The current nanotechnology boom necessitates timely research into the health and environmental impacts of nanomaterials to enhance their eco-responsible manufacture, use, and disposal. Using the water-insoluble C60 as a model nanomaterial, the potential environmental impacts of a C60 water suspension, termed nC60, are here assessed with bacteria as a receptor. nC60 was evaluated for antibacterial activity, antibacterial mechanisms, impact on natural microbial systems, and potential disinfection applications. nC60 is a potent antibacterial agent when tested against pure cultures of different bacteria. Whereas neither light nor oxygen affects its potency, toxicity is increased by smaller particle size and mitigated by salts which promote precipitation. In complex environments, toxicity was lessened by salts or by natural organic matter that sorbed or coated nC60, reducing its bioavailability. The applicability of nC60 as a disinfectant is thus limited to situations with limited organic matter and debris (e.g., drinking water disinfection); it is not recommended for antibiofouling coatings where precipitating debris occluded the nC60 coating and promoted biofilm formation. In contrast to literature showing nC60 -generated reactive oxygen species damaging eukaryotic systems, this research shows that nC60 behaves as an oxidant upon direct contact with the cell, leading to uncoupled respiration and/or damaged respiratory proteins. The methods that were previously used to detect ROS-mediated damage are shown to be ambiguous and susceptible to interference by nC60, implying that the evidence of ROS-mediated oxidative stress needs to be re-evaluated. Overall, this research reflects an overall image of preventable or negligible environmental impact of nC60, and provides a methodology by which the potential environmental impacts of other nanomaterials can be evaluated.

Elevated levels of arsenic in groundwater have generated great attention worldwide because of its wide occurrences throughout the world and toxicity at low concentration. This work introduces a possible application at household levels to provide arsenic-safe water using nanoscale iron oxide (i.e., magnetite nanoparticles) and iron salts (i.e., ferric nitrate and ferric chloride) as adsorbents and coagulants, respectively. Recent publications illustrate that more than 70 million people are chronically exposed to arsenic-contaminated groundwater and suffer from skin lesions and cancers worldwide. A number of technologies (for example, ion exchange and membrane methods) are currently available to remove arsenic; however, each technique has drawbacks to be applicable in the developing countries. Therefore, it is crucial to develop a technology to treat arsenic-contaminated groundwater. Our results show an immediate reduction of arsenic concentration in solution to meet the maximum contaminant level of arsenic (10 microg L-1) in drinking water. Also, iron concentrations in solution are below the World Health Organization guideline value of 300 microg L-1. Contrary to previous results reported by other researchers, arsenic(III), known as more problematic in natural water, is also removed as effectively as arsenic(V) by using our method. When citrate, one of most common organic ligands in environments, is initially added to arsenic-containing solutions, the formation of iron oxides from iron salts is completely inhibited and resulting arsenic concentration remains the same as the initial arsenic concentration, indicating that arsenic removal does not occur. However, other common carboxylic acids such as tartarate, succinate, malate, formate, and tricarballylate, have a negligible impact on preventing the formation of iron hydroxides and resulting arsenic removal from solution. This work shows the efficient method to reduce high arsenic concentrations in groundwaters and better understanding of arsenic removal mechanisms using iron salts and iron oxides.

Ethanol is playing a key role in current discussions on energy, agriculture, taxes and the environment. This work addresses the potential environmental impacts and behavior of subsurface fuel-ethanol releases. A continuous-flow 8,150-L pilot-aquifer tank packed with sand was used to simulate two spill scenarios: (1) fuel-grade ethanol (E95, 95% v/v ethanol, 5% v/v hydrocarbon mixture as a denaturant) into uncontaminated soil, and (2) neat ethanol (100% v/v) release onto gasoline-contaminated soil. Measurement of ethanol and hydrocarbon concentrations in groundwater and capillary-fringe pore water from over 30-locations over 120+ days provided a quantitative evaluation of the extent of plume migration, longevity, and impacts to groundwater quality. Real-time quantitative PCR (RTQ-PCR) was also used to estimate temporal and spatial trends in concentrations of total bacteria (16s rDNA) and various genotypes that inhabit different electron-accepting zones at sites undergoing natural attenuation. Furthermore, the anaerobic catabolic gene bssA (coding for benzylsuccinate synthase), and the aerobic catabolic genes dmpN (coding for phenol hydroxylase) and todC1 (coding for toluene dioxygenase) were also quantified as biomarkers for BTEX biodegradation. Ethanol, which is buoyant and hygroscopic, quickly migrated upwards and spread laterally within the capillary-zone. Horizontal migration of ethanol occurred through a shallow thin layer with minimal vertical dispersion, and was consistently 10-times slower than the preceding bromide tracer. Dyes, one hydrophobic (Sudan-IV) and one hydrophilic (Fluorescein) provided evidence that the fuel hydrocarbons phase separated from the E95 mixture as ethanol was diluted by pore water and its cosolvent effect was diminished. The neat ethanol spill mobilized the pre-existing hydrocarbon NAPL down-gradient. Neither of the highly concentrated spills had a bactericidal impact on the microbial community, and cell growth coincided with ethanol availability. Bacteria concentrations increased by at least one-order of magnitude as did bacteria harboring todC1 and dmpN after each spill. However, bacteria harboring bssA were not detected, suggesting that longer acclimation time may be required to establish anaerobic hydrocarbon degraders. It appears that microbial impacts are mainly related to O 2 depletion, but rebound can be relatively fast, and fortuitous proliferation of aerobic BTEX degraders (growing on ethanol) is likely following the relatively rapid ethanol washout.

Three anaerobic, dechlorinating consortia were enriched from different origins using methanol and tetrachloroethene (PCE) and maintained for approximately three years. Characterization of the consortia with terminal restriction fragment length polymorphism (TRFLP) and qualitative and quantitative PCR (qPCR) demonstrated that all three dechlorinating communities were dominated by Dehalococcoides and Dehalobacter spp. Monitoring methane production combined with qPCR for archaea demonstrated that complete PCE dechlorination occurred in the presence and absence of methanogenesis. Combining results for denaturing gradient gel electrophoresis (DGGE) and qPCR for reductive dehalogenase genes suggested that one consortium contained a strain 195-type organism with the ability to respire vinyl chloride (VC). The effect of the anionic surfactant SteolRTM CS-330 on PCE dechlorination was evaluated using pure and mixed dechlorinating cultures. Sulfurospirillum multivorans was the only pure culture able to dechlorinate in the presence of SteolRTM CS-330. S. multivorans was present in consortia OW and CH, and these consortia were capable of partial dechlorination to cis-dichloroethene ( cis-DCE) in the presence of SteolRTM CS-330. Monitoring Dehalobacter spp., Sulfurospirillum spp. and Dehalococcoides cell numbers in consortium OW during exposure to SteolRTM CS-330 with qPCR demonstrated that the cell numbers were reduced by 79%, 88% and 99%, respectively. Dechlorination past cis-DCE was never recovered after resuspension into surfactant free media. Two experimental controlled release systems (ECRS) were employed to examine PCE source zone bioremediation and the efficacy of bioaugmentation. Results obtained demonstrated that bioaugmentation enhanced PCE removal by a factor of 1.6 over biostimulation alone, but minimal ethene production was observed in both systems. Interestingly, both systems contained Dehalococcoides capable of growth on VC; but VC dechlorination was not observed. It was also demonstrated that the bioaugmented populations became dominant, and that the dechlorinating organisms were not washed out of either system. Analysis of energy flow demonstrated that the dechlorinating populations consumed more energy than the methanogens until chloroethenes became limiting. A comparison of cell numbers between archaea and dechlorinating organisms showed that cell numbers did not correlate to activity, since methanogens had higher cell numbers throughout the experiment.

Release of residual aviation gasoline saturation from field contaminated sandy aquifer material was investigated using six soil columns. Addition of a biodegradable non-ionic surfactant (5g/L) to the flushing solution produced an immediate increase in concentrations of methylated alkanes which declined over 20 pore volumes to below initial levels. 15g/L of surfactant produced higher effluent concentrations over 6 pore volumes. Adding 50% (v/v) 2-propanol caused a spike release of contaminants in less than 2 pore volumes. Methanol at 50% released contaminants at fairly low concentrations over 30 pore volumes. At 20% neither alcohol produced much increase in effluent concentrations. Combination of 20% 2-propanol and 5g/L Triton X-100 did not improve the performance of surfactant alone. Soil analysis showed more than 96% of the residual saturation was removed in all six columns. Solvophobic theory, including the effects of reduction in interfacial surface tension, predicted the relative results of both concentrations of alcohols.

Surface application offers an inexpensive, non-invasive alternative to injection wells and infiltration galleries for in situ bioremediation applications. The technology employs artificial recharge to create favorable hydraulic conditions for mixing and vertical transport of electron acceptor and nutrients. A field scale infiltration test and a conservative tracer test qualitatively indicated the feasibility of transporting solutes to the subsurface via recharging water. Modeling of the experiments provided quantitative estimates of site specific hydrogeologic and transport parameters. Results also indicated that dilution was a dominant BTEX attenuation mechanism during the experiment. Models calibrated to data from the infiltration experiment were scaled up for the design of nitrate delivery system for a pilot scale, bioremediation experiment to study enhanced in situ biodegradation of BTEX under denitrifying conditions. Modeling results suggest that dilution effects and stimulation of aerobic processes by oxygen in the recharging water may limit the effectiveness of the experiment.

The role of various particle size fractions in determining urban storm water quality (pH, suspended solids, total organic carbon, turbidity, metals, polyaromatic hydrocarbons and pesticide) has been evaluated in a series of field sampling efforts and laboratory experiments. Water quality during two storm events was monitored over time and changes in contaminant fractionation recorded. The potential for aggregation of suspended matter in the runoff stream and the importance of aggregation on partitioning of the polyaromatic hydrocarbon fluoranthene in various size fractions has been tested in laboratory experiments. Results confirmed the polluting nature of urban runoff and showed a considerable increase in the contaminants loading during storm events. Different pollutants reached their peak concentration during different stages of the storm. It was concluded that the rate and extent of aggregation processes are sufficient to significantly affect the apparent partitioning, fate and transport of associated contaminants.

This study was designed to characterize the quality of Houston area stormwater and its potential impact on receiving waters, including Galveston Bay. Stormwater samples were analyzed with regard to standard water quality parameters, as well as for metals. Large increases in the concentration of particles, suspended solids, organic carbon, iron, mercury and zinc were observed in storm runoff. Concentrations of barium and strontium, which occur naturally in area soils, decreased as result of a storm. Data suggested a link between increasing concentrations of smaller solids (0.45-20$\mu$m) and that of iron and mercury. Organic carbon showed evidence of being similarly related to zinc and larger solids ($>$20$\mu$m). Higher concentrations of these materials, in conjunction with increased runoff flows, resulted in storm loadings equivalent to months or even years of background flow. Particle size distributions measured in situ and laboratory simulations indicated significant aggregation in the runoff stream.

The use of surfactant and aqueous cosolvent soil washing for the restoration of contaminated aquifers was investigated by laboratory experimentation and literature review. The effect of surfactants on hydrocarbon biodegradation and the ability of aqueous cosolvents to mobilize residual gasoline from saturated porous media were addressed. Hydrocarbon degrading microorganisms were cultured in a flow-through sand column. Cultured organisms mineralized $\sp{14}$C-benzene and $\sp{14}$C-naphthalene, but not $\sp{14}$C-anthracene. Mineralization of radiolabeled substrates was inhibited by the presence of surfactant. Surfactants were at least partially biodegradable on the basis of oxygen utilization. Soil washing with surfactant solutions did not enhance removal of residual gasoline beyond that obtained with water. Aqueous ethanol solutions increased the desorption of gasoline components from aquifer material. Cosolvent soil washing should be further investigated. Surfactant soil washing may not be suitable for aquifer restoration because of oxygen demand, mobilization of soil fines, and increased fluid viscosity.

Microorganisms have been added to the subsurface in an attempt to enhance bioremediation. The transport, attachment and fate of these organisms as well as their possible contribution to remediation remain poorly understood. The effect of hydraulic conductivity and injection velocity on microbial transport through porous media was investigated. Glass chromatography columns were packed separately with clean quartz sand of two diameters (0.368 mm or 0.240 mm) and two hydraulic conductivities (1.37 $\times$ 10$\sp{-1}$ cm/sec and 3.65 $\times$ 10$\sp{-2}$ cm/sec respectively). Three injection velocities, 1.18 $\times$ 10$\sp{-3}$, 2.35 $\times$ 10$\sp{-3}$ and 4.73 $\times$ 10$\sp{-3}$ cm/sec were investigated. Microbial transport under the conditions tested was limited and could be predicted mathematically using a model based on filtration theory which incorporated particle trajectory analysis.