Physicochemical Approaches for the Remediation of Manufactured Gas Plant Tar in Porous Media

Tars produced as a by-product of coal and oil gasification at former manufactured gas plants (FMGPs) during the 19th and early 20th centuries were often released into the environment through poor disposal practices or leaks in holding tanks and piping. These tars are persistent contaminants, leaching polycyclic aromatic hydrocarbons (PAHs) into groundwater and posing a significant risk to human and ecological health. FMGP tars also have several properties that make them notoriously difficult to remediate. They are dense non-aqueous phase liquids (DNAPLs), so they can migrate to depths which make removal by excavation difficult or impossible, and their relatively high viscosities and ability to alter the wetting characteristics of porous media result in inefficient removal by traditional pump-and-treat methods. This work investigates the relationship between tar composition and properties, and explores several remediation approaches. The interfacial tension (IFT) of a set of FMGP tars was measured as a function of pH and correlated with compositional features. It was observed that IFT is a strongly decreasing function of pH, suggesting the potential use of high pH (alkaline) solutions to mobilize FMGP tar in porous media systems. Laboratory column experiments were conducted to investigate the use of alkaline solutions, alone and in combination with natural polymers (xanthan gum) and surfactants, to remediate tar-contaminated porous media. The results of these experiments indicated that alkaline-surfactant-polymer (ASP) solutions could efficiently remove 95% of residual tar. Surfactant-polymer (SP) solutions removed an even greater fraction of residual tar, over 99%, but required a larger flushing volume to do so. These experiments also illustrated that both ASP and SP flushing significantly reduced dissolved-phase PAH concentrations, which are often the primary concern at contaminated FMGP sites.Doctor of Philosoph

Mobilization of Manufactured Gas Plant Tar with Alkaline Flushing Solutions

This experimental study investigates the use of alkaline and alkaline-polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar-aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01–1 wt.%) were found to significantly reduce tar-aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar-wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81–93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods

Efficient Transduction of Vascular Endothelial Cells with Recombinant Adeno-Associated Virus Serotype 1 and 5 Vectors

Recombinant adeno-associated virus (rAAV) has become an attractive tool for gene therapy because of its ability to transduce both dividing and nondividing cells, elicit a limited immune response, and the capacity for imparting long-term transgene expression. Previous studies have utilized rAAV serotype 2 predominantly and found that transduction of vascular cells is relatively inefficient. The purpose of the present study was to evaluate the transduction efficiency of rAAV serotypes 1 through 5 in human and rat aortic endothelial cells (HAEC and RAEC). rAAV vectors with AAV2 inverted terminal repeats containing the human α1-antitrypsin (hAAT) gene were transcapsidated using helper plasmids to provide viral capsids for the AAV1 through 5 serotypes. True type rAAV2 and 5 vectors encoding β-galactosidase or green fluorescence protein were also studied. Infection with rAAV1 resulted in the most efficient transduction in both HAEC and RAEC compared to other serotypes (p < 0.001) at 7 days posttransduction. Interestingly, expression was increased in cells transduced with rAAV5 to levels surpassing rAAV1 by day 14 and 21. Transduction with rAAV1 was completely inhibited by removal of sialic acid with sialidase, while heparin had no effect. These studies are the first demonstration that sialic acid residues are required for rAAV1 transduction in endothelial cells. Transduction of rat aortic segments ex vivo and in vivo demonstrated significant transgene expression in endothelial and smooth muscle cells with rAAV1 and 5 serotype vectors, in comparison to rAAV2. These results suggest the unique potential of rAAV1 and rAAV5-based vectors for vascular-targeted gene-based therapeutic strategies

Compositional and pH Effects on the Interfacial Tension Between Complex Tar Mixtures and Aqueous Solutions

Tars at former manufactured gas plants (FMGPs) are a major environmental concern and present a number of challenges to remediators. This experimental study investigates the relationship between composition and tar–water interfacial tension (IFT), a property of primary importance in determining the transport of tar in porous media. Nine field-collected FMGP tars and a commercially available coal tar were characterized by means of fractionation, gas chromatography, Fourier transform infrared (FTIR) spectrometry, and vapor pressure osmometry. The tar-aqueous IFT of the tars, as well as resins and asphaltenes extracted therefrom, were measured over a range of pH. The IFTs were found to be strongly dependent on pH, with the lowest values obtained at high pH. The reduction of IFT at high pH was found to correlate well with the <i>I</i>_CO values from the FTIR analysis, which provide an indication of the relative amount of carbonyl groups present. Reductions of IFT at low pH were also observed and found to correlate well with the extractable base concentration. The aromaticity and asphaltene average molar mass are also correlated with IFT reductions at both low and high pH, suggestive of compositional patterns related to the tar source material

Did increasing seasonality and fire frequency cause the c4 grassland transition in South America (SA)? Investigations from two paleosol sites in NW Argentina using δ13c isotopes, molecular biomarkers, phytoliths, and X-ray fluorescence (XRF)

Recent advances in molecular biomarkers along with traditional bulk δ13C isotopic analysis, phytolith assemblages, and XRF analysis allow for the detailed reconstruction of continental paleoecological and paleoclimatic conditions. We use these methods to reconstruct conditions during the expansion of C4 grasses, considered one of the most important biological events during the Cenozoic. We hypothesize that in SA, the spread of C4 grasses was driven by the intensification of the SA Summer Monsoon and that this increase in C4 vegetation caused an intensification of fire regimes, due to both seasonality fire and fireC4 expansion feedbacks, that has long been suspected but poorly documented and never studied in this context in SA. This study presents resultsfrom welldated paleosols from two sites in N.W. Argentina: La Viña (LV) and Palo Pintado (PP) in the Salta Province. The LV site includes the Jesus Maria Formations, Guanaco and Piquete (~15 4Ma), while the PP site includes the Palo Pintado Formation (~7.5 6 Ma). Previous studies have interpreted these sites as foreland basin sediments deposited in a meandering stream tolacustrine environment. Shifts in the δ13C obtained from bulk organic matter and phytolith assemblages in these paleosols are used to identify vegetation transitions from C3dominatedgrasslands and forests, to C4dominated grasslands. Leaf wax biomarkers include higher order nalkanes (C20 to C36), and are used to independently determine vegetation composition and changes to aridity and seasonality. XRF analysis is carried out to determine the chemical index of alteration in paleosols, which is a comparable proxy for precipitation seasonality. Polycyclic aromatic hydrocarbons (PAH) are used to determine fire regimes, in order to verify whether C4 expansion promoted fires. δ13C analysis of LV reveals a steady change from a C3dominatedecosystem at 15 Ma to a C3C4 intermediary ecosystem by 7.5 Ma. The PP site does not show any directional change in vegetation type during the investigated period between 7.2 Ma to 6 Ma, though δ13C values indicate a mixed C3C4 ecosystem throughout this period. However, results from the PP site show that increasing C4 cover, determined from bulk organic matter δ13C, is positively correlated with an increased fire frequency, determined from increasing PAH concentrations. Ultimately, these data contribute to constraining the causes of C4 expansion in NW Argentina, including the most important climatic controls and feedbacks from fire regimes, in continental SA.Fil: Ghosh, Adit. California State University; Estados UnidosFil: Cotton, Jennifer M.. California State University; Estados UnidosFil: Hyland, Ethan G.. North Carolina State University; Estados UnidosFil: Hauswirth, Scott C.. California State University; Estados UnidosFil: Raigemborn, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Tineo, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaThe Geological Society of America Connects 2021PasadenaEstados UnidosGeological Society of Americ

Mobilization of Manufactured Gas Plant Tar with Alkaline Flushing Solutions

This experimental study investigates the use of alkaline and alkaline–polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar–aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01–1 wt.%) were found to significantly reduce tar–aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar–wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81–93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods

Adeno-associated virus vector-mediated IL-10 gene delivery prevents type 1 diabetes in NOD mice

The development of spontaneous autoimmune diabetes in nonobese diabetic (NOD) mice provides for their use as a model of human type 1 diabetes. To test the feasibility of muscle-directed gene therapy to prevent type 1 diabetes, we developed recombinant adeno-associated virus (rAAV) vectors containing murine cDNAs for immunomodulatory cytokines IL-4 or IL-10. Skeletal muscle transduction of female NOD mice with IL-10, but not IL-4, completely abrogated diabetes. rAAV-IL-10 transduction attenuated the production of insulin autoantibodies, quantitatively reduced pancreatic insulitis, maintained islet insulin content, and altered splenocyte cytokine responses to mitogenic stimulation. The beneficial effects were host specific, as adoptive transfer of splenocytes from rAAV IL-10-treated animals rapidly imparted diabetes in naive hosts, and the cells contained no protective immunomodulatory capacity, as defined through adoptive cotransfer analyses. These results indicate the utility for rAAV, a vector with advantages for therapeutic gene delivery, to transfer immunoregulatory cytokines capable of preventing type 1 diabetes. In addition, these studies provide foundational support for the concept of using immunoregulatory agents delivered by rAAV to modulate a variety of disorders associated with deleterious immune responses, including allergic reactions, transplantation rejection, immunodeficiencies, and autoimmune disorders