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91.
Storage and interaction of compositionally heterogeneous magmas from the 1986 eruption of Augustine Volcano, Alaska 总被引:2,自引:0,他引:2
Diana C. Roman Katharine V. Cashman Cynthia A. Gardner Paul J. Wallace John J. Donovan 《Bulletin of Volcanology》2006,68(3):240-254
Compositional heterogeneity (56–64 wt% SiO2 whole-rock) in samples of tephra and lava from the 1986 eruption of Augustine Volcano, Alaska, raises questions about the
physical nature of magma storage and interaction beneath this young and frequently active volcano. To determine conditions
of magma storage and evolutionary histories of compositionally distinct magmas, we investigate physical and chemical characteristics
of andesitic and dacitic magmas feeding the 1986 eruption. We calculate equilibrium temperatures and oxygen fugacities from
Fe-Ti oxide compositions and find a continuous range in temperature from 877 to 947°C and high oxygen fugacities (ΔNNO=1–2)
for all magmas. Melt inclusions in pyroxene phenocrysts analyzed by Fourier-transform infrared spectroscopy and electron probe
microanalysis are dacitic to rhyolitic and have water contents ranging from <1 to ∼7 wt%. Matrix glass compositions are rhyolitic
and remarkably similar (∼75.9–76.6 wt% SiO2) in all samples. All samples have ∼25% phenocrysts, but lower-silica samples have much higher microlite contents than higher-silica
samples. Continuous ranges in temperature and whole-rock composition, as well as linear trends in Harker diagrams and disequilibrium
mineral textures, indicate that the 1986 magmas are the product of mixing between dacitic magma and a hotter, more mafic magma.
The dacitic endmember is probably residual magma from the previous (1976) eruption of Augustine, and we interpret the mafic
endmember to have been intruded from depth. Mixing appears to have continued as magmas ascended towards the vent. We suggest
that the physical structure of the magma storage system beneath Augustine contributed to the sustained compositional heterogeneity
of this eruption, which is best explained by magma storage and interaction in a vertically extensive system of interconnected
dikes rather than a single coherent magma chamber and/or conduit. The typically short repose period (∼10 years) between Augustine's
recent eruptive pulses may also inhibit homogenization, as short repose periods and chemically heterogeneous magmas are observed
at several volcanoes in the Cook Inlet region of Alaska. 相似文献
92.
Ismael L.Schneider Elba C.Teixeira Guilherme L.Dotto Diana Pinto Cheng-Xue Yang Luis F.O.Silva 《地学前缘(英文版)》2022,(1):417-429
Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization.In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization(PMF)in receptor modeling in the Metropolitan Area of Porto Alegre,Brazil.The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites.Major ion and trace element concentrations were assessed.The average concentrations were 12.8 and 15.2μg/m3 for Canoas and Sapucaia do Sul sites,respectively.Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate.Trace elements,especially Cu,Pb,Zn,Cd,and Ni also made important contributions which are directly associated with anthropogenic contributions.Our results show significantly higher levels in winter than in summer.Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources,especially road traffic,combustion processes and industrial activities,which are grouped in 7 major contributing sources.A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations.This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions,combined with awareness-raising actions for citizens concerning the impact of indoor sources. 相似文献
93.
Towards sustainable groundwater use: setting long-term goals, backcasting, and managing adaptively 总被引:7,自引:0,他引:7
Gleeson T Alley WM Allen DM Sophocleous MA Zhou Y Taniguchi M VanderSteen J 《Ground water》2012,50(1):19-26
The sustainability of crucial earth resources, such as groundwater, is a critical issue. We consider groundwater sustainability a value-driven process of intra- and intergenerational equity that balances the environment, society, and economy. Synthesizing hydrogeological science and current sustainability concepts, we emphasize three sustainability approaches: setting multigenerational sustainability goals, backcasting, and managing adaptively. As most aquifer problems are long-term problems, we propose that multigenerational goals (50 to 100 years) for water quantity and quality that acknowledge the connections between groundwater, surface water, and ecosystems be set for many aquifers. The goals should be set by a watershed- or aquifer-based community in an inclusive and participatory manner. Policies for shorter time horizons should be developed by backcasting, and measures implemented through adaptive management to achieve the long-term goals. Two case histories illustrate the importance and complexity of a multigenerational perspective and adaptive management. These approaches could transform aquifer depletion and contamination to more sustainable groundwater use, providing groundwater for current and future generations while protecting ecological integrity and resilience. 相似文献
94.
Diana Jordanova Petar Petrov Viktor Hoffmann Tilman Gocht Cristian Panaiotu Tsenka Tsacheva Neli Jordanova 《Studia Geophysica et Geodaetica》2010,54(3):417-442
Detailed magnetic study on vegetation samples from several strongly polluted and clean sites in Bulgaria is carried out in
order to evaluate suitability of different species as passive dust collectors in magnetometry. From each location, available
species among lichens, mosses, poplar leaves, dandelion, needles have been sampled. Magnetic susceptibility calculated on
mass-specific basis shows wide variability between diamagnetic signal up to 846 × 10−8 m3/kg. Lichens and mosses are found to be the species, showing magnetic signals with the strongest contrast between clean and
polluted environment. The main magnetic phase is magnetite-like according to the results from thermomagnetic analysis of susceptibility
on magnetic extracts. Scanning electron microscopy (SEM) microphotographs reveal the presence of abundant particulate matter
on vegetation surface both with anthropogenic (spherules) and lithogenic origin. Magnetic grain size deduced by the ratio
of saturation remanent magnetization (SIRM) and mass-specific magnetic susceptibility (χ) and coercivities (Bc and Bcr) suggest that different species accumulate preferentially small SD-like grains from pollution emissions. Contrasting relationship
of the ratio of anhysteretic remanent magnetization (ARM) and χ for polluted vs clean sites deduced by needles and lichens
may be related to transformation of the accumulated dust particles within lichens’ tissue. This finding indicates that the
exact species used as biological dust collector is of importance when studying spatial grain size distribution of magnetic
dust particles. Pilot study on polycyclic aromatic hydrocarbons (PAH) content and its relation to magnetic parameters shows
good correspondence between high levels of PAHs and high SIRM values for locations affected by non-ferrous industrial production. 相似文献
95.
Jose Henrique G. M. Alves Diana J. M. Greenslade Michael L. Banner 《Journal of Atmospheric & Ocean Science》2002,8(4):239-267
The impact of a modified parametric form of the dissipation source function S ds on the skill of an operational spectral wind-wave model is investigated. Numerical experiments are made with a version of the WAM model presently used operationally by the Australian Bureau of Meteorology to produce sea-state forecasts within the Australian region. Performances of wave hindcasts obtained using several alternative forms of this newly proposed dissipation source function are compared to those produced with forms of S ds commonly used operationally. A new ad hoc technique to compare modelled and observed wave spectra is introduced to assess the quality of calculated one-dimensional frequency spectra.
Our results indicate that wave model performance in terms of integral spectral parameters, such as the significant wave height H s , may benefit from improved parameterisations of the dissipation source term S ds . On the other hand, we also found that model performance was relatively poor in terms of predictions of the one-dimensional frequency spectrum, regardless of the chosen form of S ds . These results suggest that further refinements of the dissipation source term are strongly dependent on improved parametrisations of the nonlinear interactions source term S nl . 相似文献
Our results indicate that wave model performance in terms of integral spectral parameters, such as the significant wave height H s , may benefit from improved parameterisations of the dissipation source term S ds . On the other hand, we also found that model performance was relatively poor in terms of predictions of the one-dimensional frequency spectrum, regardless of the chosen form of S ds . These results suggest that further refinements of the dissipation source term are strongly dependent on improved parametrisations of the nonlinear interactions source term S nl . 相似文献
96.
Abstract This study reports on testing of the peatland version of the Canadian Land Surface Scheme (CLASS) for simulating the energy balance of subarctic open woodland terrain. Model results are compared against several years of measured data from a site near Churchill, Manitoba. In contrast to most forest environments, the floor of the open forest plays a large role in total ecosystem energy exchange. This behaviour presents a significant challenge for land surface models like CLASS and their simplified treatment of vegetation canopies. Simulations of summer energy balance for seven years encompassing a wide range of meteorological conditions produced consistent results. Root mean square errors for sensible and latent heat fluxes fell between 11 and 28 W m?2. CLASS consistently underestimated slightly the daily latent heat flux and overestimated the sensible heat flux, average mean bias errors being ‐7.6 and 9.1 W m?2, respectively. The soil heat flux was less well represented. In general, CLASS was able to capture the diurnal and seasonal behaviour of the measured fluxes under a range of conditions with reasonable accuracy. In a full year simulation, CLASS reproduced the annual variations in energy balance with some discrepancies associated with snow accumulation and ablation periods. The model performance was sensitive to both snow density and specification of the surface cover. Recommendations for improving the model for subarctic woodlands and terrain types with similar features are discussed. 相似文献
97.
Mental preparation for climate adaptation: The role of cognition and culture in enhancing adaptive capacity of water management in Kiribati 总被引:3,自引:0,他引:3
Natasha KuruppuAuthor Vitae Diana LivermanAuthor Vitae 《Global Environmental Change》2011,21(2):657-669
In many Least Developed Countries (LDCs) and Small Island Developing States (SIDS), such as in Kiribati, formal national adaptation programmes are currently being operationalised or are in the pipeline. A key focus is on motivating householders to adapt in anticipation of climate change through pilot community projects. In this paper, we argue that the water sector must pay equal attention to how communities cognitively perceive the process of adaptation if interventions are to be effective. Adopting a cognitive model to gain such insights we conclude that individual's belief in their own abilities to manage water stress play a crucial role in driving intentions to adapt and therefore greater attention needs to be placed on understanding the underling drivers shaping such beliefs. 相似文献
98.
Diana I. Montemayor Alejandro D. Canepuccia Jesus Pascual Oscar O. Iribarne 《Estuaries and Coasts》2014,37(2):411-420
Salt marsh zonation patterns generate different abiotic and biotic conditions that can accentuate species inherent differences in primary production and biomass. In South West Atlantic marshes, there are two Spartina species: Spartina alterniflora in the low intertidal and Spartina densiflora in the high intertidal. These two species are generally found in all marshes but with different dominance: In some marshes, the S. densiflora zone occupies higher extents, and in others, the S. alterniflora zone is the one that prevails. We found through field sampling that, in six studied marshes, there is greater S. densiflora live and total (i.e., dead+live) aboveground biomass (g m?2) in the marshes dominated by S. densiflora than in the ones dominated by S. alterniflora. Spartina alterniflora had similar aboveground biomass in the six marshes, regardless of the dominance of each species. When comparing the two Spartina species within each marsh, S. densiflora had greater live and total biomass in the marshes it dominates. In the marshes dominated by S. alterniflora, both species had similar live and total biomass. In all marshes, there was greater dead S. densiflora biomass. A multivariate analysis using selected abiotic factors (i.e., salinity, latitude, and tidal amplitude) showed that S. alterniflora aboveground biomass patterns are mainly correlated with salinity, while S. densiflora live biomass is mainly correlated with salinity and latitude, dead biomass with salinity and tidal amplitude, and total biomass with salinity alone. We conclude that in S. densiflora dominated marshes, the main processes of that species zone (i.e., nutrient accumulation) will be accentuated because of its higher biomass. We also conclude that climatic conditions, in combination with specific Spartina biotic and ambient abiotic parameters, can affect marsh ecological functions. 相似文献
99.
Analysis of State and Provincial Atlas Reviews* 总被引:1,自引:0,他引:1
Ninety-eight reviews of state and provincial atlases are examined in order to address several questions. Reviews are subjected to content analysis to identify the judgement criteria that experts use in evaluating a provincial or state atlas, and the aspects of each criterion that reviewers praise or condemn. An attempt is made to search for expert consensus and to identify a provincial or state atlas review recipe. The research reported here is part of a larger study undertaken to assist those in the process of planning a new provincial or state atlas initiative. This paper also assists individuals who are searching for rules and guidelines when undertaking an atlas review. 相似文献
100.
Diana Kjurkchieva Dragomir Marchev Waldemar Ogloza 《Astrophysics and Space Science》1998,262(1):53-74
BVRI photometry of SS Cyg from the end of 1996 and the beginning of 1997 is presented. The star underwent an eruption around December 11. The amplitude of which was slightly bigger than those of observed earlier eruptions. We saw some indication of the future outburst in the decreasing of brightness in all colours by about 0.4 mag during the last two weeks before the event. The emission of the system moved strongly to the shorter wavelengths at outburst. Our multicolour data confirm the existence of a light variability with the orbital (spectroscopic) period at quiescence. Moreover we found for the first time that this variability exists also at outburst but its amplitude is 3–5 times smaller. Whereas the amplitudes of the orbital variability at quiescence decrease to the longer wavelengths, they increase at outburst to the longer wavelengths. The orbital folded curve at quiescence has two-wave shape and was fitted well by the different visibility of two diametrical opposite hot spots (210000 K) with angular size 100 on the magnetic poles of the white dwarf. An analogy between the two basic states of the U Gem-star SS Cyg, the polar AM Her and Z Cam-star RX And was found. 相似文献