Detection and Quantification of Aromatic Hydrocarbon Compounds in Water Using SH-SAW Sensors and Estimation-Theory-Based Signal Processing

This work investigates a sensor system for direct groundwater monitoring, capable of aqueous-phase measurement of aromatic hydrocarbons at low concentrations (about 100 parts per billion (ppb)). The system is designed to speciate and quantify benzene, toluene, and ethylbenzene/xylenes (BTEX) in the presence of potential interferents. The system makes use of polymer-coated shear-horizontal surface acoustic wave devices and a signal processing method based on estimation theory, specifically a bank of extended Kalman filters (EKFs). This approach permits estimation of BTEX concentrations even from noisy data, well before the sensor response reaches equilibrium. To utilize estimation theory, an analytical model for the sensor response to step-changes, starting from clean water, to mixtures of multiple analytes is first formulated that makes use of both equilibrium frequency shifts and response times (for individual analyte), the latter being specific for each combination of coated device and analyte. The model is then transformed into state-space form, and the bank of EKFs is used to estimate BTEX concentrations in the presence of interferents from transient responses prior to attainment of equilibrium. Samples used in the experiments were either manually mixed in the laboratory or taken from real monitoring sites; they contained multiple chemically similar analytes with concentrations of individual BTEX compounds in the range of 10–2000 ppb. The estimated BTEX concentrations were compared to independent gas chromatography measurements and found to be in very good agreement (within about 5–10% accuracy), even when the sample contained multiple interferents such as larger aromatic compounds or aliphatic hydrocarbons

Infiltration of Sulfate to Enhance Sulfate Reduction of Petroleum Hydrocarbons

The lack of sufficient electron acceptors, particularly sulfate, can limit the rate of biodegradation of petroleum hydrocarbons (PHCs). Hence there is a growing interest by remediation practitioners to deliver sulfate to a PHC impacted saturated zone to enhance biodegradation. When shallow contamination is present in a relatively permeable aquifer and site constraints allow, a cost-effective approach is to apply sulfate on the ground surface. In this investigation a pilot-scale experiment was conducted to increase our understanding of the delivery of sulfate using a surface-based method and the resulting impact on a shallow PHC contaminated aquifer. A surficial infiltration pond positioned on the ground surface above a well-characterized residual PHC source zone was used to control sulfate dosing. A high-resolution network near the infiltration pond and downgradient of the source zone was employed to monitor relevant geochemical indicators and PHC concentrations. Compound specific isotope analysis (CSIA) was used to identify biodegradation patterns and to investigate the occurrence of microbial sulfate reduction. Selected metabolites and reverse-transcriptase quantitative polymerase chain reaction analyses of expressed biodegradation genes (as mRNA) were also used to characterize the response of indigenous microorganisms (especially sulfate reducing bacteria) to the added sulfate. Three sulfate application episodes (5000 L each) at various Na 2 SO 4 concentrations were allowed to infiltrate under a constant hydraulic head. Although the applied sulfate solution was impacted by density driven advection, detailed monitoring data indicated that the sulfate-enriched water mixed with up-gradient groundwater as it migrated downward through the residual PHC zone and formed a co-mingled downgradient plume with the dissolved PHC compounds. The enrichment of δ 34 S of sulfate in conjunction with a decrease in sulfate concentration showed the occurrence of sulfate reduction due to the applied sulfate. Increased dissolved inorganic carbon (DIC) concentrations associated with a shift toward more depleted values of δ 13 C of DIC was indicative of an input of isotopically depleted DIC from biodegradation of benzene, toluene and o-xylene (BTX). Despite fluctuations in the BTX concentrations, the CSIA data for BTX showed that these compounds were biodegraded. The biomarker data provided supporting evidence that toluene and o-xylene were undergoing anaerobic biodegradation due to sulfate reduction. This study provides insight into factors controlling surface-based delivery of sulfate to shallow PHC impacted groundwater systems, and the value of isotopic and molecular-biological procedures to augment conventional monitoring tools

Integrated Plume Treatment Using Persulfate Coupled with Microbial Sulfate Reduction

The integration or sequential use of different remediation technologies, also referred to as a combined remedy, has become an emerging strategy for the treatment of contaminated sites. Coupling chemical oxidation using persulfate with enhanced bioremediation (EBR) under sulfate reducing conditions is a plausible combined remedy. To characterize the role of the mass removal processes (e.g., chemical oxidation vs. sulfate reduction) and to quantify the impact of persulfate on indigenous microbial processes in a combined persulfate/EBR treatment system, a pilot-scale field experiment was conducted in a 24-m long sheet pile-walled gate over a period of approximately 400d. After dissolved benzene, toluene, and o-xylene (BTX) quasi steady-state plumes were developed, two persulfate injection episodes were performed 10d apart to create a chemical oxidation (ChemOx) zone. High-resolution monitoring was conducted to observe the migration of the ChemOx zone and transition into an EBR zone. Mass loss estimates and geochemical indicators were used to identify the distinct transition between the ChemOx and enhanced biological reactive zones. Compound specific isotope analysis (CSIA) was used to distinguish the dominant mass removal process, and to investigate the occurrence of microbial sulfate reduction. BTX metabolites and reverse-transcriptase quantitative polymerase chain reaction analyses of expressed biodegradation genes (as mRNA) were also used to characterize the response of indigenous microorganisms (especially sulfate-reducing bacteria) to the added persulfate. Multiple lines of evidence supported the conclusion that chemical oxidation was the dominant mass removal process in the vicinity of the injection zone, while enhanced biodegradation dominated BTX degradation in the downgradient portions of the system. The CSIA and supporting molecular biological data were critical in documenting temporally and spatially distinctive zones in this system that were dominated by either chemical-oxidation or anaerobic-biodegradation processes. Initially, persulfate had an inhibitory impact on the activity of the indigenous microbial community, but this was followed by a substantial rebound of microbial activity to above baseline levels. The results from this investigation demonstrate that the suite of diagnostic tools employed can be used to distinguish between chemical oxidation using persulfate and the subsequent effects of the produced sulfate

Cathepsin B Degradable Star-Shaped Peptidic Macromolecules for Delivery of 2‑Methoxyestradiol

2-Methoxyestradiol (2ME), a natural metabolite of estradiol, has antiproliferative and antiangiogenic activity. However, its clinical success is limited due to poor water solubility and poor pharmacokinetic parameters suggesting the need for a delivery vehicle. In this study we evaluated cathepsin B degradable star-shaped peptidic macromolecules (SPMs) that can potentially be used to create higher generation and high molecular weight peptidic polymer as delivery vehicle of 2ME. Two peptidic macromolecules having positively charged amine (ASPM) or negatively charged carboxyl surface groups (CSPM) were synthesized and evaluated for their degradation in the presence of cathepsin B and stability in the presence of neutral or acidic buffer and serum. Both ASPM and CSPM degraded rapidly in the presence of cathepsin B. Both were stable in neutral and acidic buffer whereas only CSPM exhibited substantial stability in the presence of serum. Both macromolecules were nontoxic toward breast cancer cells whereas 2ME-containing macromolecules exhibited antiproliferative activity in the micromolar range. Overall, results from the current study indicate that tetrapeptide GFLG can be used to create star-shaped macromolecules that are degraded in the presence of cathepsin B and have the potential to be developed as delivery vehicles of 2ME

Detection and Quantification of Aromatic Hydrocarbon Compounds in Water Using SH-SAW Sensors and Estimation-Theory-Based Signal Processing

This work investigates a sensor system for direct groundwater monitoring, capable of aqueous-phase measurement of aromatic hydrocarbons at low concentrations (about 100 parts per billion (ppb)). The system is designed to speciate and quantify benzene, toluene, and ethylbenzene/xylenes (BTEX) in the presence of potential interferents. The system makes use of polymer-coated shear-horizontal surface acoustic wave devices and a signal processing method based on estimation theory, specifically a bank of extended Kalman filters (EKFs). This approach permits estimation of BTEX concentrations even from noisy data, well before the sensor response reaches equilibrium. To utilize estimation theory, an analytical model for the sensor response to step-changes, starting from clean water, to mixtures of multiple analytes is first formulated that makes use of both equilibrium frequency shifts and response times (for individual analyte), the latter being specific for each combination of coated device and analyte. The model is then transformed into state-space form, and the bank of EKFs is used to estimate BTEX concentrations in the presence of interferents from transient responses prior to attainment of equilibrium. Samples used in the experiments were either manually mixed in the laboratory or taken from real monitoring sites; they contained multiple chemically similar analytes with concentrations of individual BTEX compounds in the range of 10–2000 ppb. The estimated BTEX concentrations were compared to independent gas chromatography measurements and found to be in very good agreement (within about 5–10% accuracy), even when the sample contained multiple interferents such as larger aromatic compounds or aliphatic hydrocarbons

Diagnostic Tools to Assess Mass Removal Processes During Pulsed Air Sparging of a Petroleum Hydrocarbon Source Zone

During remediation of contaminated aquifers, diagnostic tools can help evaluate whether an intended mass removal process was success- fully initiated and acted on specific contaminants of concern. In this study, several diagnostic tools were tested in a controlled-release in situ air sparging experiment that focused on the treatment of target hydrocarbons (e.g., benzene, toluene, ethylbenzene, and xylenes). The tools included compound-specific isotope analysis (CSIA), expression of functional genes (mRNA), and metabolites characteristic of aerobic and anaerobic biodegradation. Total and compound-specific mass balances were established and used, along with traditional monitoring parameters, to validate the results from the various tools. CSIA results indicated biodegradation as the main process contributing to benzene and toluene removal. Removal process-specific isotope shifts were detected in groundwater as well as in the system effluent gas. CSIA, metabolite, and mRNA biomarkers consistently indicated that both aerobic and anaerobic biodegradation of benzene and toluene occurred, but that their rela- tive importance evolved over time and were related to the treatment system operation. While the indicators do not allow quantification of the mass removed, they are particularly useful to identify if a removal process has been initiated, and to track relative changes in the predominance of in situ contaminant attenuation processes resulting from remediation efforts

Conditioning of Cardiovascular Tissue Using a Noncontact Magnetic Stretch Bioreactor with Embedded Magnetic Nanoparticles

Bioreactor systems, an integral component of tissue engineering, are designed to simulate complex in vivo conditions to impart functionality to artificial tissue. All standard forms of stretch bioreactors require physical contact with artificial heart muscle (AHM). However, we believe that noncontact stretch bioreactors have the potential to lead to higher functional benefit of AHM. Our work is focused on the fabrication of a noncontact magnetic stretch bioreactor (MSB) that uses magnetic nanoparticles to simulate stretch conditions to impart functionality. During our development of this system, we applied magnetically induced stretch conditioning through application of an oscillating magnetic field to a ferromagnetic heart muscle model. Fibrin scaffolds were loaded with magnetic nanoparticles prior to tissue model formation. Oscillating magnetic fields were applied by a novel bioreactor system through displacement of a neodymium magnet. The addition of commercially obtained iron­(III) oxide (Fe₂O₃) in sufficient quantities to allow for physiologically relevant stretches (15% axial displacement) caused toxic effects after 4 days of culture. In contrast, loading scaffolds with monodispersed, high-saturation-magnetization magnetite (Fe₃O₄) nanoparticles specifically prepared for these experiments increased the field strength of the magnetized fibrin 10-fold over polydispersed, low-saturation magnetization, Fe₂O₃. Additionally, loading with Fe₃O₄ enabled magnetically actuated stretching with markedly reduced toxicity over 8 days of culture. Using a 20% stretch 0.5 Hz protocol, we observed a significant increase in twitch force over controls at days 4 and 6. This work provides a technology for controlled noncontact mechanical stretch to condition AHM