Comprobantes: Presentaciones: Seminarios y Conferencias

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1 Comprobantes: Presentaciones: Seminarios y Conferencias

2 Teleseminarios: Research Corporation/Sematech Eng. Research Center for Environ, 1 de diciembre de Host: Jim Field, Chemical and Environmental Engineering, University of Arizona Presented by: Wenjie "Alex" Sun, Chemical and Environmental Engineering, University of Arizona. Authors: Wenjie Sun, Antonia Luna-Velasco, Reyes Sierra-Alvarez, Jim A. Field-University of Arizona Topic title: "The Role of Protein Oxidation in the Toxicity of Inorganic Nanoparticles" Abstract: Growth in the nanotechnology application is leading to increased production of nanoparticles (NPs). The semiconductor manufacturing industry is already using NPs of SiO 2, Al 2 O 3 and CeO 2 in the chemical mechanical planarization process. Additionally, a wide variety of inorganic NPs are being considered for emerging processes in the industry. This has given rise to concerns about the potential adverse and toxic effects to the biological system and environment. Oxidative stress to cells caused by NPs through the formation of reactive oxygen species (ROS) or via direct oxidation of biomolecules is considered to be an important mechanism of NPs toxicity. A rapid method has been established to monitor the ROS production by NPs via the reaction with L-dopa in the presence of oxygen at the University of Arizona. In this study, a protein oxidation assay was developed to determine the role of protein oxidation in NPs toxicity. The protein oxidation was evaluated by use of the enzyme-linked immunosorbent assay (ELISA) to measure the protein carbonyl derivatives as the product of protein oxidation. The testing identified that Cu, CuO, Mn 2 O 3 and Fe 0 are the reactive NPs causing protein oxidation; whereas, many of the other NPs tested are not reactive or very slow reactive with proteins. Particle size and presence of oxygen also played important roles in the protein oxidation. Link:

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5 Teleseminarios: Research Corporation/Sematech Eng. Research Center for Environ, 23 de septiembre de Host: Jim Field, Chemical and Environmental Engineering, University of Arizona Presentation by: Antonia Luna, Chemical and Environmental Engineering, University of Arizona Topic title: Oxidation of a Reactive Oxygen Species (ROS) Indicator Dye by Inorganic Nanoparticles Abstract: Numerous reports published in recent years indicate a growing concern for the potential toxicity of engineered nanoparticles (NPs). Study of the potential risk of NPs is a top priority for the semiconductor industry due to the fact that some inorganic NPs (e.g., CeO 2, Al 2 O 3, SiO 2 etc.) are currently used in its manufacturing processes. Recently toxicity studies have hypothesized several NP toxicity mechanisms, such as catalytic interaction, solubilization, and increased production of reactive oxygen species (ROS), such as superoxide ( O 2 ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical ( OH). Numerous studies suggest that a common mechanism of NP toxicity is via oxidative stress by ROS which are strong oxidants that react rapidly with most biological molecules. That finding suggests that the toxicity of NPs might be predicted from their ROS generating capability in vitro. The aim of this research is to determine if the chemical reaction of NPs with dissolved oxygen or with other biological molecules (e.g., phenolic compounds susceptible to oxidation such as catechol and L-dopa) can cause formation of ROS. This was tested with a ROS-sensitive dye, 2,7 - dichlorodihydrofluorescein (DCFH), which is oxidized to its highly fluorescent product 2,7 -dichlorofluorescin (DCF) in the presence of ROS. We found that most inorganic NPs assayed reacted with L-dopa and dissolved oxygen enhancing ROS production. Nano-sized Mn 2 O 3 could cause direct oxidative reaction with DCF without dissolved oxygen or L-dopa, which may indicate its potential to directly oxidize certain cell components. Experiments with electron paramagnetic resonance (EPR) analysis are currently being performed to confirm and identify the ROS species formed by the NPs studied. Liga:

6 Microbial Perchlorate Reduction Using Sulfur as an Electron Donor Annemarie Nauert, Antonia Luna-Velasco, Reyes Sierra-Alvarez, Jim A Field Seminars: 2008-Research Experience for Undergraduates (REU) Abstract Perchlorate (ClO4-) is a water contaminant that interferes with thyroid function; this study investigates the use of a packed-bed sulfur bioreactor inoculated with wastewater treatment sludge containing perchlorate reducing bacteria (PRB) to eliminate perchlorate from drinking water. Perchlorate (2 mmol) in the influent was completely reduced when media flow rate was 1.50 L/day. Media was reformulated to include 1 g/l of sodium bicarbonate to achieve an influent ph near 8.20 and an effluent ph near 7.0. Negligible amounts of sulfide were detected in the column. This paper also examines the effect of temperature and nutrient-content in a batch experiment. The activity of PRB and sulfidedisproportionating bacteria (competing bacteria both found endogenously in wastewater sludge) was measured as indicated by perchlorate reduction and sulfide production, respectively. Anaerobic batches were incubated at 20º and 30º. Only PRB in complete treatments (inocula, perchlorate, sulfur, nutrients) at 30º were able to completely reduce perchlorate. Sulfide-producing bacteria performed most effectively at 30º after PRB had reduced all available perchlorate. PRB were most effective when provided nutrients; sulfide production was more strongly governed by availability of sulfur. The results of this research suggest that nutrients should be used as an effective means of promoting PRB growth without encouraging sulfide-producing bacteria competition. Introduction Perchlorate (CLO4-) is a man-made (and occasionally naturally occurring) compound historically used for rocket propellant and fireworks. The majority of ClO4 in the environment comes from industrial discharge, leaching, and military applications 1. Although perchlorate has been detected in over half of the United States 2, groundwater contamination is of particular concern to states like Arizona, California, Nevada, and others where there is current and anticipated water scarcity. Perchlorate is dangerous to human health: the compound, alone or in the form of a salt, affects thyroid function by inhibiting iodine uptake. Two major methods are in existence for removal of perchlorate from water: bioremediation and ion exchange 3. The most successful process for eliminating perchlorate is bioremediation, which involves harnessing the biochemical capabilities of bacteria to eradicate unwanted contaminants giving environmentally benign end products Some bacteria are able to use perchlorate as an electron acceptor in a process by which they derive energy and reduce it to chloride under anaerobic conditions. For the process of reduction to be most efficient, an electron donor such as elemental sulfur or hydrogen may be supplied to the bacteria. Inorganic electron donors such as Feº, and Sº have been studied for ClO4 reduction since they have some advantages as slow release electrons; they are also lower cost and lower maintenance than organic electron donors (for example, acetate) 4. Granular Sº in a packed-bed bioreactor has been used successfully as an electron donating substrate in a denitrifying process 5 and perchlorate reduction process 6. 1 Coates and Achenbach, EPA data 3 Xu et al., Xu et al., Sierra-Alvarez et al., Byrnes,

7 Uranium bioreduction and denitrification using two packed bed columns containing zerovalent iron and elemental sulfur Travis S. Conner a, Reyes Sierra-Alvarez b, Jim A. Field b, and Antonia Luna b. a Department of Chemical Engineering, Virginia Tech, Blacksburg, VA , USA b Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ , USA Abstract: Uranium has been recognized as a groundwater contamination in need of treatment in many parts of the United States. In particular, historical uranium mills in Arizona have left tailings exhibiting high uranium contamination levels, and these tailings are often associated with nitrate contamination due to the use of nitric acid for the processing of uranium ores. The objective of this study was to investigate the biological reduction of uranium and denitrification by a series of reactions including a necessarily first step of biotic denitrification to dinitrogen gas and a second step of reducing the soluble uranium(vi) to its insoluble form, uranium(iv). The sulfur and limestone autotrophic denitrification (SLAD) process was used to achieve denitrification via operation of a packed bed reactor with elemental sulfur and limestone at a 50:50 ratio by volume. Uranium biomineralization was conducted in a second reactor packed with zero valent iron (ZVI) and sand at a 5:95 ratio (ZVI:sand). ZVI was the intended electron donor for the stimulation of microorganism autotrophic uranium reduction for biomineralization. The sulfur column demonstrated 99.03% efficient denitrification after a slow start-up, which has inhibited progress in the project. The ZVI column achieved 95.45% efficiency a few days after start-up. The reactors have been operating in parallel to date, but the eventual goal is to demonstrate sustainable nitrate and uranium removal from co-contaminated water by operating the columns in series. This paper describes the set-up of the columns and noteworthy issues and observations noted during operation of the columns in parallel.