Influence of sample size on line-based positional assessment methods for road data

Sample size influences considerably the variability of results of estimation processes, but this issue has never previously been analyzed for line-based positional assessment methods. The basis of the analysis is a simulation process which extracts homologous road axes from the product and from the control survey and applies the four methods. Sample sizes of road axes range from 10 Km up to 200 Km, and for each sample size 1000 simulations were run. Results for each sample size were compared to population parameters or population distribution functions by means of statistical tests. The variability of estimations was reduced in the order of 2.5-4.5 times when sample size increased from 10 Km to 200 Km.     

The 1511 Eastern Alps earthquakes: a critical update and comparison of existing macroseismic datasets

Three earthquakes condition the seismic hazard estimates of the Eastern Alps: the 1348 “Villach”, the 1511 “Idrija”, and the 1976 Gemona events. Only the last one can be well documented, while doubts remain for location and size of the other two. New documents have been found about the 1511 quake that, together with a complete revision of the information already available, offer some new indications on the location and size of the event.     

How the aggressiveness of rainfalls in the Mediterranean lands is enhanced by climate change

Rainfall and overland flow are fundamental processes for Earth’s ecosystems but can also be land disturbing forces, particularly when triggered by extreme hydro-meteorological events. Examples of these extremes are rainstorms and related phenomena due to rainfall aggressiveness. They produce high-impact land processes such as soil erosion and nutrient losses. Economic and social consequences of these processes can be quite severe. However, hydrological extremes and their environmental implications are still poorly understood, particularly if analyzed in the context of climate change. Here, we analyze a 300 year long times series of historical rainfall patterns across the Mediterranean in the last three centuries and we investigate changes in the erosive forcing as related to climate changes. Our results show that the erosive forcing increased towards the end of the Little Ice Age (~1850) over western and central Mediterranean and that has been increasing in the recent warming period at low Mediterranean latitudes, due to a higher frequency of intensive storms. Such increased concentrated precipitation may lead to an intensification of land degradation processes triggered by soil erosion and transport across a range of scales from hillslopes to small catchments.     

Chemical and physical characterization of iron-intercalated vermiculite compounds

Herein we report on synthetic iron-intercalated vermiculites prepared from a Mg-vermiculite mineral from Santa Olalla, Huelva, Spain, by means of an ion exchange process from aqueous solutions of FeCl₂ and FeCl₃. Thermogravimetric, X-ray diffraction, magnetic susceptibility and Mössbauer spectral studies have been used to characterize the synthetic iron-intercalated vermiculites. The results suggest that the intercalation process employed induces modifications in both the interlayer spacing and in the octahedral sheet; the disordered structure of the Mg-vermiculite mineral is not altered. The presence of solvated Fe(H₂O) _n ²⁺ ions has been shown by the Mössbauer spectroscopy. No magnetic order has been observed between 2 and 300 K neither in the Mg-vermiculite mineral nor in the two synthetic iron-intercalated vermiculites.     

Microencapsulation of okadaic acid as a tool for studying the accumulation of DSP toxins in mussels

The possibility and effectiveness of microencapsulation of okadaic acid (OA) in gelatin-acacia microcapsules has been studied. The encapsulation efficiency was higher than 33%. The microcapsules were shown to be very stable, not leaching more than 9% of the encapsulated OA in a 20-h period. OA from the microcapsules was absorbed by the mussels very efficiently, accumulating--after 3 days of feeding and one of depuration--65% of the OA in microcapsules and 22% of the total OA used at the beginning of the microencapsulation process. These efficiencies and the possibility of encapsulating single DSP toxins and derivatives constitute a valuable tool for the study of the accumulation and biotransformation of DSP toxins in bivalves.     

Comparative study of digestion methods EPA 3050B (HNO₃--H₂O₂--HCl) and ISO 11466.3 (aqua regia) for Cu, Ni and Pb contamination assessment in marine sediments

Knowing the metal extraction capacity of a digestion method is crucial for a better environmental interpretation of metal concentrations determined in sediments. One of the main problems at the present is the lack of harmonization of information obtained by two of the most popular sediment partial digestion methods: ISO 11466.3 (aqua regia) and EPA 3050B (HNO?--H?O?--HCl). In the present work, the amount of Cu, Ni and Pb leached by using both methods was compared with the total content of those elements in marine sediments collected, as an example, from the Cienfuegos Bay, Cuba. Similar amounts of Cu were extracted by both methods; while leaching of Ni and Pb were different. Generally, the EPA method extracted more Ni than the ISO method. In contrast, Pb was extracted in a larger amount by the ISO method. Some explanations are given for the observed results. X-ray Diffraction, X-ray Fluorescence, Particle Induced X-ray Emission Spectrometry and Energy Dispersive X-ray coupled to Scanning Electron Microscopy were employed for this purpose. On the other hand, none of the methods studied extracted simultaneously the fraction of all the metals, probably provided by human activity (Theoretical Anthropogenic Fraction) in both sediments studied. The use of ISO 11466.3 or EPA 3050B is recommended since the analytical performance parameters of both, in combination with Flame Atomic Absorption Spectrometry, are adequate. For a better environmental interpretation of the analytical results, information on the extraction efficiency of the selected method for specific elements and sediments under study should also be provided, together with the determined concentrations.     

Mediterranean saline streams in southeast Spain: What do we know?

Many Mediterranean streams in arid and semiarid areas are naturally saline systems due to the presence of evaportic rocks of Miocene or Triassic origin. Despite the fact that these aquatic ecosystems are rare in Europe, they are common in southeast of Spain. The environmental constraints of these semiarid saline streams are imposed by both geological and climatic conditions. This paper is a compilation and summary of the principal results obtained from various studies on semiarid saline streams in the Iberian southeast. Available data for these typical environments in the region covers diverse issues such as those regarding their physical and chemical features, typology, biodiversity, community structure and ecosystem functioning, as well as different ecological and evolutionary aspects of their biota (e.g. ecophysiological responses, life cycles and phylogeography). Issues concerning the conservation of these habitats, such as the main human uses, impacts, threats and their management are also summarised. Finally, topics in need of further research are provided. The current knowledge of saline streams in southeastern Spain highlights the physical and ecological singularity of these environments, and their high conservation value. Saline streams are particularly interesting due to their halotolerant/halophilic biota and high number of rare and endemic species.     

INTEGRAL/RXTE high-energy observation of a state transition of GX 339–4

On 2004 August 15, we observed a fast (shorter than 10 h) state transition in the bright black hole transient GX 339–4 simultaneously with Rossi X-Ray Timing Explorer ( RXTE ) and INTEGRAL . This transition was evident both in timing and spectral properties. Combining the data from the Proportional Counter Array (PCA), the High-Energy X-ray Timing Experiment (HEXTE) and the Imager on Board the INTEGRAL Satellite (IBIS), we obtained good quality broad-band (3–200 keV) energy spectra before and after the transition. These spectra indicate that the hard component steepened. Also, the high-energy cut-off that was present at ∼70 keV before the transition was not detected after the transition. This is the first time that an accurate determination of the broad-band spectrum across such a transition has been measured on a short time-scale. It shows that, although some spectral parameters do not change abruptly through the transition, the high-energy cut-off increases/disappears rather fast. These results constitute a benchmark on which to test theoretical models for the production of the hard component in these systems.     

Sugar cane nutrient requirements and the role of atmospheric deposition supplying supplementary fertilization in a Venezuelan sugar cane plantation

As a consequence of high industrial and agricultural activities, acidic rains loaded with pollutants—including nutrients—are characteristic of northern central Venezuela, a region dominated by sugar cane plantations. Canopies of forest and agricultural crops can modify the chemistry of rainfall through uptake, leaching and outwash of deposited ions. This paper describes the change in the chemistry of acid rains after passing through a sugar cane canopy. Four plots of 300 m² within a 4.5 ha experimental area, planted with Saccharum officinarum had rain and throughfall collectors installed. The study corresponds to the analysis of the growing season of the third ratoon. The pH of the rain in the agroecosy stem increased after passing through the canopy. The magnitudes of the changes were important and partially related to the significant amount of cations leached from the leaves or washed out from dry deposition to the leaves. N inputs for wet and dry deposition in the agroecosystem were high (25.25 kg ha^?1 yr^?1) as a consequence of the agricultural activity in the area, the local burning of sugar cane before cropping, and the location of the experimental area close to petrochemical and fertilizer industries. Rainfall constitutes an important source of nutrient inputs to the sugar cane system. In the case of macronutrients (N, P and K) the inputs were high and supply an important fraction of plant nutrient needs, as occurs for zinc and copper.     

Strain and stress fields along the Gibraltar Orogenic Arc: Constraints on active geodynamics

The Gibraltar Orogenic Arc, in the Western Mediterranean, represents a complex region of active deformation related to the oblique Nubia–Eurasia convergence process. To increase the knowledge on the ongoing active processes in this region, we have used the most up-to-date and comprehensive geodetic crustal motion and stress fields. To this end, we analyzed both continuous and campaign-mode GPS data collected between 1999.00 and 2011.00 across the area and compiled a multidisciplinary dataset of well-constrained stress indicators to be compared with the geodetic results. The main results highlight the oblique nature of the Nubia–Eurasia convergence, which provides the largest component of the observed stress-pattern and is responsible for a significant strain-rate field along the Gibraltar Orogenic Arc. We discuss our findings with respect to available geological, seismological and geophysical data in order to verify their coherency compared to more relevant geodynamical models proposed in literature. According to previous studies, we confirmed how much of the secondary stress-pattern can be related to the gravitational potential energy field, which may also be responsible for some 2D stress–strain-rate angular discrepancies observed in large areas of the Betics. In addition, taking into account the sub-orthogonal azimuthal relationship between the S_Hmax and ε_hmin directions and the Fast Polarization Directions, we conjectured a deep dynamic process controlling both the crustal stress field and the surface deformation on large areas of the orogenic arc. Finally, although the models proposed to explain the geodynamic pattern of the Gibraltar Orogenic Arc are supported by a discrete number of geological and geophysical observations, it is only the back-arc extension and westward rollback model that is able to adequately account for the vast majority of the observations. Based on our findings and other evidences, we retain that this process could still be active beneath the Gibraltar Orogenic Arc.