1,720,964 research outputs found
Using the Trace Element Contents in Bronchoalveolar Lavages to Probe the Human Exposure to Inhaled Particulates
No full textExplosive volcanic eruptions eject large volumes of high surface area, metal-rich dust and ash into the atmosphere. In areas near major volcanic eruptions, humans often interact with these materials and may bioaccumulate heavy and toxic metals. To evaluate these interactions, we examine bronchoalveolar lavage samples (BAL) collected from people exposed to the paroxysmal 2001 Etna eruption. BAL samples reveal a strong enrichment of many toxic heavy metals and the capacity for trace elements released from inhaled particles to induce crystallisation of phosphatic microcryst biominerals in intraaveolar spaces. BAL rare earth element (REE) concentration patterns normalised to shale reveal a ‘V-shaped’ feature caused by the depletion of elements from Nd to Tb (mid-REEs) as compared to the variable enrichments of heavy lanthanides, Y, La and Ce. This pattern is consistent with solutions that experience phosphate mineral crystallisation in laboratory conditions and suggests that phosphate precipitation occurs in vivo in the lungs through interactions between volcanic particles and lung fluids. The BAL trace element patterns allow us to reconstruct the source of inhaled materials and depict the fluid mineral processes that occur between lung fluids and inhaled particles
Dynamics of the Mount Nyiragongo lava lake
No full textThe permanent and presently rising lava lake at Mount Nyiragongo constitutes a major potential geological hazard to the inhabitants of the Virunga volcanic region in the Democratic Republic of Congo (DRC) and Rwanda. Based on two field campaigns in June 2010 and 2011, we estimate the lava lake level from the southeastern crater rim (∼400 m diameter) and lava lake area (∼46,550 m2), which constrains, respectively, the lava lake volume (∼9 × 106 m3) and volume flow rate needed to keep the magma in a molten state (0.6 to 3.5 m3 s-1). A bidirectional magma flow model, which includes the characterization of the conduit diameter and funnel-shaped lava lake geometry, is developed to constrain the amount of magma intruded/emplaced within the magmatic chamber and rift-related structures that extend between Mount Nyiragongo's volcanic center and the city of Goma, DRC, since Mount Nyiragongo's last eruption (17 January 2002). Besides matching field data of the lava lake level covering the period 1977 to 2002, numerical solutions of the model indicate that by 2022, 20 years after the January 2002 eruption, between 300 and 1700 × 106 m3 (0.3 to 1.7 km3) of magma could have intruded/emplaced underneath the edifice, and the lava lake volume could exceed 15 × 10 6 m3. ©2014. American Geophysical Union. All Rights Reserved
Differentiating natural and anthropogenic impacts on water quality in a hydrothermal coastal aquifer (Mondragone Plain, Southern Italy)
No full textGroundwater from the Mondragone Plain (Southern Italy) has been investigated by a monthly sampling regimen over the course of a hydrologic year in order to analyze geochemical signatures and has been experienced methods for detecting natural and anthropogenic contamination dynamics that affect resources for human water supply. The Mondragone Plain aquifer is characterized by (1) anthropogenic land uses, (2) varying degrees of hydrothermal interactions, and (3) the potential for seawater intrusion. Anomalies induced by anthropogenic pollution produce non-normally distributed time series and an alteration of the natural SO42− background of groundwater. Variables depending on natural processes are related to water–rock interactions along groundwater flow path, i.e., the hosting aquifer lithology of hydrothermal systems, the recharging massifs of Mt. Petrino and Mt. Massico, and more recent volcanic and alluvial formations. Solute transport in groundwater affects the urban aquifer, both by mixing of thermal waters and by ions deriving from agricultural activity (NO3−, SO42−, NH4+), compromising the quality of a resource largely used by locals. The two thermal systems in the studied area [Levagnole and Padule–San Rocco] are two different aquifers with an independent circulation and chemical composition. Seawater intrusion, both into thermal systems and into shallow aquifers, seems to be unlikely despite the detected increase of salinity in the LEV system close to the shoreline
Gas chemistry of the Dallol region of the Danakil Depression in the Afar region of the northern-most East African Rift
No full textA combination of noble and major gas composition and isotope geochemistry provides a window into the source of volatiles and the mechanisms of transport associated with a series of hot springs located near the Dallol volcano within the Danakil Depression along the Red Sea arm of the Afar triple junction. The helium isotopic composition of these gases range up to 11.9 times the atmospheric ratio (11.9R/Ra), which suggests that the Afar plume interacts with the Afar depression across at least the 300km transect from Tendaho-Gabo basin to Dallol within the Danakil Depression. The 4He/40Ar* of ~14 in the mantle-rich end-member at Dallol indicates significant degassing prior to emplacement at Dallol either during basaltic dyke intrusions beneath the Danakil Depression or during the release and transport of fluids from a degassed subsolidus source in the upper mantle along high permeability fracture zones. The CO2/3He of the magmatic end-member is ~2× higher (7.7×109) and more positive δ13C (CO2) (-2.1%;) than other archetypal plumes (e.g. Hawaii, Iceland, etc.). The Dallol composition is consistent with a hypothetical model that assumes a plume-type starting composition and experiences ~92% degassing (where helium is preferentially degassed with respect to CO2) and the addition of CO2 from the thermal degradation of carbonate. Non-atmospheric excess N2 with a δ15N (N2) of +3.5 to +4%; dominates the Dallol volatiles and suggests interaction between mantle fluids and Proterozoic meta-sediments. By comparing and modeling the range in atmospherically (e.g. 20Ne, 36Ar, 84Kr) and mantle-derived (e.g. 4He/40Ar*and CO2/3He) components in Dallol volatiles, we propose that the coherent variations in these gases result from mixing of magmatic volatiles with extremely degassed remnant fluids present within the hydrothermal reservoir. © 2012 Elsevier B.V
Impact of volcanic plume emissions on rain water chemistry during the January 2010 Nyamuragira eruptive event: Implications for essential potable water resources
No full textOn January 2, 2010 the Nyamuragira volcano erupted lava fountains extending up to 300m vertically along an ∼1.5km segment of its southern flank cascading ash and gas on nearby villages and cities along the western side of the rift valley. Because rain water is the only available potable water resource within this region, volcanic impacts on drinking water constitutes a major potential hazard to public health within the region. During the 2010 eruption, concerns were expressed by local inhabitants about water quality and feelings of physical discomfort (e.g. nausea, bloating, indigestion, etc.) after consuming rain water collected after the eruption began. We present the elemental and ionic chemistry of drinking water samples collected within the region on the third day of the eruption (January 5, 2010). We identify a significant impact on water quality associated with the eruption including lower pH (i.e. acidification) and increases in acidic halogens (e.g. F- and Cl-), major ions (e.g. SO42-, NH4+, Na+, Ca2+), potentially toxic metals (e.g. Al3+, Mn2+, Cd2+, Pb2+, Hf4+), and particulate load. In many cases, the water's composition significantly exceeds World Health Organization (WHO) drinking water standards. The degree of pollution depends upon: (1) ash plume direction and (2) ash plume density. The potential negative health impacts are a function of the water's pH, which regulates the elements and their chemical form that are released into drinking water. © 2012 Elsevier B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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