Environmental and Water Resources
The Analysis of the Behavior of Anthropogenic Nanomaterials in the Environment
Itzel Godinez-PhD Candidate, Advisor: Dr. Darnault
To date, there are few studies that have analyzed the behavior of anthropogenic nanomaterials in the environment. However, the use of nanomaterials in commercially available products is rapidly increasing. As our society utilizes these nanosize materials in greater quantities, it is imminent that at some point they will be released into the environment either as waste and/or by accidental spills. Thus, it is crucial that scientific data is generated to explain the movement of nanomaterials in air, water and soil. The focus of my research is to investigate the fate and transport of two engineered nanoscale materials—single-wall carbon nanotubes (SWNT) and fullerenes (C60
)—in the vadose zone under preferential flow. The objective is to develop non-intrusive, high spatial and temporal models to describe the transport of these nanomaterials in porous media. To assess the movement and behavior of SWNTs and C60
through the vadose zone 3D experiments, which consist of soil columns subjected to fingering and gravitational flow phenomena, will be implemented. The soil columns will serve to investigate the transport of SWNTs and C60
in unsaturated and saturated conditions as well as when undergoing wetting and drying cycles. A micromodel will also be employed to examine the fate and transport of these nanomaterials at the pore scale. The pore-scale visualization method is expected to provide information on the interactions of SWNTs and C60
with the air-water interface, the soil-water interface, and the soil-water-air interface. It is hoped that through the experimental results a comprehensive understanding on the transport of nanomaterials in porous media is elaborated.
I am a recipient of the Bridge to the Doctorate Fellowship at the University of Illinois at Chicago. I work under the supervision and guidance of Professor Darnault.
Nucleation and Precipitation Processes in the Vadose Zone during Contaminant Transport
Burcu Uyusur, PhD Candidate, Advisor: Dr. Darnault
Leakage has been determined in the vadose zone sediments of Hanford Site, U.S. Department of Energy Complex in Washington since 1950s. The site consists of high pH, high temperature and high ionic strength solution as well as radioactive elements such as uranium. The mode of transport of contaminants in the porous media, adsorption reactions, formation of secondary precipitates and colloids are important aspects for understanding the contaminant mobility in the environment of the site. This project aims to characterize
and quantify the mechanisms of nucleation and precipitation of uranium secondary precipitates, specifically zeolitic and uranium-silicate in quartz sand and feldspar minerals under flow conditions. Both 3-D column and 2-D light transmission visualization experiments will be conducted under simulated unsaturated flow. The effluent will be analyzed for uranium, silica, etc. as well as colloids. Light transmission method will be used to quantify water content and solute concentrations in 2-D chamber. Surface analysis techniques such as BET gas adsorption technique and Atomic Force Microscopy (AFM), insight analysis such as Time Resolved Laser Fluorescence Spectroscopy (TRLFS) and Extended X-Ray Absorption Fine Structure (EXAFS) will be used to characterize mineral surfaces. The data will also be incorporated into a reactive transport model. The results can be of particular interest in terms of uranium reactions, particularly nucleation reactions of new phases and incorporation of uranium into these phases, with the quartz sand and feldspar during vadose zone flow. Also, the effect of these new precipitates on the flow of vadose zone sediments can be understood. Although the general emphasis is Hanford site, the conclusions are expected to be manageable for other similar field conditions.
Active Capping for Sediment Remediation and Active Capping Potential in the Chicago River
Priscilla Viana- PhD Candidate-Advisor: Dr. Karl Rockne
I am working with active capping for sediment remediation. Active capping isolates contaminated sediments from the water phase offering continuous remediation and/or sequestration by the active material. The active material is chosen after an extensive site characterization. Bioaugmentation (addition of microorganisms), biostimulation (addition of amendments), use of sequestration additives (granular activated carbon, organo-clay, coke, and apatite) and hydraulic sequestration (water-expanding clay) are some proposed active capping amendment options.
Surface grabs and core samples were collected at Collateral Channel and at the turning basin of Bubbly Creek in the Chicago River (Chicago, IL). An extensive characterization of the solid and moisture content, organic matter and organic carbon content, and anion concentration (mainly nitrate and sulfate) was performed. This extensive characterization of the Channels was performed to assist choosing the correct active materials and thickness and gas controls in the design of a demonstrative active capping to be implemented at both Channels. Our group is collaborating with the Metropolitan Water Reclamation District of Greater Chicago, the Wetlands Initiative, and Patrick Engineering. Experiments to measure gas production rates along the Channels were completed and the effect of temperature in the reaction rate constant was determined using the Arrhenius equation for both Channels. Using this data we are able to predict the amount of gas that could be produced along each of the Channels through an entire year period and decide whether gas control systems will be necessary. The ratio of methane to carbon dioxide was measured in the sediment to observe the effect of temperature on methane production. Microbiological studies are being performed to quantify the levels of hydrogenotrophic and acetoclastic methanogens using quantitative polymerase chain reaction (qPCR) of 16S rDNA targets.
A mixed contaminant transport modeling for a variety of different active cap materials was also completed. I performed this work in collaboration with Ke Yin, also Dr. Rockne’s research assistant. These simulations are useful to understand the efficacy of selected cap materials and its thickness for containing and/or degrading organic and metal pollutant mixtures (five capping materials and 22 contaminants are being modeled).
A detailed evaluation of in situ
processes that might compromise cap effectiveness is vital to guarantee cap effectiveness. We have identified gas ebullition due to methanogenic activity is one of the critical processes for cap release because bubbles are hydrophobic and tend to accumulate hydrophobic contaminants and colloids on their surface. Gas bubble migration may not only release contaminants to the water column and even to the atmosphere, but may also cause cap damage and even burst the cap, providing additional pathways for contaminant release. Studies quantifying contaminant release to the water phase due to gas ebullition are very limited. Thus, our future research will focus in understanding and quantifying the flux of contaminants through cap due to gas migration. We will also perform experiments to understand the microbial community involved in the gas production process to predict gas production rates, finding out values that would result in cap breach, with the goal of assisting the design of guidelines for site assessment and gas control measures.
Ke (Ink) Yin, Ph.D Candidate, Advisor: Dr. Rockne
I am currently a Ph.D student in the department of Civil and Materials Engineering at the University of Illinois at Chicago under Professor Karl Rockne.
I am focusing on my research area on active capping potential for remediation of polluted sediments in the Chicago River, Collateral Channel, which has very high levels of polycyclic aromatic hydrocarbons (PAHs). With application of the Monti Carlo modeling of our contaminated site, we have found active capping effectively prevents PAHs from release for periods of decades to centuries. However, considerations regarding the placement technology, bioturbation need to be carefully taken care of during the design before the project’s complementation.
My goal is to try to apply several active capping materials and combined several placement technologies into our project design. We will build in an in-situ monitoring system to obtain a long term observation of the ongoing capping installation for our continuous research on capping efficiency. Comparison of our simulation result with the in-situ observations will validate the effectiveness of our modeling design, which will be very beneficial for a future project design and widespread application of the technology.
Mercury Methylation in Dental Wastewater
Xiuhong Zhao, PhD Candidate, Advisor: Dr. Rockne
My research is focused on mercury methylation in the dental wastewater. Mercury from dental office is a big source of mercury contamination which can contribute up to 78% loading to the public owned wastewater treatment plant. There is high possibility for the mercury in the dental waste water (DWW) to converted to a more toxic form methyl Hg (MeHg
) via biotic activity. My objective was to confirm MeHg
generation in DWW and identify biological parameters that may affect MeHg
generation potential. Through my study, I hope I can find an effective way to decrease and/or eliminate mercury methylation in DWW or preclude its introduction into the wastewater collection system.
Currently, I confirmed the MeHg
generation in DWW, which can reach to 58 µg l-1
. At the same time, the hypothesis that sulfate reducing bacteria (SRB) play an important role in MeHg
generation is strongly supported by DNA analysis of the DWW. In the future, I want to determine whether there is a causal link between methyl Hg levels and population and species composition of SRB through high frequency monitoring coupled with microbial inhibitor studies and coupled quantitative polymerase chain reaction (qPCR) of 16S rRNA.
Enhanced Anaerobic Biodegradation of PCBs in Contaminated Sediments using Hydrogen
Ravikumar Srirangam, PhD Candidate, Advisor: Dr. Khodadoust
I am currently conducting research on remediation and destruction of Polychlorinated biphenyls (PCBs) in contaminated fresh-water sediments. The release of PCBs from sediments to overlying waters can occur by desorption, especially when PCB concentrations are high or when sudden hydrographic activity like flooding or dredging causes sediments to be re-suspended and redistributed.
Due to their environmental persistence, PCBs have the tendency to biomagnify in the higher trophic levels of the food chain, and therefore pose potential health risks. PCBs are suspected to cause cancer or adverse skin and liver effects.
Biostimulation of anaerobic biodegradation of PCBs by the amendment of appropriate electron donors like hydrogen to contaminated sediments should stimulate the reductive dechlorination process. Addition of elemental zerovalent iron (Fe0
) for production of hydrogen in contaminated sediments may enhance the microbial dechlorination of the PCBs which can be an efficient biostimulation technique for remediation and destruction of PCBs. Factors like pH, hydrogen levels, concentration of PCBs and microbial populations in sediments could be vital in governing the anaerobic biodegradation process. Microcosm experiments performed on contaminated sediments obtained from Lake Hartwell and Indiana Harbor (Lake Michigan) will give a clear idea on the effect of direct and indirect addition of electron donor on PCB biodegradation. Addition of controlled amounts of microscale iron metal to sediments has the potential to be developed as an efficient and cost effective technology for remediation and destruction of PCBs in contaminated sediments by providing a continuous source of electron donor for anaerobic biodegradation.
Leaching Characteristics of Arsenic from Aged Alkaline Coal Fly Ash
Pratibha Naithani, PhD Candidate, Advisor: Dr. Khodadoust
The focus of my research is to determine the chemical composition and leaching characteristics of arsenic from alkaline aged coal fly ash samples collected from Retired Ash Basin at Brunner Island site belonging to PPL Generation Company. Groundwater near the aged coal fly ash impoundment is affected by arsenic contamination from ash leachate. Arsenic is adsorbed on subsurface soils from leachate and contaminates groundwater. Arsenic is listed as one of 129 priority pollutants by the Environmental Protection Agency. Arsenic causes skin problems and several internal cancers, chronic exposure to high levels of arsenic results in cardiovascular and neurological disorders.
The toxic effects of arsenic are related to its oxidation state. The main factors which affect leaching of arsenic are pH, Eh, calcium, inorganic carbon. Multiple batch sequential leaching tests and column leaching experiments have been performed. Coal fly ash was found to be overall dependent on the pH of ash samples. Despite the high iron content of ash, and the association of arsenic with the iron oxide fraction of ash, little or no iron leached out from ash under ambient pH conditions. The calcium content of ash mainly determined the pH of ash, where calcium was mostly in the form of CaCO 3
in ash. The main calcium compounds present in the leachate system were CaSO 4
, CaCO 3
and CaHAsO 4
. The pH was controlled by calcium bicarbonate present in the system. Arsenic leached out mainly as calcium hydrogen arsenate from the calcium arsenate present in ash. Batch and column leaching experiments have shown the similarity of leaching parameters for arsenic in both systems. Column leaching of ash samples from other depths at same location is expected to be similar to the batch leaching results for those samples.