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1.
The interplay of the geochemistry of the lower stretch of the Luján River is analyzed with its natural geomorphology (basin
features), local hydrometeorology (tidal regime and “sudestada” events) and the impact of polluted tributaries. Major ions,
dissolved heavy metals and limnological variables were analyzed using multivariate techniques. The water quality of the mainstream
of the Luján River, flowing through urbanized and industrialized areas is strongly and positively influenced by the input
of the Paraná River through deltaic watercourses and is negatively impacted after receiving the discharge from polluted watercourses.
The longitudinal spatial variations evidenced major discontinuities in the Lower Luján Basin, showing clearly the riverine
and the deltaic water influenced zones. Seasonal variations were also marked and were either temperature driven or associated
with the estuarine cycle and the “sudestada”. 相似文献
2.
This paper demonstrates techniques for pre-eruption prediction of lahar-inundation zones in areas where a volcano has not
erupted within living memory and/or where baseline geological information about past lahars could be scarce or investigations
to delimit past lahars might be incomplete. A lahar source (or proximal lahar-inundation) zone is predicted based on ratio
of vertical descent to horizontal run-out of eruptive deposits that spawn lahars. Immediate post-eruption distal lahar-inundation
zones are predicted based on “pre-eruption” distal lahar-inundation zones and on spatial factors derived from a digital elevation
model. Susceptibility to distal lahar-inundation is estimated by weights-of-evidence, by logistic regression and by evidential
belief functions. Predictive techniques are applied using a geographic information system and are tested in western part of
Pinatubo volcano (Philippines). Predictive maps are compared with a forecast volcanic-hazard map through validation against
a field-based volcanic-hazard map. The predictive model of proximal lahar-inundation zone has “true positive” prediction accuracy,
“true negative” prediction accuracy, “false positive” prediction error and “false negative” prediction error that are similar
to those of the forecast volcanic-hazard map. The predictive models of distal lahar inundation zones have higher “true positive”
prediction accuracy and lower “false negative” prediction error than the forecast volcanic-hazard map, although the latter
has higher “true negative” prediction accuracy and lower “false positive” prediction error than the former. The results illustrate
utility of proposed predictive techniques in providing geo-information could be used, howbeit with caution, for planning to
mitigate potential lahar hazards well ahead of an eruption that could generate substantial source materials for lahar formation. 相似文献
3.
Comparison of Mathematical Methods of Potential Modeling 总被引：1，自引：0，他引：1
Helmut Schaeben 《Mathematical Geosciences》2012,44(1):101-129
Various attempts are known to turn the “catalogue” of mineral deposit models compiled by Cox and Singer (1986) operational, and have initiated activities called “potential mapping”, “potential modeling”, or “targeting”. The common
ultimate objective is to estimate the probability for a given location that a mineralization of a given type occurred. The
mathematics range from “weights of evidence” and others featuring a Bayesian approach to logistic regression by maximum likelihood,
and include other realizations by means of fuzzy methods, genetic programming, and artificial neural nets. Once developed
and coded, applications are not restricted to mineral prospection and exploration but include any kind of occurrences and
their estimated probabilities, e.g., risk assessment of land slides and many others. 相似文献
4.
The present study explored the effect of assimilation of Advanced TIROS Vertical Sounder (ATOVS) temperature and humidity
profiles and Spectral sensor microwave imager (SSM/I) total precipitable water (TPW) on the simulation of a monsoon depression
which formed over the Arabian Sea during September 2005 using the Weather Research and Forecast model. The three-dimensional
variational (3DVAR) data assimilation technique has been employed for the purpose of assimilation of satellite observations.
Statistical scores like “equitable threat score,” “bias score,” “forecast impact,” and “improvement parameter” have been used
to examine the impact of the above-mentioned satellite observations on the numerical simulation of a monsoon depression. The
diagnostics of this study include verification of the vertical structure of depression, in terms of temperature anomaly profiles
and relative vorticity profiles with observations/analysis. Additional diagnostics of the study include the analysis of the
heat budget and moisture budget. Such budget studies have been performed to provide information on the role of cumulus convection
associated with the depression. The results of this study show direct and good evidence of the impact of the assimilation
of the satellite observations using 3DVAR on the dynamical and thermodynamical features of a monsoon depression along with
the effect of inclusion of satellite observation on the spatial pattern of the simulated precipitation associated with the
depression. The “forecast impact” parameter calculated for the wind speed provides good evidence of the positive impact of
the assimilation of ATOVS temperature and humidity profiles and SSM/I TPW on the model simulation, with the assimilation of
the ATOVS profiles showing better impact in terms of a more positive value of the “forecast impact” parameter. The results
of the study also indicate the improvement of the forecast skill in terms of “equitable threat score” and “bias score” due
to the assimilation of satellite observation. 相似文献
5.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
6.
A Shear Model Accounting Scale Effect in Rock Joints Behavior 总被引：1，自引：0，他引：1
F. Vallier Y. Mitani M. Boulon T. Esaki F. Pellet 《Rock Mechanics and Rock Engineering》2010,43(5):581-595
Understanding the scale effect on the mechanical behavior of a single rock joint is still very important in rock engineering.
Rock joints can be classified into three different categories depending on their scale: the “micro scale” which is the scale
of the asperities; the “meso scale” is the scale of the specimens tested in laboratory; and the “macro scale” which is the
scale of the rock mass. The purpose of this paper is to propose an effective way to model rock joints at both the meso and
macro scale. An original constitutive mechanical model, in which parameters are deduced from experimental results, has been developed.
This model is then extended to simulate the discontinuities occurring at a larger size. At the macro scale, the constitutive
modeling was carried out for both small and large relative displacements. Large displacements lead to substantial changes
in dilation. For both cases, the peak shear stress vanishes for joints longer than 2 m. 相似文献
7.
West North Pacific typhoon track patterns and their potential connection to Tibetan Plateau snow cover 总被引：1，自引：0，他引：1
The spatial characteristics and temporal variability of the West North Pacific (WNP) typhoon tracks are studied by analyzing
the spatial pattern and temporal variability of the empirical orthogonal functions (EOFs) of the WNP typhoon track density
function (TTDF) from 1945 to 2004. The results show that WNP typhoon tracks exhibit three principal EOF Modes. The first EOF
Mode represents the contrasting “active” versus “inactive” typhoons defined by the overall frequency and life span of the
typhoons that develop in the WNP basin. The second EOF shows a north–south dipole Mode in the TTDF depicting a seesaw pattern
in typhoon frequency between Northeast Asia and Southeast Asia. The third EOF describes an east–west dipole Mode in TTDF depicting
a zonal seesaw pattern between typhoons that tend to make landfalls in East Asia and typhoons that tend to stay away from
the East Asia landmasses. Further analysis of the EOF time series of the WNP TTDF indicates that an important climatic factor
associated with the WNP typhoon activity is the snow cover over the Tibetan Plateau (TP), which is also correlated with the
East Asia summer monsoon (EASM). Thus, a mechanism linking the TP snow cover and the WNP typhoon activity is the response
of the EASM in the WNP region to the TP snow cover, and the subsequent effect of EASM on the development and steering of the
WNP typhoons. 相似文献
8.
Piotr W. Mirowski Daniel M. Tetzlaff Roy C. Davies David S. McCormick Nneka Williams Claude Signer 《Mathematical Geosciences》2009,41(4):447-474
This research introduces a novel method to assess the validity of training images used as an input for Multipoint Geostatistics,
alternatively called Multiple Point Simulation (MPS). MPS are a family of spatial statistical interpolation algorithms that
are used to generate conditional simulations of property fields such as geological facies. They are able to honor absolute
“hard” constraints (e.g., borehole data) as well as “soft” constraints (e.g., probability fields derived from seismic data,
and rotation and scale). These algorithms require 2D or 3D training images or analogs whose textures represent a spatial arrangement
of geological properties that is presumed to be similar to that of a target volume to be modeled. To use the current generation
of MPS algorithms, statistically valid training image are required as input. In this context, “statistical validity” includes
a requirement of stationarity, so that one can derive from the training image an average template pattern. This research focuses
on a practical method to assess stationarity requirements for MPS algorithms, i.e., that statistical density or probability
distribution of the quantity shown on the image does not change spatially, and that the image shows repetitive shapes whose
orientation and scale are spatially constant. This method employs image-processing techniques based on measures of stationarity
of the category distribution, the directional (or orientation) property field and the scale property field of those images.
It was successfully tested on a set of two-dimensional images representing geological features and its predictions were compared
to actual realizations of MPS algorithms. An extension of the algorithms to 3D images is also proposed. As MPS algorithms
are being used increasingly in hydrocarbon reservoir modeling, the methods described should facilitate screening and selection
of the input training images. 相似文献
9.
Matthew G. Hannah 《GeoJournal》2010,75(4):397-406
Ewald’s recent genealogy of constructions of risk in Western societies argues that the 1980s saw an important paradigm shift
to the “precautionary principle”. Critical scholars have taken up this idea as a lens through which to interpret the Bush
administration’s ‘war on terror’. I argue that 11 September 2001 actually brought about qualitative changes to this paradigm.
Bush’s pre-emptive doctrine is driven, and perhaps even more importantly, continually justified to the US population, by what
might be called the “trans-precautionary principle”, a move from “decisionism” to “actionism”, and a new radicalization of
the way fear is produced and managed. Donald Rumsfeld’s famous typology of different articulations of knowledge and ignorance
offers an excellent analytical window onto the connections between ignorance, fear and geopolitical action in this new regime.
In the latter part of the essay, his four modes of knowledge/ignorance are arrayed, for heuristic purposes, in an abstract
spatial grid organized along dimensions of the specificity and possession of knowledge. This allows a ‘mapping’ of some of
the Bush administration’s more controversial strategies in the ‘war on terror’, as a set of different pathways through Rumsfeld
Space. 相似文献
10.
Groundwater is a very important natural resource in Khanyounis Governorate (the study area) for water supply and development.
Historically, the exploitation of aquifers in Khanyounis Governorate has been undertaken without proper concern for environmental
impact. In view of the importance of quality groundwater, it might be expected that aquifer protection to prevent groundwater
quality deterioration would have received due attention. In the long term, however, protection of groundwater resources is
of direct practical importance because, once pollution of groundwater has been allowed to occur, the scale and persistence
of such pollution makes restoration technically difficult and costly. In order to maintain basin aquifer as a source of water
for the area, it is necessary to find out, whether certain locations in this groundwater basin are susceptible to receive
and transmit contamination. This study aims to: (1) assess the vulnerability of the aquifer to contamination in Khanyounis
governorate, (2) find out the groundwater vulnerable zones to contamination in the aquifer of the study area, and (3) provide
a spatial analysis of the parameters and conditions under which groundwater may become contaminate. To achieve that, DRASTIC
model within geographic information system (GIS) environment was applied. The model uses seven environmental parameters: depth
of water table, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity to
evaluate aquifer vulnerability. Based on this model and by using ArcGIS 9.3 software, an attempt was made to create vulnerability
maps for the study area. According to the DRASTIC model index, the study has shown that in the western part of the study area
the vulnerability to contamination ranges between high and very high due to the relatively shallow water table with moderate
to high recharge potential, and permeable soils. To the east of the previous part and in the south-eastern part, vulnerability
to contamination is moderate. In the central and the eastern part, vulnerability to contamination is low due to depth of water
table. Vulnerability analysis of the DRASTIC Model indicates that the highest risk of contamination of groundwater in the
study area originates from the soil media. The impact of vadose zone, depth to water level, and hydraulic conductivity imply
moderate risks of contamination, while net recharge, aquifer media, and topography impose a low risk of aquifer contamination.
The coefficient of variation indicates that a high contribution to the variation of vulnerability index is made by the topography.
Moderate contribution is made by the depth to water level, and net recharge, while impact of vadose zone, hydraulic conductivity,
soil media, and Aquifer media are the least variable parameters. The low variability of the parameters implies a smaller contribution
to the variation of the vulnerability index across the study area. Moreover, the “effective” weights of the DRASTIC parameters
obtained in this study exhibited some deviation from that of the “theoretical” weights. Soil media and the impact of vadose
zone were the most effective parameters in the vulnerability assessment because their mean “effective” weights were higher
than their respective “theoretical” weights. The depth of water table showed that both “effective” and “theoretical” weights
were equal. The rest of the parameters exhibit lower “effective” weights compared with the “theoretical” weights. This explains
the importance of soil media and vadose layers in the DRASTIC model. Therefore, it is important to get the accurate and detailed
information of these two specific parameters. The GIS technique has provided an efficient environment for analysis and high
capabilities of handling large spatial data. Considering these results, DRASTIC model highlights as a useful tool that can
be used by national authorities and decision makers especially in the agricultural areas applying chemicals and pesticides
which are most likely to contaminate groundwater resources. 相似文献
11.
The sediment-hosted disseminated gold deposits in the Oinling region are of sedimentation-slight-metamorphic origin superimposed by hydrothermal reworking at moderate-low temperatures and are well comparable with the typical Carlin gold deposits in the United States.In view of the confusing concept concerning the “sediment-hosted”and “Carlin-type” gold deposits,the authors propose that the term“sediment-hosted gold deposit”should be used in a broad sense which encompasses at least the four subtypes,i.e.,the Carlin type,the metamorphic fine clastic type,the hydrothermal sedimentary type and the vein type.In oter words,the “Carlin-type”should not be used as a synonym for “sediment-hosted”but is recommended as a subtype under the general category of “sediment-hosted gold deposits” 相似文献
12.
Samuel Wildemeersch Philippe Orban Ingrid Ruthy Olivier Grière Philippe Olive Abdelkhalek El Youbi Alain Dassargues 《Environmental Earth Sciences》2010,60(8):1753-1769
Located in the Mid-Atlas (Morocco), the Oulmes plateau is famous for its mineral water springs “Sidi Ali” and “Lalla Haya”
commercialised by the company “Les Eaux minérales d’Oulmès S.A”. Additionally, groundwater of the Oulmes plateau is intensively
exploited for irrigation. The objective of this study, essentially performed from data collected during isotopic (summer 2004)
and piezometric and hydrogeochemical field campaigns (spring 2007), is to improve the understanding of the Oulmes hydrogeological
system. Analyses and interpretation of these data lead to the statement that this system is constituted by a main deep aquifer
of large extension and by minor aquifers in a perched position. However, these aquifers interact enough to be in total equilibrium
during the cold and wet period. As highlighted by isotopes, the origin of groundwater is mainly infiltration water except
a small part of old groundwater with dissolved gas rising up from the granite through the schists. 相似文献
13.
Hani Serhal Daniel Bernard Jamal El Khattabi Bastin-Lacherez Sabine Isam Shahrour 《Environmental Geology》2009,57(7):1579-1592
Since 1975, Europe sets up its policy to limit the degradation and the pollution of the aquatic environments through 30 directives
and regulations. In the north of France, the nitrate concentrations measured in the groundwater exceed the water drinking
limit fixed at 50 mg/L by the European framework directive in the field of water (2000/60/EC). This high concentration is
due to intensive agriculture, industrialization and demographic growth. Several programs were launched in order to resolve
this situation: “Ferti-better” or the use of fertilizer in moderation and installation and amelioration of wastewater collect
and treatment systems. In order to estimate the influence of the anthropic activities on the quality of groundwater in the
“Artois-Picardy” basin, a preliminary validation on parcel and district scale were necessary. The impact of these programs
in the “Cambrai district” was evaluated using an integrated approach, which is based on the use of four numerical models:
AgriFlux, VS2DT, Modflow and MT3D. The results illustrate an improvement due to the “Ferti-Better” program initiated in 1990
and punctual degradation under urbanized areas. Predictions (2015) show a spatial evolution of nitrates concentration varying
with the thickness of unsaturated layer. The integrated model constitutes an efficient tool for predicting the evolution of
the groundwater quality. This approach is important to control the application of the new European laws in the water field. 相似文献
14.
15.
Shumei XU Shikui ZHAI Aibin ZHANG Huaijing ZHANG Haijian LU 《Frontiers of Earth Science》2008,2(1):10-16
The grain size and element (including redox sensitive elements and terrigenous elements) concentration of surface sediments
from the Changjiang Estuary hypoxia zone and its adjacent sea area were measured in this research. Based on the obtained data,
the hypoxic environment’s influence on the distribution of elements in surface sediments was further studied. We believe that
the “redox environment effect” greatly influences the distribution of the RSE, which reveals the “patchy enrichment pattern”
offshore in the hypoxia zone, while the distribution of the terrigenous elements which shows the “stripped enrichment pattern”
near shore is mainly affected by “granularity effects”. Due to the existence of the hypoxia zone of the Changjiang Estuary,
the distribution of the RSE such as Mo, Cd and V in the study area exhibits the characteristics of “redox environment effects”.
__________
Translated from Marine Geology & Quaternary Geology, 2007, 27(3):1–8 [译自: 海洋地质与第四纪地质] 相似文献
16.
17.
A. Gritsun 《Doklady Earth Sciences》2011,438(1):636-640
We have investigated the relationship between periodic trajectories of barotropic atmospheric model and the modes of the model
variability. In particular, we have studied the nature of “25 day” mode of variability (Branstator, 1987; Kushnir 1987). This
mode arises as a first complex empirical orthogonal function (or “Hilbert EOF” according to (H. von Storch, Zwiers)) for a
given system and is a dominant rotational component of the system dynamics. It was shown that the mode structure coincides
with several least unstable periodic orbits of the system. The phase portrait of the system in the plane of the first complex
EOF has regular shape with maximum of the probability density function in the vicinity of these weakly unstable periodic orbits. 相似文献
18.
This paper studies the depth variability of uniaxial compressive laboratory test results on intact Toki granite (i.e., sound
rock without macroscopic fractures) from the Shobasama and Mizunami Construction Sites, Japan. Some of the depth variability
observed in the laboratory results can be indirectly attributed to the high fracture frequency of the “upper highly fractured
rock domain” from which some of the samples were taken. For samples taken from the “lower sparsely fractured rock domain,”
however, the uniaxial compressive strength of the granite seems to be very strongly correlated to the level of in situ rock
stress (i.e., maximum shear stress) determined by measurement results obtained from hydrofracturing tests. The correlation
between the laboratory results and the level of in situ stress is explained by the damage due to the complex stress path that
the cores undergo during drilling, besides the stress concentrations at the drill-bit/rock contact, which can also affect
the microcracking of the samples. An attempt to adjust laboratory test results to estimate the in situ intact rock strength
of Toki granite based on its correlation with in situ stresses was carried out. 相似文献
19.
Yu. B. Gladenkov 《Stratigraphy and Geological Correlation》2010,18(6):660-673
The problems of zonal stratigraphy of the early 21st century are discussed. The great advances achieved in recent years in
using zones in geological practice are noted. At the same time, attention is drawn to the controversies existing in the interpretation
of the concepts “biostratigraphic zone” and “chronozone,” in the methods of drawing the boundaries of such zones, and in the
assessment of the spatial scale of zones and in the understanding of them as stratigraphic units. 相似文献
20.
H. L. Vacher Larry D. Seale Lee J. Florea Robert Brinkmann 《Environmental Geology》2008,54(5):1007-1015
We apply the logic of clinical epidemiological studies to quantify the accuracy of mapping sinkholes by ALSM in the 750 km2 Pinellas County. By such studies, a new diagnostic procedure is tested by comparing the diagnoses in a clinical trial to
diagnoses on the same patients from a more reliable, but more elaborate and expensive procedure (“gold standard” in epidemiological
context). A relatively undeveloped, 65 km2 focus area where we have aerial photographs that are effectively contemporaneous with the ALSM flights serves as the “clinical
trial”. The xy-locations in the focus area are the “patients” in the trial. The “diagnostic test” for having “sinkhole disease” is inclusion
in a database of sinkhole polygons delimited by ALSM contours (“ALSM-alone”), as detailed in Part 1. The standard of comparison
(“gold standard” would be an overstatement in the absence of geophysical testing) is inclusion in a database of sinkhole outlines
derived by best judgment of conjunctive interpretation of ALSM and aerial photography. GIS intersections that indicate the
sensitivity and specificity of the test (ALSM-alone) are 43 and 98.3%, respectively, and, in the focus area where the prevalence
of “sinkhole disease” is 4.7%, the positive and negative predictive values are 55.5 and 97.2%, respectively. Over much of
the rest of the county, where only the test can be applied, the prevalence of sinkholes is sufficiently small that it cannot
be determined to be any different from zero given the paucity of interpreted sinkholes (positive diagnoses) and the low specificity
of the test method. The conclusion, therefore, is that contemporaneous aerial photography is essential to compile an ALSM-derived
database that aims to state that the given xy-points lay inside or outside of topographic depressions in the covered karst of west-central Florida. 相似文献