Richard E. Jackson

Partitioning Tracer Test for Detection, Estimation, and Remediation Performance Assessment of Subsurface Nonaqueous Phase Liquids

In this paper we present a partitioning interwell tracer test (PITT) technique for the detection, estimation, and remediation performance assessment of the subsurface contaminated by nonaqueous phase liquids (NAPLs). We demonstrate the effectiveness of this technique by examples of experimental and simulation results. The experimental results are from partitioning tracer experiments in columns packed with Ottawa sand. Both the method of moments and inverse modeling techniques for estimating NAPL saturation in the sand packs are demonstrated. In the simulation examples we use UTCHEM, a comprehensive three-dimensional, chemical flood compositional simulator developed at the University of Texas, to simulate a hypothetical two-dimensional aquifer with properties similar to the Borden site contaminated by tetrachloroethylene (PCE), and we show how partitioning interwell tracer tests can be used to estimate the amount of PCE contaminant before remedial action and as the remediation process proceeds. Tracer tests results from different stages of remediation are compared to determine the quantity of PCE removed and the amount remaining. Both the experimental (small-scale) and simulation (large-scale) results demonstrate that PITT can be used as an innovative and effective technique to detect and estimate the amount of residual NAPL and for remediation performance assessment in subsurface formations.

Partitioning of strontium-90 among aqueous and mineral species in a contaminated aquifer.

The geochemical partitioning of a toxic metal contaminant, /sup 90/Sr, during its migration through a shallow sand aquifer is discussed. Adsorption of /sup 90/Sr from the contaminated groundwaters (pH approx. 6, I approx.0.001) causes it to have a migration velocity of only 3% of that of transporting ground water. Five microscopically identified adsorbents were isolated in the aquifer sediments and showed the following affinity sequence for /sup 90/Sr: vermiculite > feldspar > biotite > muscovite > quartz. While 4a80% of the adsorbed /sup 90/Sr is exchangeable with 0.1 M SrCl/sub 2/, the residual adsorbed /sup 90/Sr is strongly correlated with extractable Fe, Al, and Mn, suggesting specific adsorption by these metal oxides. An equilibrium adsorption model was used to determine the partitioning of /sup 90/Sr between adsorbents and between solid and solution phases. Over 90% of all /sup 90/SR in the aquifer is adsorbed. Approximately 90% of all adsorbed /sup 90/SR is equally divided between vermiculite and feldspar minerals.

Surfactant Based Enhanced Oil Recovery and Foam Mobility Control

Surfactant flooding has the potential to significantly increase recovery over that of conventional waterflooding. The availability of a large number of surfactant structures makes it possible to conduct a systematic study of the relation between surfactant structure and its efficacy for oil recovery. Also, the addition of an alkali such as sodium carbonate makes possible in situ generation of surfactant and significant reduction of surfactant adsorption. In addition to reduction of interfacial tension to ultra-low values, surfactants and alkali can be designed to alter wettability to enhance oil recovery. An alkaline surfactant process is designed to enhance spontaneous imbibition in fractured, oil-wet, carbonate formations. It is able to recover oil from dolomite core samples from which there was no oil recovery when placed in formation brine.

Control of downward migration of dense nonaqueous phase liquid during surfactant flooding by design simulations

[1] Sand tank experiments have been used to study a surfactant-enhanced aquifer remediation (SEAR) process during which downward migration of dense nonaqueous phase liquid (DNAPL) has been observed in some of these experiments. Through numerical simulation of one particular sand tank experiment conducted at Sandia National Laboratories we show in this paper that this downward migration of DNAPL can be anticipated and controlled even in a very difficult geosystem environment. The results indicate that design simulations play a significant role in the design of either laboratory column experiments or field SEAR application and that surfactant flooding can be accomplished without loss of hydraulic control of DNAPL under typical alluvial aquifer/aquitard conditions and with only minor vertical mobilization within the aquifer (i. e., < 1% of the DNAPL present). The design simulations are considered as a sensitivity analysis exercise in which the heterogeneity in the permeability field and DNAPL saturation and other critical variables are varied to produce a robust design. The simulation results indicate that the significant downward mobilization of DNAPL as observed in the Sandia sand tank experiment is a result of the use of high-permeability materials, weak viscous (horizontal) forces, and low surfactant solubilization potential. The downward mobilization of DNAPL is a design issue to be evaluated and controlled rather than an inevitable consequence of the use of surfactants to remove DNAPL.

Bioavailability and Kidney Responses to Diclofenac in the Fathead Minnow (Pimephales promelas)

Diclofenac is one of the most widely prescribed nonsteroidal anti-inflammatory drugs worldwide. It is frequently detected in surface waters; however, whether this pharmaceutical poses a risk to aquatic organisms is debated. Here we quantified the uptake of diclofenac by the fathead minnow (Pimephales promelas) following aqueous exposure (0.2-25.0 μg L-1) for 21 days, and evaluated the tissue and biomolecular responses in the kidney. Diclofenac accumulated in a concentration- and time-dependent manner in the plasma of exposed fish. The highest plasma concentration observed (for fish exposed to 25 μg L-1 diclofenac) was within the therapeutic range for humans. There was a strong positive correlation between exposure concentration and the number of developing nephrons observed in the posterior kidney. Diclofenac was not found to modulate the expression of genes in the kidney associated with its primary mode of action in mammals (prostaglandin-endoperoxide synthases) but modulated genes associated with kidney repair and regeneration. There were no significant adverse effects following 21 days exposure to concentrations typical of surface waters. The combination of diclofenacs uptake potential, effects on kidney nephrons and relatively small safety margin for some surface waters may warrant a longer term chronic health effects analysis for diclofenac in fish.

Ancient Floods, Modern Hazards: Principles and Applications of Paleoflood Hydrology : (Edited by P. K. House, R. H. Webb, V. R. Baker, and D. R. Levish)

Paleoflood hydrology, as it developed in the 1970s, identified slackwater flood deposits (SWD) as the primary indicator of a historically high stage of a river, i.e., a “paleostage indicator.” Such SWDs are believed to have formed in eddies at the mouths of tributaries of rivers that caused sedimentation of sands and silts in topographically elevated locales relative to the present position of such rivers. If undisturbed by even larger floods, there is a reasonable likelihood that pedogenic processes will create a soil horizon within the SWD that can be age-dated using 14C. Thus an approximate age of the paleoflood can be estimated as well as the paleostage, i.e., the maximum flood stage. Using one-dimensional hydraulic models of bedrock channels and estimates of bed roughness described by Mannings coefficient, the paleoflood hydrologist employs the same tools as used by engineering hydrologists to estimate peak flood discharges, e.g., the step-backwater method. Consequently, geomorphologists and paleoflood hydrologists have been able to contribute their insight to flood-frequency analysis, previously the sole domain of engineering hydrologists. Some years have past since Environmental & Engineering Geoscience published a research paper on low-probability floods and their estimation (Malamud et al., 1996). Paleoflood hydrology is, however, a vibrant area of scientific research that has particular significance to dam safety and floodplain protection of critical structures, such as nuclear reactors, and to engineering geology and fluvial geomorphology in general. This monograph, by the principal actors in paleoflood hydrology, is rich in detail, definitive in scope, and of moderate cost (

Stereographic Projection Techniques for Geologists and Civil Engineers, Second Edition (Richard J. Lisle and Peter R. Leyshon)

75 hardback). Ancient …

SURFACTANT BASED ENHANCED OIL RECOVERY AND FOAM MOBILITY CONTROL

It is likely that many readers of this journal learned to use stereographic projection in the geometric description of rocks, their structural elements, and their discontinuities from Hoek and Brays Rock Slope Engineering (1981) or from a textbook on structural geology. More recent texts on rock mechanics (e.g., Goodmans Introduction to Rock Mechanics, 1989; or Brady and Browns Rock Mechanics for Underground Mining, 1993; or Wyllies Foundations on Rock , 1999) contain detailed reviews of this aspect of structural geology in the early pages of their textbooks. Therefore, we can conclude that the use of stereonets is of importance in geological engineering practice and, by inference, to the education and training of engineering geologists, as well as those hydrogeologists whose work involves the analysis of fractures in rocks. Lisle and …

In-Situ Characterization of Dense Non-Aqueous Phase Liquids Using Partitioning Tracers

Surfactant flooding has the potential to significantly increase recovery over that of conventional waterflooding. The availability of a large number of surfactants makes it possible to conduct a systematic study of the relation between surfactant structure and its efficacy for oil recovery. Also, the addition of an alkali such as sodium carbonate makes possible in situ generation of surfactant and significant reduction of surfactant adsorption. In addition to reduction of interfacial tension to ultra-low values, surfactants and alkali can be designed to alter wettability to enhance oil recovery. An alkaline surfactant process is designed to enhance spontaneous imbibition in fractured, oil-wet, carbonate formations. It is able to recover oil from dolomite core samples from which there was no oil recovery when placed in formation brine. Mobility control is essential for surfactant EOR. Foam is evaluted to improve the sweep efficiency of surfactant injected into fractured reservoirs. UTCHEM is a reservoir simulator specially designed for surfactant EOR. A dual-porosity version is demonstrated as a potential scale-up tool for fractured reservoirs.

Occurrence and fate of organic solvent residues in anoxic groundwater at the Gloucester landfill, Canada

Majors advances have been made during the past three years in our research on interwell partitioning tracers tests (PITTs). These advances include (1) progress on the inverse problem of how to estimate the three-dimensional distribution of NAPL in aquifers from the tracer data, (2) the first ever partitioning tracer experiments in dual porosity media, (3) the first modeling of partitioning tracers in dual porosity media (4) experiments with complex NAPLs such as coal tar, (5) the development of an accurate and simple method to predict partition coefficients using the equivalent alkane carbon number approach, (6) partitioning tracer experiments in large model aquifers with permeability layers, (7) the first ever analysis of partitioning tracer data to estimate the change in composition of a NAPL before and after remediation (8) the first ever analysis of partitioning tracer data after a field demonstration of surfactant foam to remediate NAPL and (9) experiments at elevated temperatures .