Rhyolitic pumice in the basaltic pyroclasts from the 1971 eruption of Teneguía volcano,Canary Islands

Fragments of acid pumice have been found among the basic pyroclastics thrown out by the Teneguía volcano during its explosive phases. The presence of these pumice fragments brings up the problem of their origin and their relationships to the mechanism of the eruption.The composition of the analysed samples coincides exactly with the low temperature trough in petrogeny's residua system, albits-orthoclase-silica. The samples can be classified as rhyolites and trachytes.The authors propose that the pumice was produced by the fusion of the acid phase in a subvolcanic complex located beneath the island of La Palma.     

Elucidation of different forms of organic carbon in marine sediments from the Atlantic coast of Spain using thermal analysis coupled to isotope ratio and quadrupole mass spectrometry

Analysis of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO₂) and m/z 18 (H₂O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ¹³C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.     

Fluid Geochemistry as Indicator of Tectonically-Related,Deep Water Circulations in the Sardinian Rift-Campidano Graben (Italy): New Insights from Environmental Isotopes

The EC funded Geochemical Seismic Zonation program (EEC GSZ Project 1996–1998) chose Sardinia as a low-seismicity site, in which the relationships between fluid geochemistry and seismo-tectonics had to be investigated and results compared with outcomes from other selected high-seismicity sites. A first article, examining the role of fault segmentation and seismic quiescence on the geochemical composition of groundwaters and gases, has already been presented (Angelone et al. 2005). This article deals with environmental isotopes which, together with selected hydrochemical data, give hints on tectonically-related fluid circulations. Four water-dominated hydrothermal systems were considered, all located along regional fault systems and discharging groundwaters belonging to the Na–HCO₃ and Na–Cl facies. In the considered systems, groundwater circulation takes place, principally, in the Palaeozoic Crystalline Basement (PCB), with the exception of the Logudoro system, where hydrological circuits develop in the Mesozoic Carbonate Platform (MCP). The high CO₂ contents, the non-attainment of fluid-rock equilibrium and the large lithological variability prevent the construction of a unique hydrogeological–geochemical conceptual model. In this case, stable isotopes provide a useful tool to describe the origin of fluids and their subterranean movements. Stable isotopes of water, integrated with hydrochemical data, indicate that fluids are derived from three main end members. The dominant component is a relatively recent local meteoric water; the second one is marine water; and the third one is a fossil freshwater, depleted in heavy isotopes with respect to modern rains. The latter end member entered the aquifer system in the past, when climatic conditions were greatly different from today. At least two circulation systems can be recognised, namely a shallow cold system and a deep hydrothermal system, as well as two distinct hydrological processes: (1) gravity-controlled descent of cold water towards greater depths and (2) convection linked to a thermal gradient, causing deep fluids to rise up from the hydrothermal reservoir towards the surface. The highly variable δ¹³C_TDIC values suggest the presence of two distinct CO₂ sources, namely, a biogenic one and a thermogenic one. The relation between the isotopic compositions of CO₂ and He indicates an increased mantle signature in uprising CO₂-rich fluids.     

Characterization of an Area Polluted by Copper and Zinc:the Relation between Soil Texture,Mineralogy and Pollutant Concentration

Abstract: Twenty-four soil samples were collected at three depths from an approximately 2.5 acre contaminated site in southern Piedmont (Italy) and then analyzed. The main soil parameters determined were: pH, Cation Exchange Capacity (CEC), particle size distribution, total organic carbon (TOC) content and retained metal concentration. The mineral phases were identified by X-Ray Powder Diffraction (XRPD). All of the samples contained Zn and Cu resulting from industrial contamination during the last century, and those obtained at depths of 20-40 cm consistently showed the highest levels. To determine which size fraction was most active in the retention process, the samples were separated into four fractions (≤2 mm, ≤63 μm, ≤30 μm and ≤2 μm) and the amount of pollutant measured in each. It was found that metal retention was the highest in the clayey fraction, whose clay minerals were identified by XRPD after K+ and Mg2+ saturation, glycerol treatment and heating to 550°C. The clayey fraction was also the richest in TOC, and a direct correlation between TOC amount and metal retention was observed.     

Social identity, perception and motivation in adaptation to climate risk in the coffee sector of Chiapas, Mexico

Most investigation into climate adaptation to date has focused on specific technological interventions and socio-economic aspects of adaptive capacity. New perspectives posit that socio-cognitive factors may be as or more important in motivating individuals to take adaptive actions. Recent research indicates that incorporating insights from motivation theory can enhance theorization of adaptive capacity. Yet unexplored, and what we propose here, is the addition of social identity to models of adaptive capacity and adaptation. To apply this conceptual framework, the first author undertook in-depth interviews with a sample of farmers who had participated in broader surveys the previous year to explore their perceptions of their social identity, climate-related information and its sources, and climate risk. These interviews elicited compelling evidence that social identity mediates between risk perception and adaptation through its influence on motivation. Interviews revealed significant links between social identity and perception of information, risk perception and adaptation, of which the most salient were the relative credibility and legitimacy of information sources (related to us vs. them social group differentiation); the role of coffee organizations; and ethnicity and geographic marginalization. Strong in-group identity and perceptions of potentially influential out-groups such as the scientific community appear to particularly influence perception and use of information. These findings have rich policy implications for adaptation management and merit further investigation to identify how, where and why social identity plays a role in climate-risk perception, motivation and adaptation in other geographic areas of vulnerability worldwide.     

Large Earthquakes at the Ibero-Maghrebian Region: Basis for an EEWS

Large earthquakes (M_w > 6, I_max > VIII) occur at the Ibero-Maghrebian region, extending from a point (12ºW) southwest of Cape St. Vincent to Tunisia, with different characteristics depending on their location, which cause considerable damage and casualties. Seismic activity at this region is associated with the boundary between the lithospheric plates of Eurasia and Africa, which extends from the Azores Islands to Tunisia. The boundary at Cape St. Vincent, which has a clear oceanic nature in the westernmost part, experiences a transition from an oceanic to a continental boundary, with the interaction of the southern border of the Iberian Peninsula, the northern border of Africa, and the Alboran basin between them, corresponding to a wide area of deformation. Further to the east, the plate boundary recovers its oceanic nature following the northern coast of Algeria and Tunisia. The region has been divided into four zones with different seismic characteristics. From west to east, large earthquake occurrence, focal depth, total seismic moment tensor, and average seismic slip velocities for each zone along the region show the differences in seismic release of deformation. This must be taken into account in developing an EEWS for the region.