Modelling hydrostratigraphy and groundwater flow of a fractured and karst aquifer in a Mediterranean basin (Salento peninsula, southeastern Italy)

The control exerted by the hydrostratigraphic structure on aquifer recharge, groundwater flow and discharge along the coastal areas of a Mediterranean basin (Salento peninsula, about 5,000?km² wide, southern Italy) is assessed through the development and application of a groundwater flow model based on the reconstruction of the hydrostratigraphic architecture at the regional scale. The hydrostratigraphic model, obtained by processing surface and subsurface data, is applied to map the top of the main aquifer, which is hosted in the deep hydrostratigraphic unit corresponding to Cretaceous and Oligocene limestones with complex geometrical relationships with the sea. It is also used to estimate the aquifer recharge, which occurs by percolation through overlying younger sediments with low permeability. These data are completed with information about the soil use to estimate water abstraction for irrigation and with literature data to estimate the water abstraction for drinking and industrial purposes. The above-sketched conceptual model is the basis for a finite difference groundwater 2D pseudo-stationary flow model, which assumes the following fundamental approximations: the fractured and karst limestone hydrostratigraphic unit can be approximated, at the model scale, as a continuous medium for which the discrete Darcy??s law is valid; the transition zone between salt and fresh water is so small with respect to the grid spacing that the Ghyben?CHerzberg??s approximation for a sharp interface can be applied. Along the coastline different boundary conditions are assigned if the top of the limestone hydrostratigraphic unit lies either above the sea level (the aquifer has a free surface and fresh water is drained), or below the sea level (the aquifer is under pressure and the contact with sea occurs off-shore). The groundwater flow model correctly predicts the areas where the aquifer is fully saturated with salt water.     

Integration of biochemical, histochemical and toxicogenomic indices for the assessment of health status of mussels from the Tamar Estuary, U.K

The aim of this study was to examine whether a combination of biochemical, histopathological and toxicogenomic data could be used as a valuable tool for the assessment of biological risk associated with pollutants within the Tamar River and Estuary, S.W. England, U.K. Accordingly, biochemical and histopathological biomarkers (protein carbonyls, lipofuscin, neutral lipids, lysosomal stability [N-acetyl-β-hexosaminidase and neutral red], lysosomal volume, ferric reducing antioxidant power [FRAP] and malonaldehyde [MDA]) and gene expression profiles were assessed in 5 sites from the Tamar River and Estuary (Neal Point, Town Quay, Wilcove, Cremyll Ferry and Whitsand; and a reference site, Trebarwith Strand, N. Cornwall). PAHs were measured in mussel tissue and sediment and metals were measured in mussel tissue only. Data from the biomarkers was integrated into a Mussel Expert System (MES) model to produce a simple assessment of mussel stress. Clear gradients of mussel toxicity were identified by the biomarkers (with the exception of neutral lipids) with the highest impacted animals found furthest up the Tamar, whilst the MES was unable to identify a gradient of effect. Gene expression profiles also indicated a gradient of stress with the greatest number of significantly up- or down- regulated genes found at the uppermost 2 sites. The MES did, however, determine that mussels from all sites, except the reference site, were highly stressed; a conclusion that could not be inferred from the biomarker data alone. It is concluded that the MES is a valuable tool that permits integration and interpretation of complex sets of biomarker data by identifying the biological meaning of biomarker changes.     

Physical explanations of variations in river meander migration rates from model comparison

In meandering rivers, the local channel migration rate increases with increasing bend sharpness until it reaches a maximum at a certain critical value of the bend sharpness. Beyond this critical value, the migration rate decreases if bend sharpness increases. Similarly, reach‐averaged migration rates attain a maximum at a certain river sinuosity. This work investigates the physics of these phenomena by comparing the results of two physics‐based models of different complexity, in which the migration rates are proportional to the near‐bank flow velocity excess. In the computational tests the river was allowed to meander progressively, starting from an almost straight planimetry. Both models reproduced the observed peak in the curve describing the local migration rate as a function of the ratio radius of curvature‐channel width (R/B), with a rising limb at lower R/B values and a falling limb at higher R/B values. The rising limb can be explained by the decrease in relative lag distance between near‐bank flow velocity and forcing curvature as R/B increases. The falling limb results from the decrease in local channel curvature and near‐bank flow velocity excess. Since the models do not include flow separation, the results indicate that this phenomenon is not needed to explain the decrease of channel migration rates in sharp bends. The models reproduced also the peak in the curve describing the reach‐averaged migration rates as a function of river sinuosity The increase and then decrease of reach‐averaged migration rates as sinuosity increases appears to be mainly caused by the variation of the reach‐averaged value of the ratio R/B. Copyright © 2009 John Wiley & Sons, Ltd.     

Inhibition of Fertilization and Larval Metamorphosis of the Coral Acropora millepora (Ehrenberg, 1834) by Petroleum Products

Accidental oil spills from ships or rigs and inputs of effluent such as production formation water (PFW) are key perceived threats to tropical biota from industry activities. Scleractinian corals are an important functional component of tropical reefs and the abundance, diversity and resilience of coral communities can be used as an indicator of ecosystem health. In this paper, we report the effects of petroleum products, including water accommodated fractions (WAF) of crude oil, PFW and dispersant (Corexit 9527), on fertilization and larval metamorphosis of the widespread scleractinian coral, Acropora millepora (Ehrenberg, 1834) in laboratory-based assays. At 20% v/v PFW fertilization was inhibited by 25%. This concentration was equivalent 0.0721 mg l⁻¹ total hydrocarbon (THC). In contrast, larval metamorphosis was more sensitive to this effluent, with 98% metamorphosis inhibited at the same concentration. Crude oil WAF did not inhibit fertilization of gametes until dispersant was introduced. Dispersed oil was slightly more toxic to fertilization than dispersant alone, suggesting toxicity to that event may be additive. The minimum concentration of dispersed oil which inhibited fertilization was 0.0325 mg l⁻¹ THC. Larval metamorphosis was more sensitive than fertilization to crude oil. Although crude oil and dispersant inhibited larval metamorphosis individually, this toxicity was magnified when larvae were exposed to combinations of both. Crude oil inhibited metamorphosis at 0.0824 mg l⁻¹ THC and at 0.0325 mg l⁻¹ THC when dispersed in 10% v/v (dispersant/oil). Management of petroleum-related risks to spawning corals should consider not only the occurrence of the annual coral spawning event, but also the subsequent 1–3-week period during which most larval metamorphosis and recruitment occur.     

Analytical study of the swing-by maneuver in an elliptical system

The objective of the present paper is to derive a set of analytical equations that describe a swing-by maneuver realized in a system of primaries that are in elliptical orbits. The goal is to calculate the variations of energy, velocity and angular momentum as a function of the usual basic parameters that describe the swing-by maneuver, as done before for the case of circular orbits. In elliptical orbits the velocity of the secondary body is no longer constant, as in the circular case, but it varies with the position of the secondary body in its orbit. As a consequence, the variations of energy, velocity and angular momentum become functions of the magnitude and the angle between the velocity vector of the secondary body and the line connecting the primaries. The “patched-conics” approach is used to obtain these equations. The configurations that result in maximum gains and losses of energy for the spacecraft are shown next, and a comparison between the results obtained using the analytical equations and numerical simulations are made to validate the method developed here.     

Nonequilibrium Processes in the Solar Corona,Transition Region,Flares, and Solar Wind <Emphasis Type="Italic">(Invited Review)</Emphasis>

We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modeling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for the detection of these non-equilibrium phenomena in various spectral ranges.     

A Comparison Between Machine Learning and Functional Geostatistics Approaches for Data-Driven Analyses of Sediment Transport in a Pre-Alpine Stream

Mathematical Geosciences - The problem of providing data-driven models for sediment transport in a pre-Alpine stream in Italy is addressed. This study is based on a large set of measurements...     

Infrared micro-spectroscopy of the martian meteorite Zagami: Extraction of individual mineral phase spectra

Zagami, a well characterized SNC meteorite, represents a reference sample to verify the feasibility of the non-destructive infrared micro-spectroscopy technique to extract spectral signatures from individual mineral phases in a meteorite sample. For the first time individual infrared spectra of the major mineral phases, in the 6000-600 cm⁻¹ (1.67-16.7 μm) spectral interval, whose identification is confirmed by energy dispersive X-ray analysis and backscattered imaging, are measured. The signatures of the main mineral phases we identified in the Zagami chip are: (1) maskelynite characterized by broad and smooth SiO vibrational bands in the 1000 cm⁻¹ spectral region; (2) crystalline pyroxenes showing well defined fine structures; and (3) an oxide mineral phase with an almost featureless and flat spectrum. In the part of the spectrum centered around 2 μm, by analyzing the different positions of the Fe²⁺ bands, we were able to discern the high-Ca from the low-Ca pyroxene phases. This result demonstrates that by means of the infrared micro-spectroscopy technique it is possible to retrieve directly the composition of pyroxenes in the En-Fs-Wo system, without relying on the use of deconvolution techniques. In addition IR signatures due to water and aliphatic hydrocarbons were observed to be more abundant in the pyroxenes than in maskelynite. This could be an indication that the organic and water signatures are due to indigenous compounds in Zagami rather than laboratory contamination, however, further investigations are necessary before this conclusion can be confirmed.