Identification of preferential flow effects on hydraulic conductivity measurements using a fluorescent tracer

2000 ◽  
Vol 37 (2) ◽  
pp. 479-484
Author(s):  
Tom A Al ◽  
David W Blowes
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Errors ◽  
Preferential Flow ◽  
Conductivity Measurements ◽  
Fine Grained ◽  
The Core ◽  
Core Samples ◽  
Dye Tracer ◽  
Order Of Magnitude ◽  
Constant Head

Core samples were collected from fractured and unfractured zones within fine-grained, unconsolidated mine tailings. The hydraulic conductivity of the core samples was measured in a constant-head permeameter. A fluorescent dye tracer was added to the constant-head reservoir in the permeameter. The tests were run for approximately 48 h, then the cores were sectioned to observe the distribution of dye. Flow through the fractures results in hydraulic conductivity measurements up to one order of magnitude greater than that of unfractured tailings. Observations of the dye distribution in samples following permeameter measurements are used to identify cases where preferential flow in fractures has influenced the hydraulic conductivity measurements. The dye tracer distribution also indicates where measurement errors may be suspected due to flow leakage around the core sample.Key words: tracers, hydraulic conductivity, fractures, tailings.

Spatial Variability of Contaminant Transport in a Fractured Till, Avedøre Denmark

1999 ◽  
Vol 30 (4-5) ◽  
pp. 333-360 ◽  
Author(s):  
Larry McKay ◽  
Johnny Fredericia ◽  
Melissa Lenczewski ◽  
Jørn Morthorst ◽  
Knud Erik S. Klint
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Field Experiment ◽  
Contaminant Transport ◽  
Tracer Test ◽  
Conductivity Measurements ◽  
Fine Grained ◽  
Downward Migration ◽  
Rapid Transport ◽  
High Degree

A field experiment shows that rapid downward migration of solutes and microorganisms can occur in a fractured till. A solute tracer, chloride, and a bacteriophage tracer, PRD-1, were added to groundwater and allowed to infiltrate downwards over a 4 × 4 m area. Chloride was detected in horizontal filters at 2.0 m depth within 3-40 days of the start of the tracer test, and PRD-1 was detected in the same filters within 0.27 - 27 days. At 2.8 m depth chloride appeared in all the filters, but PRD-1 appeared in only about one-third of the filters. At 4.0 m depth chloride appeared in about one-third of the filters and trace amounts of PRD-1 were detected in only 2 of the 36 filters. Transport rates and peak tracer concentrations decreased with depth, but at each depth there was a high degree of variability. The transport data is generally consistent with expectations based on hydraulic conductivity measurements and on the observed density of fractures and biopores, both of which decrease with depth. Transport of chloride was apparently retarded by diffusion into the fine-grained matrix between fractures, but the rapid transport of PRD-1, with little dispersion, indicates that it was transported mainly through the fractures.

A constant-head pumping test method using direct-push equipment for in situ hydraulic conductivity measurements

Géotechnique ◽  
2012 ◽  
Vol 62 (3) ◽  
pp. 253-262 ◽  
Author(s):  
T. KOBAYASHI ◽  
H. ONOUE ◽  
S. OBA ◽  
N. YASUFUKU ◽  
K. OMINE
Keyword(s):  
Hydraulic Conductivity ◽  
Pumping Test ◽  
Test Method ◽  
Conductivity Measurements ◽  
Direct Push ◽  
Constant Head

Estimating hydraulic conductivity of a sandy soil under different plant covers using minidisk infiltrometer and a dye tracer experiment

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Marián Homolák ◽  
Jozef Capuliak ◽  
Viliam Pichler ◽  
Ľubomír Lichner
Keyword(s):  
Hydraulic Conductivity ◽  
Sandy Soil ◽  
Plant Cover ◽  
Soil Surface ◽  
Tracer Experiment ◽  
Forest Site ◽  
Moss Species ◽  
Brilliant Blue Fcf ◽  
Dye Tracer ◽  
Order Of Magnitude

AbstractThe objective of this study was to estimate the hydraulic conductivity of sandy soil under different plant cover at the locality Mláky II at Sekule (southwest Slovakia). Two sites were demarcated at the locality, with mainly moss species at glade site, and pine forest at forest site. The estimation of unsaturated hydraulic conductivity was conducted by (a) minidisk infiltrometer and (b) the analysis of a dye tracer total resident concentration. The latter approach assumed the applicability of the stochastic—convective flow theory in the sandy soil. In the dye tracer experiment, two plots (1 × 1 m each) were established in both sites, and 100 mm of dye tracer (Brilliant Blue FCF) solution was applied on the soil surface. Similar results were obtained in both plots, with more than 70 % area of horizons stained in the depth of 30–50 cm. In some cases, the predicted and measured hydraulic conductivity were found within an order of magnitude, thus revealing similar impact of different plant cover on hydraulic properties of sandy soil studied. In contrast to sandy soils used for agriculture, the influence of the plant/surface humus and topsoil interface extended in the form of a highly heterogeneous matrix flow to the depth of 50–60 cm, where it was dampened by horizontal layering.

Fossil diatoms from the Volga Delta Holocene sediments (Damchik region) as indicators of the paleoecological conditions of sedimentation

2019 ◽  
pp. 270-273
Author(s):  
Yelena I. Shtyrkova ◽  
Yelena I. Polyakova
Keyword(s):  
Nature Reserve ◽  
Diatom Analysis ◽  
Volga Delta ◽  
The Core ◽  
Core Samples ◽  
Holocene Sediments ◽  
Fossil Diatoms

The results of fossil diatoms investigation from the deltaic sediments are presented. Samples were obtained from the core DM-1 and two Holocene outcrops from the Damchik region of the Astrakhan Nature Reserve. In the core samples eight periods of sedimentation based on diatom analysis were identified: the sediments formed in shallow freshwater basins and deltaic channels. The samples from the outcrops were investigated in much greater detail.

Assessment of clogging in constructed wetlands by saturated hydraulic conductivity measurements

2019 ◽  
Vol 79 (2) ◽  
pp. 314-322 ◽  
Author(s):  
F. Licciardello ◽  
R. Aiello ◽  
V. Alagna ◽  
M. Iovino ◽  
D. Ventura ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Hydraulic Conductivity ◽  
Constructed Wetlands ◽  
Spatial Scales ◽  
Pilot Scale ◽  
Laboratory Scale ◽  
Test Method ◽  
Conductivity Measurements ◽  
Multiple Spatial Scales ◽  
Ks Values

Abstract This study aims at defining a methodology to evaluate Ks reductions of gravel material constituting constructed wetland (CW) bed matrices. Several schemes and equations for the Lefranc's test were compared by using different gravel sizes and at multiple spatial scales. The falling-head test method was implemented by using two steel permeameters: one impervious (IMP) and one pervious (P) on one side. At laboratory scale, mean K values for a small size gravel (8–15 × 10−2 m) measured by the IMP and the P permeameters were equal to 19,466 m/d and 30,662 m/d, respectively. Mean Ks values for a big size gravel (10–25 × 10−2 m) measured by the IMP and the P permeameters were equal to 12,135 m/d and 20,866 m/d, respectively. Comparison of Ks values obtained by the two permeameters at laboratory scale as well as a sensitivity analysis and a calibration, lead to the modification of the standpipe equation, to evaluate also the temporal variation of the horizontal Ks. In particular, both permeameters allow the evaluation of the Ks decreasing after 4 years-operation and 1–1.5 years' operation of the plants at full scale (filled with the small size gravel) and at pilot scale (filled with the big size gravel), respectively.

scholarly journals Difficulties and modifications in the use of available methods for hydraulic conductivity measurements in highly clogged horizontal subsurface flow constructed wetlands

2017 ◽  
Vol 76 (7) ◽  
pp. 1666-1675 ◽  
Author(s):  
Mateus Pimentel Matos ◽  
André Baxter Barreto ◽  
Gabriel Rodrigues Vasconcellos ◽  
Antonio Teixeira Matos ◽  
Gustavo Ferreira Simões ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Constructed Wetlands ◽  
Subsurface Flow ◽  
The Other ◽  
Good Representation ◽  
Horizontal Distance ◽  
Conductivity Measurements ◽  
Construction Time ◽  
Horizontal Subsurface Flow ◽  
Subsurface Flow Constructed Wetlands

Despite the fact that several authors consider the available measurement methods of hydraulic conductivity (ks) suitable for a good representation of the bed condition and clogging potential in horizontal subsurface flow constructed wetlands, others have questioned their adequacy. In this work, hydraulic conductivity measurements with conventional and modified methods were undertaken in two small full-scale units, one planted with cattail (Typha latifolia) and the other unplanted. Both units had already been operating for seven years and showed a high degree of clogging. It was observed that the use of the falling head method, with the introduction of the tubes during the test, provided results without a clear spatial trend. On the other hand, tests done on monitoring wells inserted during construction time showed, as expected, ks increasing with the horizontal distance from the inlet, but without reflecting actual field conditions. It was observed that, as the bed became more clogged, the use of the reported methods became more complex, suggesting the need of other methodologies. The use of planted fixed reactors (removable baskets installed in the bed) with evaluation of ks at constant head in the laboratory showed potential for the characterization of the hydrodynamic properties of the porous medium.

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

Simplified estimation of unsaturated soil hydraulic conductivity using bulk electrical conductivity and particle size distribution

Soil Research ◽  
2013 ◽  
Vol 51 (1) ◽  
pp. 23 ◽  
Author(s):  
Mohammad Reza Neyshabouri ◽  
Mehdi Rahmati ◽  
Claude Doussan ◽  
Boshra Behroozinezhad
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Hydraulic Conductivity ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Unsaturated Soil ◽  
Soil Core ◽  
Soil Hydraulic Conductivity ◽  
Core Samples ◽  
Soil Hydraulic

Unsaturated soil hydraulic conductivity K is a fundamental transfer property of soil but its measurement is costly, difficult, and time-consuming due to its large variations with water content (θ) or matric potential (h). Recently, C. Doussan and S. Ruy proposed a method/model using measurements of the electrical conductivity of soil core samples to predict K(h). This method requires the measurement or the setting of a range of matric potentials h in the core samples—a possible lengthy process requiring specialised devices. To avoid h estimation, we propose to simplify that method by introducing the particle-size distribution (PSD) of the soil as a proxy for soil pore diameters and matric potentials, with the Arya and Paris (AP) model. Tests of this simplified model (SM) with laboratory data on a broad range of soils and using the AP model with available, previously defined parameters showed that the accuracy was lower for the SM than for the original model (DR) in predicting K (RMSE of logK = 1.10 for SM v. 0.30 for DR; K in m s–1). However, accuracy was increased for SM when considering coarse- and medium-textured soils only (RMSE of logK = 0.61 for SM v. 0.26 for DR). Further tests with 51 soils from the UNSODA database and our own measurements, with estimated electrical properties, confirmed good agreement of the SM for coarse–medium-textured soils (<35–40% clay). For these textures, the SM also performed well compared with the van Genuchten–Mualem model. Error analysis of SM results and fitting of the AP parameter showed that most of the error for fine-textured soils came from poorer adequacy of the AP model’s previously defined parameters for defining the water retention curve, whereas this was much less so for coarse-textured soils. The SM, using readily accessible soil data, could be a relatively straightforward way to estimate, in situ or in the laboratory, K(h) for coarse–medium-textured soils. This requires, however, a prior check of the predictive efficacy of the AP model for the specific soil investigated, in particular for fine-textured/structured soils and when using previously defined AP parameters.

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