125,148 research outputs found
Effects 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
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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
“SALINE INTRUSION AND REFRESHENING IN A MULTILAYER COASTAL AQUIFER IN THE CATANIA PLAIN (SICILY, SOUTHERN ITALY): DYNAMICS OF DEGRADATION PROCESSES ACCORDING TO THE HYDROCHEMICAL CHARACTERISTICS OF GROUNDWATERS”. JOURNAL OF HYDROLOGY 307 (2005) 1–16
No full textThe Catania Plain is a large alluvial depression which represents one of the most important hydrogeological units in eastern Sicily. A detailed hydrochemical and hydrogeological investigation focussed on its north-eastern corner has provided new insights into the past and present relationship between freshwater and seawater in shallow and deep aquifers. According to hydrochemical data, over the last centuries the area has been affected by local variations of the sea level, giving rise to sequential processes of re-equilibration of the exchangeable complex, involving freshwater and seawater in both surficial and deep aquifers. These ongoing processes consist in the refreshening of both deep aquifers >500 m from the shoreline and, to a lesser extent due to lower freshwater influx, shallow aquifers. In the former case, there is a shift of the groundwater compositions towards the Na–HCO3 type and a significant drop in the salt contents, while in the latter case, the salt contents do not drop significantly. At a distance <500 m from the shoreline the exchangeable complex of deep aquifers is presently subject to salinization. According to the temporal variabilities in the hydrochemical data over the period 1995/96, the apparent dualism can be attributed to a general worsening of the current freshwater/seawater relationship in deep aquifers. This new tendency appears to be related to a sharp increase in water consumption by the local industrial plant, which has reversed the natural refreshening tendency, giving rise to a new saline intrusion that is particularly severe close to the shoreline
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
The origin of thermal waters from the eastern flank of the Dead Sea Rift Valley (western Jordan)
No full textActa Vulcanologica
No full textActa Vulcanologica is the continuation of the Bollettino del Gruppo Nazionale per la Vulcanologia (GNV), published from 1985 to 1989 and collecting papers and reports on the researches sponsored by GNV. Acta Vulcanologica will publish an volume of miscellaneous papers covering all research aspects of volcanology; it will contain an annex with information on the activity of italian volcanoes recorded during the year. In addition, a series of monographs will be published on specific themes or on active or recent volcanic areas, mainly of Italy
Indagini mineralogiche e chimiche sull'arenaria cambrica dell'Umm Ishirin (sito archeologico di Petra, Giordania): una nuova ipotesi sui meccanismi di degrado.
No full textStratigraphy, eruptive mechanisms and depositional processes of the Pitigliano Formation (Latera Volcanic Complex, Vulsini District, Italy)
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