Search results for "QE"
showing 10 items of 457 documents
Ground-Based measurements of the 2014-2015 holuhraun volcanic cloud (Iceland)
2018
he 2014–2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO2, with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO2 were …
Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 1: M…
2012
Bioapatite in mammalian teeth is readily preserved in continental sediments and represents a very important archive for reconstructions of environment and climate evolution. This project provides a comprehensive data base of major, minor and trace element and isotope tracers for tooth apatite using a variety of microanalytical techniques. The aim is to identify specific sedimentary environments and to improve our understanding on the interaction between internal metabolic processes during tooth formation and external nutritional control and secondary alteration effects. Here, we use the electron microprobe to determine the major and minor element contents of fossil and modern molar enamel, …
The ABCflux database: Arctic–boreal CO2 flux observations and ancillary information aggregated to monthly time steps across terrestrial ecosystems
2022
Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO2) fluxes in terrestrial ecosystems across the rapidly warming Arctic–boreal zone (ABZ) have provided valuable information but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of Arctic–boreal CO2 fluxes (ABCflux) that aggregates in situ measurements of terrestrial net ecosystem CO2 exchange and its derived partitioned…
Preparation protocols for SEM visualization of charred fossil plants: the case of Weichselia reticulata pinnule anatomy
2021
The cosmopolite Mesozoic fern Weichselia reticulata presents many peculiarities in the anatomy of its stem as well as in the architecture of its leaves. Previous analyses of the ultrastructure of their pinnule laminas provided some insight on xeromorphic traits. In this work new protocols for the preparation of charred compression foliage specimens embedded in a limestone matrix for their observation under SEM are presented, which enhance the observation of different plant tissues. The preparation with HCl allows for the visualization of the whole lamina, from the upper to the lower epidermis, which had not been done to date. Additionally, collodion, latex, or wax coverings of the fossils b…
Reversing land degradation through grasses: a systematic meta-analysis in the Indian tropics
2017
Abstract. Although intensive agriculture is necessary to sustain the world's growing population, accelerated soil erosion contributes to a decrease in the environmental health of ecosystems at local, regional and global scales. Reversing the process of land degradation using vegetative measures is of utmost importance in such ecosystems. The present study critically analyzes the effect of grasses in reversing the process of land degradation using a systematic review. The collected information was segregated under three different land use and land management situations. Meta-analysis was applied to test the hypothesis that the use of grasses reduces runoff and soil erosion. The effect of gra…
Halogen (Cl, F) release during explosive, effusive, and intrusive phases of the 2011 rhyolitic eruption at Cordón Caulle volcano (Chile)
2019
We investigate sulphur, chlorine and fluorine release during explosive, effusive and intrusive phases of the 2011 Cordon Caulle eruption, with a focus on halogen devolatilization. Petrological analysis shows halogen release to have been promoted by isobaric crystallization in slowly-cooled magma that was emplaced in a lava flow and sub-vent intrusion. Fluorine in particular mobilized only after extensive groundmass crystallization and incipient devitrification. By 2017, the gas emitted from vent-proximal fumaroles had hydrothermal compositions, with HCl/HF ratios decreasing with decreasing temperature. We estimate that the eruption could eventually emit up to 0.84 Mt of SO2, 6.3 Mt of HCl, …
David Malcolm Raup (1933-2015) at the starting point of a new paradigm for Palaeontology
2020
This is a tribute to the late David Malcolm Raup, one of the major palaeontologists of the second half of the 20 th century. In addition, it is a critical review of his outstanding contributions, mainly in the field of theoretical palaeontology: quantitative modelling, the introduction of probabilistic methods in palaeontology, as well as his great imagination to use techniques from other fields, such as insurance actuary. After a general outline of his youth, I present a general depiction of the main topics of his research as a palaeobiologist: morphology, the structure of the fossil record, evolution, and extinction. He covered areas ranging from the theoretical morphology of coiled shell…
Has palaeontology answers for some current environmental problems?
2021
History as an irreversible process has no role from a uniformitarian point of view in geology and palaeobiology. Contingency is another trait of history and particle palaeontology has its foundation on such principles. However, new approaches in physics and the theory of systems point out the need to consider a time arrow. Moreover, chance and necessity are interwoven in synergetics and self-organization theory and there may be some possibility of prediction. The global biota has a history resulting from a process of self-organization. A rich fossil record was produced during the Phanerozoic times and this fossil record shows us how life overcame several important crisis. A clear understand…
The negligence and lazy of the Administration: the greatest danger to the conservation of the unique lagerstätte sites
2019
An example is given of one of the most important sites in the Spanish fossil record, such as the almost a hundred moulds of ancient jellyfish of hydrozoan Medusozoa, Cnidaria, exceptionally preserved in an arkosic greywacke bedding plane of the Corduban/Terreneuvian Epoch (lowermost Cambrian) in the municipal district of Constantina (Seville). In spite of its scientific-patrimonial importance and the fact that it has been brought to the attention of the Andalusian autonomous administration for more than twenty-five years, it has still not been the object of an adequate legal protection figure. This lack of interest or bureaucratic slowness is causing an irreparable loss in many of its eleme…
Sedimentología y paleontología del yacimiento Finimioceno de La Portera (Valencia)
1986
14 páginas, 8 figuras, 1 tabla, 1 lámina.