87,146 research outputs found
Le istituzioni della memoria nel nuovo stato unitario: temi e problemi
No full textA memory institution is a term used about institutions such as libraries, archives, museums "which serve as memories for given societies or mankind" (f. Wikipedia)."Progress can be made" wrote Michael Buckland "towards a coherent, unified view of the roles of archives, libraries, museums, online information services, and related organizations if they are treated as information-providing services".
In this essay, the author examines the Italian memory institutions and the most important events in the last 15
Spatter and welded air fall deposits generated by fire-fountaining eruptions: Cooling of pyroclasts during transport and deposition
No full textAccording to the physico-mathematical model presented here, juvenile ballistic fragments can travel through the
atmosphere during fire-fountaining eruptions preserving enough heat to agglutinate or to weld on impact with the ground’s
surface, even a few kilometres from the source area. The range is mostly related to exit velocity and ejection angle as well as
to such typical properties of the transported particles as size, density and shape. The selective nature of the transport system
can give rise to inverse lateral size/density grading. The most important interdependent factors that control the degree of final
agglutination or welding are accumulation rate, grain size and duration of deposition. In the investigated grain size range, an
accumulation rate of 0.2 m/h appears as a minimum value to promote welding. This value cannot be considered as an
absolute threshold because it can be significantly lowered by increasing the grain size. Duration of deposition appears as
another critical factor because it controls the maximum temperature of the whole deposit and its final thickness, and
therefore, the cooling rate of its main portion after the end of deposition. In the case of high accumulation rates of coarse
particles but during a short period of time, primary agglutination may be the dominant factor in controlling the final sintering
of particles. Conversely, high accumulation rates of coarse particles during a long period of time give rise to both primary
agglutination and welding
Non-methane Volatile Organic Compounds (VOCs) at El Chichón volcano (Chiapas, México):Geochemical features, origin and behavior
No full textSe presenta un estudio de las características geoquímicas de la fracción orgánica en las fumarolas del volcán Chichón (Estado de Chiapas, México) para obtener información sobre el origen de los compuestos orgánicos volátiles exceptuando el metano (VOCs) y los procesos que rigen su comportamiento. Los VOCs en fumarolas y pozas burbujeantes consisten principalmente de alcanos (C2-C5) cuya abundancia total tiene un orden de magnitud menor que el metano, y concentraciones altas de aromáticos (benceno y tolueno) y C2-C3 alquenos (principalmente propano e iso-butano). Se encontraron también concentraciones significativas de compuestos de azufre substituidos que en su mayoría pertenecen al grupo de los heterocíclicos. Esta composición, similar a la de las emisiones gaseosas relacionadas a sistemas geotérmicos, sugiere que la producción de gases orgánicos en el volcán El Chichón es principalmente debida a procesos termogénicos. La abundancia total de VOCs es relativamente baja en comparación con la composición típica de fluidos hidrotermales, lo que podría estar relacionado a una contribución importante de fluidos de origen magmático al reservorio que alimenta las emisiones termales del cráter. Sin embargo, la ausencia de compuestos de O-substituidos parece indicar que la composición de los fluidos hidrotermales no es afectada por el aporte de especies orgánicas producidas en profundidades someras por la descomposición de material vegetal reciente, como aquél sepultado por los productos de la erupción de 1982.
doi: https://doi.org/10.22201/igeof.00167169p.2009.48.1.10
Geochemical monitoring of active volcanoes: organic compounds in low-to-high gas exalations at Vulcano Island (Aeolian Islands; Italy)
No full textGeochemical monitoring at the Phlegrean Fields (Naples, Italy): new insights from organic gas compounds
No full textTemporal variability of hydrocarbons composition in the volcanic/hydrothermal system of El Chichon volcano (Chiapas State, Mexico): 8 years of discontinuous geochemical monitoring
No full textEffects of a temporary HDPE cover on landfill gas emissions: Multiyear evaluation with the static chamber approach at an Italian landfill
No full textAccording to the European Landfill Directive 1999/31/EC and the related Italian Legislation (‘‘D. Lgs. No.
36/2003”), monitoring and control procedures of landfill gas emissions, migration and external dispersions
are clearly requested. These procedures could be particularly interesting in the operational circumstance
of implementing a temporary cover, as for instance permitted by the Italian legislation over
worked-out landfill sections, awaiting the evaluation of expected waste settlements.
A possible quantitative approach for field measurement and consequential evaluation of landfill CO2,
CH4 emission rates in pairs consists of the static, non-stationary accumulation chamber technique. At
the Italian level, a significant and recent situation of periodical landfill gas emission monitoring is represented
by the sanitary landfill for non-hazardous waste of the ‘‘Fano” town district, where monitoring
campaigns with the static chamber have been annually conducted during the last 5 years (2005–2009).
For the entire multiyear monitoring period, the resulting CO2, CH4 emission rates varied on the whole
up to about 13,100 g CO2 m2 d1 and 3800 g CH4 m2 d1, respectively.
The elaboration of these landfill gas emission data collected at the ‘‘Fano” case-study site during the
monitoring campaigns, presented and discussed in the paper, gives rise to a certain scientific evidence
of the possible negative effects derivable from the implementation of a temporary HDPE cover over a
worked-out landfill section, notably: the lateral migration and concentration of landfill gas emissions
through adjacent, active landfill sections when hydraulically connected; and consequently, the increase
of landfill gas flux velocities throughout the reduced overall soil cover surface, giving rise to a flowing
through of CH4 emissions without a significant oxidation. Thus, these circumstances are expected to
cause a certain increase of the overall GHG emissions from the given landfill site
Scrubbing processes on light hydrocarbons: an example from Ahuachapan and Berlin geothermal fields (Salvador)
No full textLight hydrocarbons in gas discharges from active volcanoes, geothermal fields and hydrothermal systems: constraints on the chemical-physical conditions of fluid reservoirs
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