排序方式： 共有33条查询结果，搜索用时 15 毫秒
11.
Andrea I. Pasquini Stella M. Formica Gabriela A. Sacchi 《Environmental Earth Sciences》2012,65(2):453-467
Suquía River is a medium-sized hydrological system (basin area of ~7,700 km2) that supplies fresh water to Córdoba city, a town of ~1,500,000 inhabitants in central Argentina. This paper examines the
present-day hydrochemistry of Suquía River urban catchment analyzing its major and minor dissolved components, and the nutrients
variability by means of QUAL-2K modeling software. The Suquía River has bicarbonate-type waters upstream the city and sulfate-type
waters right downstream, whereas they exhibit a mixed-to-alkali-type cationic composition. The seasonal analysis of its major
dissolved constituents clearly showed a dilution process during the wet season (i.e. austral summer). In the last 20 years,
the Suquía River has modified its anionic composition, now showing higher relative concentrations of SO4
2− as a consequence of urban activities. However, trace elements dissolved concentrations do not evidence a strong pollution
effect. Nutrients [nitrogen species, total phosphorous (TP)] and related parameters, such as biochemical oxygen demand (BOD),
and dissolved oxygen (DO), evidence a clear influence of human activities. The QUAL-2K model was used to evaluate the spatial
behavior of selected nutrients and associated variables, (i.e. TP, N–NH4
+, N–NO3
−, DO, BOD). Nutrient concentrations are affected by point sources of contaminants, particularly domestic waste and sewage,
as well as by diffuse agricultural pollution. A calibrated QUAL-2K modeling exercise clearly shows the impact of the Córdoba
city’s municipal wastewater treatment plant on the Suquía River water quality. 相似文献
12.
This paper reviews the fundamentals of Radon-based methods using examples from global seismic applications. By exploiting the move-out or curvature of signal of interest, Least-squares and High-resolution Radon transform methods can effectively eliminate random or correlated noise, enhance signal clarity, and simultaneously constrain travel time and ray angles. The inverse formulation of the Radon transform has the added benefits of phase isolation and spatial interpolation during data reconstruction. This study presents a ‘cookbook’ for Radon-based methods in analyzing shear wave bottom-side reflections from mantle interfaces, also know as SS precursors. We demonstrate that accurate and flexible joint Radon- and frequency-domain approaches are particularly effective in resolving the presence and depth of known and postulated mantle reflectors. 相似文献
13.
The reassignment method remaps the energy of each point in a time‐frequency spectrum to a new coordinate that is closer to the actual time‐frequency location. Two applications of the reassignment method are developed in this paper. We first describe time‐frequency reassignment as a tool for spectral decomposition. The reassignment method helps to generate more clear frequency slices of layers and therefore, it facilitates the interpretation of thin layers. The second application is to seismic data de‐noising. Through thresholding in the reassigned domain rather than in the Gabor domain, random noise is more easily attenuated since seismic events are more compactly represented with a relatively larger energy than the noise. A reconstruction process that permits the recovery of seismic data from a reassigned time‐frequency spectrum is developed. Two approaches of the reassignment method are used in this paper, one of which is referred to as the trace by trace time reassignment that is mainly used for seismic spectral decomposition and another that is the spatial reassignment that is mainly used for seismic de‐noising. Synthetic examples and two field data examples are used to test the proposed method. For comparison, the Gabor transform method, inversion‐based method and common deconvolution method are also used in the examples. 相似文献
14.
D. D. Insinga P. Petrosino I. Alberico G. J. de Lange C. Lubritto F. Molisso M. Sacchi R. Sulpizio J. Wu F. Lirer 《第四纪科学杂志》2020,35(1-2):213-231
Five cores from the southern Tyrrhenian and Ionian seas were studied for their tephra and cryptotephra content in the 4.4–2.0 ka time interval. The chronological framework for each core was obtained by accelerator mass spectrometry 14C dating, the occurrence of distinct marker tephra and stratigraphic correlation with adjacent records. Tephrochronology allowed us to correlate the analyzed deposits with tephra markers associated with Somma-Vesuvius (79 ad ), Ischia Island (Cretaio), Mt Etna (FG, FL and FS) and Campi Flegrei (Astroni-Agnano Monte Spina) events. For the first time in the marine setting, a large single glass data set is provided for the Late Holocene Etnean marker beds including the FS tephra (ca. 4.3 ka). Moreover, unknown deposits from Lipari (ca. 2.2–2.0 ka) and Vulcano (3.6–3.3 ka) are also recognized at more distal sites than previously reported. These results contribute to improve the high-resolution tephrostratigraphic framework of the central Mediterranean Sea. They also provide new insights into the chemical composition and dispersal pattern of tephras that can be used as inter-archive tools for regional and ‘local’ stratigraphic correlations and for addressing paleoclimate research. 相似文献
15.
Autoregressive modeling is used to estimate the spectrum of aliased data. A region of spectral support is determined by identifying the location of peaks in the estimated spatial spectrum of the data. This information is used to pose a Fourier reconstruction problem that inverts for a few dominant wavenumbers that are required to model the data. Synthetic and real data examples are used to illustrate the method. In particular, we show that the proposed method can accurately reconstruct aliased data and data with gaps. 相似文献
16.
17.
F. Quattrocchi R. Pik L. Pizzino M. Guerra P. Scarlato M. Angelone M. Barbieri A. Conti B. Marty E. Sacchi G.M. Zuppi S. Lombardi 《Journal of Seismology》2000,4(4):567-587
After the earthquakes of September 26, 1997, that hit the Umbria-Marcheboundary (Apennine, Central Italy), with a maximum 6.0 Mw, aprogram of geochemical surveying together with a collection ofhydrogeological changes episodes was extended throughout theepicentre-area, taking the yearly period of the seismic sequence as a whole.After a first areal screening, the Bagni di Triponzo thermal spring wasselected for a discrete temporal monitoring (weekly and monthly basis),being the unique thermal spring throughout the epicentre area. This sitedeserves peculiar interest in deepening the knowledge about deep fluidscirculation changing during seismicity.Laboratory and on-field analyses included major, minor and trace elementsas well as dissolved gases (He, Ar, CH4, CO2, H2S,222Rn, NH4, As, Li, Fe, B, etc...) and selected isotopic ratios(C, H, O, He, Sr, Cl), meaningful from tectonic point of view.The chemistry and isotopic chemistry of the spring were fully outlined anddiscussed, pointing out the main process involving the thermal aquifer: thewater-rock interaction inside the Evaporite Triassic Basement (ETB),possibly involving also the Paleozoic Crystalline Basement. On theother hand, sudden and apparent geochemical and hydrogeologicalvariations during the seismic sequence ruled out an evolution in thewater-rock interaction processes. They occurred both at depth, i.e.,induced by fluid remobilization within the crust explained by the Coseismic Strain Model and by the Fault Valve Activity Model, and in the shallow part of the reservoir (i.e., meteoric watercontamination). A statistical multivariable analysis (Factor Analysis) wasaccomplished to better constrain the correlation between the paroxysmalphases of the seismic sequence and the observed trends and spike-likeanomalies. The groundwater variations was inferred to occur mainly insidethe ETB, from depth (1–2 km) up to surface, particularly in associationof the Sellano earthquake (14/10/1997) and of the seismic re-activationof the sequence at the end of March 1998 (Gualdo Tadino-Rigali andVerchiano areas). The lack of deeper input from below the ETB (slightsignature of PCB), as the lack of He mantle signature, during the seismicperiod as a whole, accounted for seismogenic fault segments rooted onlyin the crust. The results also provide useful information about theearthquake-related response mechanisms occurring at this site, thatrepresent the basic task for planning and managing the impendinghydro-geochemical network aimed at defining the relationships betweenseismic cycle, fluids and reliable earthquake forerunners. 相似文献
18.
19.
Flores Avil&#;s Gabriela Patricia Spadini Lorenzo Sacchi Elisa Rossier Yvan Savarino Joel Ramos Oswaldo Eduardo Duwig C&#;line 《Hydrogeology Journal》2022,30(1):181-201
Hydrogeology Journal - A hydrogeochemical and stable isotopic ( $${\updelta }^{15}{\mathrm{N}}_{{\mathrm{NO}}_{3}}$$ and $${\updelta }^{18}{\mathrm{O}}_{{\mathrm{NO}}_{3}}$$ ) multitracer approach... 相似文献
20.
T. J. Ulrych D. R. Velis A. D. Woodbury M. D. Sacchi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(1):50-68
It is well known that the computation of higher order statistics, like skewness and kurtosis, (which we call C-moments) is
very dependent on sample size and is highly susceptible to the presence of outliers. To obviate these difficulties, Hosking
(1990) has introduced related statistics called L-moments. We have investigated the relationship of these two measures in
a number of different ways. Firstly, we show that probability density functions (pdf ) that are estimated from L-moments are
superior estimates to those obtained using C-moments and the principle of maximum entropy. C-moments computed from these pdf's
are not however, contrary to what one may have expected, better estimates than those estimated from sample statistics. L-moment
derived distributions for field data examples appear to be more consistent sample to sample than pdf 's determined by conventional
means. Our observations and conclusions have a significant impact on the use of the conventional maximum entropy procedure
which typically uses C-moments from actual data sets to infer probabilities. 相似文献