Combining the Arc Marine Framework with Geographic Metadata to Support Ocean Acoustic Modeling

A data model for use in a rapid environmental assessment system is constructed. The data model is used in an information layer that supports acoustic assessments of the ocean environment. Such an assessment requires use of both historic and real‐time oceanographic data. The foundation of the data model is Arc Marine, a framework specification for geospatial oceanographic databases that provides structures for containing the basic data types used in oceanographic research. Arc Marine also allows design extensions to account for application specific data structures as demonstrated through incorporation of aspects of the International Organization for Standardization (ISO) 19115 Geographic Information–Metadata standard. The ISO 19115 standard provides structures for recording the historic processing of the data sets. The data model is used to construct a database in the open source database management system (DBMS) PostgreSQL. The resulting system also incorporates the concept of user exits, the seamless extension of the DBMS through inclusion of application‐specific software.     

Detection of Earth-mass and super-Earth Trojan planets using transit timing variation method

We have carried out an extensive study of the possibility of the detection of Earth-mass and super-Earth Trojan planets using transit timing variation method with the Kepler space telescope. We have considered a system consisting of a transiting Jovian-type planet in a short period orbit, and determined the induced variations in its transit timing due to an Earth-mass/super-Earth Trojan planet. We mapped a large section of the phase space around the 1:1 mean-motion resonance and identified regions corresponding to several other mean-motion resonances where the orbit of the planet would be stable. We calculated transit timing variations (TTVs) for different values of the mass and orbital elements of the transiting and perturbing bodies as well as the mass of central star, and identified orbital configurations of these objects (ranges of their orbital elements and masses) for which the resulted TTVs would be within the range of the variations of the transit timing of Kepler’s planetary candidates. Results of our study indicate that in general, the amplitudes of the TTVs fall within the detectable range of timing precision obtained from the Kepler’s long-cadence data, and depending on the parameters of the system, their magnitudes may become as large as a few hours. The probability of detection is higher for super-Earth Trojans with slightly eccentric orbits around short-period Jovian-type planets with masses slightly smaller than Jupiter. We present the details of our study and discuss the implications of its results.     

Ejection behavior characteristics in experimental cratering in sandstone targets

Abstract– Within the frame of the MEMIN research unit (Multidisciplinary Experimental and Numerical Impact Research Network), impact experiments on sandstone targets were carried out to systematically study the influence of projectile mass, velocity, and target water saturation on the cratering and ejection processes. The projectiles were accelerated with two‐stage light‐gas guns (Ernst‐Mach‐Institute) onto fine‐grained targets (Seeberger sandstone) with about 23% porosity. Collection of the ejecta on custom‐designed catchers allowed determination of particle shape, size distribution, ejection angle, and microstructures. Mapping of the ejecta imprints on the catcher surface enabled linking of the different patterns to ejection stages observed on high‐speed videos. The increase in projectile mass from 0.067 to 7.1 g correlates with an increase in the total ejected mass; ejecta angles, however, are similar in range for all experiments. The increase in projectile velocity from 2.5 to 5.1 km s^?1 correlates with a total ejecta mass increase as well as in an increase in comminution efficiency, and a widening of the ejecta cone. A higher degree of water saturation of the target yields an increase in total ejecta mass up to 400% with respect to dry targets, higher ejecta velocity, and a steeper cone. These data, in turn, suggest that the reduced impedance contrast between the quartz grains of the target and the pores plays a primary role in the ejecta mass increase, while vaporization of water determines the ejecta behavior concerning ejecta velocity and particle distribution.     

Annual dynamics of pelagic primary production and respiration in a shallow coastal basin

The Wadden Sea (North Sea, Europe) is a shallow coastal sea with high benthic and pelagic primary production rates. To date, no studies have been carried out in the Wadden Sea that were specifically designed to study the relation between pelagic respiration and production by comparable methods. Because previous studies have suggested that the import of primary-produced pelagic organic matter is important for benthic Wadden Sea carbon budgets, we hypothesised that on an annual average the northern Wadden Sea water column is autotrophic. To test this hypothesis, we studied annual dynamics of primary production and respiration at a pelagic station in a shallow tidal basin (List Tidal Basin, northern Wadden Sea). Since water depth strongly influences production estimates, we calculated primary production rates per unit area in two ways: on the basis of the mean water depth (2.7 m) and on the basis of 1 m depth intervals and their respective spatial extent in the List Tidal Basin. The latter more precise estimate yielded an annual primary production of 146 g C m^− 2 y^− 1. Estimates based on the mean water depth resulted in a 40% higher annual rate of 204 g C m^− 2 y^− 1. The total annual pelagic respiration was 50 g C m^− 2 y^− 1. The P/R ratio varied between seasons: from February to October the water column was autotrophic, with the highest P/R ratio of 4–5 during the diatom spring bloom in April/May. In autumn and winter the water column was heterotrophic. On an annual average, the water column of the List Tidal Basin was autotrophic (P/R 3). We suggest that a large fraction of the pelagic produced organic matter was respired locally in the sediment.     

Effects of soil organic matter composition on unfrozen water content and heterotrophic CO2 production of frozen soils

Several recent studies have highlighted the importance of soil organic matter (SOM) mineralization at high latitudes during winter for ecosystem carbon (C) balances, and the ability of the soil to retain unfrozen water at sub-zero temperatures has been shown to be a major determinant of C mineralization rates. Further, SOM is believed to strongly influence the liquid water contents in frozen surface layers of boreal forest soils and tundra, but the mechanisms and specific factors involved are currently unknown. Here we evaluate the effects of the chemical composition of SOM on the amount of unfrozen water, the pore size equivalents in which unfrozen water can exist, and the microbial heterotrophic activity at sub-zero temperatures in boreal forest soils. To do this, we have characterized the chemical composition of SOM in forest soil samples (surface O-horizons) using solid state CP-MAS (cross polarization magic angle spinning) NMR spectroscopy. The acquired information was then used to elucidate the extent to which different fractions of SOM can explain the observed variations in unfrozen water content, pore size equivalents, and biogenic CO₂ production rates in the examined soil samples under frozen conditions (−4 °C). The data evaluation was done by the use of principal component analysis (PCA) and projections to latent structures by means of partial least square (PLS). We conclude that aromatic, O-aromatic, methoxy/N-alkyl and alkyl C are the major SOM components affecting frozen boreal forest soil’s ability to retain unfrozen water and sustain heterotrophic activity (95% confidence level). Our results reveal that solid carbohydrates have a significant negative impact (95% confidence level) on CO₂ production in frozen boreal spruce forest soils, in contrast to the positive effects of carbohydrate polymers during unfrozen conditions. We conclude that the hierarchy of environmental factors controlling SOM mineralization changes as soils freeze. The effect of SOM composition on pore size distribution and unfrozen water content has a superior influence on SOM mineralization and hence on heterotrophic CO₂ production of frozen soils.     

The biogeochemistry of sorbed methane in marine sediments

Sorption of volatile hydrocarbon gases (VHCs) to marine sediments is a recognized phenomenon that has been investigated in the context of petroleum exploration. However, little is known about the biogeochemistry of sorbed methane and higher VHCs in environments that are not influenced by thermogenic processes. This study evaluated two different extraction protocols for sorbed VHCs, used high pressure equipment to investigate the sorption of methane to pure clay mineral phases, and conducted a geochemical and mineralogical survey of sediment samples from different oceanographic settings and geochemical regimes that are not significantly influenced by thermogenic gas. Extraction of sediments under alkaline conditions yielded higher concentrations of sorbed methane than the established protocol for acidic extraction. Application of alkaline extraction in the environmental survey revealed the presence of substantial amounts of sorbed methane in 374 out of 411 samples (91%). Particularly high amounts, up to 2.1 mmol kg⁻¹ dry sediment, were recovered from methanogenic sediments. Carbon isotopic compositions of sorbed methane suggested substantial contributions from biogenic sources, both in sulfate-depleted and sulfate-reducing sediments. Carbon isotopic relationships between sorbed and dissolved methane indicate a coupling of the two pools. While our sorption experiments and extraction conditions point to an important role for clay minerals as sorbents, mineralogical analyses of marine sediments suggest that variations in mineral composition are not controlling variations in quantities of sorbed methane. We conclude that the distribution of sorbed methane in sediments is strongly influenced by in situ production.     

Slip rate variations on faults in the Basin-and-Range Province caused by regression of Late Pleistocene Lake Bonneville and Lake Lahontan

Late Pleistocene regression of two large pluvial lakes—Lake Bonneville and Lake Lahontan—caused considerable lithospheric rebound in the Basin-and-Range Province, USA. Here, we use finite-element models to show how lake growth and regression affect the temporal and spatial slip evolution on faults near the former lakes. Our results show that fluctuations in the volume of Lake Bonneville caused along-strike slip variations on the Wasatch normal fault, with a pronounced slip rate increase on its northern and central parts during lake regression. The response of normal and strike-slip faults near the ring-shaped Lake Lahontan depends on their location within the rebound area. Faults located in the centre of rebound show a slip rate increase during lake regression, whereas strike-slip faults at the periphery decelerate. All slip rate variations are caused by differential stress changes owing to changing lake levels, regardless of the individual fault response.     

Isotope Geochemistry of the Pb-Zn-Ba(-Ag-Au) Mineralization at Triades-Galana,Milos Island,Greece

The Pb-Zn-Ba(-Ag-Au) mineralization in the Triades and Galana mine areas is hosted in 2.5–1.4 Ma pyroclastic rocks, and structurally controlled mostly by NE-SW or N-S trending brittle faults. Proximal pervasive silica and distal pervasive sericite-illite alteration are the two main alteration types present at the surface. The distribution of mineralization-alteration in the district suggests at least two hydrothermal events or that hydrothermal activity lasted longer at Galana. The Sr isotope signature of sphalerite and barite (⁸⁷Sr/⁸⁶Sr = 0.709162 to 0.710214) and calculated oxygen isotope composition of a fluid in equilibrium with barite and associated quartz at temperatures of around 230°C are suggestive of a seawater hydrothermal system and fluid/rock interaction. Lead isotope ratios of galena and sphalerite (²⁰⁶Pb/²⁰⁴Pb from 18.8384 to 18.8711; ²⁰⁷Pb/²⁰⁴Pb from 15.6695 to 15.6976; ²⁰⁸Pb/²⁰⁴Pb from 38.9158 to 39.0161) are similar to those of South Aegean Arc volcanic and Aegean Miocene plutonic rocks, and compatible with Pb derived from an igneous source. Galena and sphalerite from Triades-Galana have δ³⁴S_VCDT values ranging from +1 to +3.6‰, whereas barite sulfate shows δ³⁴S_VCDT values from +22.8 to +24.4‰. The sulfur isotope signatures of these minerals are explained by seawater sulfate reduction processes. The new analytical data are consistent with a seawater-dominated hydrothermal system and interaction of the hydrothermal fluid with the country rocks, which are the source of the ore metals.     

A GCSS Boundary-Layer Cloud Model Intercomparison Study Of The First Astex Lagrangian Experiment

Three single-column models (all with an explicit liquid water budget and compara-tively high vertical resolution) and three two-dimensional eddy-resolving models (including one with bin-resolved microphysics) are compared with observations from the first ASTEX Lagrangian experiment. This intercomparison was a part of the second GCSS boundary-layer cloud modelling workshop in August 1995.In the air column tracked during the first ASTEX Lagrangian experiment, a shallow subtropical drizzling stratocumulus-capped marine boundary layer deepens after two days into a cumulus capped boundary layer with patchy stratocumulus. The models are forced with time varying boundary conditions at the sea-surface and the capping inversion to simulate the changing environment of the air column.The models all predict the observed deepening and decoupling of the boundary layer quite well, with cumulus cloud evolution and thinning of the overlying stratocumulus. Thus these models all appear capable of predicting transitions between cloud and boundary-layer types with some skill. The models also produce realistic drizzle rates, but there are substantial quantitative differences in the cloud cover and liquid water path between models. The differences between the eddy-resolving model results are nearly as large as between the single column model results. The eddy resolving models give a more detailed picture of the boundary-layer evolution than the single-column models, but are still sensitive to the choice of microphysical and radiative parameterizations, sub-grid-scale turbulence models, and probably model resolution and dimensionality. One important example of the differences seen in these parameterizations is the absorption of solar radiation in a specified cloud layer, which varied by a factor of four between the model radiation parameterizations.     

Field multi-step limestone and MgO passive system to treat acid mine drainage with high metal concentrations

Passive treatment systems have become one of the most sustainable and feasible ways of remediating acid mine drainage (AMD). However, conventional treatments show early clogging of the porosity or/and coating of the reactive grains when high acidity and metal concentrations are treated. The performance of fine-grained reagents dispersed in a high porosity matrix of wood shavings was tested as an alternative to overcome these durability problems. The system consisted of two tanks of 3 m³ filled with limestone sand and wood shavings, and one tank of 1 m³ with caustic magnesia powder and wood shavings, separated by several oxidation cascades and decantation ponds. The system treated about 1.5 m³/day of AMD containing an average of 360 mg/L Fe, 120 mg/L Al, 390 mg/L Zn, 10 mg/L Cu, 300 μg/L As and 140 μg/L Pb, a mean pH of 3.08 and a net acidity of 2500 mg/L as CaCO₃ equivalent. The water reached pH 5 and 6 in the first and second limestone tanks, respectively (suitable to remove trivalent metals); and pH 8–9 in the MgO tank (suitable to remove divalent metals). After 9 months of operation, the system achieved an average removal of 100% Al, Cu, As, Pb, more than 70% Fe, about 25% Zn and 80% acidity. Goethite, schwertmannite, hydrobasaluminite, amorphous Al(OH)₃ and gypsum were the main precipitates in the two limestone tanks. Precipitation of divalent metals (Fe (II), Zn, and traces of Cd, Ni and Co) were complete inside the third tank of MgO, but preferential flow along the walls was responsible for its low treatment performance. Goethite, gypsum, Zn-schulenbergite and sauconite are the crystalline solid phases identified in the MgO tank.