scholarly journals In Situ Measurements in Fractured Till Using Sidewall Sensors

1999 ◽  
Vol 30 (4-5) ◽  
pp. 257-266 ◽  
Author(s):  
Larry Murdoch ◽  
Bill Harrar ◽  
Bertel Nilsson ◽  
William Slack ◽  
Robert Siegrist
Keyword(s):  
Hydraulic Head ◽  
Core Sample ◽  
Contaminated Site ◽  
Platinum Electrodes ◽  
Glacial Sediments ◽  
Fine Grained ◽  
In Situ Sensors ◽  
The Usa ◽  
A Site

Subsurface parameters, such as hydraulic head, often vary markedly with depth in fine-grained glacial sediments, but sensors placed in vertical boreholes are poorly suited to resolve these variations. One problem is that conventional methods only allow one, or perhaps a few, sensors to be placed in each borehole. To address such limitations we have developed a method for accessing the sidewall of a borehole. The method uses a device that pushes sensors or sediment samplers laterally into the sidewall to distances slightly less than the diameter of the borehole. The device can obtain a core sample 15 cm long and 4 cm in diameter, and then insert a permeable sleeve for extracting water samples. The same device has been used to insert several types of electrodes capable of measuring water content (using TDR waveguides), Eh (using platinum electrodes), or electrical resistivity (using a miniature Wenner-type array). At a site near Flakkebjerg, Denmark, we installed 22 water samplers and 19 resistivity electrodes in a single borehole to measure hydraulic head gradients in detail and to monitor the vertical migration of ionic tracers. This approach can be used to install horizontally oriented TDR waveguides at virtually any depth, thereby extending the TDR technique to the study of deep vadose zones. At a contaminated site in the USA, TDR wave guides were installed to a depth of 12 m in glacial till. Other applications include measurement of Eh at a site where in situ chemical oxidization was used, and the in situ sensors provided results that are similar to data obtained from soil cores.

In‐situ apparent conductivity measurements and microbial population distribution at a hydrocarbon‐contaminated site

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 56-63 ◽  
Author(s):  
Estella A. Atekwana ◽  
D. Dale Werkema ◽  
Joseph W. Duris ◽  
Silvia Rossbach ◽  
Eliot A. Atekwana ◽  
...  
Keyword(s):  
Microbial Degradation ◽  
Microbial Population ◽  
Population Distribution ◽  
Microbial Populations ◽  
Contaminated Site ◽  
Most Probable Number ◽  
Bulk Conductivity ◽  
Probable Number ◽  
A Site

We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light nonaqueous‐phase liquid (LNAPL). The bulk conductivity was measured using in‐situ vertical resistivity probes; the most probable number method was used to characterize the spatial distribution of aerobic heterotrophic and oil‐degrading microbial populations. The purpose of this study was to assess if high conductivity observed at aged LNAPL‐impacted sites may be related to microbial degradation of LNAPL. The results show higher bulk conductivity coincident with LNAPL‐impacted zones, in contrast to geoelectrical models that predict lower conductivity in such zones. The highest bulk conductivity was observed to be associated with zones impacted by residual and free LNAPL. Data from bacteria enumeration from sediments close to the resistivity probes show that oil‐degrading microbes make up a larger percentage (5–55%) of the heterotrophic microbial community at depths coincident with the higher conductivity compared to ∼5% at the uncontaminated location. The coincidence of a higher percentage of oil‐degrading microbial populations in zones of higher bulk conductivity suggests that the higher conductivity in these zones may result from increased fluid conductivity related to microbial degradation of LNAPL, consistent with geochemical studies that suggest that intrinsic biodegradation is occurring at the site. The findings from this study point to the fact that biogeochemical processes accompanying biodegradation of contaminants can potentially alter geoelectrical properties of the subsurface impacted media.

scholarly journals Calibrating a long-term meteoric <sup>10</sup>Be delivery rate into eroding western US glacial deposits by comparing meteoric and in situ produced <sup>10</sup>Be depth profiles

Geochronology ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 411-423
Author(s):  
Travis Clow ◽  
Jane K. Willenbring ◽  
Mirjam Schaller ◽  
Joel D. Blum ◽  
Marcus Christl ◽  
...  
Keyword(s):  
Delivery Rate ◽  
Estimation Methods ◽  
Solar Modulation ◽  
Depth Profiles ◽  
Fine Grained ◽  
Denudation Rates ◽  
Solar Intensity ◽  
A Site

Abstract. Meteoric 10Be (10Bemet) concentrations in soil profiles have great potential as a geochronometer and a tracer of Earth surface processes, particularly in fine-grained soils lacking quartz that would preclude the use of in situ produced 10Be (10Bein situ). One prerequisite for using this technique for accurately calculating rates and dates is constraining the delivery, or flux, of 10Bemet to a site. However, few studies to date have quantified long-term (i.e., millennial) delivery rates, and none have determined a delivery rate for an eroding soil. In this study, we compared existing concentrations of 10Bein situ with new measurements of 10Bemet in eroding soils sampled from the same depth profiles to calibrate a long-term 10Bemet delivery rate. We did so on the Pinedale (∼ 21–25 kyr) and Bull Lake (∼ 140 kyr) glacial moraines at Fremont Lake, Wyoming (USA), where age, grain sizes, weathering indices, and soil properties are known, as are erosion and denudation rates calculated from 10Bein situ. After ensuring sufficient beryllium retention in each profile, solving for the delivery rate of 10Bemet, and normalizing for paleomagnetic and solar intensity variations over the Holocene, we calculate 10Bemet fluxes of 1.46 (±0.20) × 106 atoms cm−2 yr−1 and 1.30 (±0.48) × 106 atoms cm−2 yr−1 to the Pinedale and Bull Lake moraines, respectively, and compare these values to two widely used 10Bemet delivery rate estimation methods that substantially differ for this site. Accurately estimating the 10Bemet flux using these methods requires a consideration of spatial scale and temporally varying parameters (i.e., paleomagnetic field intensity, solar modulation) to ensure the most realistic estimates of 10Bemet-derived erosion rates in future studies.

scholarly journals Bioremediation of groundwater contaminated with petroleum hydrocarbons applied at a site in Belgrade (Serbia)

2020 ◽  
Vol 85 (8) ◽  
pp. 1067-1081
Author(s):  
Sandra Bulatovic ◽  
Nenad Maric ◽  
Tatjana Solevic-Knudsen ◽  
Jelena Avdalovic ◽  
Mila Ilic ◽  
...  
Keyword(s):  
Petroleum Hydrocarbons ◽  
Cost Effective ◽  
Subsequent Treatment ◽  
Limiting Factors ◽  
Contaminated Site ◽  
Microbiological Activity ◽  
A Site ◽  
Specialized Population ◽  
Remediation Process

Due to their extensive use, petroleum hydrocarbons are among the most common groundwater contaminants. Compared to the traditional methods of physical pumping of contamination from the aquifer and subsequent treatment (i.e., pump and treat), bioremediation is an economically cost-effective technology. The aim of this remediation approach is to transform biologically contaminants, most often by microbiological activity, into non-toxic compounds. More precisely, it is an active remediation process that involves biostimulation (increase of aquifer oxygenation, addition of nutrients) and/or bioaugmentation (injection of a concentrated and specialized population of microorganisms). Using both biostimulation and bioaugmentation, enhanced in situ groundwater bioremediation was applied at a hydrocarbon-contaminated site in Belgrade. The bioremediation treatment, applied over twelve months, was highly efficient in reducing the concentrations of total petroleum hydrocarbon (TPH) to acceptable levels. The concentration of TPH in the piezometer P-5 was reduced by 98.55 %, in the piezometer P-6 by 98.30 % and in the piezometer P-7 by 98.09 %. These results provided strong evidence on the potential of this remediation approach to overcome site-limiting factors and enhance microbiological activity in order to reduce groundwater contamination.

scholarly journals Calibrating a long-term meteoric <sup>10</sup>Be delivery rate into Western US glacial deposits through a comparison of complimentary meteoric and in situ-produced <sup>10</sup>Be depth profiles

2020 ◽  
Author(s):  
Travis Clow ◽  
Jane K. Willenbring ◽  
Mirjam Schaller ◽  
Joel D. Blum ◽  
Marcus Christl ◽  
...  
Keyword(s):  
Careful Consideration ◽  
Delivery Rate ◽  
Estimation Methods ◽  
Depth Profiles ◽  
Fine Grained ◽  
Erosion Rates ◽  
Denudation Rates ◽  
A Site

Abstract. Meteoric 10Be (10Bemet) concentrations in soil profiles great potential as a geochronometer and a tracer of Earth surface processes, particularly in fine-grained soils lacking quartz that would preclude the use of in situ-produced 10Be (10Bein situ). One prerequisite for using this technique for accurately calculating rates and dates is constraining the delivery, or flux, of 10Bemet to a site. However, few studies to date have quantified long-term (i.e. millennial) delivery rates. In this study, we compared existing concentrations of 10Bein situ with new measurements of 10Bemet in soils sampled from the same depth profiles to calibrate a long-term 10Bemet delivery rate. We did so on the Pinedale and Bull Lake glacial moraines at Fremont Lake, Wyoming (USA) where age, grain sizes, weathering indices, and soil properties are known, as are erosion/denudation rates calculated from 10Bein situ. After ensuring sufficient beryllium retention in each profile, solving for the delivery rate of 10Bemet via Monte Carlo simulations, and normalizing to Holocene-average paleomagnetic intensity, we calculate best-fit fluxes of 0.92 (+/− 0.08) × 106 and 0.71 (+0.09/−0.08) × 106 atoms cm−2 y−1 to the Pinedale and Bull Lake moraines, respectively, and compare these values to two widely-used 10Bemet delivery rate estimation methods. Accurately estimating 10Bemet flux using these methods requires careful consideration of spatial scale as well as temporally varying parameters (e.g. paleomagnetic field intensity) to ensure the most realistic estimates of 10Bemet-derived erosion rates in future studies.

Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

How Artefacts Do Leadership: A Ventriloquial Analysis

2021 ◽  
pp. 089331892199807
Author(s):  
Jonathan Clifton ◽  
Fernando Fachin ◽  
François Cooren
Keyword(s):  
Organizational Communication ◽  
Recent Work ◽  
Distributed Leadership ◽  
Network Theory ◽  
Actor Network Theory ◽  
Fine Grained ◽  
Naturally Occurring ◽  
Human Actors

To date there has been little work that uses fine-grained interactional analyses of the in situ doing of leadership to make visible the role of non-human as well as human actants in this process. Using transcripts of naturally-occurring interaction as data, this study seeks to show how leadership is co-achieved by artefacts as an in-situ accomplishment. To do this we situate this study within recent work on distributed leadership and argue that it is not only distributed across human actors, but also across networks that include both human and non-human actors. Taking a discursive approach to leadership, we draw on Actor Network Theory and adopt a ventriloquial approach to sociomateriality as inspired by the Montreal School of organizational communication. Findings indicate that artefacts “do” leadership when a hybrid presence is made relevant to the interaction and when this presence provides authoritative grounds for influencing others to achieve the group’s goals.

scholarly journals Development of Fragility Curves for Piping and Slope Stability of River Levees

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 738
Author(s):  
Nicola Rossi ◽  
Mario Bačić ◽  
Meho Saša Kovačević ◽  
Lovorka Librić
Keyword(s):  
Slope Stability ◽  
Fragility Curves ◽  
Safety Margin ◽  
Water Levels ◽  
Flood Event ◽  
Soil Parameters ◽  
Design Code ◽  
A Site ◽  
Insight Into

The design code Eurocode 7 relies on semi-probabilistic calculation procedures, through utilization of the soil parameters obtained by in situ and laboratory tests, or by the means of transformation models. To reach a prescribed safety margin, the inherent soil parameter variability is accounted for through the application of partial factors to either soil parameters directly or to the resistance. However, considering several sources of geotechnical uncertainty, including the inherent soil variability, measurement error and transformation uncertainty, full probabilistic analyses should be implemented to directly consider the site-specific variability. This paper presents the procedure of developing fragility curves for levee slope stability and piping as failure mechanisms that lead to larger breaches, where a direct influence of the flood event intensity on the probability of failure is calculated. A range of fragility curve sets is presented, considering the variability of levee material properties and varying durations of the flood event, thus providing crucial insight into the vulnerability of the levee exposed to rising water levels. The procedure is applied to the River Drava levee, a site which has shown a continuous trend of increased water levels in recent years.

scholarly journals Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 228
Author(s):  
Rute Cesário ◽  
Nelson J. O’Driscoll ◽  
Sara Justino ◽  
Claire E. Wilson ◽  
Carlos E. Monteiro ◽  
...  
Keyword(s):  
Leaf Area ◽  
Elemental Mercury ◽  
Ambient Air ◽  
Tagus Estuary ◽  
Contaminated Site ◽  
Gaseous Elemental Mercury ◽  
Mercury Flux ◽  
Sarcocornia Fruticosa ◽  
Air Concentrations

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

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