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Title: Analysis of tracer migration in a diverging radial flow field

Abstract

No abstract prepared.

Authors:
Publication Date:
Research Org.:
Savannah River Ecology Laboratory (SREL), Aiken, SC
Sponsoring Org.:
USDOE
OSTI Identifier:
903057
Report Number(s):
SREL-3022
TRN: US200719%%164
DOE Contract Number:
DE-FC09-07SR22506
Resource Type:
Conference
Resource Relation:
Journal Name: Proceedings of the 2007 Georgia Water Resources Conference; Journal Volume: 7.4.2; Conference: Georgia Water Resources Conference, Athens, Georgia, The University of Georgia
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; WATER RESOURCES; RESOURCE ASSESSMENT; TRACER TECHNIQUES; ENVIRONMENTAL TRANSPORT

Citation Formats

Seaman, J.C., F. Majs, J. Singer, S. Aburime, S.O. Dennis, M. Wilson and P.M. Bertsch. Analysis of tracer migration in a diverging radial flow field. United States: N. p., 2007. Web.
Seaman, J.C., F. Majs, J. Singer, S. Aburime, S.O. Dennis, M. Wilson and P.M. Bertsch. Analysis of tracer migration in a diverging radial flow field. United States.
Seaman, J.C., F. Majs, J. Singer, S. Aburime, S.O. Dennis, M. Wilson and P.M. Bertsch. Mon . "Analysis of tracer migration in a diverging radial flow field". United States. doi:.
@article{osti_903057,
title = {Analysis of tracer migration in a diverging radial flow field},
author = {Seaman, J.C., F. Majs, J. Singer, S. Aburime, S.O. Dennis, M. Wilson and P.M. Bertsch},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Proceedings of the 2007 Georgia Water Resources Conference},
number = ,
volume = 7.4.2,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • No abstract prepared.
  • Hydrodynamic dispersion, the combined effects of chemical diffusion and differences in solute path length and flow velocity, is an important factor controlling contaminant migration in the subsurface environment. However, few comprehensive three-dimensional datasets exist for critically evaluating the impact of travel distance and site heterogeneity on solute dispersion, and the conservative nature of several commonly used groundwater tracers is still in question. Therefore, we conducted a series of field-scale experiments using tritiated water ({sup 3}H{sup 1}HO), bromide (Br{sup -}), and two fluorobenzoates (2,4 Di-FBA, 2,6 Di-FBA) as tracers in the water-table aquifer on the USDOE's Savannah River Site (SRS), locatedmore » on the upper Atlantic Coastal Plain. For each experiment, tracer-free groundwater was injected for approximately 24 h (56.7 L min{sup -1}) to establish a steady-state forced radial gradient before the introduction of a tracer pulse. After the tracer pulse, which lasted from 256 to 560 min, the forced gradient was maintained throughout the experiment using nonlabeled groundwater. Tracer migration was monitored using six multilevel monitoring wells, radially spaced at approximate distances of 2.0, 3.0, and 4.5 m from the central injection well. Each sampling well was further divided into three discrete sampling depths that were pumped continuously ({approx}0.1 L min{sup -1}) throughout the course of the experiments. Longitudinal dispersivity ({alpha}{sub L}) and travel times for {sup 3}H{sup 1}HO breakthrough were estimated by fitting the field data to analytical approximations of the advection-dispersion equation (ADE) for uniform and radial flow conditions. Dispersivity varied greatly between wells located at similar transport distances and even between zones within a given well, which we attributed to variability in the hydraulic conductivity at the study site. The radial flow equation generally described tritium breakthrough better than the uniform flow solution, as indicated by the coefficient of determination, r{sup 2}, yielding lower {alpha}{sub L} while accounting for breakthrough tailing inherent to radial flow conditions. Complex multiple-peak breakthrough patterns were observed within certain sampling zones, indicative of multiple major flow paths and the superposition of resulting breakthrough curves. A strong correlation was found between {alpha}L and arrival times observed from one experiment to the next, indicative of the general reproducibility of the tracer results. Temporal moment analysis was used to evaluate tracer migration rate as an indicator of variations in hydraulic conductivity and flow velocity, as well as mass recovery and retardation for the ionic solutes compared with tritiated water. Retardation factors for Br{sup -} ranged from 0.99 to 1.67 with no clear trend with respect to transport distance; however, Br{sup -} mass recovery decreased with distance, suggesting that the retardation values are biased in terms of early arrival because of limited detection and an insufficient monitoring duration. Anion retardation was attributed to sorption by iron oxides. Similar results were observed for the FBA tracers. The assumption of conservative behavior for the anionic tracers would generally result in higher {alpha}L values and lower estimated flow velocities.« less
  • This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile region where longitudinal dispersion and convection take place and a stagnant region where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared to those previously presented in literature by Moench and Ogata, Tang et al., Chen et al., and Hsieh et al. The solution is numerically inverted bymore » means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., for short times) was carried out. The influence of various dimensionless parameters that enter into the solution was investigated. A discussion of results obtained through the Crump and Stehfest algorithm is presented, concluding that the Crump method provides more reliable tracer concentrations.« less
  • This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs, with cubic blocks matrix-fracture geometry. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile where dispersion and convection take place and a stagnant where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared under proper simplified conditions to those previously presented in the literature. The coupled matrix to fracture solution in the Laplace space is numerically invertedmore » by means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., naturally fractured nearly homogeneous) was carried out. The influence of the three of the main dimensionless parameters that enter into the solution was carefully investigated. A comparison of results for three different naturally fractured systems, vertical fractures (linear flow), horizontal fractures (radial flow) and the cubic geometry model of this study, is presented.« less
  • The Wye Institute of the University of Maryland is studying the migration of fertilizer into the Chesapeake Bay from the surrounding farm land. Several different methods of investigation have been looked into including neutron activation analysis. We have attempted to find some natural trace elements in the fertilizer to study the migration. Well and surface water samples were collected at various locations around tilled and until led fields. These samples were activated in the Maryland University Training Reactor at several different power levels and irradiation times and analyzed in a calibrated GeLi detector. The resulting spectra were normalized and plottedmore » on transparencies which provided an easy method for spotting migration of trace elements. Several possible tracers were identified for use in a more detailed study at a later date. (author)« less