Kinetics of the reactions of Cl atoms with 2-buten-1-ol, 2-methyl-2-propen-1-ol, and 3-methyl-2-buten-1-ol as a function of temperature

The reactions of three structurally similar unsaturated alcohols, 2-buten-1-ol (crotyl alcohol), 2-methyl-2-propen-1-ol (MPO221) and 3-methyl-2-buten-1-ol (MBO321) with Cl atoms, have been investigated for the first time, using a 400 l Teflon reaction chamber coupled with gas chromatograph-coupled with flame-ionization detection (GC-FID). The experiments were performed at atmospheric pressure and at temperatures between 255 and 298 K, in air or nitrogen as the bath gas. The obtained kinetic data were used to derive the Arrhenius expressions , , (in units of cm³ molecule⁻¹ s⁻¹). Finally, atmospheric lifetimes of those unsaturated alcohols with respect to OH, NO₃, O₃ and Cl have been calculated.     

The Beach Crowding Index: A Tool for Assessing Social Carrying Capacity of Vulnerable Beaches

The aim of this article is to introduce the Beach Crowding Index (BCI), a procedure to assess the social carrying capacity of vulnerable beaches. The study uses the people at one time (PAOT) approach and data gathered weekly throughout the bathing season regarding the number of beachgoers in 100 m² cells of the beach to assess how many beachgoers it can comfortably hold. The procedure is based on fieldwork, interviews with beachgoers, and geographic information system (GIS) analysis and has been tested on four beaches in protected areas on the Spanish Mediterranean coast. On a scale from 0 to 4, minimum scores throughout the bathing season are 0.7 and maximum 3.7, although results showed wide variation between the beaches, the section of the beach, and the time of day. This study suggests that determining the location of beachgoers and collecting a long-term series of data is fundamental to assessing social carrying capacity and that the BCI procedure can be used for a large number of applications.     

Magnetic reorientation induced by pressure solution: A potential mechanism for orogenic-scale remagnetizations

New paleomagnetic analyses of Triassic, Cretaceous and Eocene strata in the south-central Pyrenees show evidence for a widespread remagnetization, located along the southern border of the Axial Zone, the Internal Sierras, and the northern part of the Jaca-Pamplona basin. This remagnetization, always reversed in polarity, was acquired after an extensive period of Late Eocene–Early Oligocene folding and tilting in the area, and affects limestones, sandstones, marls and red beds. In addition, a characteristic prefolding component was identified in 30% of Upper Cretaceous and Triassic red beds. These results, together with a revaluation of previously published paleomagnetic data from the central Pyrenees, indicate that the spatial distribution of the postfolding remagnetization coincides with that of a domain of pressure solution cleavage. A relationship between the intensity of the remagnetization and the characteristic (prefolding component) with respect to the density of cleavage surfaces, leads us to propose a mechanism for the remagnetization related to the development of pressure solution cleavage that is framed within the tectonic evolution of the central Pyrenees. Partial dissolution of rock under tectonic compression leads to the liberation and subsequent accumulation of insoluble minerals in cleavage planes. Magnetic grains are part of the relatively insoluble residue, and they reorient in the presence of the ambient field after they are freed during dissolution of the rock matrix. Chemical reequilibrium (dissolution and/or neoformation of magnetic carriers) during this process cannot be excluded. The remagnetization mechanism we propose can help to explain widespread remagnetizations in low to moderately deformed rocks without the need of large-scale migration of orogenic fluids.     

Analysis of anisotropy of magnetic susceptibility in iron-oolitic beds: a potential tool for paleocurrent identification

A combined sedimentological, shape-preferred orientation and anisotropy of magnetic susceptibility (AMS) analysis has been performed at the Arroyofrío Bed (Callovian–Oxfordian boundary level) in the locality of Moneva (Iberian Range, NE Spain). The Arroyofrío bed is a widespread iron-ooid limestone interval forming a condensed sequence. The present study has focused on the analysis of the potential presence of a preferred ooid orientation at the Arroyofrío bed. The obtained data show that ooids were originally ellipsoidal and had an imbricate disposition with respect to the bedding/lamination surface. The main ooid orientation within the bedding plane shows a NNE–SSW trend. Results of AMS analyses show a magnetic foliation parallel or slightly imbricated with respect to bedding and magnetic lineation parallel to the main ooid orientation. Magnetic mineralogy of studied samples shows that AMS is mainly controlled by magnetite with minor contributions of hematite and paramagnetic minerals (that can reach contributions of 35 %). The analyzed ooids show axial ratios between 1.4 and 2.8 (intrinsic anisotropy), while the anisotropy of their distribution shows lower anisotropies (e.g., Rs = 1.15) or very low values of the anisotropic magnetic parameters (e.g., P′ < 1.01). Sedimentary texture, matrix features, bioturbation and fossil content influenced both ooid main orientation and the magnetic fabric. Magnetic lineation and main orientation of long ooid axes are transverse to the inferred coastline in the studied area and parallel to the expected paleocurrent direction with respect to the Ejulve-Maestrazgo paleogeographic high. The direct correlation between AMS magnetic lineation and the ooid analysis permits to demonstrate that the paleocurrent imprint can be recorded by means of AMS despite the highly ferromagnetic context fabric and at coarse deposits. Obtained results support the interest and reliability of AMS to unravel paleocurrent imprints for paleogeographic reconstructions.     

Influence of upwelling and river runoff interaction on phytoplankton assemblages in a Middle Galician Ria and Comparison with northern and southern rias (NW Iberian Peninsula)

The first oceanographic research (hydrography, nutrient salts, chlorophyll, primary production and phytoplankton assemblages) in a Middle Galician Ria was carried out in Corme-Laxe during 2001, just a year before the Prestige oil spill, being the only reference to evaluate eventual changes in the phytoplankton community. Due to the small size of this ria (6.5 km²), oceanographic processes were driven by the continental water supplied by Anllons River during the wet season (20–30 m³ s⁻¹ in winter), and the strong oceanic influence from the nearby shelf during the dry season. The annual cycle showed a spring bloom with high levels of chlorophyll (up to 14 μg Chl-a L⁻¹) and primary production (3 g C m⁻² d⁻¹) and a summer upwelling bloom (up to 8 μg Chl-a L⁻¹ and 10 g C m⁻² d⁻¹) where the proximity of the Galician upwelling core (<13.5 °C at sea surface) favors the input of upwelled seawater (up to 9 μM of nitrate and silicate) to the bottom ria layer, even during summer stratification events (primary production around 2 g C m⁻² d⁻¹). Thus, phytoplankton assemblages form a “continuum” from spring to autumn with a predominance of diatoms and overlapping species between consecutive periods; only in autumn dinoflagellates and flagellates characterized the phytoplankton community. In the Middle Rias as Corme-Laxe, the nutrient values, Chl-a, primary production and phytoplankton abundance for productive periods were higher than those reported for the Northern (Ria of A Coruña) and Southern Rias (Ria of Arousa) for year 2001; this suggests the importance of the hydrographic events occurring in the zone of maximum upwelling intensity of the Western Iberian Shelf, where a lack of annual cycles studies exists.     

New insights into asymmetric folding by means of the anisotropy of magnetic susceptibility,Variscan and Pyrenean folds (SW Pyrenees)

Magnetic fabric allows to unravel the petrofabrics of sedimentary rocks and to assess their deformational history. The use of this technique, in addition to classical structural field observations in the limbs of seven asymmetric folds in the Pyrenees, helps to determine the differences of internal deformation as well as the folding kinematics. Three folds developed during the Variscan Orogeny in Ordovician and Devonian rocks, and four folds developed during the Pyrenean Orogeny in Eocene rocks, are studied. Folds show a variety of structural locations, in different thrust sheets of the Southern Central Pyrenees, different cleavage development, age, geometry and lithology. Sampling follows an equivalent lithological layer in the two limbs, except for one case, of the selected folds. Results show a modified tectonic magnetic fabric in most sites with the magnetic lineation on the tectonic foliation plane. A larger scattering of the magnetic lineation (maximum magnetic anisotropy axis) and a higher intensity of the preferred orientation of minerals (eccentricity of the anisotropy of magnetic susceptibility - AMS ellipsoid) is better observed in the overturned (short) limb of the asymmetric Variscan folds than in the normal (long) limb. On the other hand, the shape parameter in Alpine folds is generally larger in the overturned (short) limb then in the normal (long) one. A good clustering of the minimum magnetic anisotropy axes is observed in all limbs. The combination of the AMS data with the structural data helps to understand and better constrain the deformation degree in these asymmetric folds and to unravel the deformational history.     

Surface evolution of salt‐encrusted playas under extreme and continued dryness

Miocene continental saltpans are scattered in the Central Valley of the Atacama Desert, one of the driest regions on Earth. These evaporitic deposits are hydrologically inactive, and are detached from groundwater brines or aquifers. The surface of the saltpans, also known as salars, comprises desiccation polygons, commonly with nodular salt structures along their sides. The morphology and bulk mineralogy of salt polygons differs between and within salars, and the shape and internal structure of salt nodules varies between different polygon types. Based on field observation, and mineralogy and crystallography data, we generated a conceptual model for the genesis and evolution of these surface features, whereby rare rainfall events are responsible for the transformation of desiccation salt polygons and the initial formation of salt nodules along polygon borders. In addition, frequent, but less intense, deliquescence events further drive the evolution of salt nodules, resulting in a characteristic internal structure that includes laminations, and changes in porosity and crystal morphologies. As a result, and despite the extreme dryness, the surfaces of fossil salars are dynamic on timescales of several years to decades, in response to daily cycles in atmospheric moisture, and also to rare and meager rainfall events. We propose that fossil salars in the Atacama Desert represent an end stage in the evolution of evaporitic deposits under extreme and prolonged dryness. Copyright © 2015 John Wiley & Sons, Ltd.     

Morphological and kinematic signatures of a binary central star in the planetary nebula Hu 2-1

We present H α , [N  ii ] and [O  iii ] ground-based and HST archive images, VLA–A 3.6-cm continuum and H92 α emission-line data and high-resolution long-slit [N  ii ] spectra of the planetary nebula Hu 2-1. A large number of structural components are identified in the nebula: an outer bipolar and an inner shell, two pairs of collimated bipolar structures at different directions, monopolar bow-shock-like structures, and an extended equatorial structure within a halo. The formation of Hu 2-1 appears to be dominated by anisotropic mass ejection during the late-AGB stage of the progenitor and by variable, 'precessing' collimated bipolar outflows during the protoplanetary nebula and/or early planetary nebula phases. Different observational results strongly support the existence of a binary central star in Hu 2-1, among them (1) the observed point-symmetry of the bipolar lobes and inner shell, and the departures from axial symmetry of the bipolar lobes, (2) the off-centre position of the central star, (3) the detection of mass ejection towards the equatorial plane, and (4) the presence of 'precessing' collimated outflows. In addition, (5) an analysis of the kinematics shows that the systemic velocity of the bipolar outflows does not coincide with the systemic velocity of the bipolar shell. We propose that this velocity difference is a direct evidence of orbital motion of the ejection source in a binary system. From a deduced orbital velocity of ∼10 km s⁻¹, a semimajor axis of ∼ 9–27 au and period of ∼ 25–80 yr are obtained, assuming a reasonable range of masses. These parameters are used to analyse the formation of Hu 2-1 within current scenarios of planetary nebulae with binary central stars.     

Diffuse and concentrated recharge evaluation using physical and tracer techniques: results from a semiarid carbonate massif aquifer in southeastern Spain

In the high-permeability, semiarid carbonate aquifer in the Sierra de Gádor Mountains (southeastern Spain), some local springs draining shallow perched aquifers were of assistance in assessing applicability of the atmospheric chloride mass balance (CMB) for quantifying total yearly recharge (R _T) by rainfall. Two contrasting hydrological years (October through September) were selected to evaluate the influence of climate on recharge: the average rainfall year 2003–2004, and the unusually dry 2004–2005. Results at small catchment scale were calibrated with estimated daily stand-scale R _T obtained by means of a soil water balance (SWB) of rainfall, using the actual evapotranspiration measured by the eddy covariance (EC) technique. R _T ranged from 0.35 to 0.40 of rainfall in the year, with less than a 5% difference between the CMB and SWB methods in 2003–2004. R _T varied from less than 0.05 of rainfall at mid-elevation to 0.20 at high elevation in 2004–2005, with a similar difference between the methods. Diffuse recharge (R _D) by rainfall was quantified from daily soil water content field data to split R _T into R _D and the expected concentrated recharge (R _C) at catchment scale in both hydrological years. R _D was 0.16 of rainfall in 2003–2004 and 0.01 in 2004–2005. Under common 1- to 3-day rainfall events, the hydraulic effect of R _D is delayed from 1 day to 1 week, while R _C is not delayed. This study shows that the CMB method is a suitable tool for yearly values complementing and extending the more widely used SWB in ungauged mountain carbonate aquifers with negligible runoff. The slight difference between R _T rates at small catchment and stand scales enables results to be validated and provides new estimates to parameterize R _T with rainfall depth after checking the weight of diffuse and concentrated mechanisms on R _T during moderate rainfall periods and episodes of marked climatic aridity.