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231.
Iron concentrations in selected groundwater samples from the lower Friulian Plain,northeast Italy: importance of salinity 总被引:1,自引:1,他引:0
Elena Pezzetta Anna Lutman Ivan Martinuzzi Carlo Viola Gabriella Bernardis Vanna Fuccaro 《Environmental Earth Sciences》2011,62(2):377-391
High amounts of iron, up to 14 mg/L, were found in groundwater samples from Marano Lagoon in the Friuli Venezia Giulia Plain
(northeast Italy). In order to characterize groundwater hydrochemistry in the area, an investigation has been conducted on
35 wells that were monitored since 2006. Leaching tests were performed (under anaerobic conditions with deionized and saline
waters) on two core samples in the area to study the iron release from soils to groundwater. Collected data indicated the
main role of salinity in metal leaching and highlighted spatial correspondence between high levels of chloride and iron. To
understand the mechanism of groundwater salinization, sulphate/chloride ratio has been investigated and a statistical relation
between salinity, pH and iron was found. These data do not show any relation between past activities and high iron groundwater
contents. High iron concentrations are diffuse in the whole area and therefore comparable to background values. Consequently,
the study states that no remediation plan should have been made for iron concentrations in this area. 相似文献
232.
Seismic tomographic imaging of P- and S-waves velocity perturbations in the upper mantle beneath Iran 总被引:2,自引:0,他引:2
The inverse tomography method has been used to study the P - and S -waves velocity structure of the crust and upper mantle underneath Iran. The method, based on the principle of source–receiver reciprocity, allows for tomographic studies of regions with sparse distribution of seismic stations if the region has sufficient seismicity. The arrival times of body waves from earthquakes in the study area as reported in the ISC catalogue (1964–1996) at all available epicentral distances are used for calculation of residual arrival times. Prior to inversion we have relocated hypocentres based on a 1-D spherical earth's model taking into account variable crustal thickness and surface topography. During the inversion seismic sources are further relocated simultaneously with the calculation of velocity perturbations. With a series of synthetic tests we demonstrate the power of the algorithm and the data to reconstruct introduced anomalies using the ray paths of the real data set and taking into account the measurement errors and outliers. The velocity anomalies show that the crust and upper mantle beneath the Iranian Plateau comprises a low velocity domain between the Arabian Plate and the Caspian Block. This is in agreement with global tomographic models, and also tectonic models, in which active Iranian plateau is trapped between the stable Turan plate in the north and the Arabian shield in the south. Our results show clear evidence of the mainly aseismic subduction of the oceanic crust of the Oman Sea underneath the Iranian Plateau. However, along the Zagros suture zone, the subduction pattern is more complex than at Makran where the collision of the two plates is highly seismic. 相似文献
233.
Nelson D. Padilla Carlton M. Baugh Vincent R. Eke Peder Norberg Shaun Cole Carlos S. Frenk Darren J. Croton Ivan K. Baldry Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(1):211-225
234.
Indoor radon mapping and its relation to geology in Hungary 总被引:2,自引:0,他引:2
Mihály Minda György Tóth István Horváth Ivan Barnet Krisztián Hámori Eszter Tóth 《Environmental Geology》2009,57(3):601-609
Indoor radon mapping may show stronger dependence on geological formations if the measured homes are one-storied houses with
no basement. In Hungary, 17,244 homes were investigated on the yearly average of indoor radon concentrations; among these
homes, there were 6,154, one-storied, no-basement houses. In Hungary, 21 geological units were created relevant for indoor
radon index characterized by lithology, the position of the ground water table, and the gas permeability. Maps were drawn
of different topography (counties, grid, geological units) and different values (maximum, mean, indoor radon indexes). A kind
of standardization of houses was that only the one-storied, no-basement ones were chosen, but from geological point of view some more information was gained when the wall materials (bricks or adobe) were also taken
into account. (“Adobe” is made of clay and straw in Hungary, and not burned as brick, just dried on sunshine). Enhanced indoor
radon values can be observed on the bedrock of Cenozoic volcanic rocks and their eroded materials deposited on the local alluvial
valleys. Another group with relatively increased indoor radon values can be connected to granite bodies. The grid method is
useful for covering large state or even continental areas. For practical public use and detailed radon risk mapping geological
or administrative unit-systems could yield more reasonable and useful results. 相似文献
235.
236.
Tin Lukić Dajana Bjelajac Kathryn E. Fitzsimmons Slobodan B. Marković Biljana Basarin Dragan Mlađan Tanja Micić Randall J. Schaetzl Milivoj B. Gavrilov Miško Milanović György Sipos Gábor Mezősi Nevenka Knežević-Lukić Miroljub Milinčić Aleš Létal Ivan Samardžić 《Environmental Earth Sciences》2018,77(13):519
Among the numerous factors that trigger landslide events, the anthropogenic impact caused by inadequate planning and faulty land use in urban areas is increasing. The Zemun settlement on the northern outskirts of Belgrade has experienced a number of landslides in the last three decades, endangering buildings and roads, and claiming human lives, particularly in the case of the 2010/2011 landslides. Selected meteorological parameters were used to calculate rainfall erosivity indices such as Precipitation Concentration Index and Modified Fournier Index over the period 1991–2015. Drought indices, Lang aridity index and Palfai Drought Index were calculated as well. Mann–Kendall trend test was applied to identify potential rising and/or declining trends both in meteorological parameters and calculated indices. Trend analysis of the annual and seasonal scales yielded a statistically significant trend in the spring time series. Stable arid and pronounced drought conditions were recorded. The modified Fournier index based on monthly mean values yields moderate aggressiveness, with several extreme values indicating very high erosivity classes, especially for 2010/2011. The geological substrate is predominantly loess and hence highly susceptible to erosion and slope failure when climatological conditions are suitable. Accelerated urbanization at the end of the last century reduced vegetation cover, intensified pressure on the vertical loess slope, and lacked suitable rain drainage systems so that surface-water runoff was directed into the porous loess, thereby endangering slope stability. We proposed a geomorphic model to describe the nature of the erosional processes on the loess cliffs of the Zemun loess plateau. Results from this study have implications for mitigation strategies. 相似文献
237.
Are trends in SeaWiFS chlorophyll time-series unusual relative to historic variability 总被引:1,自引:0,他引:1
For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997–2004 with the results of an ocean coupled circulation and biogeochemical model covering the period 1958–2004. During the 1997–2004 time period, linear trends in model and satellite time series were significantly correlated at most of the 44 sites we studied. Eleven sites were selected for further study, and we used the longer time series of the model to assess whether trends observed during the SeaWiFS period at these 11 sites were unusual in relation to those observed over the longer historical period covered by the model. The results show that the trends observed during the SeaWiFS period were not unusual and fell well within the range in magnitude of linear trends observed in other 8-year periods of model output. This result implies that the SeaWiFS satellite ocean color time series is not yet sufficiently long, on its own, to directly observe any long term changes in phytoplankton chlorophyll that may be occurring in the surface waters of the open ocean as a result of increased ocean stratification linked to global climate changed. 相似文献
238.
Ivan Valtchanov Rosalind Hopwood Edward Polehampton Dominique Benielli Trevor Fulton Peter Imhof Tomasz Konopczyński Tanya Lim Nanyao Lu Nicola Marchili David Naylor Bruce Swinyard 《Experimental Astronomy》2014,37(2):207-223
We present a method to derive the relative pointing offsets for SPIRE Fourier-Transform Spectrometer (FTS) solar system object (SSO) calibration targets, which were observed regularly throughout the Herschel mission. We construct ratios R obs(ν) of the spectra for all observations of a given source with respect to a reference. The reference observation is selected iteratively to be the one with the highest observed continuum. Assuming that any pointing offset leads to an overall shift of the continuum level, then these R obs(ν) represent the relative flux loss due to mispointing. The mispointing effects are more pronounced for a smaller beam, so we consider only the FTS short wavelength array (SSW, 958–1546 GHz) to derive a pointing correction. We obtain the relative pointing offset by comparing R obs(ν) to a grid of expected losses for a model source at different distances from the centre of the beam, under the assumption that the SSW FTS beam can be well approximated by a Gaussian. In order to avoid dependency on the point source flux conversion, which uses a particular observation of Uranus, we use extended source flux calibrated spectra to construct R obs(ν) for the SSOs. In order to account for continuum variability, due to the changing distance from the Herschel telescope, the SSO ratios are normalised by the expected model ratios for the corresponding observing epoch. We confirm the accuracy of the derived pointing offset by comparing the results with a number of control observations, where the actual pointing of Herschel is known with good precision. Using the method we derived pointing offsets for repeated observations of Uranus (including observations centred on off-axis detectors), Neptune, Ceres and NGC 7027. The results are used to validate and improve the point-source flux calibration of the FTS. 相似文献
239.
This paper addresses the impact of atmospheric variability on ocean circulation in tidal and non-tidal basins. The data are generated by an unstructured-grid numerical model resolving the dynamics in the coastal area, as well as in the straits connecting the North Sea and Baltic Sea. The model response to atmospheric forcing in different frequency intervals is quantified. The results demonstrate that the effects of the two mechanical drivers, tides and wind, are not additive, yet non-linear interactions play an important role. There is a tendency for tidally and wind-driven circulations to be coupled, in particular in the coastal areas and straits. High-frequency atmospheric variability tends to amplify the mean circulation and modify the exchange between the North and the Baltic Sea. The ocean response to different frequency ranges in the wind forcing is area-selective depending on specific local dynamics. The work done by wind on the oceanic circulation depends strongly upon whether the regional circulation is tidally or predominantly wind-driven. It has been demonstrated that the atmospheric variability affects the spring-neap variability very strongly. 相似文献
240.
We propose approximate equations for P -wave ray theory Green's function for smooth inhomogeneous weakly anisotropic media. Equations are based on perturbation theory, in which deviations of anisotropy from isotropy are considered to be the first-order quantities. For evaluation of the approximate Green's function, earlier derived first-order ray tracing equations and in this paper derived first-order dynamic ray tracing equations are used.
The first-order ray theory P -wave Green's function for inhomogeneous, weakly anisotropic media of arbitrary symmetry depends, at most, on 15 weak-anisotropy parameters. For anisotropic media of higher-symmetry than monoclinic, all equations involved differ only slightly from the corresponding equations for isotropic media. For vanishing anisotropy, the equations reduce to equations for computation of standard ray theory Green's function for isotropic media. These properties make the proposed approximate Green's function an easy and natural substitute of traditional Green's function for isotropic media.
Numerical tests for configuration and models used in seismic prospecting indicate negligible dependence of accuracy of the approximate Green's function on inhomogeneity of the medium. Accuracy depends more strongly on strength of anisotropy in general and on angular variation of phase velocity due to anisotropy in particular. For example, for anisotropy of about 8 per cent, considered in the examples presented, the relative errors of the geometrical spreading are usually under 1 per cent; for anisotropy of about 20 per cent, however, they may locally reach as much as 20 per cent. 相似文献
The first-order ray theory P -wave Green's function for inhomogeneous, weakly anisotropic media of arbitrary symmetry depends, at most, on 15 weak-anisotropy parameters. For anisotropic media of higher-symmetry than monoclinic, all equations involved differ only slightly from the corresponding equations for isotropic media. For vanishing anisotropy, the equations reduce to equations for computation of standard ray theory Green's function for isotropic media. These properties make the proposed approximate Green's function an easy and natural substitute of traditional Green's function for isotropic media.
Numerical tests for configuration and models used in seismic prospecting indicate negligible dependence of accuracy of the approximate Green's function on inhomogeneity of the medium. Accuracy depends more strongly on strength of anisotropy in general and on angular variation of phase velocity due to anisotropy in particular. For example, for anisotropy of about 8 per cent, considered in the examples presented, the relative errors of the geometrical spreading are usually under 1 per cent; for anisotropy of about 20 per cent, however, they may locally reach as much as 20 per cent. 相似文献