Changes in the pattern of water masses resulting from a poleward slope current in the Cantabrian Sea (Bay of Biscay)

From September to December 1995, three hydrographic surveys were carried out in the eastern Cantabrian Sea (Bay of Biscay). Changes in the water masses pattern were examined to study the variability and main energetic features in the area. At the beginning of December, an intense Poleward Current (PC), which had come from Portuguese slopes, entered the eastern Cantabrian Sea. This current was the most energetic event in this area in winter. The PC waters increased temperature by about 2 °C (subsurface layers) and salinity by 0.2 (surface layers) in the pattern of water masses in the eastern Cantabrian Sea in winter. The core current was approximately 10 km width and 120 m depth and the water transport, estimated from geostrophic current profiles, was of about 1.3 Sv.A well-defined wavelike front with two significant ridges in the western and eastern sampling area, was observed. The variability and meandering flow of the PC were driven by dominantly baroclinic instabilities, which are due to strong vertical velocity shear. In this synoptic-scale system, the potential vorticity advection, the differential vorticity advection, and the geopotential tendency have shown to be the cause of the ageostrophic motion and the main baroclinic disturbances.One important consequence of the entrance of the PC in the eastern Cantabrian Sea was the profound effect on the pattern of nutrients. The current-induced stratification pattern drives the distribution of nutrients in the different layers and the instabilities and meandering pattern of the PC was an important mechanism of fertilisation offshore.     

The Effects of Microstructure on Shear Properties of Shallow Marine Sediments

This study was undertaken to investigate the implication of geoacoustic behaviors in the shallow marine sediments associated with the changes in geotechnical index properties. Two piston cores (270 cm and 400 cm in core length) used in this study were recovered from stations 1 and 2, the western continental margin, the East Sea. Scanning electron microscopy (SEM) was employed to illustrate the effects of microstructure on shear properties. The direct SEM observation of sediment fabrics is inevitable to understand the correlation of the changes in geoacoustic properties to the sediment structure. The consolidation of sediments by overburden stress resulting in the clay fabric alteration appears to play an important role in changing shear properties. Water contents and porosity of sediments gradually decreases with increasing depth, whereas wet bulk density shows a reverse trend. It is interesting to note that shear wave velocities increase rapidly from 8 to 20 m/s while compressional wave velocities significantly fluctuate, ranging from 1450 to 1550 m/s with depth. The fabric changes in sediment with increasing depth for example, uniform grain size and well oriented clay fabrics may cause the shear strength increase from 1 to 12 kPa. Shear wave velocity is, therefore, shown to be very sensitive to the changes in undrained strength for unconsolidated marine sediments. This correlation allows an in-situ estimation of shear stress in the subsurface from shear wave velocity data.     

The Baza Fault: a major active extensional fault in the central Betic Cordillera (south Spain)

In the Guadix-Baza Basin (Betic Cordillera) lies the Baza Fault, a structure that will be described for the first time in this paper. Eight gravity profiles and a seismic reflection profile, coupled with surface studies, indicate the existence of a NE-dipping normal fault with a variable strike with N-S and NW-SE segments. This 37-km long fault divides the basin into two sectors: Guadix to the West and Baza to the East. Since the Late Miocene, the activity of this fault has created a half-graben in its hanging wall. The seismic reflection profile shows that the fill of this 2,000–3,000 m thick asymmetric basin is syntectonic. The fault has associated seismicity, the most important of which is the 1531 Baza earthquake. Since the Late Tortonian to the present, i.e. over approximately the last 8 million years, extension rates obtained vary between 0.12 and 0.33 mm/year for the Baza Fault, being one of the major active normal faults to accommodate the current ENE–WSW extension produced in the central Betic Cordillera. The existence of this fault and other normal faults in the central Betic Cordillera enhanced the extension in the upper crust from the Late Miocene to the present in this regional compressive setting.     

Structure and organization of submarine basaltic flows: sheet flow transformation into pillow lavas in shallow submarine environments

Distal pillows occur associated with a sheet flow and megapillows in the me?akoz outcrops of the Basque–Cantabrian Basin (N Spain). Basaltic volcanic rocks are interbedded with Turonian sediments and depict typical features of shallow submarine emissions. An exceptional basaltic flow displays four types of morphology: (1) sheet lava with columnar jointing, (2) welded columnar breccia, (3) megapillows, and (4) pillow lavas with sparse megapillows. The field data from me?akoz combined with experimental and field data from the literature for similar volcanic facies can be integrated into a new propagation model for the transition from sheet flows to pillow lavas in underwater environments. At near vent high emission rates, lava flows develop a thin crust immediately after its emplacement and break at the front under the magma pressure allowing for the massive propagation of lava as a sheet flow. Increased cooling promotes thickening of the lava outer crust far from the vent while continuous supply of fresh magma increases the pressure onto the thick crust until its rupture. The lava emitted in small volumes from the flow front promotes the formation of megapillows and pillow lavas that are later on covered by the advancing sheet flow. The lava flow freezes progressively toward more distal parts, gradually increasing its viscosity until it stops. The crust temporarily holds the residual melt pressure increasing the volume of the flow distal section by inflation. Finally, the internal magma pressure breaks the crust and liberates lava at moderate-to-low flow rates producing pillows, while lava drainage inside the inflated sheet flow produces lava tunnels and gravitational collapse of the roofs by hydrostatic pressure to form breccias nurtured by columnar lava fragments.     

Measuring runoff by plots at different scales: Understanding and analysing the sources of variation

The decrease of runoff with the increase in area is not a new fact. The scale effect depends on the spatial and temporal variability of different factors, including the surface characteristics and hydrodynamic properties of the soil and the vegetation development. The purpose of our work is to study the relative influence of the sources of variation of runoff from a small Sahelian catchment on several types of soil surfaces features. Plots of different sizes (1, 50 and 150 m²) on cultivated soils and degraded soils (non-cultivated with three different types of crusts) were monitored for two consecutive years. The results show that the runoff coefficients of rainfall events range from 4 to 65% on cultivated soils and 16 to 96% on uncultivated bare and degraded soils. A statistical and dimensionless analysis shows that in degraded environments, the processes generating runoff on plots of 50 and 150 m² are identical and significantly different from the unit plot (1 m²). The decrease in runoff with increasing scale becomes more pronounced when rainfall duration decreases. In cultivated areas, this result is not observed. Additional measurements are needed to better understand the differences in functioning at various scales of observations.     

Correlation between nitrite accumulation and the concentration of AOB in a nitritation reactor

Nitritation is an innovative biological nitrogen removal method in wastewater, and it has the advantages of energy and economy. The correlation between a nitrite conversion rate and the gene copy numbers of ammonia oxidizing bacteria (AOB) in a nitritation reactor was examined to measure the effectiveness of removing a nitrogen content in a biological nitrogen removal process, using a biological process of nitritation. A laboratory scale reactor was prepared and operated for over a year, using digester supernatant to induce a stable nitritation, and to optimize the operational conditions by adjusting various operating factors. The relationship between operational results of nitritation reactor and the AOB gene copies was approximated through identification and quantitative analysis of AOB. A stable nitritation can be artificially led with the control of SRT, while treating anaerobic digester supernatant from MWTPs. And AOB gene copies showed a correlation with free ammonia (FA) inhibition and performance of nitritation, and AOB activity. Thus, AOB gene copies were found important when it comes to analyzing nitritation.     

Changes in the chemistry of shallow groundwater related to the 2008 injection of CO2 at the ZERT field site, Bozeman, Montana

Approximately 300 kg/day of food-grade CO₂ was injected through a perforated pipe placed horizontally 2–2.3 m deep during July 9–August 7, 2008 at the MSU-ZERT field test to evaluate atmospheric and near-surface monitoring and detection techniques applicable to the subsurface storage and potential leakage of CO₂. As part of this multidisciplinary research project, 80 samples of water were collected from 10 shallow monitoring wells (1.5 or 3.0 m deep) installed 1–6 m from the injection pipe, at the southwestern end of the slotted section (zone VI), and from two distant monitoring wells. The samples were collected before, during, and following CO₂ injection. The main objective of study was to investigate changes in the concentrations of major, minor, and trace inorganic and organic compounds during and following CO₂ injection. The ultimate goals were (1) to better understand the potential of groundwater quality impacts related to CO₂ leakage from deep storage operations, (2) to develop geochemical tools that could provide early detection of CO₂ intrusion into underground sources of drinking water (USDW), and (3) to test the predictive capabilities of geochemical codes against field data. Field determinations showed rapid and systematic changes in pH (7.0–5.6), alkalinity (400–1,330 mg/l as HCO₃), and electrical conductance (600–1,800 μS/cm) following CO₂ injection in samples collected from the 1.5 m-deep wells. Laboratory results show major increases in the concentrations of Ca (90–240 mg/l), Mg (25–70 mg/l), Fe (5–1,200 ppb), and Mn (5–1,400 ppb) following CO₂ injection. These chemical changes could provide early detection of CO₂ leakage into shallow groundwater from deep storage operations. Dissolution of observed carbonate minerals and desorption-ion exchange resulting from lowered pH values following CO₂ injection are the likely geochemical processes responsible for the observed increases in the concentrations of solutes; concentrations generally decreased temporarily following four significant precipitation events. The DOC values obtained are 5 ± 2 mg/l, and the variations do not correlate with CO₂ injection. CO₂ injection, however, is responsible for detection of BTEX (e.g. benzene, 0–0.8 ppb), mobilization of metals, the lowered pH values, and increases in the concentrations of other solutes in groundwater. The trace metal and BTEX concentrations are all significantly below the maximum contaminant levels (MCLs). Sequential leaching of core samples is being carried out to investigate the source of metals and other solutes.     

Pressure resistance of the corrugated stainless steel membranes of LNG carriers

Corrugated stainless steel membranes have been used as the primary barriers for LNG carriers to reduce thermal stresses at cryogenic temperatures. As the capacity of the LNG cargo is increased, however, the corrugated stainless steel membranes suffer from buckling and collapse due to increased sloshing loads in large-capacity LNG cargo carriers. In this study, the pressure resistance of the corrugated part of the stainless steel membrane was evaluated using a finite element method for better design of the LNG containment system, and an experimental equipment was developed and the pressure resistance of the stainless steel corrugations was measured and compared with the calculated results. In addition, a new membrane with high-pressure resistance and its reinforcing method were developed and evaluated experimentally.