Submarine Groundwater Discharge-Derived Nutrient Loads to San Francisco Bay: Implications to Future Ecosystem Changes

Submarine groundwater discharge (SGD) was quantified at select sites in San Francisco Bay (SFB) from radium (²²³Ra and ²²⁴Ra) and radon (²²²Rn) activities measured in groundwater and surface water using simple mass balance box models. Based on these models, discharge rates in South and Central Bays were 0.3?C7.4?m³?day^?1?m^?1. Although SGD fluxes at the two regions (Central and South Bays) of SFB were of the same order of magnitude, the dissolved inorganic nitrogen (DIN) species associated with SGD were different. In the South Bay, ammonium (NH ₄ ⁺ ) concentrations in groundwater were three-fold higher than in open bay waters, and NH ₄ ⁺ was the primary DIN form discharged by SGD. At the Central Bay site, the primary DIN form in groundwater and associated discharge was nitrate (NO ₃ ^? ). The stable isotope signatures (??¹⁵N_NO3 and ??¹⁸O_NO3) of NO ₃ ^? in the South Bay groundwater and surface waters were both consistent with NO ₃ ^? derived from NH ₄ ⁺ that was isotopically enriched in ¹⁵N by NH ₄ ⁺ volatilization. Based on the calculated SGD fluxes and groundwater nutrient concentrations, nutrient fluxes associated with SGD can account for up to 16?% of DIN and 22?% of DIP in South and Central Bays. The form of DIN contributed to surface waters from SGD may impact the ratio of NO ₃ ^? to NH ₄ ⁺ available to phytoplankton with implications to bay productivity, phytoplankton species distribution, and nutrient uptake rates. This assessment of nutrient delivery via groundwater discharge in SFB may provide vital information for future bay ecological wellbeing and sensitivity to future environmental stressors.     

A Faraday rotation template for the Galactic sky

Using a set of compilations of measurements for extragalactic radio sources, we construct all-sky maps of the Faraday rotation produced by the Galactic magnetic field. In order to generate the maps, we treat the radio source positions as a kind of 'mask' and construct combinations of spherical harmonic modes that are orthogonal on the masked sky. As long as relatively small multipoles are used, the resulting maps are quite stable to changes in the selection criteria for the sources, and show clearly the structure of the local Galactic magnetic field. We also suggest the use of these maps as templates for cosmic microwave background (CMB) foreground analysis, illustrating the idea with a cross-correlation analysis between the Wilkinson Microwave Anisotropy Probe ( WMAP ) data and our maps. We find a significant cross-correlation, indicating the presence of a significant residual contamination.     

The passivation of calcite by acid mine water. Column experiments with ferric sulfate and ferric chloride solutions at pH 2

Column experiments, simulating the behavior of passive treatment systems for acid mine drainage, have been performed. Acid solutions (HCl or H₂SO₄, pH 2), with initial concentrations of Fe(III) ranging from 250 to 1500 mg L⁻¹, were injected into column reactors packed with calcite grains at a constant flow rate. The composition of the solutions was monitored during the experiments. At the end of the experiments (passivation of the columns), the composition and structure of the solids were measured. The dissolution of calcite in the columns caused an increase in pH and the release of Ca into the solution, leading to the precipitation of gypsum and Fe–oxyhydroxysulfates (Fe(III)–SO₄–H⁺ solutions) or Fe–oxyhydroxychlorides (Fe(III)–Cl–H⁺ solutions). The columns worked as an efficient barrier for some time, increasing the pH of the circulating solutions from 2 to 6–7 and removing its metal content. However, after some time (several weeks, depending on the conditions), the columns became chemically inert. The results showed that passivation time increased with decreasing anion and metal content of the solutions. Gypsum was the phase responsible for the passivation of calcite in the experiments with Fe(III)–SO₄–H⁺ solutions. Schwertmannite and goethite appeared as the Fe(III) secondary phases in those experiments. Akaganeite was the phase responsible for the passivation of the system in the experiments with Fe(III)–Cl–H⁺ solutions.     

Heavy-mineral variability in bottom sediments of the lower Chesapeake Bay,Virginia

Heavy minerals in bottom-sediment samples of the lower Chesapeake Bay show distribution patterns and interrelationships that denote characteristic mineral suites associated with defined geographic provinces. The Baymouth province has a garnet—hornblende—pyroxene suite, which is largely attributed to the influx of littoral and shelf sediments; the Eastern Shore province has a similar suite, derived largely from coastal erosion of the Eastern Shore peninsula. The Northern and Combined River provinces have a zircon—tourmaline—staurolite assemblage, which reflects derivation from an Appalachian Piedmont—Atlantic Coastal Plain sourceland. The Western Shore province is associated with a zircon—epidote—staurolite assemblage, apparently derived jointly from tributary influx and coastal erosion of the western shore. Factor analysis identified two major factors that account for 63% of the total variation in the relative amounts of the seven most common heavy minerals. The dominant factor (44%) is based on a zircon—hornblende—staurolite—pyroxene relationship, which indicates that mineral stability, as influenced by sediment maturity, is a major contributing factor. The second factor (19%) based on a tourmaline—epidote—staurolite—garnet relationship indicates that provenance is another major cause of heavy-mineral variability within the lower bay.     

First record of the Australian ascidian Eudistoma elongatum in northern New Zealand

A colonial ascidian was first reported by marine farmers in Houhora Harbour, Northland, New Zealand in early 2005 and subsequently found on oyster racks in Parengarenga Harbour and the Bay of Islands. The Northland ascidian was identified with a combination of morphological characters and DNA cytochrome c oxidase I (COI) sequence data, as Eudistoma elongatum, a species native to Australia, where it is found from northern New South Wales to Northern Queensland, and distinguished from Eudistoma circumvallatum, the only reported species in this genus from New Zealand. Ascidian larvae are weak dispersers and long distance dispersal of E. elongatum is likely to be enhanced by vectors such as oyster barges and/or movement of cultured oysters. In its native range, E. elongatum is restricted to areas with a minimum winter sea temperature of 16°C. Assuming similar biological limitations apply in New Zealand, the spread of E. elongatum might be restricted to northern New Zealand (north of latitude 37°S).     

Festigkeit, verformbarkeit und gefügeregelung von anhydrit — experimentelle stauchverformung unter manteldrucken bis 5 kbar bei temperaturen bis 300°C

The dependence of strength, ductility, and preferred orientation of polycrystalline anhydrite upon confining pressure (up to 5 kbar), temperature (up to 300° C), and strain (up to 30%) has been evaluated by compression tests.Strength and ductility increase at room temperature with increasing mantle pressure. Up to 1 kbar mantle pressure anhydrite is brittle and failure occurs by tension and shear fractures. Homogeneous flow between 1 and 3 kbar mantle pressure is mostly due to intercrystalline slip which is sensitive to pressure. Beyond the elastic limit the stress—strain curves are nearly horizontal. No preferred orientation develops. Between 3 and 4 kbar mantle pressure the intracrystalline mechanisms become noticeable. The stress—strain curves show weak strain hardening. The (210)-planes reveal a weak preferred orientation perpendicular to the axis of compression.With increasing temperature the strength decreases at low strains (< 5%). Intracrystalline mechanisms become more dominant, because the critical resolved shear stresses are lower with increasing temperature. At high strains (> 15%) both strength and ductility increase at higher temperatures. At even higher strains, strain hardening ceases once again and the stress—strain curves become nearly horizontal. From that point on preferred orientation is no longer increased. The stress—strain curves differ with the orientation of the specimen axis to the original fabric.

Zusammenfassung

In Stauchversuchen an polykristallinem Anhydrit wurde die Abhängigkeit der Festigkeit, der Verformbarkeit und der Gefügeregelung vom Manteldruck (bis 5 kbar), von der Temperatur (bis 300°C) und vom Verformungsgrad (bis 30%) untersucht.Festigkeit und Verformbarkeit nehmen bei Raumtemperatur mit steigenden Mantel-drucken zu. Bis etwa l kbar Manteldruck verhält sich der Anhydrit spröde und es treten Trenn und Verschiebungsbrüche auf. Die gleichmässige Fliessverformung bei Manteldrucken über 1 kbar erfolgt durch überwiegend interkristalline, manteldruckempfindliche Verformungsmechanismen. Die Spannungs—Verformungskurven verlaufen nach Überschreiten der elastischen Verformung nahezu horizontal. Eine Regelung tritt nicht ein. Ab 3 kbar bis 4 kbar Manteldruck beginnen sich intrakristalline Mechanismen bemerkbar zu machen. Die Spannungs—Verformungskurven weisen eine schwache Verfestigung auf. Durch die eintretende schwache Regelung stellt sich eine (210)-Ebene bevorzugt senkrecht zur Stauchachse ein.Mit steigender Temperatur bei sonst gleichen Bedingungen nimmt die Festigkeit bei geringen Verformungsgraden (< 5%) ab. Die Verformung erfolgt überwiegend durch intrakristalline Mechanismen, deren kritische Schubspannungen mit zunehmender Temperatur geringer werden. Die Spannungs—Verformungskurven steigen nach Überschreiten des elastischen Bereichs stärker an als zuvor. Es tritt mit zunehmender Temperatur eine stärkere Verfestigung und eine intensivere Einregelung von (210) senkrecht zur Stauchachse ein. Im Bereich hoher Verformungsgrade (> 15%) liegen die Festigkeiten bei höheren Temperaturen höher als bei niedrigen Temperaturen. Bei sehr hohen Verformungsgraden wird die Verfestigung so gross, dass interkristalline Mechanismen die intrakristallinen wieder ablösen. Die Spannungs—Verformungskurven werden wieder flacher und die Zunahme in der Regelung hört auf.Je nach der Orientierung der Stauchachse zum Ausgangsgefüge verlaufen die Spannungs—Verformungskurven unterschiedlich.Die Abhängigkeit der Verformungsmechanismen vom Manteldruck, Verformungsgrad und der Temperatur wird in einem dreidimensionalen Modell vorgestellt.     

Palaeomagnetism of the Fishnish dykes, Mull, Scotland

summary . In Fishnish, eight dykes of E-W trend are all normally magnetized and all cut dykes of other trends. Normally magnetized dykes form a small minority of the dykes in the British Tertiary igneous province and this is the first reported incidence of a clearly defined group of a single polarity. The balance of the evidence - which is conflicting — favours the E—W dykes being contemporary with the later parts of the centre.     

Tectono-sedimentary evolution of Jurassic–Cretaceous diapiric structures: Miravete anticline,Maestrat Basin,Spain

Integration of extensive fieldwork, remote sensing mapping and 3D models from high-quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N–S Miravete anticline, the NW-SE Castel de Cabra anticline and the NW-SE Cañada Vellida ridge in the Maestrat Basin (Iberian Ranges, Spain). The pre shortening diapiric structures are defined by well-exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt-bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and was rejuvenated during Cenozoic shortening. Its evolution is separated into four halokinetic stages, including the latest Alpine compression. Regionally, the well-exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat Basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500-m-long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE-directed salt extrusion. A regional E-W cross section through the Ababuj, Miravete and Cañada-Benatanduz anticlines shows typical geometries of salt-related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well-developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat Basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque-Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/year. The transtensional regime is interpreted to have played a role in diapiric development.     

Novel shape indices for vector landscape pattern analysis

The formation of an anisotropic landscape is influenced by natural and/or human processes, which can then be inferred on the basis of geometric indices. In this study, two minimal bounding rectangles in consideration of the principles of mechanics (i.e. minimal width bounding (MWB) box and moment bounding (MB) box) were introduced. Based on these boxes, four novel shape indices, namely MBLW (the length-to-width ratio of MB box), PAMBA (area ratio between patch and MB box), PPMBP (perimeter ratio between patch and MB box) and ODI (orientation difference index between MB and MWB boxes), were introduced to capture multiple aspects of landscape features including patch elongation, patch compactness, patch roughness and patch symmetry. Landscape pattern was, thus, quantified by considering both patch directionality and patch shape simultaneously, which is especially suitable for anisotropic landscape analysis. The effectiveness of the new indices were tested with real landscape data consisting of three kinds of saline soil patches (i.e. the elongated shaped slightly saline soil class, the circular or half-moon shaped moderately saline soil, and the large and complex severely saline soil patches). The resulting classification was found to be more accurate and robust than that based on traditional shape complexity indices.