progressive build up of deposits and appearance of dust, impacting the plasma operation as the plasma fluence increased. In total, the cumulated injected energy during the first campaigns reached 43 GJ and the cumulated plasma time exceeded 5 h. Demonstration of controlled X-Point Radiator regime is also reported, opening a promising route for investigating plasma exhaust and plasma-wall interaction issues in more detached regime. This paper summarises the lessons learned from the manufacturing and the first operation of the ITER-grade divertor, describing the progress achieved in optimising operation in a full W environment with a focus on long pulse operation and plasma wall interaction

Sustaining the future through virtual worlds

Virtual worlds (VWs) continue to be used extensively in Australia and New Zealand higher education institutions although the tendency towards making unrealistic claims of efficacy and popularity appears to be over. Some educators at higher education institutions continue to use VWs in the same way as they have done in the past; others are exploring a range of different VWs or using them in new ways; whilst some are opting out altogether. This paper presents an overview of how 46 educators from some 26 institutions see VWs as an opportunity to sustain higher education. The positives and negatives of using VWs are discussed

Entrainment in plane turbulent pure plumes

AbstractTurbulent jets and plumes are commonly encountered in industrial and natural environments; they are, for example, key processes during explosive eruptions. They have been the objects of seminal works on turbulent free shear flows. Their dynamics is often described with the concept of the so-called entrainment coefficient, $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\alpha$, which quantifies entrainment of ambient fluid into the turbulent flow. This key parameter is well characterized for axisymmetric jets and plumes, but data are scarcer for turbulent planar plumes and jets. The data tend to show that the Gaussian entrainment coefficient in plane pure plumes is about twice the value for plane pure jets. In order to confirm and to explain this difference, we develop a model of entrainment in turbulent plane jets and plumes taking into account the effect of buoyancy on entrainment, as a function of the shape of the velocity, buoyancy and turbulent shear stress profiles. We perform new experiments to better characterize the rate of entrainment in plane pure plumes and to constrain the values of the model parameters. Comparison between theory and experiments shows that the enhancement of entrainment in plane turbulent pure plumes relative to plane turbulent pure jets is well explained by the contribution of buoyancy.</jats:p

Second-order model of entrainment in planar turbulent jets at low Reynolds number

International audienceTurbulent jets and plumes are commonly encountered in natural and industrial environments, and have been the objects of seminal works on turbulent free shear flows. The dynamics of turbulent jets is most often described as a function of the so-called entrainment coefficient, α, which quantifies the entrainment of ambient fluid into the jets. This key parameter has been determined in numerous and extensive experimental, numerical, and theoretical studies of axisymmetric jets. However, data remain scarce on turbulent planar jets. Available studies have shown that at low distance from the source, α increases with the source Reynolds number, and that α increases with distance from the source for large source Reynolds number. But no link has been made between these two kinds of observation so far. To study the relative influence of source Reynolds number, Re0, and distance from source on entrainment in planar turbulent jets, we perform new experiments at low Re0 (between 59 and 424) with three different aspect ratio (185, 370, and 925) and at small and large distances from the source. Our experimental results show no systematic variations of α as a function of Re0 or as a function of the distance from the source. To interpret these observations, we develop a formalism based on the flow velocity profiles, which yields an expression of α as a function of the evolution of the Reynolds shear stress and of the turbulent fluctuations of the radial and vertical velocities. We obtain that the main contribution to entrainment is related to the turbulent shear stress, and that second-order fluctuations of the velocity account for the observed variations of α. The evolution to a fully self-similar regime in which these fluctuations are fully negligible is too slow at small Re0 for this regime to be observed in our experiments, even at the largest distances from the source