A pockmark field in the Patras Gulf (Greece) and its activation during the 14/7/93 seismic event

During a recent oceanographical-geophysical survey carried out in the southeastern part of the Gulf of Patras in Western Greece for the construction of an outfall, an active pockmark field was found. The pockmark field was formed in soft layered Holocene silts. The pockmarks are associated with acoustic anomalies attributed to gas-charged sediments. The pockmarks vary in size and shape from 25 to 250 m in diameter and from 0.5 to 15 m in depth and are among the largest and deepest observed in the world.

On July 14th, 1993, during the survey, a major earthquake of magnitude 5.4 on the Richter scale occurred in the area. During the 24 hour period prior to the earthquake the bottom water temperature anomalously increased on three occasions, whilst for a few days after the earthquake it was noted that the majority of the pockmarks were venting gas bublles.

It is considered that the three abrupt sea-water temperature increases were probably the result of upward migrating high-temperature gas bubbles in the water column. It is further suggested that the earthquake was the triggering mechanism and that the gas expulsion was caused by the reduction in the pore volume in the sediments resulting from changes in the stress regime prior to the earthquake. Therefore, it can be suggested that in seismic areas adjacent to pockmark fields, earthquake prediction may be achieved by monitoring the water temperature and/or the rate of gas venting in the pockmark field.

Our analysis indicates that the pockmark field in the Patras Gulf has formed slowly during the Holocene by continuous gas venting, which is periodically being interrupted by short-duration events of enhanced gas seepage triggered by earthquakes.     

On the Distance Function Between Two Keplerian Elliptic Orbits

The problem of finding critical points of the distance function between two Keplerian elliptic orbits is reduced to the determination of all real roots of a trigonometric polynomial of degree 8. The coefficients of the polynomial are rational functions of orbital parameters. Using computer algebra methods we show that a polynomial of a smaller degree with such properties does not exist. This fact shows that our result cannot be improved and it allows us to construct an optimal algorithm to find the minimal distance between two Keplerian orbits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Occurrence and Distribution of Organic Contaminants in the Aquatic System in Berlin.Part II: Substituted Phenols in Berlin Surface Water

In a surface water screening, 30 representative surface water samples collected from rivers, canals, and lakes in Berlin were investigated for the presence of 22 substituted phenols. The phenols selected include the 11 phenols considered as “priority pollutants” by the US Environmental Protection Agency (US-EPA). Surface water samples were extracted applying solid-phase extraction with styrenedivinylbenzene adsorbent. The recoveries, determined in spiking experiments, were between 80 % and 103 %. After derivatization with N-(tert-butyldimethylsilyl)-N-methyl-trifluoroacetamide (MTBSTFA) the samples were analyzed by capillary gas chromatography-mass spectrometry (GC-MS). Phenol, cresols, 2-ethylphenol, 2-chlorophenol, 4-chloro-3-methylphenol, pentachlorophenol, 2-nitrophenol, and 4-nitrophenol were detected in the surface water samples at concentrations between 0.02 μg/L and 7.8 μg/L, respectively. The distribution of these residues in the Berlin surface waters showed that the phenolic residues, with the exception of pentachlorophenol and 2-ethylphenol, do not originate primarily from municipal sewage treatment plants discharges. Some of the phenols are formed naturally or occur as ubiquitous anthropogenic contaminants in the aquatic system.     

Diffusive equilibrium in thin films provides evidence of suppression of hyporheic exchange and large‐scale nitrate transformation in a groundwater‐fed river

The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from upwelling, polluted groundwater. However, the coarse‐scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine‐scale (<1 cm) biogeochemical patterns, especially in near‐surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform upwelling NO₃^?. In this study, we utilised diffusive equilibrium in thin‐films samplers to capture high resolution (cm‐scale) vertical concentration profiles of NO₃^?, SO₄^2?, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub‐reach characterised by strong vertical (upwelling) water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin‐films samplers indicate considerable cm‐scale variability in NO₃^? (4.4 ± 2.9 mg N/L), SO₄^2? (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface‐subsurface water mixing in the shallow sediments of our sub‐reach under baseflow conditions. The significance of this is that upwelling NO₃^?‐rich groundwater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub‐reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper‐seated groundwater fluxes and hydro‐stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub‐reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd.     

Structure Function Analysis of Two-Scale Scalar Ramps. Part II: Ramp Characteristics and Surface Renewal Flux Estimation

Ramp features in the turbulent scalar field are associated with turbulent coherent structures, which dominate energy and mass fluxes in the atmospheric surface layer. Although finer scale ramp-like shapes embedded within larger scale ramp-like shapes can readily be perceived in turbulent scalar traces, their presence has largely been overlooked in the literature. We demonstrate the signature of more than one ramp scale in structure functions of the turbulent scalar field measured from above bare ground and two types of short plant canopies, using structure-function time lags ranging in scale from isotropic to larger than the characteristic coherent structures. Spectral analysis of structure functions was used to characterize different scales of turbulent structures. By expanding structure function analysis to include two ramp scales, we characterized the intermittency, duration, and surface renewal flux contribution of the smallest (i.e., Scale One) and the dominant (i.e., Scale Two) coherent structure scales. The frequencies of the coherent structure scales increase with mean wind shear, implying that both Scale One and Scale Two are shear-driven. The embedded Scale One turbulent structure scale is ineffectual in the surface-layer energy and mass transport process. The new method reported here for obtaining surface renewal-based scalar exchange works well over bare ground and short canopies under unstable conditions, effectively eliminating the α calibration for these conditions and forming the foundation for analysis over taller and more complex surfaces.     

Mapping of sound scattering objects in the northern part of the Barents Sea and their geological interpretation

On cruises 25 (2007) and 28 (2011) of the R/V Akademik Nikolai Strakhov in the northern part of the Barents Sea, the Geological Institute, Russian Academy of Sciences, conducted comprehensive research on the bottom relief and upper part of the sedimentary cover profile under the auspices of the International Polar Year program. One of the instrument components was the SeaBat 8111 shallow-water multibeam echo sounder, which can map the acoustic field similarly to a side scan sonar, which records the response both from the bottom and from the water column. In the operations area, intense sound scattering objects produced by the discharge of deep fluid flows are detected in the water column. The sound scattering objects and pockmarks in the bottom relief are related to anomalies in hydrocarbon gas concentrations in bottom sediments. The sound scattering objects are localized over Triassic sequences outcropping from the bottom. The most intense degassing processes manifest themselves near the contact of the Triassic sequences and Jurassic clay deposits, as well as over deep depressions in a field of Bouguer anomalies related to the basement of the Jurassic–Cretaceous rift system     

Tellurides from Sunrise Dam gold deposit, Yilgarn Craton, Western Australia: a new occurrence of nagyágite

Summary The Cu–Fe–Au–Mo (W) deposits in southeastern Hubei are an important component of the Middle–Lower Yangtze River metallogenic belt. Molybdenite from the Fengshandong Cu- (Mo), Ruanjiawan W–Cu- (Mo), Qianjiawan Cu–Au, Tongshankou Cu–Mo and Tonglüshan Cu- (Fe) deposits yielded Re–Os ages of 144.0 ± 2.1 Ma, 143.6 ± 1.7 Ma, 137.7 ± 1.7 Ma, 142.3 ± 1.8–143.7 ± 1.8 Ma and 137.8 ± 1.7–138.1 ± 1.8 Ma, respectively. Phlogopite from the Tieshan Fe- (Cu) deposit yielded an Ar–Ar age of 140.9 ± 1.2 Ma. These data and other published isotopic ages (Re–Os molybdenite and Ar–Ar mica ages) for the Cu–Fe–Au–Mo (W) deposits in the Middle–Lower Yangtze River metallogenic belt show that Cu–Fe–Au–Mo (W) mineralisation in the Tongling, Anqing, Jiurui and Edong ore districts developed in a narrow time span between 135.5 and 144.9 Ma, reflecting an important regional metallogenic event. An integrated study of available petrological and geochronological data, together with relationships to magmatism and the regional geodynamic framework, indicate that the Cu–Fe–Au–Mo (W) mineralisation in the Middle–Lower Yangtze River belt occurred during a regime of lithospheric extension. This extension is probably related to Late Mesozoic processes of lower crustal delamination and lithospheric thinning in East China.     

Stability and phase relations of nonstoichiometric clinopyroxenes in the join diopside-Ca-Eskola component at high pressures

The stability of nonstoichiometric clinopyroxenes in the Di-CaEsk join was experimentally studied, and phase diagrams were constructed for this join at pressures of 2.0 and 3.0 GPa. It was found that melting in the diopside part of the join occurs at anomalously low temperatures, and nonstoichiometric clinopyroxene coexists with a phase approaching diopside in composition. Phase relations along the Di-CaEsk join can be described and consistently interpreted only assuming that the diopside phase (α-diopside) is thermodynamically stable. The following phase volumes were observed along the solidus of the join at a pressure of 3.0 GPa: Cpx, αDi+Cpx, αDi+Cpx+Qtz, αDi+Cpx+Grt+Qtz, Cpx+Grt+Qtz, Cpx+Grt+Ky+Qtz, Grt+Ky+Qtz. Melting occurs via the eutectic reaction αDi+Cpx+Grt+Qtz=L at a temperature of about 1200°C in the diopside part of the system and via the eutectic reaction Cpx+Grt+Ky+Qtz=L at a temperature of 1400°C in the calcium-rich part of the system. At a pressure of 2.0 GPa, melting occurs at temperatures of 1200–1300°C via the eutectic reaction αDi+Cpx+ An + Qtz=L. The invariant equilibrium (L, An, Cpx, Grt, αDi, Qtz) lies within the pressure range 2.0–3.0 GPa. Nonstoichiometric clinopyroxenes form complex solid solutions, the compositions of which are not strictly confined to the Di-CaEsk join and depend on temperature, pressure, and phase association. Grossular garnets coexist with nonstoichiometric clinopyroxenes and α-diopside.     

Eignung mikrobieller Biotests für gebundene Schadstoffe Suitability of Microbial Bioassays for Bound Contaminants

Toxicity of soil spiked with water soluble and insoluble contaminants was assessed with bacteria. Three bioassays were used with common soil bacteria. Water soluble fractions from the soils were estimated in microtiterplates via dehydrogenase activity of B. cereus and growth of P. putida. A new method was developed using B. cereus to include effects of soil particles with bound contaminants. As contaminants p-nitrophenol and 2-naphthol were tested in these systems. Results indicated that the concentration of the contaminants in the soil solution is determined by soil properties. Toxicity of water soluble fractions was not only a result of the toxicant's concentration but further modified by soluble components of the soils. It is not possible to assess soil pollution from toxicity of the water soluble fraction in general, because unknown factors of the soluble soil fraction can influence toxicity greatly. The newly developed contact bioassay with B. cereus showed clearly higher toxicity of 2-naphthol estimated in soil suspension than did the comparable test system with the same bacteria using water soluble fractions only. The results stress the importance of including soil particles into bioassay procedures. It was shown that also water insoluble, bound contaminants can act as toxicants. For an estimation of toxicity under conditions more relevant for the environment, the suggested test system can provide useful information to bioavailability of bound contaminants.