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23rd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 11 Apr 2010 - 15 Apr 2010
- Location: Keystone, Canada
- Published: 11 April 2010
81 - 100 of 131 results
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Correlations Between Direct Current Resistivity And Seismic Attribute Tests Across An Active Methane Hydrate Vent In Mississippi Canyon Block 118, Gulf Of Mexico
Authors Alan R. Gunnell and John A. DunbarAn active methane vent in Mississippi Canyon Block 118 (MC118), Gulf of Mexico, has been the focus of persistent research. This vent area contains both active and dormant vents as well as blocks of methane hydrate outcropping on the seafloor. It is proposed that methane hydrate blocks also form within the Hydrate Stability Zone (HSZ) beneath the vent. Through collaborative work done by the Gulf of Mexico-Hydrate Research Consortium (GOM-HRC), surficial characteristics and mound chemistry is understood, but quantifiable distributions of hydrate with the HSZ is unknown. High-frequency seismic imaging of the mound is hindered by the presence of free gas, hydrate, and biogenic carbonate blocks on the surface. A direct current resistivity (DCR) land system is adapted to function on the sea floor and to locate the sub-seafloor distributions of hydrate. Continuous resistivity profiling (CRP), totaling 26.4 km in length, is able to resolve the distribution of hydrate whereas further distinguishing between disseminated gas and hydrate. This distribution of hydrate trends along faults and fractures while disseminated methane is found within sediment pores. Through combinations of resistivity profiles and seismic attribute tests, correlations between incoherent and coherent areas beneath the vent represent gas and hydrate respectively.
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Geothermal Investigation Of Waunita Hot Springs Utilizing A Variety Of Geophysical Survey Methods And Techniques
Authors Joyce Hoopes, Gordon Johnson, Kristen Swaim and Ariel ThomasThe results of a geothermal investigation will be presented. The project, part of the Colorado School of Mines Undergraduate Geophysics curriculum, is conducted throughout a student’s senior year. The geothermal reservoir studied has surficial manifestations at Waunita Hot Springs, located in the southeastern corner of Gunnison County. The springs have been identified by the Colorado Geological Survey as a resource with potential for geothermal power generation, (Barrett and Pearl, 1978). The project goals are to better understand the geothermal reservoir and its geologic structure. To understand the fracturing system that defines and controls the reservoir, geophysical mapping of the subsurface conductivity will be presented. An image of the deeper conductivity distribution will be displayed as a result of a time domain electromagnetic survey. For imaging at shallower depths, with greater detail, the electrical methods, specifically SP and DC resistivity, were utilized. Detailed geologic maps of the area are limited; therefore, a geologic survey will be conducted along with the collection of hydrological data. A geochemical analysis of the water from the springs and temperature gradients calculated from borehole measurements will also be presented. The observations and data will be useful in assessing the geothermal potential of Waunita Hot Springs.
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Stable Parameter Estimation Method Applied To Characterization Of Plume Transport In Environmental Inverse Problems
Authors Hugo Bertete-Aguirre and Elena CherkaevThe talk discusses a geophysical environmental inverse problem of characterization of water flow model from monitoring of plume transport. We present a stable method to calibrate transport models using measurements of concentration of a chemical over time. Such observations can be used as an input for geophysical environmental inverse problems. The ability to produce realistic characterization of plume transport relies on the calibration of the parameters of the flow, which in the presented case study is described by the two dimensional advection-diffusion equation. The inverse problem of transport model calibration from inaccurate observations of contaminant concentrations is ill-posed and requires regularization. In the current work, the regularized problem is solved by an adaptive gradient minimization. Stable prediction of plume transport parameters allows to describe the dynamics and transport of solutes or suspensions within the system.
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Using Ground Penetrating Radar To Determine The Quantity Of Impounded Sediment Behind A Dam
Authors David J. Santaniello, David J. Santaniello and Allen M. GontzWe investigate the viability of ground penetrating radar (GPR) as a method to estimate the quantity of sediment stored behind the Merrimack Village Dam on the Souhegan River in southeastern New Hampshire. If the pre-dam riverbed can be imaged, the thickness and volume of the reservoir deposit can be calculated without sampling. We surveyed six cross sections with a Mala Geosciences ProEx 100 MHz GPR unit in May 2008. In a related study, topographic and bathymetric surveys were conducted in 2007, 2008, and 2009 to monitor the sediment flux associated with the removal. By 2009, these surveys measured the pre-dam riverbed in the uppermost cross sections from the dam. We compare these surveys to the interpreted GPR images to calculate a calibrated velocity through the impounded sand of 0.043 m/ns. Using this velocity, the average thickness of the sediment above the interpreted pre-dam riverbed calculated for each of the six cross sections varies between 0.81 m and 3.11 m. The estimate of the quantity of sediment stored behind the dam is ~67,000 m3 compared to a 2004 estimate of ~62,000 m3 based on probing the sediment with a steel rod to the point of refusal.
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Magnetic Prospection Of A Tumulus In The Ancient Histria Necropolis
Authors Dumitru Iouane, Sorin Anghel and Alexandra DuduNear surface geophysical investigations are employed in archaeology in order to estimate the location, depth, shape and physical properties of buried ancient structures. The geophysical study initiated in 2008 on tumuli located in the Histria necropolis was based on magnetics, the measurements being carried out with a proton precession magnetometer / gradientmeter. The networks where measurements of total magnetic field and magnetic vertical gradient were performed covered each tumulus and small adjacent areas. The magnetic measurement points situated at 2 m interval represented detailed rectangular networks. The necropolis is situated at ca 2 km north-west of Histria ancient Greek city and includes a great number of tumuli of various dimensions and trends. Previous archaeological studies evidenced different rituals of burial for the ca 1300 years of continuous inhabitation during Greek colonization and Roman / Byzantine empires. The magnetic data obtained for the tumulus analyzed in this paper, located toward the north-western limit of the Histria necropolis, suggest quite complex archaeological features, similar to those observed in the excavations. Generally, metallic artifacts, a clay layer affected by fire or active magnetic rocks employed in the buried infrastructures may represent sources of high magnetic anomalies. The magnetic total field and vertical gradient anomalies are interpreted as being here mainly due to burnt materials and buried greenshist structure (high anomalies), or to an outer stone belt made of limestone boulders (low anomalies). Key words: Histria, necropolis, tumulus, magnetic method, magnetic anomalies.
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Studies Of Electrical Characteristics Of Hukou, Hsincheng And Sanchiao Active Faults, Northern Taiwan
Authors Hsing-Chang Liu and Chieh-Hou YangTaoyuan, Hsinchu, and Taipei are three major metro areas in northern Taiwan. This study attempts to survey the resistivity structures and locations of the three active faults – Hukou Fault, Hsinchen Fault, and Sanchiao Fault – passing through the three metro areas and has thus provided resistivity imager profilings (RIP), vertical electrical soundings (VES), and audio-frequency magnetotellurics method (AMT) for this purpose. This study has examined the relationships between faults and profilings in addition to the underground resistivity and has acquired following results accordingly: 1. Both Hukou Fault and Hsincchen Fault are thrust faults wherein the hanging walls are lowly resistivity and fault footwall are highly resistivity. Discontinuous geoelectrical or lateral rapid change resistivity is shown in electrical layers, especially in the fault trace or fault zone. Anomalous bands in a homogenous layer are one of the features shown in the Hsinchen fault. In addition to a large lateral resistivity contrast shown in the Sanchiao fault, the contacts surface is very rough. 2. The advantage of RIP result has a better stability, higher resolution and less time-consuming than other resistivity sounding methods. But in the study area, surface obstacles limited the spread of some survey lines, thus the targeted depth of investigation was unattained. AMT survey can be interfered by culture EM wave; the quality of its sounding results is always severely affected, especially in the Taipei area. However, combining the AMT sounding results with the gravity result, geologic data, and formal logging information, the Sanchiao fault and the boundary between the sediment and basement of Taipei Basin can be recognized.
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3D Loop-Source Em Inversion Using Non-Linear Conjugate
Authors Mark S. Hickey and Mark E. EverettElectromagnetic (EM) exploration on land has advanced a long way, but it still needs additional refinement. A 3D inversion would make the interpretation aspect simpler for a complicated subsurface, and make EM exploration easier to implement. We have formulated a 3D inverse solution for land-based loop-source EM exploration using a non-linear conjugate gradient method. This code was developed for exploration of complex subsurface structures like those of a meteorite impact crater or of a contamination plume. A finite element forward model is used to generate predicted data. The forward model uses a finite element mesh as well as coulomb-gauged potentials to solve the governing Maxwell equations and generate data for a single frequency. The finite element forward model code also permits discretization of the subsurface into an unstructured grid, allowing element edges to coincide with the boundaries of irregular subsurface inhomogeneities. The forward model can also take into account topography and its resultant effect on the response. A quasi adjoint Green’s function approach is used to calculate the sensitivity matrix. For this presentation we will show our initial results from synthetic data as well as some preliminary results from actual field data.
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Measurement Of Seismic Local Effects And 1D Numerical Modeling At Selected Sites Affected By The 2009 Seismic Sequence Of L’Aquila
More LessStrong local effects occurred during the seismic sequence that affected the area of L’Aquila (Central Italy) in 2009, which culminated with a main shock of magnitude (Mw) 6.3 on the 6 April. Bearing in mind the magnitude, the vicinity of a regional capital to the epicentre, the presence of several historic centers and villages, which caused significant damage (IMCS max=9.5) and approximately 300 victims, among the main characteristics of this earthquake, was the variability of the recorded damages within the scale of 100 m in spite of the near field conditions and a distinct source mechanism. These local effects were measured with an array of geophones at selected sites near the city of L’Aquila. In one of the sites, located at Onna village which experienced maximum damage levels, the 1D numerical modeling allowed verifying the influence that the frequencey of the input motion has in the determination of superficial seismic effects. The numerical modeling, which was undertaken on the basis of the results from geomechanical, seismic and geoelectrical surveys, also allowed verifying that underestimation of local seismic amplification can be introduced by the current regulatory framework (Italian seismic regulatory guidance “Norme Tecniche per le Costruzioni” – D.M. of 14 January 2008) in contexts similar to that of L’Aquila.
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Solid Wastes Landfill Monitoring By Means Of Differential High-Resolution Infrared Thermography
Differential thermal imaging has been proposed to characterize the ground temperature distribution of two solid wastes landfills. The differential approach permitted to detect regions with thermal abnormalities potentially associated with either biogas leakage and migration or improper landfill settlement and management. Methods, results, limits, and potentialities of the proposed approach are discussed.
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Rayleigh-Wave Dispersion Curves For Long, Linear Arrays At A Predominantly-Gravel Site
Experimental Rayleigh-type surface wave dispersion curves were developed for a gravel site over limestone bedrock. The work was performed as part of an earthquake site-response study. The SASW, MASW, and ReMi methods were applied in linear arrays that approached 1 km in length. For the SASW method, a Vibroseis source was used. The other methods used primarily ambient noise. Dispersion curves were resolved to a minimum frequency of 1 Hz, which corresponded to a maximum wavelength of well over 1 km. Dispersion curves from the three methods were in good agreement over a broad frequency band but differed at low and high extremes. The ambient noise at the site did not appear to introduce directional bias in the passive-source survey results.
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Stream Valley Resistivity In Central Texas: Laying The Foundation For Multi-Disciplinary Research
Increasing land-use and a changing climate can drastically modify floodplain habitats along low-order streams in central Texas. Investigating stream response to these factors on the site-scale can be costly. In an effort to streamline future site-specific investigations, a near-surface geophysical method was used along Williams Creek in Axtell, Texas. A 2-D dipole-dipole resistivity reconnaissance study was employed to estimate depth to bedrock and locate buried channels in a partial-valley cross-section. Auger borings provided ground-truth along the resistivity profile, which confirmed depth to bedrock and the significance of varying resistivities. The 276 meter resistivity profile was completed across a flowing Williams Creek and a portion of its floodplain, revealing a number of different fluvial landforms. Hand-augering confirmed the presence of a coarse-grained paleochannel fill that corresponds with a high-resistivity zone (50-100 ohm-m). At one location, auger refusal at bedrock occurred 3.15 meters below ground surface, consistent with the observed change to lower resistivity values. This decrease in resistivity at the bedrock contact is associated with groundwater flow along the fissile marl bedding planes. These data suggest that resistivity and ground-truthing combined, provide a cost-effective foundation to guide future research on the effects of climate and land-use on Williams Creek.
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Near Surface Borehole Geophysical Imaging In A Highly Structural Area, Beartooth Hills, Montana
Authors Tania Mukherjee and Dr. R.R StewartUniversity of Houston conducted a student geophysical field camp at YBRA (Yellowstone Bighorn Research Association), Red Lodge Montana. The idea was to provide a detailed interpretation of the sub vertical Mississippian Madison lime stone bed beneath the YBRA camp using seismic and well logs. Several 2D seismic lines (E-W) were acquired and several logs were run in the two wells drilled in the camp.The depth of the wells are 30m and 60m , the wells were drilled then cemented and cased with PVC. SP, gamma, sonic, temperature, conductivity and sonic televiewer logs were run in the wells. Several multicomponent VSP (Vertical Seismic Profile) with different offset were also done. A shot offset of 3.5 m was selected for VSP. Both the wells were compared to see high frequency noise and shot signature. The limestone P wave velocity is about 2600 m and shale velocity is about 2800 m /s. The Vp/Vs is 2 for limestone and 1.7 for the shale unit. As there is very steep dipping reflectors, there is only little upgoing wave in the data .A VSP-NMO was also done and a corridor stack was then created. With the help of all dataset,composite plot and a quick look interpretation shows the limestone-Redbed encounter to be at 40 m and the probable dip of the bed looks to be 45° towards south.
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Groundwater Investigation In Giginyu, Nassarawa Local Government Kano State Nigeria
Authors A.U. Farouq, H.U. Suru, Bello Maruff Akande and U.A. AminuDC Vertical Electrical Soundings were carried out in 10 stations in order to determine areas with groundwater potentials. Data collected were reduced and interpreted according to profiles (profile one and profile two). The interpretation yielded two geoelectric sections of (3) geoelectric layers for profile one and four (4) geoelectric layers for profile two. The topsoil thickness ranges between 0.8 and 2.6 m with resistivity values ranging between 103 Ohm-meter and 1031.2 Ohm–meter across the study area. The topsoil is lateritic clay, sandy clay and clayey sand. The thickness of the weathered layer ranges from 3.3 m to 20 m and resistivity ranges between 11.5 Ohm-meter to 294 Ohm-meter, this indicates the aquiferous formation. Depth to aquifer ranging between 1.6 m to 15.9 m. The partially weathered/fractured basement resistivity ranges between 98 Ohm-meter to 692.4 Ohm-meter, which indicate high degree of fracture and or water saturation with thickness range between 7.2 m and 52 m. Fresh bedrock is the last layer with resistivity values ranging between 1266 Ohm-meter to 100000 Ohmmeter at all the VES points in the study area at a depth ranging between 4.1 m to 70 m. Hence, VES9 and VES10 on profile two, having highest groundwater potentials.
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Geophysical Investigations At The Chimney Rock Great House, Colorado
Authors Sarah Devriese, Michael A. Mitchell and Roxanna FraryIn conjunction with the National Forest Service, a number of different geophysical datasets were collected over the region adjoining the southwest end of the Great House at Chimney Rock, Colorado. The investigations aim to determine if the foundations for more rooms exist in this region, as early archeological sketches indicate. The following types of datasets were collected: magnetic, frequencydomain electromagnetic (FEM), DC resistivity (middle gradient and 2D dipole-dipole), and microgravity. This multipronged approach was used to provide a diverse range of data types, all of which have different physical property sensitivities. Since the expected physical property contrast between the wall foundations and possible room infill has yet to be characterized, it is difficult to determine which of the utilized methods will produce the best results. A thorough analysis of our geophysical field data along with the results gleamed from processing and inversion, will allow us to develop a meaningful interpretation, upon which recommendations for future investigations can be based. By determining whether or not the additional rooms exist, this study will help archeologists and the National Forest Service characterize the extent of the Chimney Rock Great House, plan future archeological studies, and set a basis for future geophysical investigations at the site.
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Mec Classification Parameter Selection Based On Site-Specific Munitions Characteristics
Authors Steve Saville, Nathan Harrison and Craig MurrayParsons has participated in the Environmental Security Technology Certification Program (ESTCP) unexploded ordnance (UXO) Discrimination Study at Camp Sibert, Alabama, and most recently at Camp San Luis Obispo (SLO), California. In 2008, ground truth results from Camp Sibert were used to identify commonly used target parameters from EM61-MK2 data that would improve the classification of munitions and clutter. UXA-Size (size), a parameter based on instrument response across the three major axes of an object, and a decay constant were identified as having the greatest potential for classifying the 4.2-inch mortar seed items found at Camp Sibert. A simple rule-based classification was developed based on size and decay, and the resulting receiver operating characteristic (ROC) curve showed improvement over a previous rule-based classification of the Camp Sibert ground truth results. In 2009, Parsons participated in a similar target classification study for the SLO site. Unlike Camp Sibert, which included only the 4.2-inch mortar, the SLO site included a range of munitions types: 2.36-inch rockets, 4.2-inch mortars, 60-millimeter (mm) projectiles, and 81mm projectiles. This range of munition types made application of the size and decay based classification of anomalies detected using the EM61-MK2 at Camp Sibert more challenging for the SLO site. Because of the variety of munitions types at SLO, a single size parameter could not be identified for effective classification of all munitions types from clutter. Attempts to define unique rules involving size per munitions type were not as diagnostic for the SLO data set due the wider range of size values observed for munitions and clutter at this site. The most effective rule-based classification at the SLO site was to use two sets of decay values from the EM61-MK2 data to classify the munitions and clutter.
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Self-Guiding Robotic Geophysical Surveying For Shallow Ojects In Comparison To Traditional Survey Methods
Authors Nathan Harrison, Bob Selfridge, Craig Murray and David HodoThe quality of geophysical data is a critical aspect of the digital geophysical mapping process. Human factors in geophysical mapping can affect navigation, background noise, and speed control, impacting data quality. An important issue facing MEC geophysicists is to find ways to limit these factors as a first step towards successful consistent reproducible geophysical surveying. Human data acquisition errors can be significantly improved with self-guidance/robotic technology. ESTCP and the Huntsville Innovative Technology Program funded Auburn University to develop a path-following robotic vehicle to address those problems. Parsons worked with the Innovative Technology Program to perform the first technology transfer to a contractor of the government’s semi-autonomous robotic Segway geophysical platform to a Remedial Investigation/Feasibility Study RI/FS MEC project at the former Great Salt Plains Bombing Range (GSPBR) in Alfalfa County, Oklahoma and a removal action at a former firing range within Camp Sibert, Alabama. To characterize two munitions response site’s (MRS) during the RI/FS at the Great Salt Plains, a total of 16.5 acres of transect data and 12.1 acres of grid-based data were collected between 12/1/08 and 1/12/09 using time-domain electromagnetics (TDEM). Three methods of data collection included towing either two Geonics EM61-MKII coils with a self-guiding robotic system or a small utility vehicle, or one coil operated by a person. Two of these three methods, including the selfguiding robotic system and the one coil operated by a person, were also used to geophysically map the 20 acre range at Camp Sibert. This study compares the three methods based on overall performance, including geophysical prove-outs, data quality and productivity. Site conditions and equipment problems inhibited productivity of the robotic system, however future improvements or careful site selection could make the self-guiding technology useful to UXO projects. The Great Salt Plains field tests identified system weaknesses and solutions, which were applied to the Camp Sibert project allowing for high production rates with the Segway System. The results of these projects indicate that the robotic system is a viable option for DGM on many future UXO projects.
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Multi-Channel Analysis Of Surface Waves: An Application To Montana Field Data
Authors Soumya Roy and Dr. Robert R. StewartThe multi-component (3C or 4C) seismic method is being used to more fully capture the seismic wavefield and to generate complementary P-wave and S-wave (PS) images of the subsurface. One of the complicating issues in processing PS data is the effect of receiver statics. The S-wave receiver static can be quite large due to low S-wave near-surface velocities. We are thus interested in techniques to estimate the shallow S-wave velocity (Vs) structure. The analysis of surface waves (especially Rayleigh waves) has been useful to delineate Vs in near-surface. Multi-Channel Analysis of Surface Waves (MASW) uses the dispersion properties of Rayleigh waves to create a dispersion curve (Park et al., 1998), then S-wave near-surface velocity profile (Xia et al., et al., 1999). We have applied the MASW method to seismic datasets from Elk Basin Oilfield in Bighorn Basin, Montana/Wyoming acquired by students of University of Houston. Vertical and horizontal component seismic lines are analyzed. Preliminary results show extracted S-wave velocities for vertical and horizontal component lines varying between 400-1000 m/sec.
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Ground Penetrating Radar Investigation Of Dinosaur Quarries In Morrison, Colorado
Authors Renee Francese and Orion SandovalStudents conducting the investigation are doing so through the Colorado School of Mines Undergraduate Geophysics curriculum as a senior project. Investigation has been done in Morrison, Colorado for similar purposes, however little geophysical data has been collected in the area of interest. The goal of this project is to image the dinosaur bones and model the sandstone to mudstone boundary, where the extent of dinosaur bones has been found. A quarry about 100 feet to the north of the site has been previously excavated to find large dinosaur artifacts. The director at the Morrison Museum of Natural History, Matt Mossbrucker, has reason to believe that Quarry XYZ will contain dinosaur artifacts based on geology trends, bone fragments found at the surface, and notes by Arthur Lakes (A. Hunt, M. Lockley, S.White, 2002). By experimenting with different antennas and other GPR equipment, the students will find the optimal setup to better model the geology boundaries and find large targets beneath the surface up to depths of 1015 feet. The data collected will be useful in further understanding the geology and ability to locate dinosaur artifacts in the Morrison area.
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Fracture Imaging In The Upper Kama Potash Mine Using 3-D GPR Data
More LessFracture detection and delineation is very important for salt mines operation because fracturing significantly increases the probability of failure of supporting pillars and overlaying water protective beds. Results of forward modeling studies confirmed the feasibility of georadar with a 400 MHz antenna to reliably detect the millimetric scale fracture. 3-D GPR data were acquired in the potash mine near the city of Solikamsk, Russia to evaluate the effectiveness of imaging technology to detect and delineate the fractures in heterogeneous salt rock. Continuous common-offset data were obtained at seven parallel profiles across the fracture exposed in the wall of a mine pillar. The pillar was 4.5 m thick and comprised of interbedded layers of salt rock and clay. The open millimetric scale subvertical fracture crosscuts the pillar at angle of 25°. Data were collected using commercial OKO georadar system (Logis, Russia) with a 400 MHz shielded antenna. ReflexW and OpendTect software were used for processing and interpretation of the 2-D radargrams and combined 3-D data set. The 3-D migration allowed generating a true image of subsurface structures and creating a spatial model of fractures. Using the image of known fracture as interpretation template, fracture having no surface evidence was detected.
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Laboratory Assessment Of Nano-Silver Transport In Sand Columns Using Complex Conductivity Measurements
More LessNano-materials are emerging into the global marketplace. Nanoparticles, and other throwaway nano-devices may constitute a whole new class of non-biodegradable pollutants that scientists have very little understanding of. Therefore, the production of significant quantities of nano-materials will inevitably result in the introduction of these materials to the environment with important implications for both environmental and human health. Currently there are many unanswered questions related to the release of nano-materials, their fate, transport, and transformation in the environment, and their potential toxic effects. Due to their desirable chemical–physical, electronic, and optical properties, metal nanoparticles have attracted much attention and demonstrated a wide range of applications (Kamat, 2002; Oliveira et al., 2005). Among metal nanoparticles, silver nanoparticles possess many superior properties, such as increased electrical conductivity, antimicrobial activity, catalytic effect, etc. (Kabashin et al., 2003).
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