Behavior of epidote at high pressure and high temperature: a powder diffraction study up to 10 GPa and 1,200 K

The thermo-elastic behavior of a natural epidote [Ca_1.925 Fe_0.745Al_2.265Ti_0.004Si_3.037O₁₂(OH)] has been investigated up to 1,200 K (at 0.0001 GPa) and 10 GPa (at 298 K) by means of in situ synchrotron powder diffraction. No phase transition has been observed within the temperature and pressure range investigated. P–V data fitted with a third-order Birch–Murnaghan equation of state (BM-EoS) give V ₀ = 458.8(1)ų, K _T0 = 111(3) GPa, and K′ = 7.6(7). The confidence ellipse from the variance–covariance matrix of K _T0 and K′ from the least-square procedure is strongly elongated with negative slope. The evolution of the “Eulerian finite strain” vs “normalized stress” yields Fe(0) = 114(1) GPa as intercept values, and the slope of the regression line gives K′ = 7.0(4). The evolution of the lattice parameters with pressure is slightly anisotropic. The elastic parameters calculated with a linearized BM-EoS are: a ₀ = 8.8877(7) Å, K _T0(a) = 117(2) GPa, and K′(a) = 3.7(4) for the a-axis; b ₀ = 5.6271(7) Å, K _T0(b) = 126(3) GPa, and K′(b) = 12(1) for the b-axis; and c ₀ = 10.1527(7) Å, K _T0(c) = 90(1) GPa, and K’(c) = 8.1(4) for the c-axis [K _T0(a):K _T0(b):K _T0(c) = 1.30:1.40:1]. The β angle decreases with pressure, β_P(°) = β_P0 −0.0286(9)P +0.00134(9)P ² (P in GPa). The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α₀ + α₁ T ^−1/2. The refined parameters for epidote are: α₀ = 5.1(2) × 10⁻⁵ K⁻¹ and α₁ = −5.1(6) × 10⁻⁴ K^1/2 for the unit-cell volume, α₀(a) = 1.21(7) × 10⁻⁵ K⁻¹ and α₁(a) = −1.2(2) × 10⁻⁴ K^1/2 for the a-axis, α₀(b) = 1.88(7) × 10⁻⁵ K⁻¹ and α₁(b) = −1.7(2) × 10⁻⁴ K^1/2 for the b-axis, and α₀(c) = 2.14(9) × 10⁻⁵ K⁻¹ and α₁(c) = −2.0(2) × 10⁻⁴ K^1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α₀(a): α₀(b): α₀(c) = 1 : 1.55 : 1.77. The β angle increases continuously with T, with β_T(°) = β_T0 + 2.5(1) × 10⁻⁴ T + 1.3(7) × 10⁻⁸ T ². A comparison between the thermo-elastic parameters of epidote and clinozoisite is carried out.     

The BEAM-project: prediction and assessment of mixture toxicities in the aquatic environment

Freshwater and marine ecosystems are exposed to various multi-component mixtures of pollutants. Nevertheless, most ecotoxicological research and chemicals regulation focus on hazard and exposure assessment of individual substances only, the problem of chemical mixtures in the environment is ignored to a large extent. In contrast, the assessment of combination effects has a long tradition in pharmacology, where mixtures of chemicals are specifically designed to develop new products, e.g. human and veterinary drugs or agricultural and non-agricultural pesticides. In this area, two concepts are frequently used and are thought to describe fundamental relationships between single substance and mixture effects: Independent Action (Response Addition) and Concentration Addition. The question, to what extent these concepts may also be applied in an ecotoxicological and regulatory context may be considered a research topic of major importance, as the concepts would allow to make use of already existing single substance toxicity data for the predictive assessment of mixture toxicities. Two critical knowledge gaps are identified: (a) There is a lack of environmental realism, as a huge part of our current knowledge about the applicability of the concepts is restricted to artificial situations with respect to mixture composition or biological effect assessment. (b) The knowledge on what exactly is needed for using the concepts as tools for the predictive mixture toxicity assessment is insufficient. Both gaps seriously hamper the necessary, scientifically sound consideration of mixture toxicities in a regulatory context.In this paper, the two concepts will be briefly introduced, the necessity of considering the toxicities of chemical mixtures in the environment will be demonstrated and the applicability of Independent Action and Concentration Addition as tools for the prediction and assessment of mixture toxicities will be discussed. An overview of the specific aims and approaches of the BEAM project to fill in the identified knowledge gaps is given and first results are outlined.     

Controls on event runoff coefficients in the eastern Italian Alps

Analyses of event runoff coefficients provide essential insight on catchment response, particularly if a range of catchments and a range of events are compared by a single indicator. In this study we examine the effect of climate, geology, land use, flood types and initial soil moisture conditions on the distribution functions of the event runoff coefficients for a set of 14 mountainous catchments located in the eastern Italian Alps, ranging in size from 7.3 to 608.4 km². Runoff coefficients were computed from hourly precipitation, runoff data and estimates of snowmelt. A total of 535 events were analysed over the period 1989–2004. We classified each basin using a “permeability index” which was inferred from a geologic map and ranged from “low” to “high permeability”. A continuous soil moisture accounting model was applied to each catchment to classify ‘wet’ and ‘dry’ initial soil moisture conditions. The results indicate that the spatial distribution of runoff coefficients is highly correlated with mean annual precipitation, with the mean runoff coefficient increasing with mean annual precipitation. Geology, through the ‘permeability index’, is another important control on runoff coefficients for catchments with mean annual precipitation less than 1200 mm. Land use, as indexed by the SCS curve number, influences runoff coefficient distribution to a lesser degree. An analysis of the runoff coefficients by flood type indicates that runoff coefficients increase with event snowmelt. Results show that there exists an intermediate region of subsurface water storage capacity, as indexed by a flow–duration curve-based index, which maximises the impact of initial wetness conditions on the runoff coefficient. This means that the difference between runoff coefficients characterised by wet and dry initial conditions is negligible both for basins with very large storage capacity and for basins with small storage capacity. For basins with intermediate storage capacities, the impact of the initial wetness conditions may be relatively large.     

Emerging trends in urbanizing Palestine: neglected city-builders beyond the occupation

In this article, we draw attention to trends in land transformation in the West Bank since the Second Intifada, after which a surge of investment from Gulf countries entered Palestine, almost exclusively in the West Bank. The occupied Palestinian territories have attracted a great deal of attention from media and academics, yet the vast majority of scholarship focuses on the conflict and the variety of social, economic, and political repercussions of the on-going Israeli occupation. While the occupation has undeniably serious impacts on every aspect of life for Palestinians, the near-exclusive focus on the conflict means that significant new trends, such as urban mega-developments and emerging market-based urbanisation processes, have been largely overlooked. We outline three directions for future research: the assemblage of “neglected city-builders” shaping current urbanization processes in Palestine; the ideas, policies, and norms circulating in the West Bank; and the social, spatial, economic, and other impacts of these new urban developments.     

Families of periodic orbits in Hill’s problem with solar radiation pressure: application to Hayabusa 2

This work studies periodic solutions applicable, as an extended phase, to the JAXA asteroid rendezvous mission Hayabusa 2 when it is close to target asteroid 1999 JU3. The motion of a spacecraft close to a small asteroid can be approximated with the equations of Hill’s problem modified to account for the strong solar radiation pressure. The identification of families of periodic solutions in such systems is just starting and the field is largely unexplored. We find several periodic orbits using a grid search, then apply numerical continuation and bifurcation theory to a subset of these to explore the changes in the orbit families when the orbital energy is varied. This analysis gives information on their stability and bifurcations. We then compare the various families on the basis of the restrictions and requirements of the specific mission considered, such as the pointing of the solar panels and instruments. We also use information about their resilience against parameter errors and their ground tracks to identify one particularly promising type of solution.     

Latitudinal variation in the aerial/aquatic ratio of oxygen consumption of a supratidal high rocky‐shore crab

The colonisation of the terrestrial environment by crustaceans is more apparent in tropical latitudes because of the high diversity of semi‐terrestrial and terrestrial crabs. However, in temperate regions there are also great numbers of crustaceans that inhabit ecological niches at the water–air interface. Grapsidae crabs (Decopoda) are especially important in studies of water‐to‐land transition as the family contains species occupying the intertidal and adjacent regions. A way to evaluate the ability of intertidal invertebrates to breathe air is to measure the aerial/aquatic oxygen consumption ratio. The objective of this study was to test the effect of thermal variation on the aquatic and aerial metabolism. We selected as study model the decopoda crab Cyclograpsus cinereus Dana and utilised five populations of the species spread over 2000 km along the Chilean coast. To determine the compensation capacity in respiration with respect to latitude, we evaluated metabolic rate at the same temperature in a common garden design in the laboratory, to examine the extent to which variation in crab physiology is environmentally determined. Whereas in our study, m_b (body mass) varied significantly with latitude, the difference in mass‐independent metabolism both in air and water persisted, indicating that observed differences in MR (Metabolic Rate) were not an effect of differences in body size. We demonstrated that C. cinereus is able to breath oxygen from air and water as expected for an amphibious crab. Almost all the studied populations of C. cinereus show a aerial/aquatic metabolism ratio near 1. The pattern found indicates an increase in metabolic rate, both aerial and aquatic, in low latitudes and therefore does not support the latitudinal compensation hypothesis for temperate habitats. Finally, these kinds of studies are required to make the necessary link between ecological physiology and macroecology and to help develop a global understanding of organismal function in marine systems.     

Robustness and the Paradox of Bridging Organizations: The Exit Problem in Regional Water Governance Networks in Central America

Bridging organizations facilitate a range of governance processes, including cooperation and social learning, and are theorized to be a key component of robust governance systems. In this article, we use node removal simulations to test structural hypotheses of robustness in a regional water governance network in Central America. We investigate the response of network measures supporting core governance processes to the targeted removal of bridging organizations and other actors, which we compare to random and centrality-based simulations. The results indicate removing bridging organizations has a greater impact on the network than any other type of actor, suggesting bridging organizations are critical to the robustness of the governance system. Furthermore, network structures supporting cooperation may be less robust than structures facilitating social learning. We conclude with policy implications of the research findings as they relate to the exit problem in governance systems with a large presence of international development actors.     

Roles of methane and carbon dioxide in geological processes on Mars

We discuss in this paper possible roles of methane and carbon dioxide in geological processes on Mars. These volatiles in the martian crust may migrate upward from their sources either directly or via various traps (structural, sedimentary, ground ice, gas hydrates). They are then likely emitted to the atmosphere by seepage or through diverse vent structures. Though gas hydrates have never been directly detected on Mars, theoretical studies favor their presence in the crust and polar caps; they could have played an important role as significant gas reservoirs in the subsurface. The martian gas hydrates would possibly be a binary system of methane and carbon dioxide occupying clathrate cavities. Landforms such as mud volcanoes with well-known linkage to gas venting are extensively distributed on Earth, and methane is the primary gas involved. Thus, identification of these landforms on Mars could suggest that methane and possibly carbon dioxide have contributed to geological processes of the planet. For example, we present a newly identified field in Chryse Planitia where features closely resembling terrestrial mud volcanoes occur widely, though with no observable activity. We also present results of a preliminary search for possible recent or present-day, methane-emission zones in the regions over which enrichments of atmospheric methane have been reported.     

Mechanisms linking active rock glaciers and impounded surface water formation in high‐mountain areas

Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier–marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self‐potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub‐surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice‐free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub‐surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly‐fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically‐complex hydrological settings which could be possibly transferred to wider scales of investigation. Copyright © 2017 John Wiley & Sons, Ltd.