Estimates of eruption velocity and plume height from infrasonic recordings of the 2006 eruption of Augustine Volcano,Alaska     

Jacqueline Caplan-Auerbach  Anna Bellesiles  Jennifer K. Fernandes 《Journal of Volcanology and Geothermal Research》2010,189(1-2):12-18

The 2006 eruption of Augustine Volcano, Alaska, began with an explosive phase comprising 13 discrete Vulcanian blasts. These events generated ash plumes reaching heights of 3–14 km. The eruption was recorded by a dense geophysical network including a pressure sensor located 3.2 km from the vent. Infrasonic signals recorded in association with the eruptions have maximum pressures ranging from 13–111 Pa. Eruption durations are estimated to range from 55–350 s. Neither of these parameters, however, correlates with eruption plume height. The pressure record, however, can be used to estimate the velocity and flux of material erupting from the vent, assuming that the sound is generated as a dipole source. Eruptive flux, in turn, is used to estimate plume height, assuming that the plume rises as a buoyant thermal. Plume heights estimated in this way correlate well with observations. Events that exhibit strongly impulsive waveforms are underestimated by the model, suggesting that flow may have been supersonic.  相似文献   

Vertical equilibrium with sub-scale analytical methods for geological CO2 sequestration     

S. E. Gasda  J. M. Nordbotten  M. A. Celia 《Computational Geosciences》2009,13(4):469-481

Large-scale implementation of geological CO₂ sequestration requires quantification of risk and leakage potential. One potentially important leakage pathway for the injected CO₂ involves existing oil and gas wells. Wells are particularly important in North America, where more than a century of drilling has created millions of oil and gas wells. Models of CO₂ injection and leakage will involve large uncertainties in parameters associated with wells, and therefore a probabilistic framework is required. These models must be able to capture both the large-scale CO₂ plume associated with the injection and the small-scale leakage problem associated with localized flow along wells. Within a typical simulation domain, many hundreds of wells may exist. One effective modeling strategy combines both numerical and analytical models with a specific set of simplifying assumptions to produce an efficient numerical–analytical hybrid model. The model solves a set of governing equations derived by vertical averaging with assumptions of a macroscopic sharp interface and vertical equilibrium. These equations are solved numerically on a relatively coarse grid, with an analytical model embedded to solve for wellbore flow occurring at the sub-gridblock scale. This vertical equilibrium with sub-scale analytical method (VESA) combines the flexibility of a numerical method, allowing for heterogeneous and geologically complex systems, with the efficiency and accuracy of an analytical method, thereby eliminating expensive grid refinement for sub-scale features. Through a series of benchmark problems, we show that VESA compares well with traditional numerical simulations and to a semi-analytical model which applies to appropriately simple systems. We believe that the VESA model provides the necessary accuracy and efficiency for applications of risk analysis in many CO₂ sequestration problems.  相似文献   

A benchmark study on problems related to CO2 storage in geologic formations   总被引：1，自引：0，他引：1  

Holger Class  Anozie Ebigbo  Rainer Helmig  Helge K. Dahle  Jan M. Nordbotten  Michael A. Celia  Pascal Audigane  Melanie Darcis  Jonathan Ennis-King  Yaqing Fan  Bernd Flemisch  Sarah E. Gasda  Min Jin  Stefanie Krug  Diane Labregere  Ali Naderi Beni  Rajesh J. Pawar  Adil Sbai  Sunil G. Thomas  Laurent Trenty  Lingli Wei 《Computational Geosciences》2009,13(4):409-434

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Gemini/GMOS IFU gas velocity 'tomography' of the narrow line region of nearby active galaxies     

F. K. B. Barbosa  T. Storchi-Bergmann  R. Cid Fernandes  C. Winge  H. Schmitt 《Monthly notices of the Royal Astronomical Society》2009,396(1):2-18

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Methylmercury Bioaccumulation in an Urban Estuary: Delaware River,USA     

Kate Buckman  Vivien Taylor  Hannah Broadley  Daniel Hocking  Prentiss Balcom  Rob Mason  Keith Nislow  Celia Chen 《Estuaries and Coasts》2017,40(5):1358-1370

Spatial variation in mercury (Hg) and methylmercury (MeHg) bioaccumulation in urban coastal watersheds reflects complex interactions between Hg sources, land use, and environmental gradients. We examined MeHg concentrations in fauna from the Delaware River estuary, and related these measurements to environmental parameters and human impacts on the waterway. The sampling sites followed a north to south gradient of increasing salinity, decreasing urban influence, and increasing marsh cover. Although mean total Hg in surface sediments (top 4 cm) peaked in the urban estuarine turbidity maximum and generally decreased downstream, surface sediment MeHg concentrations showed no spatial patterns consistent with the examined environmental gradients, indicating urban influence on Hg loading to the sediment but not subsequent methylation. Surface water particulate MeHg concentration showed a positive correlation with marsh cover whereas dissolved MeHg concentrations were slightly elevated in the estuarine turbidity maximum region. Spatial patterns of MeHg bioaccumulation in resident fauna varied across taxa. Small fish showed increased MeHg concentrations in the more urban/industrial sites upstream, with concentrations generally decreasing farther downstream. Invertebrates either showed no clear spatial patterns in MeHg concentrations (blue crabs, fiddler crabs) or increasing concentrations further downstream (grass shrimp). Best-supported linear mixed models relating tissue concentration to environmental variables reflected these complex patterns, with species specific model results dominated by random site effects with a combination of particulate MeHg and landscape variables influencing bioaccumulation in some species. The data strengthen accumulating evidence that bioaccumulation in estuaries can be decoupled from sediment MeHg concentration, and that drivers of MeHg production and fate may vary within a small region.  相似文献   

Application of the K?ppen classification for climatic zoning in the state of Minas Gerais, Brazil     

Arionaldo de Sá Júnior  Luiz Gonsaga de Carvalho  Fábio Fernandes da Silva  Marcelo de Carvalho Alves 《Theoretical and Applied Climatology》2012,108(1-2):1-7

The knowledge of the climatic conditions of a region is crucial for its agricultural development. It is also extremely important for understanding the fact that certain cultures have to develop under prevailing temperature and humidity conditions and assist in the adoption of a suitable irrigation technique, as well as its management and operationalization. The K?ppen system of climate classification is widely used for the identification of homogeneous climate zones as it considers only rainfall and temperature as the meteorological elements for classification. For this study, we used climatic databases of rainfall and temperature in a raster format, with a spatial resolution of 30″ of arc (an approximate area of 0.86?km²?pixel^?1), from 1961 to 1990. Through geoprocessing techniques, we obtained a map of climatic classification for the state of Minas Gerais. We found that the state has the following three major climatic groups: A, B and C, which correspond to tropical rainy, dry and warm temperate climates, respectively. The climate classes obtained were Aw, Am, BSh, Cwa and Cwb, with Aw, Cwa and Cwb classes occupying 99.89% of the territorial area of the state. The validation of the results showed a satisfactory agreement, with 93.75% reliability.  相似文献   

Mass balance simulation and principal components analysis applied to groundwater resources: Essaouira basin (Morocco)   总被引：2，自引：1，他引：1  

Paula Galego Fernandes  Paula M. Carreira  Mohammed Bahir 《Environmental Earth Sciences》2010,59(7):1475-1484

The water resources of the Essaouira coastal basin (west of Marrakesh) are characteristic of a semi-arid climate and are severely impacted by the climate in terms of quantity and quality. Considering the importance of the Essaouira aquifer in the groundwater supply of a vast region (nearly 1,200 km²), a research study was conducted in order to better understand groundwater evolution in this aquifer system. It is a coastal aquifer located on the Atlantic coastline, southern Morocco, and salinization problems have been reported. Covering the Palaeozoic bedrock, the sedimentary series range from the Triassic to the Quaternary. Besides the possibility of seawater intrusion problems, the geological structures delineate a syncline bordered by the Tidzi diapir (of Triassic age) outcropping to the east and south. This is a recharge area for the aquifer, whereas the main groundwater flow direction is from SE to NW towards the Atlantic Ocean. In spite of the occurrence of calcareous and dolomitic levels, all waters in the Essaouira basin are of the Na–Cl-type. Based on a range of experimental methodologies, combined with PCA and geochemical modelling, it was possible to identify the mineralization processes occurring in the groundwater system, and the importance of the water–rock interaction in the water chemistry. Scenarios were tested using a simple mass balance model through the PHREEQC programme. The reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters. An important contribution of water–rock interaction in groundwater mineralization was found, corroborating the influence of preferential recharge from the Tidzi diapir in the water’s signature. Anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future, in a country with scarce water resources.  相似文献   

Zircon U–Pb SHRIMP dating of gneissic basement of the Dom Feliciano Belt, southernmost Brazil     

J. A. D. Leite  L. A. Hartmann  L. A. D. Fernandes  N. J. McNaughton  Ê. Soliani  Jr.  E. Koester  J. O. S. Santos  M. A. Z. Vasconcellos   《Journal of South American Earth Sciences》2000,13(8):739

The age of a basement gneiss of the Dom Feliciano Belt along the coast of Rio Grande do Sul has been determined by zircon U–Pb SHRIMP to be about 2.08 Ga for the K-granitic magmatism and 800–590 Ma for the associated low-angle and sub-vertical shear zone deformations. The gneiss is the G3 granitic phase of the Arroio dos Ratos Complex of previous authors, and it now defines a geotectonic environment of juvenile accretion of island arcs in the Paleoproterozoic. The superposition of deformation events during the Neoproterozoic precludes the precise determination of the age of each event in this investigation, but we suggest that the collisional low-angle shear zones occurred at ca. 800 Ma and the sub-vertical shear zones at ca. 600 Ma. Th/U ratios are typically magmatic (about 0.4) in the homogeneous cores of zircons (about 2000 Ma), but are metamorphic (0.01) in the zoned euhedral rims (about 590 Ma).All the Paleoproterozoic gneisses in the region are part of the Encantadas Complex. Archean units, such as the Santa Maria Chico granulites, were all deformed in this major event of the Transamazonian Cycle. The dated gneiss may be correlative with the Epupa Complex north and south of the Kaoko Belt of SW Africa. Ages of the Neoproterozoic deformation are younger in the Kaoko Belt of Namibia than in its Brazilian counterpart.  相似文献   

Marine sediment contamination of an industrial site at Port of Bagnoli, Gulf of Naples, Southern Italy   总被引：1，自引：0，他引：1  

Romano E  Ausili A  Zharova N  Celia Magno M  Pavoni B  Gabellini M 《Marine pollution bulletin》2004,49(5-6):487-495

For almost one century an important steel plant has been active at the Bagnoli industrial area (Naples, Southern Italy). The environmental survey of near shore and offshore sediments has been carried out as fundamental part of a clean up project. The characteristics of the area, supposed type of pollution, national and international protocols in force were taken into consideration in designing sampling schemes and selecting analytical parameters. For this work, sediment grain size, PAHs, PCBs, trace elements, total hydrocarbons and organic matter were considered. Factor analysis evidenced two main types of pollution in the proximity of the industrial plant, both probably attributable to the activity of the industrial site. The first one, due to Cd, Pb, Zn and Mn seems determined by localised activities at the southern part of the plant. The second one, due to Fe and Mn, appears directly linked to the whole contaminated area.  相似文献   

Surface velocity field of the Ibero-Maghrebian segment of the Eurasia-Nubia plate boundary   总被引：1，自引：0，他引：1  

R. M. S. Fernandes  J. M. Miranda  B. M. L. Meijninger  M. S. Bos  R. Noomen  L. Bastos  B. A. C. Ambrosius  R. E. M. Riva 《Geophysical Journal International》2007,169(1):315-324

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