Experimental data on SOA formation from mixtures of anthropogenic and biogenic organic compounds

Secondary organic aerosols (SOA) constitute a significant fraction of the atmospheric particulate matter. Theses particles are formed as a consequence of the oxidation reaction of certain organic gases that leads to the formation of low-volatility compounds. As for other pollutants, air quality models allow the simulation of particle levels and thus models constitute a powerful tool in air quality management. Nevertheless, the accepted use of models must be based on the validation of its capacity to reproduce observed concentrations. Air monitoring sites provide measured information of a large variety of ambient pollutants. Unfortunately, measurements on SOA are not normally available, as current monitoring networks do not include instrumentation to distinguish primary from secondary sources of organic carbonaceous aerosol. This paper presents a set of photooxidation experiments performed in the European Photorreactor (EUPHORE) smog chamber (CEAM, Spain) under different experimental conditions to investigate SOA formation. The use of chambers allows the isolation of atmospheric chemistry and aerosol formation processes. Thus, although these measurements were obtained at initial precursor concentrations higher than those in atmospheric conditions, they constitute a valuable set of information for SOA model evaluation purposes.     

Streamwise Versus Spanwise Spacing of Obstacle Arrays: Parametrization of the Effects on Drag and Turbulence

A Reynolds-averaged Navier–Stokes model is used to investigate the evolution of the sectional drag coefficient and turbulent length scales with the layouts of aligned arrays of cubes. Results show that the sectional drag coefficient is determined by the non-dimensional streamwise distance (sheltering parameter), and the non-dimensional spanwise distance (channelling parameter) between obstacles. This is different than previous approaches that consider only plan area density $(\lambda _\mathrm{p})$ . On the other hand, turbulent length scales behave similarly to the staggered case (e. g. they are function of $\lambda _\mathrm{p}$ only). Analytical formulae are proposed for the length scales and for the sectional drag coefficient as a function of sheltering and channelling parameters, and implemented in a column model. This approach demonstrates good skill in the prediction of vertical profiles of the spatially-averaged horizontal wind speed.     

Moisture transport and seasonal variations in the stable isotopic composition of rainfall in Central American and Andean Páramo during El Niño conditions (2015–2016)

High‐elevation tropical grassland systems, called Páramo, provide essential ecosystem services such as water storage and supply for surrounding and lowland areas. Páramo systems are threatened by climate and land use changes. Rainfall generation processes and moisture transport pathways influencing precipitation in the Páramo are poorly understood but needed to estimate the impact of these changes, particularly during El Niño conditions, which largely affect hydrometeorological conditions in tropical regions. To fill this knowledge gap, we present a stable isotope analysis of rainfall samples collected on a daily to weekly basis between January 2015 and May 2016 during the strongest El Niño event recorded in history (2014–2016) in two Páramo regions of Central America (Chirripó, Costa Rica) and the northern Andes (Cajas, south Ecuador). Isotopic compositions were used to identify how rainfall generation processes (convective and orographic) change seasonally at each study site. Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT) air mass back trajectory analysis was used to identify preferential moisture transport pathways to each Páramo site. Our results show the strong influence of north‐east trade winds to transport moisture from the Caribbean Sea to Chirripó and the South American low‐level jet to transport moisture from the Amazon forest to Cajas. These moisture contributions were also related to the formation of convective rainfall associated with the passage of the Intertropical Convergence Zone over Costa Rica and Ecuador during the wetter seasons and to orographic precipitation during the transition and drier seasons. Our findings provide essential baseline information for further research applications of water stable isotopes as tracers of rainfall generation processes and transport in the Páramo and other montane ecosystems in the tropics.     

Geochemical and mineralogical characterization of surficial sediments from the Northern Rias: Implications for sediment provenance and impact of the source rocks

A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine surficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined.The influence of the river-borne sediments is only detected in the innermost part of the three Rias. Regional variations of the mineral assemblages are governed by the source-rock composition of the different geological complexes and the relative source-rock contribution controlled by the continental hydrology. Mineralogical composition of the Ortigueira Ria and adjacent shelf surficial sediments are mainly made up of mafic and ultramafic rocks of the Cape Ortegal complex indicated by the high content of Mg, Mn and chrysotile and riebeckite minerals. In areas nearby Ortegal complex the imprint of heavy minerals present in the surrounding rocks has also been recorded. Barqueiro and Viveiro Rias bed-sediments are influenced by granitic and metamorphic rocks from the Ollo de Sapo complex as revealed by the high contribution of muscovite and quartz.Mining activities in the continental domain left strong imprints on marine surficial sediments. Pyrite content is high in the innermost areas of the Ortigueira Ria since this mineral is exploited in the Mera River basin, whereas high muscovite percentages characterize the Viveiro Ria owing to the abundance of granitic rocks and its exploitation in the Landro River basin. Quartz content is high nearby Cape Estaca de Bares, induced by the presence of an important excavation of this material.     

A statistical approach to disentangle environmental forcings in a lacustrine record: the Lago Chungará case (Chilean Altiplano)

A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the “outsiders” as result of anomalous XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water availability. The chronological model of this sedimentary sequence was constructed using 17 AMS ¹⁴C and 1 ²³⁸U/²³⁰Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years BP. Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni) showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities, lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events.     

Massive star formation in local luminous infrared galaxies

Luminous infrared galaxies (LIRGs) provide insights into star formation (SF) and nuclear activity (AGN) under extreme conditions. We are carrying out a multi-wavelength (X-rays, ultraviolet through mid-infrared, and radio) program to obtain high angular resolution observations of a volume-limited sample of local LIRGs. The typical distances to these LIRGs (D=35–75 Mpc) allow us to identify star clusters and H II regions on scales of tens to hundreds of parsecs. We present here recent results on properties of the massive star-forming regions and star clusters in two LIRGs in our sample, Arp 299 and NGC7469.     

Cenozoic studies in northernmost Chile

The Cordillera de la Costa is constructed from a block-faulted Paleogene landscape. The range is cut by canyons and bordered by a high cliff and a zone of marine terraces. To the east the longitudinal depression is infilled by Neogene deposits which were laid-down over the Paleogene surface and have since been locally structurally disturbed. In the Andes stratovolcanoes rise above the Andean plateau and are surrounded by internal drainage basins.In northernmost Chile subsidence of the submarine continental margin has been complemented by uplift of the Andes. Ingestion of sial and sima in the trench area seems to have led to magma production, and there has been an eastward movement in both igneous and structural events. The present plate motions have produced a compressive tectonism, but local distension has occurred at the edge of the continental plate. The longitudinal depression is believed to be a tectonically neutral zone west of the eastward-dipping reverse faulting of the Andean region. Wave-action on a subsiding coast is considered responsible for carving the high cliff, whereas littoral terraces reflect a recent zonally-atypical uplift phase.N-S strike-slip faulting is attributed to ancient plate-closure patterns. Problematic approximately E-W faults could reflect the adjustment of the continental margin to the stresses generated during recent relative plate motions.Early Tertiary erosion produced a Paleogene pediplain. The resulting large quantities of Paleogene sediment are considered to have been subducted during plate convergence. Tectonic movements formed the longitudinal depression and other smaller basins in the late Oligocene. Towards the south, Neogene planation has eroded the Paleogene pediplain, although major pediplanation and aggradation had everywhere ceased by the Upper Miocene when canyon formation commenced. Ignimbritic eruption waned in the Upper Miocene, and gave way to andesitic stratovolcano production that modified the Altiplano internal drainage. Post-Miocene capture of some of this drainage has occurred by headward erosion along Andean flank channels. Canyons across the coastal mountains were established at about the same time, although some of the long channels in the south are of greater antiquity.

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Zusammenfassung Die Küstenkordillere Nordchiles stellt eine paleogene Landschaft mit Blockverwerfungen dar. Das Gebirge ist von Canyons zerlegt und im Westen von einem hohen Cliff und marinen Terrassen begrenzt. Ostwärts befindet sich der Längstalgraben, gefüllt mit neogenen Ablagerungen. Die neogenen Formationen sind lokal gestört. In den Hochanden haben sich Stratovulkane auf dem andinen Plateau gebildet.Im nördlichsten Chile ist das Abtauchen des submarinen Kontinentalrandes vom Aufstieg der Anden begleitet. Sial und Sima, die im Grabenbereich verschwanden, haben wahrscheinlich eine Magmaproduktion hervorgerufen. Die magmatischen und strukturellen Vorgänge bewegen sich dort ostwärts. Die Plattenbewegungen hatten eine kompressive Tektonik zur Folge, aber lokale Dehnung hat am Rande der kontinentalen Platte stattgefunden. Die Längstaldepression ist als eine tektonisch neutrale Zone westlich der ostwärts fallenden Aufschiebung der Anden zu betrachten. Die Küstenterrassen stellen eine rezente, für die Zone atypische Hebungsphase dar.Horizontale N-S-Verwerfungen sind alten Plattenverschiebungen zuzusprechen. Problematische, ungefähr E-W verlaufende Verwerfungen könnten die Einordnung der Kontinentalränder zu dem durch rezente relative Plattenbewegungen hervorgerufenen Stre\ darstellen.Frühtertiäre Erosion hat eine paleogene Landschaft geformt. Die dadurch verursachten gro\en Mengen paleogener Sedimente sind wohl während der Plattenkonvergenz verschluckt worden. Tektonische Bewegungen im späten Pliozän haben die Längstal- und andere kleinere Depressionen gebildet. Im Süden hat die neogene Erosion die paleogene Landschaft geformt, aber zur Zeit des oberen Miozäns hat jede wichtigere Pediplanation und Aggradierung aufgehört und die Bildung der Canyons eingesetzt. Im oberen Miozän haben die Ignimbritergüsse aufgehört, während die Produktion der andesitischen Stratovulkane einsetzte, die das interne Abflu\system des Altiplano modifizierte. Die rückwirkende Erosion in den Kanälen längs der Anden hat einige dieser Flu\systeme nach dem Miozän eingefangen. Die Canyons durch das Küstengebirge waren auch zu ungefähr dieser Zeit etabliert, aber einige der längeren Kanäle im Süden sind älter.

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Résumé La Cordillère cotière du Nord du Chili apparaÎt comme un horst découpant une surface morphologique paleogène. La chaÎne est entaillée par des canyons et domine en falaise une étroite bande de terrasses marines. La dépression longitudinale qui la limite à l'Est est remplie de dépÔts néogènes qui ensevelissent la surface paléogène faiblement deformée.Dans les Andes, des stratovolcans parsèment le plateau andin.Dans l'extrÊme Nord du Chili, la subsidence de la marge continentale sous-marine a été accompagnée par le soulèvement des Andes. L'ingestion de sial au niveau de la fosse semble responsable de la gènèse des magmas et de la migration vers l'Est des manifestations ignées et structurales.L'actuel mouvement de plaques a produit une tectonique en compression avec des distensions locales sur la marge de la plaque continentale. La dépression longitudinale est interpretée comme une zone tectonique neutre à l'Ouest de la faille à plongement Est remontant la zone andine.L'abrasion marine sur la cÔte en voie de subsidence est rendue responsable de la mégafalaise cotière bien que les terrasses littorales témoignent d'une phase de soulèvement local.Les décrochements Nord-Sud représenteraient des mouvements différentiels au sein de la plaque. Le système de failles E-W répondrait au réajustement de la marge continentale. La pédiplaine paléogène résulterait de la phase d'érosion du début du tertiaire. Les produits d'érosion auraient été entraÎnés dans la subduction durant la convergence des plaques. Les mouvements tectoniques de la fin de l'oligocène for mèrent la dépression longitudinale et d'autres petits bassins. Vers le Sud la pénéplanation néogène a érodé les restes de la pédiplaine paléogène; enfin toute érosion planaire a cessé à la fin du Miocène avec la formation des canyons. Le volcanisme ignimbritique s'est achevé à la fin du Miocène supérieur et a été relayé par le volcanisme central andésitique qui modifia le drainage de l'Altiplano. La capture post-miocène par érosion regressive de quelques-uns de ces réseaux a été effectuée par les cours d'eau du flanc occidental de la Cordillère. Les canyons qui entraillent la Cordillère cotière furent creusés à la mÊme époque, bien que certains au Sud semblent plus anciens.

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Analysis of secular polar motion and continental drift

The secular latitude variations of the five ILS stations of Mizusawa, Kitab, Carloforte, Gaithersburg and Ukiah were analyzed taking into account the recent continental drift theory. Using Le Pichon's 1968 reconstruction, the rate of rotation was computed from the astronomical data, fixing the pole of rotation by Le Pichon's determination. The most reasonable solution was obtained considering Mizusawa, Kitab and Carloforte lying on the Eurasia plate, the two American stations as one on the American plate (Gaithersburg) and the other on the North—East Pacific plate (Ukiah). The resulting relative rate between the Euro-American plates is found to be 0".0028/year and between the American—Pacific plates 0".0032/ years, or about 1°,3/10⁶ years and in excellent agreement with the plate tectonic theory. Luxembourg Meeting of the “Journées Luxembourgeoises de Géodynamique”, 1972.     

Environmental assessment of a large industrial marine complex based on a community of benthic filter-feeders

Biological quality in a bay affected by man's activities was evaluated by means of the composition of assemblages of sponges and ascidians. Our results showed that the structure of these two groups of filter-feeders aided in discriminating between undisturbed and disturbed areas, establishing different "environmental health categories" from moderately to strongly disturbed areas, and in ascertaining the extension of the area of each "health category". We were able to divide the bay into four zones based on type of disturbance or anthropogenic source: (1) stations free of any source of disturbance, (2) stations under moderate disturbance, located close to industrial ports, millworks, etc., (3) stations that are under the direct influence of industrial wastes such as a power station and oil refinery, and (4) stations near strongly disturbed areas, influenced directly by harmful steelworks activities. We differentiated clearly between four large species assemblages, and related the composition of these assemblages to different kinds of disturbances. Thus, these species could be used to manage the marine environment in this bay by comparing the observed fauna, with expected fauna in an unstressed site. Moreover, the joint presence of the sponge Cliona vastifica and tunicate Policitor adriaticum seems always to indicate a more or less pristine environmental situation, functioning as bioindicators of normal conditions. We think that the use of specific bioindicators for monitoring disturbance is a valid tool to establish baselines to predict impacts associated with industrial development in many marine ecosystems. The advantages to monitoring communities on hard rocks versus sandy or muddy bottoms are also commented upon.