Application of a novel cascade-routing and reinfiltration concept with a Voronoi unstructured grid in MODFLOW 6, for an assessment of surface-water/groundwater interactions in a hard-rock catchment (Sardon,Spain)

Hydrogeology Journal - Integrated hydrological modelling (IHM) can reliably characterize surface-water/groundwater interactions in complex hydrological systems such as hard-rock systems (HRS),...     

Intense warm and saline upper ocean inflow in the southern Bay of Biscay in autumn–winter 2006–2007

Unusually warm and saline near-surface inflow was observed in the southern Bay of Biscay (Northeast Atlantic) in autumn–winter 2006–2007. These anomalies were swiftly entrained eastward through the Iberian Poleward Current flowing over the slope and shelf. Here, we present a quasi-synoptic three dimensional view of this event, which started as early as August 2006. In situ hydrological and Lagrangian measurements were used to describe its characteristics. The warm anomaly was surface intensified over the shelf, with surface temperature above 17 °C, a monthly anomaly over 1 °C compared to the 1994–2006 period. The saline anomaly was maximum around 100–200 m deep, over the upper slope, with values above 35.9 psu. Slope and shelf were seen to exhibit a complex structure of eastward (poleward) and westward (equatorward) currents. Maximum currents, observed near surface, over the upper slope in the eastern part of the Bay of Biscay, were determined to exceed 1.3 m s^?1. This current system eventually became unstable, thereby promoting strong exchange of properties between coastal and deep ocean. The event was coincident with abnormal southerly wind conditions west of Iberia in autumn 2006, and with the unusually warm autumn–winter weather over western Europe. A dynamical analysis relying on wind forcing west and north of Iberia is proposed.     

gvSOS: A New Client for the OGC® Sensor Observation Service Interface Standard

A key problem with sensor networks is achieving interoperability between different networks potentially built using different software and hardware platforms. Services interfaced by the Open Geospatial Consortium (OGC) specifications allow GIS clients to access geospatial data without knowing the details about how these data are gathered or stored. Currently, OGC is working on a set of interoperable interfaces and metadata encodings known as Sensor Web Enablement (SWE) that enables the integration of heterogeneous sensor systems and measurements into geospatial information infrastructures. In this article we present the implementation of gvSOS, a new module for gvSIG to connect to Sensor Observation Services (SOS). The gvSOS client module allows gvSIG users to interact with SOS servers, displaying the information gathered by sensors as a layer composed by features. We present the software engineering development process followed to build the module. For each step of the process we specify the main obstacles found during the development such as restrictions of the gvSIG architecture, inaccuracies in the OGC specifications, and a set of common problems found in current SOS server implementations available on the Internet. For most of the problems found we propose a solution, or at least we present a path that might lead to it.     

Structure of heavy metal sorbed birnessite. Part III: Results from powder and polarized extended X-ray absorption fine structure spectroscopy

The local structures of divalent Zn, Cu, and Pb sorbed on the phyllomanganate birnessite (Bi) have been studied by powder and polarized extended X-ray absorption fine structure (EXAFS) spectroscopy. Metal-sorbed birnessites (MeBi) were prepared at different surface coverages by equilibrating at pH 4 a Na-exchanged buserite (NaBu) suspension with the desired aqueous metal. Me/Mn atomic ratios were varied from 0.2% to 12.8% in ZnBi and 0.1 to 5.8% in PbBi. The ratio was equal to 15.6% in CuBi. All cations sorbed in interlayers on well-defined crystallographic sites, without evidence for sorption on layer edges or surface precipitation. Zn sorbed on the face of vacant layer octahedral sites (□), and shared three layer oxygens (O_layer) with three-layer Mn atoms (Mn_layer), thereby forming a tridentate corner-sharing (TC) interlayer complex (Zn-3O_layer-□-3Mn_layer). ^TCZn complexes replace interlayer Mn²⁺ (Mn_inter²⁺) and protons. ^TCZn and ^TCMn_inter³⁺ together balance the layer charge deficit originating from Mn_layer⁴⁺ vacancies, which amounts to 0.67 charge per total Mn according to the structural formula of hexagonal birnessite (HBi) at pH 4. At low surface coverage, zinc is tetrahedrally coordinated to three O_layer and one water molecule (^[IV]TC complex: (H₂O)-^[IV]Zn-3O_layer). At high loading, zinc is predominantly octahedrally coordinated to three O_layer and to three interlayer water molecules (^[VI]TC complex: 3(H₂O)-^[VI]Zn-3O_layer), as in chalcophanite (^[VI]ZnMn₃⁴⁺O₇·3H₂O). Sorbed Zn induces the translation of octahedral layers from −a/3 to +a/3, and this new stacking mode allows strong H bonds to form between the ^[IV]Zn complex on one side of the interlayer and oxygen atoms of the next Mn layer (O_next): O_next…(H₂O)-^[IV]Zn-3O_layer. Empirical bond valence calculations show that O_layer and O_next are strongly undersaturated, and that ^[IV]Zn provides better local charge compensation than ^[VI]Zn. The strong undersaturation of O_layer and O_next results not only from Mn_layer⁴⁺ vacancies, but also from Mn³⁺ for Mn⁴⁺ layer substitutions amounting to 0.11 charge per total Mn in HBi. As a consequence, ^[IV]Zn,Mn_layer³⁺, and Mn_next³⁺ form three-dimensional (3D) domains, which coexist with chalcophanite-like particles detected by electron diffraction. Cu²⁺ forms a Jahn-Teller distorted ^[VI]TC interlayer complex formed of two oxygen atoms and two water molecules in the equatorial plane, and one oxygen and one water molecule in the axial direction. Sorbed Pb²⁺ is not oxidized to Pb⁴⁺ and forms predominantly ^[VI]TC interlayer complexes. EXAFS spectroscopy is also consistent with the formation of tridentate edge-sharing (^[VI]TE) interlayer complexes (Pb-3O_layer-3Mn), as in quenselite (Pb²⁺Mn³⁺O₂OH). Although metal cations mainly sorb to vacant sites in birnessite, similar to Zn in chalcophanite, EXAFS spectra of MeBi systematically have a noticeably reduced amplitude. This higher short-range structural disorder of interlayer Me species primarily originates from the presence of Mn_layer³⁺, which is responsible for the formation of less abundant interlayer complexes, such as ^[IV]Zn TC in ZnBi and ^[VI]Pb TE in PbBi.     

Comparison of several BHT correction methods: a case study on an Australian data set

Bottom-hole temperatures (BHT) from oil exploration provide useful constraints on the subsurface thermal regime, but they need to be corrected to obtain the equilibrium temperature. In this work, we introduce several BHT correction methods and compare them using a large Australian data set of more than 650 groups of multiple BHT measurements in about 300 oil exploration boreholes. Existing and suggested corrections are classified within a coherent framework, in which methods are divided into: line/cylinder source; instantaneous/continuous heat extraction; one/two component(s). Comparisons with reservoir test temperatures show that most of the corrections lead to reliable estimates of the formation equilibrium temperature within ±10 °C, but too few data exist to perform an intercomparison of the models based on this criterion. As expected, the Horner method diverges from its parent models for small elapsed times (or equivalently large radii). The mathematical expression of line source models suffers from an unphysical delay time that also restrains their domain of applicability. The model that takes into account the difference of thermal properties between circulating mud and surrounding rocks—that is the two-component model—is delicate to use because of its high complexity. For these reasons, our preferred correction methods are the cylindrical source models. We show that mud circulation time below 10 hr has a negligible effect. The cylindrical source models rely on one parameter depending on the thermal diffusivity and the borehole radius, which are poorly constrained, but the induced uncertainty on the extrapolations remains reasonably low.     

Analysis of central western Europe deformation using GPS and seismic data

The kinematic field of central western Europe is characterized by relatively small movements (around 1–2 mm/year) and diffuse seismicity with earthquakes occurring mostly in the shallow crust (within 15 km), prevalently concentrated along the Alps and the European Cenozoic Rift System (ECRIS). In order to study and constrain the current crustal kinematic field we reconstructed the velocity and the strain field using permanent GPS stations, belonging to different networks (AGNES, EUREF, REGAL, RGP). The 2D strain rate tensor has been calculated using the method of least-squares collocation. Our results show that the area of maximum compression is located along the Alpine chain, where maximum values of 7 ± 2 nstrain/year are found, while maximum extension is measured between the Armorican Massif and the Massif Central, where values of 4 ± 2 nstrain/year are reached.The earthquakes with M > 3.0, have been used to estimate the seismic strain rates, while the style of the seismic deformation was reconstructed from the fault plane solutions (FPS) available from the literature. Relatively high values of seismic strain rates (around 10 nstrain/year) are measured along the Alpine Chain and the ECRIS. Results obtained by geodetic and seismic data are quite in agreement and reflect the different tectonic evolution of the geological features characterizing the area of study. The orientation of the compressional geodetic and seismic strain axes are NW-SE in most of the area of study, on account of the action of plate boundary forces. A rotation of the same axes to N-S direction along the eastern Alps, possibly related to the Adria convergence, is found.