Biodegradative potential and characterization of psychrotolerant polychlorinated biphenyl-degrading marine bacteria isolated from a coastal station in the Terra Nova Bay (Ross Sea, Antarctica)

Antarctic marine bacteria were screened for their ability to degrade polychlorinated biphenyls (PCB) as the sole carbon and energy source at both 4 degrees C and 15 degrees C. PCB-degrading isolates (7.1%) were identified by sequencing their 16S rDNA as Pseudoalteromonas, Psychrobacter and Arthrobacter members. One representative isolate per genera was selected for evaluating the biodegradative potential under laboratory scale and phenotypically characterized. Removal of individual PCB congeners was between 35.6% and 79.8% at 4 degrees C and between 0.4% and 82.8% at 15 degrees C. Differences in the removal patterns of PCB congeners were observed in relation to the phylogenetic affiliation: Arthrobacter isolate showed similar biodegradation efficiencies when growing at 4 degrees C and 15 degrees C, while Pseudoalteromonas better degraded PCBs at 15 degrees C. No biodegradation was detected for Psychrobacter isolate at 4 degrees C. Results obtained highlight the occurrence of PCB-degrading bacteria in Antarctic seawater and suggest the potential exploitation of autochthonous bacteria for PCB bioremediation in cold marine environments.     

Relationship between soil CO<Subscript>2</Subscript> flux and volcanic tremor at Mt. Etna: Implications for magma dynamics

Large variations of the CO₂ flux through the soil were observed between November 2002 and January 2006 at Mt. Etna volcano. In many cases, the CO₂ flux was strongly influenced by changes in air temperature and atmospheric pressure. A new filtering method was then developed to remove the atmospheric influences on soil CO₂ flux and, at the same time, to highlight the variations strictly related to volcanic activity. Successively, the CO₂ corrected data were quantitatively compared with the spectral amplitude of the volcanic tremor by cross correlation function, cross-wavelet spectrum and wavelet coherence. These analyses suggested that the soil CO₂ flux variations preceded those of volcanic tremor by about 50 days. Given that volcanic tremor is linked to the shallow (a few kilometer) magma dynamics and soil CO₂ flux related to the deeper (~12 km b.s.l.) magma dynamics, the “delayed similarity” between the CO₂ flux and the volcanic tremor amplitude was used to assess the average speed in the magma uprising into the crust, as about 170–260 m per day. Finally, the large amount of CO₂ released before the onset of the 2004–2005 eruption indicated a deep ingression of new magma, which might have triggered such an eruption.     

Homogenization estimates for texture evolution in halite

In this work, the recently developed “second-order” self-consistent method [Liu, Y., Ponte Castañeda, P., 2004a. Second-order estimates for the effective behavior and field fluctuations in viscoplastic polycrystals. J. Mech. Phys. Solids 52 467–495] is used to simulate texture evolution in halite polycrystals. This method makes use of a suitably optimized linear comparison polycrystal and has the distinguishing property of being exact to second order in the heterogeneity contrast. The second-order model takes into consideration the effects of hardening and of the evolution of both crystallographic and morphological texture to yield reliable predictions for the macroscopic behavior of the polycrystal. Comparisons of these predictions with full-field numerical simulations [Lebensohn, R.A., Dawson, P.R., Kern, H.M., Wenk, H.R., 2003. Heterogeneous deformation and texture development in halite polycrystals: comparison of different modeling approaches and experimental data. Tectonophysics 370 287–311], as well as with predictions resulting from the earlier “variational” and “tangent” self-consistent models, included here for comparison purposes, provide insight into how the underlying assumptions of the various models affect slip in the grains, and therefore the texture predictions in highly anisotropic and nonlinear polycrystalline materials. The “second-order” self-consistent method, while giving a softer stress-strain response than the corresponding full-field results, predicts a pattern of texture evolution that is not captured by the other homogenization models and that agrees reasonably well with the full-field predictions and with the experimental measures.     

On the sun's pole-equator flux differences

We study the possibility that large flux differences between the poles and the equator at the bottom of the solar convective zone are compatible with the small differences observed at the surface. The consequences of increasing the depth of the convective zone due to overshooting are explored.A Boussinesq model is used for the convective zone and we assume that the interaction of the global convection with rotation is modelled through a convective flux coefficient whose perturbed part is proportional to the local Taylor number. The numerical integration of the equations of motion and energy shows that coexistence between large pole-equator flux differences at the bottom and small ones at the surface is possible if the solar convective zone extends to a depth of 0.4R . The angular velocity distribution inside the convective zone is in agreement with the -dynamo theories of the solar cycle.     

Geomorphology and GIS analysis for mapping gully erosion susceptibility in the Turbolo stream catchment (Northern Calabria, Italy)

This work summarizes the results of a geomorphological and bivariate statistical approach to gully erosion susceptibility mapping in the Turbolo stream catchment (northern Calabria, Italy). An inventory map of gully erosion landforms of the area has been obtained by detailed field survey and air photograph interpretation. Lithology, land use, slope, aspect, plan curvature, stream power index, topographical wetness index and length-slope factor were assumed as gully erosion predisposing factors. In order to estimate and validate gully erosion susceptibility, the mapped gully areas were divided in two groups using a random partitions strategy. One group (training set) was used to prepare the susceptibility map, using a bivariate statistical analysis (Information Value method) in GIS environment, while the second group (validation set) to validate the susceptibility map, using the success and prediction rate curves. The validation results showed satisfactory agreement between the susceptibility map and the existing data on gully areas locations; therefore, over 88% of the gullies of the validation set are correctly classified falling in high and very high susceptibility areas. The susceptibility map, produced using a methodology that is easy to apply and to update, represents a useful tool for sustainable planning, conservation and protection of land from gully processes. Therefore, this methodology can be used to assess gully erosion susceptibility in other areas of Calabria, as well as in other regions, especially in the Mediterranean area, that have similar morphoclimatic features and sensitivity to concentrated erosion.     

Thermodynamic modeling assisted by multivariate statistical image analysis as a tool for unraveling metamorphic P-T-d evolution: an example from ilmenite-garnet-bearing metapelite of the Peloritani Mountains, Southern Italy

An ilmenite-garnet-bearing schist from the medium-grade metapelite complex of the Mandanici Unit in the Peloritani Mountains has been investigated to constrain the P-T conditions attained in this sector of the southern European Hercynian chain. Microprobe investigations assisted by statistical handling of X-ray maps via principal component analysis allowed us to better elucidate the porphyroblast-matrix relationships, the geometry of the elemental distribution in garnet porphyroblasts and the average volume percentage of the reactant garnet during retrograde metamorphic evolution. Selected microprobe data were then used to constrain, by means of P-T pseudosections, the main P-T stages of the metamorphic evolution, using the XRF bulk-rock chemistry as the equilibrium chemical composition for the prograde and peak stages and an effective bulk-rock composition for the retrograde one. Peak metamorphic P-T estimates (~530?°C; 0.9?GPa) are consistent with a Hercynian crustal thickening stage at middle-lower crustal conditions, while subsequent evolution, constrained at 420–460?°C; 0.30–0.60?GPa, depicts a retrograde clockwise P-T trajectory linked to exhumation under likely extensional shearing conditions. The results obtained in this paper lead to envisage a new scenario for the crustal evolution of the Peloritani Mountains and stimulate a revision of previous interpretations in the light of the new investigation techniques.     

Alluvial terraces on the Ionian coast of northern Calabria, southern Italy: Implications for tectonic and sea level controls

In this paper we present the results of an integrated geomorphological, pedological and stratigraphical study carried out along the Ionian coast of northern Calabria (southern Italy). This area is characterised by the occurrence of five orders of alluvial terraces that are striking features of the landscape, where large and steep catchments debouch from the mountain front to the hilly coastal belt.Field investigations indicate that the deposits of all five terraces are suggestive of shallow gravel-bed braided streams.On the basis of the age of the Pleistocene substratum and morphostratigraphic correlation with marine terraces cropping out in the nearby areas, each order has been associated to specific marine oxygen isotope stages.Consequently, we focused on the interplay of allocyclic factors influencing stream aggradation/degradation. Soil features and other climatic proxies suggest that climate didn't play an important role with respect to tectonic and base-level changes in controlling fluvial dynamics.In particular, we recognised that during the middle Pleistocene the study area experienced a period of subaerial landscape modelling, as suggested by the thick and complex alluvial sequence of the highest terrace (T1). The onset of regional uplift marks a change in the geomorphic scenario, with tectonic and eustatically driven changes in base-level working together in causing switches in fluvial aggradational/erosional phases (T2–T5 terraces). Because of the uplift, river dissection occurred during phases of sea level fall, whereas aggradation phases occurred during periods of climate amelioration (sea level rise) just before highstands were attained.As a consequence, the stepped terraces in the study area reflect the interplay between tectonics (uplift) and sea level changes, in which terraces define episodes of relative sea level fall during the late Quaternary.