scholarly journals Tracer Dispersion through Karst Conduit: Assessment of Small-Scale Heterogeneity by Multi-Point Tracer Test and CFD Modeling

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 168
Author(s):  
Romain Deleu ◽  
Sandra Soarez Frazao ◽  
Amaël Poulain ◽  
Gaëtan Rochez ◽  
Vincent Hallet
Keyword(s):  
Spatial Heterogeneity ◽  
Single Point ◽  
Tracer Tests ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Cfd Modeling ◽  
Small Scale ◽  
Tracer Concentration ◽  
Tracer Dispersion ◽  
The Impact

Tracer tests are widely used for characterizing hydrodynamics, from stream-scale to basin-wide scale. In karstic environments, the positioning of field fluorometers (or sampling) is mostly determined by the on-site configuration and setup difficulties. Most users are probably aware of the importance of this positioning for the relevance of data, and single-point tests are considered reliable. However, this importance is subjective to the user and the impact of positioning is not well quantified. This study aimed to quantify the spatial heterogeneity of tracer concentration through time in a karstic environment, and its impact on tracer test results and derived information on local hydrodynamics. Two approaches were considered: on-site tracing experiments in a karstic river, and Computational Fluid Dynamics (CFD) modeling of tracer dispersion through a discretized karst river channel. A comparison between on-site tracer breakthrough curves and CFD results was allowed by a thorough assessment of the river geometry. The results of on-site tracer tests showed significant heterogeneities of the breakthrough curve shape from fluorometers placed along a cross-section. CFD modeling of the tracer test through the associated discretized site geometry showed similar heterogeneity and was consistent with the positioning of on-site fluorometers, thus showing that geometry is a major contributor of the spatial heterogeneity of tracer concentration through time in karstic rivers.

scholarly journals Groundwater circulation and earthquake-related changes in hydrogeological karst environments: a case study of the Sibillini Mountains (central Italy) involving artificial tracers

2020 ◽  
Vol 28 (7) ◽  
pp. 2409-2428 ◽  
Author(s):  
T. Nanni ◽  
P. M. Vivalda ◽  
S. Palpacelli ◽  
M. Marcellini ◽  
A. Tazioli
Keyword(s):  
Central Italy ◽  
Tracer Tests ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Water Circulation ◽  
Test Results ◽  
Flow Rates ◽  
Aquifer System ◽  
Structural Framework ◽  
Groundwater Circulation

Abstract Using artificial tracer tests, this study confirms the presence of a single basal aquifer feeding the springs in the wide and complex hydrogeological boundary of the Sibillini Mountains of central Italy. The tracer was introduced into the sinkhole of the Castelluccio di Norcia plain. The tracer test results, observed at the studied springs, highlight the changes induced by the 2016/2017 earthquake in the water circulation of the aquifer system. In particular, the seismic events increased the hydraulic conductivity of the basal aquifer, with a consequent increase in the springs’ flow rates at the western hydrogeological boundary and a decrease in the flow rates at the eastern Adriatic hydrogeological boundary. This phenomenon is in accordance with the hydro-structural framework of the area. The study also investigated the relation between groundwater circulation and tracer behaviour in the springs during the pre- and post-earthquake periods. The tracer test results led to the formulation of hypotheses about water circulation of the area. The trend of the tracer breakthrough curves demonstrates that the upper portion of the basal aquifer is characterised by fast water circulation similar to that in the epiphreatic area of karst aquifers, while a slow circulation due to fissures with interconnected drains occurs in the deepest portion of the aquifers. The obtained results highlight how tectonics and karst can affect the hydrogeological setting of the Apennine carbonate chain; in particular, the seismicity of central Italy may alter groundwater circulation for a long period of time when great magnitude earthquakes occur.

Bacterial Transport in Fractured Rock – A Field-Scale Tracer Test at the Chalk River Nuclear Laboratories

1988 ◽  
Vol 20 (11-12) ◽  
pp. 81-87 ◽  
Author(s):  
D. R. Champ ◽  
J. Schroeter
Keyword(s):  
Water Movement ◽  
Fractured Rock ◽  
Tracer Tests ◽  
Crystalline Rock ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Water Recovery ◽  
Field Scale ◽  
Particulate Contaminants ◽  
Conservative Tracers

The potential for transport of bacteria by groundwater in fractured crystalline rock was assessed in a series of field-scale tracer tests. The breakthrough curves for injected Escherichla coll and “non-reactive” particle tracers were compared with those for conservative inorganic and radioactive tracers. Rapid transport, relative to the conservative tracers, of both bacteria and non-reactive particles was observed. The first appearance of both was with, or slightly before, the conservative tracers for water movement. Removal of the bacteria and particles by filtration processes occurred and was quantified through the calculation of filter factors. The filtration process in this fracture system is similar to that found in a gravel aquifer. From the results we can conclude that particulate contaminants can be very rapidly transported in fracture systems and that continuing sources of contamination could lead to relatively high local concentrations of particulate contaminants compared with the average at any given distance from the source. It was also concluded that the use of traditional conservative tracers, for water movement, to assess the potential for movement of particulate contaminants could lead to significant underestimates of exposure to particulate contaminants due to consumption of water from water recovery wells located in fractured media.

scholarly journals Characterization of Karst Conduit Network Using Long-Distance Tracer Test in Lijiang, Southwestern China

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 949 ◽  
Author(s):  
Jihong Qi ◽  
Mo Xu ◽  
Xinyu Cen ◽  
Lu Wang ◽  
Qiang Zhang
Keyword(s):  
Groundwater Level ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Southwestern China ◽  
Long Distance ◽  
Tracer Concentration ◽  
Injection Point ◽  
Ancient City ◽  
Karst Conduit ◽  
Conduit Network

The Ancient City in Lijiang of southwestern China was endowed as World Cultural Heritage by UNESCO, and the karst springs located in Black Dragon Pool are its main water source. However, the springs have dried up several times in recent years, which caused serious damages to the landscape as well as the city water supply. Triggered by the dried-up event in Black Dragon Pool, a long-distance artificial tracer test up to 17 km was employed to investigate the karst conduit network distributing in the study area. Based on the tracer concentration breakthrough curves (BTCs), the hydraulic connection from the same injection point (located in a giant depression named the Jiuzi Sea) to the springs on both sides of the topography watershed was proven, and the conduit structure was discussed. According to the characteristics of BTCs and considering the low tracer concentration and tracer recovery, a conceptual structure of leaky reservoir with threshold effect above a certain groundwater level was established to interpret why the springs in Black Dragon Pool dried up several times in history, but those in the Ancient City never did. Furthermore, a method of injecting surface water into the Jiuzi Sea to raise the groundwater level up to the height of Black Dragon Pool was proposed to restore the springs. Our study provides insights into the long-distance artificial tracer test, and opens a new avenue for groundwater resource recovery of this Ancient City.

Research on the Influence of Complex Terrain on Atmospheric Dispersion After Accident

2018 ◽  
Author(s):  
Nan Wu ◽  
Na Xue ◽  
Xinjian Liu
Keyword(s):  
Flow Field ◽  
Complex Terrain ◽  
Atmospheric Dispersion ◽  
Gaussian Model ◽  
Emergency Evacuation ◽  
Cfd Modeling ◽  
Small Scale ◽  
Local Flow ◽  
Cfd Method ◽  
The Impact

Emergency condition should be evaluated during the siting of Nuclear Power Plants (NPP). One of the criteria is the capability of emergency evacuation for the purpose of protecting the NPP staff and public. Exposure dose received by evacuees is a key factor to evaluate the effectiveness of emergency evacuation, which can be characterized by the atmospheric dispersion factors over the evacuation paths. Gaussian plume model is usually applied in the atmospheric dispersion factor calculation for NPPs. However, for some NPP sites with complex terrain like mountain and lake which has significant influence on the local flow field and the nuclides transportation, the calculations based on Gaussian model will not be accurate enough for the evaluation of the evacuation capability. In such cases, Computational Fluid Dynamics (CFD) method with fine calculation grids and rich physical models can be used in the atmospheric dispersion modeling of small-scale region, to get much more accurate results. This paper is devoted to the research on the impact of these complex terrain on atmospheric dispersion with CFD method. The local atmospheric dispersion around a NPP site located on an island is modeled, where there is a mountain on the way of evacuation. For the limitation of the geographic barrier, two evacuation paths, which are located closely with small difference in direction, are planned along different sides of the mountain. Utilizing STAR-CCM+ CFD software, local atmospheric dispersion factors are fine simulated under six worse wind directions. Based on the simulation results, the impact of the mountain on the flow field and of the radiological plume on the evacuation paths is analyzed. Results show that due to the blocking effect of the mountain, those two evacuation paths have little probability to be simultaneously covered by the radiological plume. By the choosing of suitable routes during the evacuation, the radiological risk of public is acceptable and emergency evacuation can be carried out effectively. These results also demonstrate that CFD modeling method is effective in the evaluation of local atmospheric dispersion over complex terrain, which can be applied in the analysis of emergency evacuation of NPP sites with complex terrain.

Interwell Tracer Tests To Optimize Operating Conditions for a Surfactant Field Trial: Design, Evaluation, and Implications

2012 ◽  
Vol 15 (02) ◽  
pp. 229-242 ◽  
Author(s):  
Hao Cheng ◽  
G. Michael Shook ◽  
Malik Taimur ◽  
Varadarajan Dwarakanath ◽  
Bruce R. Smith
Keyword(s):  
Oil Recovery ◽  
Field Trial ◽  
Tracer Tests ◽  
Tracer Test ◽  
Operating Conditions ◽  
Small Scale ◽  
Hydraulic Control ◽  
Sweep Efficiency ◽  
Reservoir Properties ◽  
Swept Volume

Summary Enhanced oil recovery (EOR) by surfactant flooding is the key to unlocking the next billion barrels of oil for Minas, one of the world's largest waterflood fields. An interwell tracer test (ITT-1) was performed before a surfactant field trial (SFT) to ensure well injectivity, demonstrate pattern confinement, quantitatively describe interwell connectivity and sweep efficiency, and provide sufficient data for reservoir evaluation. The tracer test was designed by numerical simulation. The test started in November 2009 and was terminated in February 2010. Analytical interpretation based on moment analysis and numerical reservoir simulations was conducted to evaluate ITT-1 results. Interpretation of the test results indicated various operational and reservoir properties that would have likely led to failure of the surfactant pilot. Hydraulic control of the SFT pattern was not achieved; in fact, less than 20% of one tracer was recovered. Many small-scale heterogeneities were identified that led to a lower-than-expected reservoir volume contacted. Unexpected communication between the target sand and the underlying sands outside the pattern also contributed to low tracer recovery and low swept volume. The tracer test was history matched, and additional features were incorporated in the reservoir model, and a new tracer design (ITT-2) was optimized to correct low sweep efficiency and poor hydraulic control. New information from ITT-2 will be used to further optimize operating conditions for SFTs. Failure to conduct the tracer tests would have likely revealed these unfavorable reservoir and operational conditions during the SFT. Had oil recovery been poor (because of low swept volume), it would have erroneously been attributed to a poor SFT rather than to the true causes. ITT-1 is considered successful because it allowed us to redesign injection/hydraulic control during the relatively inexpensive tracer test and thus evaluate the surfactant trial without bias.

Validation of CALPUFF Applicability within Urban Area

2013 ◽  
Vol 726-731 ◽  
pp. 1813-1816
Author(s):  
Long Xiang Dong ◽  
Hong Chao Zuo ◽  
Wen Cheng Dong
Keyword(s):  
Urban Area ◽  
Single Point ◽  
Urban Canopy ◽  
Tracer Experiment ◽  
Gansu Province ◽  
Canopy Layer ◽  
Tracer Concentration ◽  
Tracer Dispersion ◽  
Simulation Error ◽  
Atmospheric Tracer

An atmospheric tracer dispersion study known as Urban Meteorological and Tracer Experiment was carried out in Yuzhong County, Gansu province in northwest of China, during October of 2011. By using the observational data, the applicability of CALPUFF model based on Gaussian formula was verified within urban area. The results show that (i) CALPUFF model can reasonably reflect the actual observations on the whole, and the high value centers of tracer concentration was changed with wind direction over the urban canopy layer. (ii) The simulated plume central axis has a bias of 10-15° with observations, and the simulation error is very much big at the single point, especially at the ground.

scholarly journals Grassland Management Regimens Reduce Small-Scale Heterogeneity and Species Diversity of β-Proteobacterial Ammonia Oxidizer Populations

2002 ◽  
Vol 68 (1) ◽  
pp. 20-30 ◽  
Author(s):  
Gordon Webster ◽  
T. Martin Embley ◽  
James I. Prosser
Keyword(s):  
Spatial Heterogeneity ◽  
16S Rdna ◽  
Soil Management ◽  
Soil Characteristics ◽  
Ammonia Oxidizer ◽  
Ammonium Concentration ◽  
Small Scale ◽  
Rrna Gene ◽  
Research Station ◽  
The Impact

ABSTRACT The impact of soil management practices on ammonia oxidizer diversity and spatial heterogeneity was determined in improved (addition of N fertilizer), unimproved (no additions), and semi-improved (intermediate management) grassland pastures at the Sourhope Research Station in Scotland. Ammonia oxidizer diversity within each grassland soil was assessed by PCR amplification of microbial community DNA with both ammonia oxidizer-specific, 16S rRNA gene (rDNA) and functional, amoA, gene primers. PCR products were analysed by denaturing gradient gel electrophoresis, phylogenetic analysis of partial 16S rDNA and amoA sequences, and hybridization with ammonia oxidizer-specific oligonucleotide probes. Ammonia oxidizer populations in unimproved soils were more diverse than those in improved soils and were dominated by organisms representing Nitrosospira clusters 1 and 3 and Nitrosomonas cluster 7 (closely related phylogenetically to Nitrosomonas europaea). Improved soils were only dominated by Nitrosospira cluster 3 and Nitrosomonas cluster 7. These differences were also reflected in functional gene (amoA) diversity, with amoA gene sequences of both Nitrosomonas and Nitrosospira species detected. Replicate 0.5-g samples of unimproved soil demonstrated significant spatial heterogeneity in 16S rDNA-defined ammonia oxidizer clusters, which was reflected in heterogeneity in ammonium concentration and pH. Heterogeneity in soil characteristics and ammonia oxidizer diversity were lower in improved soils. The results therefore demonstrate significant effects of soil management on diversity and heterogeneity of ammonia oxidizer populations that are related to similar changes in relevant soil characteristics.

Can Values of Honesty, Hard Work, Loyalty and Discipline Predict Entrepreneurial Orientation of Muslim Owner Managers?

2015 ◽  
Vol 3 (1) ◽  
pp. 31 ◽  
Author(s):  
Rohani Mohd ◽  
Badrul Hisham Kamaruddin ◽  
Khulida Kirana Yahya ◽  
Elias Sanidas
Keyword(s):  
Entrepreneurial Orientation ◽  
Two Dimensions ◽  
Hard Work ◽  
Small Scale ◽  
Sampling Frame ◽  
Policy Makers ◽  
Learning Institutions ◽  
Innovative Orientation ◽  
The Impact ◽  
True Values

The purpose of the present study is twofold: first, to investigate the true values of Muslim owner managers; second, to examine the impact of these values on entrepreneurial orientations of Muslim small-scale entrepreneurs. 850 Muslim owner managers were selected randomly using the sampling frame provided by MajlisAmanah Rakyat Malaysia (MARA). 162 completed questionnaires were collected and analyzed. For this paper only two dimensions of entrepreneurial orientations were analyzed: proactive orientation and innovative orientation. Interestingly, the findings revealed that Muslim businessmen/women are honest, loyal, disciplined and hard working. Loyalty and honesty are positively related to proactive orientation, while discipline and hard-work are positively related to innovative orientation. The findings provide implications for existing relevant theories, policy makers, practitioners and learning institutions. 

Mixing and Detention Time Distribution in Activated Sludge Tanks

1985 ◽  
Vol 17 (2-3) ◽  
pp. 197-208 ◽  
Author(s):  
H. Bode ◽  
C. F. Seyfried
Keyword(s):  
Activated Sludge ◽  
Time Distribution ◽  
Strong Influence ◽  
Tracer Tests ◽  
Tracer Test ◽  
Evaluation Procedure ◽  
Response Curves ◽  
Detention Time ◽  
Test Study ◽  
Mixing Characteristics

The interrelationship between mixing characteristics and tracer response curves in activated sludge tanks is explained. In some cases the return sludge cycle has a strong influence on the tracer response curves. Results from tracer tests in the field are hard to interpret because the tracer in the return sludge interferes with the initial tracer. Therefore a special evaluation procedure has to be applied. The paper closes with results from a field tracer test study.

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