Variogram-Based Descriptors for Comparison and Classification of Rock Texture Images

Mathematical Geosciences - Rock characterization is typically performed by geologists in mining companies and involves the analysis of several meters of drill-hole samples to describe distinctive...     

Polarimetric receiver in the forty gigahertz band: new instrument for the Q-U-I joint Tenerife experiment

This paper describes the analysis, design and characterization of a polarimetric receiver developed for covering the 35 to 47 GHz frequency band in the new instrument aimed at completing the ground-based Q-U-I Joint Tenerife Experiment. This experiment is designed to measure polarization in the Cosmic Microwave Background. The described high frequency instrument is a HEMT-based array composed of 29 pixels. A thorough analysis of the behaviour of the proposed receiver, based on electronic phase switching, is presented for a noise-like linearly polarized input signal, obtaining simultaneously I, Q and U Stokes parameters of the input signal. Wideband subsystems are designed, assembled and characterized for the polarimeter. Their performances are described showing appropriate results within the 35-to-47 GHz frequency band. Functionality tests are performed at room and cryogenic temperatures with adequate results for both temperature conditions, which validate the receiver concept and performance.     

Humic substances in estuarine soils colonized by Spartina maritima

This study characterizes humic substances (HS) from two soils colonized by Spartina maritima at different physiographical positions in estuarine environments on the north-western coast of the Iberian Peninsula: the Villaviciosa site, a stand close to the main tidal channel, and the Ortigueira site, located in the low salt marsh. Humic and fulvic acids were extracted from the soils and characterized qualitatively by the following spectroscopic techniques: Fourier transform infrared spectroscopy, fluorescence spectroscopy and solid-state ¹³C nuclear magnetic resonance.The characterized HS showed a predominance of low humified compounds with a high proportion of aliphatic components and a low degree of aromaticity. The HS composition differed substantially between sites. In the Villaviciosa soil, the large amount of nonpolar aliphatic components and the very low degree of aromaticity may indicate a significant contribution of marine organic matter and/or microbial material to the HS. However, in the HS from the Ortigueira soil, the higher proportion of polysaccharides together with the presence of lignin-derived compounds may indicate greater inputs of vascular plant material. The δ¹³C isotopic composition of the bulk soils highlights the large input of Spartina maritima debris to the Ortigueira site, whereas in the Villaviciosa site, organic contributions from this C4 vascular plant were not so evident.The results indicate that in these soils colonized by Spartina maritima, physiographical position has an important effect on the composition of soil HS and, therefore, must be considered in the study of organic matter characteristics in such estuarine environments.     

Human impacts overwhelm the effects of sea-level rise on Basque coastal habitats (N Spain) between 1954 and 2004

According to coastal measurements, global mean sea-level has risen at a rate of 1.8 mm yr⁻¹ between 1950 and 2000, with large spatial variability at regional scales. Within the Bay of Biscay, trends computed from coastal tide gauges records have revealed that sea-level rise is accelerating over this period of time; this is in agreement with rates obtained from satellite imagery in the open ocean since 1993. The objectives of the present study are: (1) to assess the evidence of the relative sea-level rise on coastal morphology and habitats in the Gipuzkoan littoral zone (Basque coast, northern Spain) for the period 1954–2004, and (2) to evaluate the relative contribution of local anthropogenic versus sea-level rise impacts for explaining inter-supratidal habitat changes. A high-resolution airborne laser altimetry data (LIDAR) has been used to derive a Digital Terrain Model (DTM) of 15-cm vertical resolution. Coastal habitats were mapped for two periods, using historic airborne photography (1954) and high-resolution imagery (2004). Analysis of tide gauge records from Santander (northern Spain) has revealed that relative mean sea-level has been rising at a rate of 2.08 ± 0.33 mm yr⁻¹ from 1943 to 2004; this is consistent with sea-level trends from other measurements within the area (St. Jean de Luz and Bilbao), obtained over shorter periods of time, and with previous results obtained in the Bay of Biscay. Based upon this sea-level trend and by means of a LIDAR-based DTM, the results have indicated that the predicted change along the Gipuzkoan coast due to sea-level rise was of 11.1 ha within the 50-yr period. In contrast, comparison of historical and recent orthophotography has detected only 2.95 ha of change, originated possibly from sea-level rise, and 98 ha transformed by anthropogenic impacts. Hence, coastal changes due to sea-level rise might be overwhelmed by excessive human impacts, at the spatial and temporal scales of the analysis. This work highlights that local anthropogenic impact is the major threat to Basque coastal and estuarine habitats, compared with natural erosive processes and global climate change driving forces over recent times.     

SPATIO‐TEMPORAL SPECIFICS OF HYDRO‐GEOMORPHIC PROCESSES IN HEADWATER PARTS OF MID‐MOUNTAINS RECONSTRUCTED BASED ON TREE‐RING DATA: A CASE STUDY FROM THE HRUBÝ JESENÍK MOUNTAINS (CZECH REPUBLIC)

Debris flows and debris floods cause frequent geomorphic hazards, even in the mid‐mountains of Central Europe. In the Hrubý Jeseník Mountains (Eastern Sudetes, Czech Republic), strong anthropogenic interventions have created specific conditions for erosion, transport and accumulation of material released by debris flow/flood events. We present a detailed spatio‐temporal reconstruction of the hydro‐geomorphic process activity in two adjacent sub‐catchments using dendrogeomorphic methods applied to the steep, narrow channels. An analysis of 172 sampled trees [Picea Abies (L.) Karst.] revealed 14 torrential events since 1943 in the Klepá?ský stream sub‐catchment and 11 events since 1897 in the Keprnický stream sub‐catchment. Identical events were identified in 1965, 1991, 1997, 2002 and 2010. The event return periods were comparable with return periods from the foothills of the European Alps. A higher frequency of events in the first sub‐catchment may be caused by the presence of a deep‐seated landslide, steeper slopes and a higher susceptibility to shallow slope deformations. Different spatial patterns of events were presented using the Kernel Density analysis in ArcMap 10.1. Clusters of affected trees in the valley floor during the last decades may be due to increased erosion below the check dams and increased accumulation above. The presence of check dams and slope stabilization works since the 1960s has mitigated the processes in several gullies, but due to the current non‐interventional management, the risk of their damage is increasing, particularly when increased activity is observed in the adjacent unprotected gullies.     

A Marine Biotic Index to Establish the Ecological Quality of Soft-Bottom Benthos Within European Estuarine and Coastal Environments

In this paper, a marine Biotic Index (BI) for soft-bottom benthos of European estuarine and coastal environments is proposed. This is derived from the proportions of individual abundance in five ecological groups, which are related to the degree of sensitivity/tolerance to an environmental stress gradient. The main difference with previously published indices is the use of a simple formula that produces a continuous Biotic Coefficient (BC) – which makes it more suitable for statistical analysis, in opposition with previous discreet biotic indices – not affected by subjectivity. Relationships between this coefficient and a complementary BI with several environmental variables are discussed. Finally, a validation of the proposed index is made with data from systems affected by recent human disturbances, showing that different anthropogenic changes in the environment can be detected through the use of this BI.     

An approach to the intercalibration of benthic ecological status assessment in the North Atlantic ecoregion, according to the European Water Framework Directive

The European Water Framework Directive (WFD) establishes a framework for the protection and improvement of transitional and coastal waters; its final objective is to achieve at least 'good water status' for all waters, by 2015. The WFD requires Member States (MSs) to assess the Ecological Status (ES) of water bodies. This assessment will be based upon the status of the biological, hydromorphological and physico-chemical quality elements, by comparing data obtained from monitoring networks to reference (undisturbed) conditions, and then deriving an Ecological Quality Ratio (EQR). One of the biological quality elements to be considered is the benthic invertebrate component and some structural parameters (composition, diversity and disturbance-sensitive taxa) must be included in the ES assessment. Following these criteria, several approaches to benthic invertebrate assessment have been proposed by MSs. The WFD requires that these approaches are intercalibrated. This contribution describes the comparison of the different methodologies proposed by United Kingdom, Spain, Denmark and Norway. Results show a high consistency between the approaches, both with regard to determining the EQR and boundary settings for the ES.     

High gene flow promotes the genetic homogeneity of the fish goby Pomatoschistus marmoratus (Risso, 1810) from Mar Menor coastal lagoon and adjacent marine waters (Spain)

The extreme environmental variability of coastal lagoons suggests that physical and ecological factors could contribute to the genetic divergence among populations occurring in lagoon and open‐coast environments. In this study we analysed the genetic variability of lagoon and marine samples of the sand goby, Pomatoschistus marmoratus (Risso, 1810) (Pisces: Gobiidae), on the SW Spain coast. A fragment of mitochondrial DNA control region (570 bp) was sequenced for 196 individuals collected in five localities: Lo Pagan, Los Urrutias and Playa Honda (Mar Menor coastal lagoon), and Veneziola and Mazarrón (Mediterranean Sea). The total haplotype diversity was h = 0.9424 ± 0.0229, and the total nucleotide diversity was π = 0.0108 ± 0.0058. Among‐sample genetic differentiation was not significant and small‐scale patterns in the distribution of haplotypes were not apparent. Gene flow and dispersal‐related life history traits may account for low genetic structure at a small spatial scale. The high genetic diversity found in P. marmoratus increases its potential to adapt to changing conditions of the Mar Menor coastal lagoon.