John C. Fountain

The use of surfactants for in situ extraction of organic pollutants from a contaminated aquifer

Many common organic pollutants are characterized by low solubilities and high interfacial tensions; these characteristics combine to render pump-and-treat processes ineffective. Surfactants can dramatically increase the solubility of organic compounds in groundwater and lower their interfacial tensions; both effects theoretically can greatly increase the extraction efficiency of pump-and-treat systems. Lowering of interfacial tensions can result in movement of dense contaminants downward in an aquifer, potentially contaminating underlying layers. Increasing a pollutants solubility increases the fraction of pollutant present as dissolved phase, increasing the efficiency of extraction using a modified pump-and-treat technique. Thus we propose that a surfactant solution intended for extraction of dense organic liquids should be optimized for solubilization, with a minimal reduction of interfacial tensions. The results of porous media experiments comparing the extraction efficiency of over 100 surfactants indicate that solubilization ability is the most important factor; although both the extent of reduction of interfacial tension and the tendency to form spontaneous emulsions must also be considered. Using a suitable surfactant mixture, a pool of tetrachloroethylene can be extracted from a lab-scale saturated porous media model in 7 to 14 pore volumes, depending upon the geometry of the contamination. Mass balance calculations indicate complete removal of the contaminant and analysis of sand samples at the conclusion of the experiment indicates less than 1 milligram of contaminant remains. In contrast, concentrations of the effluent average only 6 ppm when distilled water is used for flushing, producing no measurable reduction in the volume of the pool in 14 pore volumes. These experiments suggest that utilizing surfactants to increase the solubility of dense organic pollutants can be an effective and relatively inexpensive way of in situ remediation of contaminated aquifers.

Permeability reductions induced by sorption of surfactant

Surfactant enhanced aquifer remediation (SEAR) is an attractive alternative to traditional pump and treat methods for remediating aquifers contaminated with nonaqueous phase liquids. However, initial studies indicate that the application of surfactant can reduce aquifer permeability by more than an order of magnitude, limiting the efficiency of SEAR. A series of column experiments using mixtures of medium sand and montmorillonite clay demonstrate that existing permeability reduction models for biofouling and deep-bed filtration poorly predict surfactant induced permeability reductions. An alternative permeability reduction model is proposed which is based on the assumption that the sorbed surfactant effectively increases the volume fraction of the clay. The model is shown to reasonably predict observed permeability reductions, particularly for clay fractions less than 20%. A numerical simulation of surfactant transport that incorporates the effective clay fraction model demonstrates that induced permeability reductions significantly influence the transport of surfactant through an aquifer.

Melt segregation in anatectic granites: a thermo-mechanical model

Abstract The generation and initial migration of magma produced by crustal anatexis involves partial melting and at least partial separation of melt from residual solid. The generation of anatectic granitic magma is thus governed by the flow of heat, melt and residual solid. A model which couples two-phase flow in porous media and heat flow was developed to simulate the evolution of anatectic melt around a mantle-derived mafic heat source. Results of our modelling suggest that emplacement of a mafic intrusion in the lower crust may result in partial melting of the crustal rocks and, if sufficient porosity is produced by melting, in migration and segregation of the anatectic melt. Segregation of the melt and its residuum was significant in models in which at least 25% melting of the host rock occurred. As an example, our calculations indicated that a 5-km-thick mafic intrusion emplaced in country rocks with an initial temperature of 800°C will create a zone of partial melting 5 km thick above and below the intrusion. In this case migration and segregation of the melt will produce a layer of magma approximately 1 km thick above the intrusion, and an even larger volume of melt below the intrusion. The anatectic magma moves upward by disaggregating the partially melted country rocks which form the roof of the evolving magma chamber. Upward migration by this process is limited to the portion of the crust which is partially melted by heat from the intrusion. The process of melt migration will modify the melt composition by both zone-refining and fractional crystallization in the initial stages of melt accumulation.

Geochemistry and petrogenesis of the Laramie anorthosite complex, Wyoming

Abstract A geochemical investigation of the Laramie anorthosite complex determined that monsonite associated with the complex are characterized by positive Eu anomalies and display a regular variation in composition with distance from the monzonite/county rock contact. Anorthositic rocks have major and trace element abundance typical of similar complexes. The internal variations in the monzonite were produced by in situ fractionation and contamination. The data indicate that anorthosite and monzonite cannot be comagmatic. It is proposed that the anorthosite and monzonite of the complex evolved from two distinct magmas, and that two stages of anatectic melting contributed to the evolution of the monzonite. An initial stage of partial melting was induced by intrusion of a gabbroic anorthosite magma into the lower crust; a second partial melting event occurred after emplacement where heat from the intrusions melted country rocks resulting in extensive contamination ofthe monzonite.

The Effectiveness of Surfactants for Remediation of Organic Pollutants in the Unsaturated Zone

In laboratory experiments performed to evaluate the efficiency of surfactant flushing for remediation of non-aqueous phase liquid (NAPL) in the unsaturated zone, less than 0.001% of the original mass of tetra-chloroethylene (PCE) remained in the column after 15 pore volumes of a 1% sorbitan monooleate solution or after 7 pore volumes of a 1% Ethomid O/17 solution were passed through the columns. Mass removed as dissolved phase in the effluent accounted for more than 90% of PCE removed; the remainder was lost by volatilization. To determine the influence of parameters that may affect the remediation process, column tests were repeated with different values of parameters, including grain size, application rate, surfactant type, surfactant concentration, and solution viscosity. The results from the column experiments were simulated with the two-dimensional finite element computer code for multiphase flow and transport, MOTRANS. Results of the simulation were similar to those from the experiments. Both experi...

Geochemistry of Brokeoff volcano, California

Brokeoff volcano, a High Cascade stratovolcano located in Lassen Volcanic National Park, California, is composed primarily of andesite, with subordinate amounts of basalt, basaltic andesite, dacite, rhyodacite, and rhyolite. A geochemical study was undertaken to investigate the genetic relationship between members of the basalt-andesite-dacite-rhyolite magma series. Both major-element and trace-element abundances vary regularly with the silica content of the lavas. Relatively small increases in K, Rb, and Ba abundances preclude derivation of most of the rhyodacites by fractional crystallization. A model is proposed for the generation of andesite by partial melting of a garnet peridotite and generation of rhyodacite by partial melting of a similar source at greater depths, followed by hornblende fractionation. A small volume of dacites and rhyodacites have distinctly higher incompatible element abundances and were probably produced by fractional crystallization of the andesite. Andesites and dacites produced by flank eruptions are characterized by complex phenocryst assemblages and were most likely formed by mixing of andesite and rhyodacite magma. It is concluded that members of the basalt-andesite-dacite-rhyolite magma series are not related by a single process, but probably by several processes, even at a single volcanic center.

Calcium diffusion: A new dating method for archeological materials

Investigation of calcium migration across clay-cement interfaces in building bricks and other similar artifacts ranging in age from about 68 to 3,800 yr shows that calcium diffusion coefficients in the samples9 clay layers are equivalent in all of the artifacts studied to date. Consequently, the age of the samples may be estimated from the distance that calcium migrated from the cement into the clay. To investigate the stability of clay barriers proposed for nuclear-waste containment systems, the rate of calcium diffusion from calcium-based materials (e.g., cement, plaster, and mortar) into adjacent clay-based materials (e.g., riverbed clay, mud brick, and fired clay brick) was determined from electron-microprobe analyses of Ca distribution in samples of known age. In seven samples with well-preserved clay-cement interfaces, an apparent Ca diffusion coefficient on the order of 10 −20 m 2 /s was calculated from Ca distribution in the clay layer. The resulting calcium-concentration front migrates about 9 µm in 100 yr, and can be located to ±2 µm, corresponding to about ±25 yr error. Thus, although only preliminary, these results indicate that Ca diffusion may provide the basis for a rapid and relatively inexpensive method of dating building bricks and other similar materials that have hitherto defied conventional dating techniques.

INNOVATIVE METHODOLOGY FOR DETECTION OF FRACTURE-CONTROLLED SWEET SPOTS IN THE NORTHERN APPALACHIAN BASIN

The primary goal was to enter Phase 2 by analyzing geophysical logs and sidewall cores from a verification well drilled into the Trenton/Black River section along lineaments. However, the well has not yet been drilled; Phase 2 has therefore not been accomplished. Secondary goals, not dependent upon well drilling, were completed. In the structure task, the objectives for this reporting period were to: (1) add additional sites along the west side of Cayuga Lake where we had critical gaps in our data set, and (2) complete analyses of structure data along the west side of Cayuga Lake. We have completed data input and analyses for this goal, and discuss the results. The additional data from the 2003 field season (and additional revised data from the previous season) demonstrate that zones of closely-spaced NNW- and N-striking fractures (FIDs) occur west of Cayuga Lake. EarthSat (1997) did not recognize NNW- or N-striking Landsat lineaments in this area. Packets of E-and ENE-striking EarthSat (1997) lineaments coincide with FIDs observed in outcrop, but the bedrock FIDs are significantly more numerous than the lineaments. West of Cayuga Lake, NE-striking EarthSat (1997) were not confirmed by FIDs. It appears that Landsat lineaments (EarthSat, 1997) indicate parts of the structural fabric, but the ground-truthing reveals added significant complexity. The E-striking lineaments and FIDs are related to Alleghanian folds and faults (e.g., Firtree Anticline), and the ENE-striking lineaments and FIDs are probably related to reactivated Trenton/Black River faults. ASTER images, with an order of magnitude higher resolution than Landsat, are presently being analyzed for lineaments. The lineament patterns are more complex than the Landsat lineaments, and include a number of trends not observed in the Landsat data (EarthSat, 1997). These trends include NS, NNW and NNE. These data continue to demonstrate that integration of aeromagnetic and remote sensing lineaments, surface structure, soil gas and seismic allows us to extrapolate Trenton-Black River trends away from confirmatory seismic lines.