B33C-1425
Use of New Composite Material Based on Nanosized Zero Valent Iron for Catalytic Transformations of Water Contaminants
A new composite material is presented for the catalytic, reductive transformation of many types of water contaminants. This material may be further mixed with an inert and/or active macroscopic scaffold, such as vermiculite, to optimize hydraulic properties. The composite material contains combinations of nanosized zero valent metals, electron mediators and natural support matrices. The composite materials are shown to degrade or transform various water contaminants with high oxidation states to relatively benign compounds. Physical, chemical and hydrological properties of the composite material are discussed, along with surface properties and composition. Measurements of transformation kinetics are demonstrated for several typical, persistent organic and metal contaminants in aqueous solutions.
B33C-1426
Magnetic Analysis of Post-mortem Hippocampal Tissue from Alzheimer's Patients: Changes with Progression of the Disease.
Increases of iron in the human brain with age have been observed and may be accompanied by the development of neurodegenerative diseases, such as Alzheimer's. We have measured the magnetic characteristics of several sets of slides of hippocampal tissue from deceased Alzheimer patients. The slides were made available by the Harvard Brain Bank. The pathology of the tissue was classified in the Braak stages I to VI used to describe the progression of the disease. In general, the slides from patients with higher Braak stages and development of fibrillary tangles and plaques had greater magnetic moments than did those with Braak stage II. However, the peak values were at stage IV and V. To mitigate errors due to the inevitable differences in masses of the tissue on individual slides and their precise location in the hippocampus, ratios of magnetic properties were also observed. Ratios of Anhysteretic Remanent Magnetizaton (ARM) to Isothermal Remanent Magnetization (IRM) were obtained and showed a decrease from Stage II to the more advanced stages, with the minimum values at stages IV and V. The acquisition and demagnetization of IRM are consistent with the presence of magnetite, but also indicate a magnetically harder phase.
B33C-1427
Crater-lake Santa Maria del Oro as a Pristine Reference for Persistent Organic Pollutants (POP' s) and Heavy Metals Content in Environmental Investigations in Western Mexico (Project Conacyt-Semarnat 2002-C01-0463, in Progress).
Santa Maria del Oro Lake ( SMO) (21.37° N, 104.57° W; 750 m a.s.l.) is a quaternary crater-lake located at western Mexico in the natural border between two geological provinces: the plio-quaternary Trans-Mexican Volcanic Belt and the oligo-miocenic silicic volcanic province Sierra Madre Occidental. SMO, a tropical freshwater lake, is a warm-monomictic lake having a diameter of ca. 2 km and a mean depth at the depocenter of ca. 60 m, where three benthos cores were recovered. Contents of POP' s, total inorganic carbon (TIC), total organic carbon (TOC) and heavy metals were analyzed. Geochemistry and mineralogy also were studied in shallow sediments which corresponded to the decade of 50-60's, otherwise the beginning of industrial development of central Mexico; which is considered the possible source of emission of POP' s and heavy metals. Dioxin, furan, plaguicides and PCB' s contents were analyzed by a GC-MS applying USEPA methods. In the first 40 cm (n= 20) of the sedimentary column ( SC) the absence of POP' s was evidenced, applying a method detection limit ( MDL) of 5 μ g/ml for dioxin, furan and PCB' s. For plaguicides like chlordane and toxaphene the MDL was 0.5 μ g/ml and for plaguicides like DDT, aldrin, endrin, dieldrin, heptachlore and mirex the MDL was 5 μ g/ml. The MDL for HCB was 1 μ g/ml. The average (n= 30) for TIC, TOC and total carbon (TC) for the first 40 cm of the SC is as follows: TIC 2.4 %, TOC 3.7 % and TC 6.12 %. The average (n= 20) content (in ppm) of heavy metals for the first 20 cm of the SC is as follows: As 5.97, Cr 27.54, Cu 16.31, Ni 12.29, Pb 21.35 and Zn 82.46. These contents are roughly similar to the clarke of these metals in volcanic rocks. After the criteria of severe effect level ( SEL) of heavy metal in sediments, the content of these metals is below SEL levels. These results permit us to conclude that the sediments of SMO can be considered in unaffected state with respect to antropogenic contamination like POP' s and heavy metals. Consequently, Santa Maria del Oro Lake can be considered as a pristine reference in paleo-ecological and environmental investigations in western Mexico.
B33C-1428
Heavy metal Assessment and Their Speciation in Sediments of Lake Chapala, Mexico.
The presence of heavy metals Cd, Pb, Mn, Cr, Fe, Ni, Cu, and Zn in waters and the speciation of Cd, Pb, Cr, Ni, Cu, and Zn in sediments of several sites of the Mexican Lake Chapala as well as some physicochemical parameters reflecting water quality, are presented here. The sites were sampled on March 2007. Metals in sediments and their partition into chemical species was determined between five geochemical phases (exchangeable, carbonates, Fe/Mn oxides, organic matter and residuals) applying the Tessier' s sequential extraction technique. Sediment cores (n=10) taken from the depocenter between the years of 1998 and 1999 allowed evaluation of sediment uniformity (geochemistry, mineralogy and particle distribution). Cadmium, lead and chromium were found to be present significantly in both exchangeable and carbonate fractions in two sites indicating that these metals were introduced to the lake via anthropogenic activities during the period of 1960 through the first quarter of 2006. The Risk Assessment Code was applied to the two sites studied and it was found that both sites pose a high level risk of pollution since the metals bound to exchangeable and carbonate fractions in the cases of Pb and Cd comprise > 45%.
B33C-1429
Impact of ZnO and Ag Nanoparticles on Bacterial Growth and Viability
Hundreds of consumer products containing nanomaterials are currently available in the U.S., including computers, clothing, cosmetics, sports equipment, medical devices and product packaging. Metallic nanoparticles can be embedded in or coated on product surfaces to provide antimicrobial, deodorizing, and stain- resistant properties. Although these products have the potential to provide significant benefit to the user, the impact of these products on the environment remains largely unknown. The purpose of this project is to study the effect of metallic nanoparticles released to the environment on bacterial growth and viability. Inhibition of bacterial growth was tested by adding doses of suspended ZnO and Ag nanoparticles into luria broth prior to inoculation of Escherichia coli cells. ZnO particles (approximately 40 nm) were obtained commercially and Ag particles (12-14 nm) were fabricated by reduction of silver nitrate with sodium borohydride. Toxicity assays were performed to test the viability of E. coli cells exposed to both ZnO and Ag nanoparticles using the LIVE/DEAD BacLight bacterial viability kit (Invitrogen). Live cells stain green whereas cells with compromised membranes that are considered dead or dying stain red. Cells were first grown, stained, and exposed to varying doses of metallic nanoparticles, and then bacterial viability was measured hourly using fluorescence microscopy. Results indicate that both ZnO and Ag nanoparticles inhibit the growth of E. coli in liquid media. Preliminary results from toxicity assays confirm the toxic effect of ZnO and Ag nanoparticles on active cell cultures. Calculated death rates resulting from analyses of toxicity studies will be presented.
B33C-1430
Role of Natural Organic Matter in Regulating the Partitioning of Th(IV) and Pa(IV, V) on Aquatic Colloids and Nanoparticles
Nanoparticles and colloids are important intermediaries in the fate, transport and bioavailability of particle reactive trace metals and radionuclides in aquatic environments. However, the interaction between nanoparticles and natural organic matter (NOM) and how the quality and quantity of NOM affect the mobility and environmental behavior of trace elements remain poorly understood. Controlled laboratory experiments have been conducted to examine the role of NOM in governing the partitioning of Th(IV) and Pa(IV, V) between truly dissolved and different sized colloidal phases. Radiotracers, model NOM, including humic substances (HS) and exopolymeric acid polysaccharides (EPS), and ultrafiltration were used in the partitioning experiments of Th and Pa between the <1 kDa, 1-10 kDa, 10-100 kDa, 100 kDa-0.4μm and >0.4 μm fractions, thus allowing the calculation of distribution coefficients between particle (Kd) or colloid (Kc) and solution phases. Our results show that in both seawater and 0.7 M NaClO4 solution, Th(IV) has a higher distribution coefficient (Kd) between dissolved and particulate phases (with a logKd of 7.03) compared to Pa(IV, V) with a logKd of 6.05. Within the <0.4 μm dissolved phase, Th(IV) and Pa(IV, V) were mostly partitioned in the >1 kDa colloidal phase resulting in a logKc value of 6.08 and 5.70, respectively, for Th(IV) and Pa(IV,V). On average, about 4% of Th(IV) was measured in the <1 kDa fraction, but this fraction was up to 42% for Pa(IV, V). In the presence of HS and EPS (0.6 and 0.9 mg C/L) , however, the fraction partitioned in the <1 kDa become virtually the same (2-3%) for both Th(IV) and Pa(IV, V). The logKc value for Th(IV) and Pa(IV, V) was 7.05 and 7.06, respectively, in the presence of HS, and was 6.81 and 7.02 in the presence of EPS. While the partitioning of Th(IV) remained similar regardless of treatments, the change in the partitioning of Pa(IV, V) between dissolved and nanoparticles or macromolecules in the >1 kDa fraction resulted likely from the reduction of Pa(V), a more soluble form, to Pa(IV), a more particle-reactive form, by NOM. This experimental result has important implications for biogeochemical and environmental cycling of Pa(V,IV), which is being used as a tracer for ocean mixing and scavenging, and other redox sensitive trace elements in aquatic environments.
B33C-1431
The Involvement of Microbially Derived Extracellular Proteins in Nanoparticle Formation and Aggregation
While humans are newcomers to the field of nanoscience, microbes have been synthesizing functional nanoscale structures for billions of years. Bacteria have evolved the capability to produce proteins that can unite cellular processes with inorganic substrates, transfer electrons, template biomineralization, and facilitate adhesion. Biominerals are commonly nano-composite materials in which biomolecules such as proteins and/or polysaccharides act as a template to direct nanoparticle nucleation and growth. Understanding the capability of microbes to form nanoparticles and influence their reactive transport properties offers potential for bioremediation and materials synthesis applications. The identification of biomolecules and functional groups associated with biogenic nanoparticle formation in both environmental and laboratory systems is the objective of our research. Two such systems in which protein-nanoparticle interactions were studied are discussed. First, the biogenic reduction of selenium oxyanions to Se0 was studied in pure cultures of Veillonella atypica, Bacillus selenitireducens and Geobacter sulfurreducens. Biogenic Se0 nanostructures were observed as spherical, fibrillar, granular or amorphous aggregates, both in the cytoplasm or periplasmic space and extracellularly. These nanoparticles formed as protein-nanoparticle complexes that could be separated from the cells on the basis of density. A protein of ~39 kDa associated with biogenic nano-Se0 was recovered via polyacrylamide gel electrophoresis for characterization by MALDI-TOF mass spectrometry. Initial results suggest that this protein plays an integral, structural role in Se0 nanosphere formation. Second, the nanoparticulate products of bacterial sulfate reduction in a biofilm growing in minewater were investigated with multiple high- spatial resolution microanalyses. Biogenic zinc-sulfide nanoparticles exhibited evidence for rapid, highly efficient aggregation to form orders-of-magnitude larger spheroids. Analysis of these spheroids revealed a formative association between ZnS nanoparticles and microbially derived extracellular proteins. Direct protein extraction and isolation yielded a dominant ~37 kDa band for ongoing mass spectrometry characterization. Parallel experimental simulations of nanoparticle-amino acid interactions suggest an important role for cysteine-bearing proteins in promoting the aggregation of nanoparticulate metal-sulfides. Identification of microbial proteins that interact with natural or synthetic nanoparticles provides potential for synthesizing specific peptide sequences for technological and environmental applications, and sheds light into environmental nanoscale biomineralization processes that may significantly impact water quality.
B33C-1432
Chemical Structures of Kerogen and Their Changes During Thermal Evolution Investigated by Advanced Solid-state NMR Spectroscopy
Kerogen is the insoluble fraction of organic matter in rocks and is the parent material for petroleum. Chemical structural characteristics of kerogen constrain the ability of source rocks to generate bitumen, oil, and natural gas. It is important to understand changes in kerogen structure with increasing thermal maturity to evaluate the organic-geochemical mechanisms of hydrocarbon generation. However, kerogen's complex and cross-linked geomacromolecules cannot yet be characterized fully on a molecular level. In this study, we use advanced solid- state NMR techniques to investigate structural changes of a series of Type II kerogens from the New Albany Shale across a range of maturity. Functional groups are identified and quantified by quantitative 13C NMR using direct polarization, separation of aromatic and alkyl resonances by 13C chemical shift anisotropy filtering, and CH and CH2 signal selection. 1H-13C two-dimensional heteronuclear correlation (2D HETCOR) NMR provides information on the proton fractions and nanometer-scale heterogeneity. Specific functional groups such as aliphatic CH3, aliphatic CH2, aliphatic CH, nonprotonatic aromatics, and protonated aromatics are identified and quantified in kerogen. Aromatics connected to alkyls are detected specifically in 2D HETCOR spectra with gated decoupling. In kerogen 554-1, spin diffusion equilibrates the magnetization of its aromatic and aliphatic protons within ~20 msec, proving proximity on the nanometer scale. 2D HETCOR with spin diffusion on kerogen IL3 reveals that there are more aliphatic than aromatic protons, even though the fraction of aliphatic carbons is 18%. With increasing thermal maturity, carbonyls, aromatic C-O groups, and alkyls decrease while aromatics increase in abundance and fewer connections between alkyls and aromatics are observed.
B33C-1433
Structural Chemistry of Cation-Reacted Bacteriogenic UO2
The chemical stability of bacteriogenic uraninite, "UO2", is one of the seminal issues governing its success as an in-situ immobilization strategy in contaminated subsurface locations. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and disordered, likely to exhibit non-stoichiometry, and capable of structurally incorporating common ground water cations and U(VI). Such fundamental changes in mineralogy are expected to substantially impact its stability in ground water. In this study, the product of microbial U(VI) reduction under varying conditions of pH, carbonate and divalent cation concentration was investigated. To facilitate x-ray scattering and oxidation kinetics measurements, cleaning methods were investigated to separate the biooxide and organic components. The local and long-range atomic and nano-scale structures of the wet oxides have been measured using EXAFS, WAXS, XPS and TEM. The lattice parameter of the nanoparticulate phase is seen to be consistent with bulk UO2. The first oxygen shell is distorted, indicating a nonstoichiometric composition. A significant change in the lattice parameter and local structure is produced when bacteriogenic UO2 is reacted with divalent cations and NaOH. These findings suggest that bacteriogenic UO2 and its reactivity can be modified by groundwater composition.
B33C-1434
Effect of Natural Organic Matter (NOM) on Properties and Mobility of Aqueous Fullerene Nanoparticles (nC60)
C60 fullerene and its derivatives have been used in a number of consumer products and the predicted industrial- scale production of fullerene reaches tons per year. Aqueous fullerene nanoparticles (nC60) could be formed through direct contact of fullerene powder with water or through organic solvent exchange. Existing toxicity data of nC60 indicate that industrial-scale production of fullerene poses a potential threat to the environment. There is a need to evaluate the fate and transport of nC60 in the aqueous environment and its subsequent impact on the bio- and eco- systems. Our study aims to determine the effect of natural organic matter (NOM) on the nC60 entry pathway, physicochemical properties, deposition and mobility in the aqueous phase. Experimental conditions cover those typical of natural waters. Stable nC60 suspensions formed under four different conditions in the presence and absence of two major NOM components, humic acid (HA) and fulvic acid (FA), were thoroughly characterized for particle size, morphology, electrophoretic mobility, and UV absorbance. nC60 deposition experiments were carried out in parallel cross-flow chambers monitored by quartz crystal microbalance (QCM) and the nC60 mass deposition kinetics was studied in the absence and presence of NOM. Our study found that the size, structure and surface properties of readily formed nC60 changed fundamentally upon addition of NOM at environmental concentrations. For example, nC60 prepared through dissolution and removal of toluene solvent by sonication decreased in particle size, and the degree of particle size reduction was a function of solution chemistries. Bulk phase fullerene powder was directly dispersed into the aqueous phase as stable nC60 colloidal suspensions in presence of NOM at environmental concentrations in less than three days. In both cases, extremely small nC60 nanoparticles with diameter less than 10 nm were prevalently formed at specific solution conditions. The nC60 mass deposition followed zero-order kinetics onto silicon dioxide surface, at an nC60 concentration of 3 mg/L regardless of the NOM concentration (0 – 20 mg/L). The nC60 mass deposition rate decreased gradually in presence of increasing amount of NOM. For example in a solution condition of 10 mM CaCl2, nC60 was deposited onto silicon dioxide surface at a rate of 24 nghr-1 without any NOM, yet the rate was decreased to 20 nghr-1 in presence of 10 mg/L HA, and was further decreased to only 10 nghr-1 in presence of 20 mg/L HA. Our study indicates that NOM significantly increases the stability and mobility of nC60 nanoparticles in the aqueous environment.
B33C-1435
The Environmental Fate of C60 Fullerenes: A Holistic Approach
The manufacture and use of carbon-based nanoparticles, for which C60 fullerenes can be considered a proxy, has grown exponentially in the past decade, and nanotechnology is now a multi-billion dollar industry, spanning disciplines such as cosmetics, biotechnology, and agriculture. Despite this, almost nothing is known of the fate of these compounds in the environment. Based upon the strong radical scavenging properties of many of these substances there are a variety of microbial and photochemical-mediated oxidative fates that will transform the physicochemical properties and control the residence time of these compounds in nature. It is essential that these fates, as well as the fates of the products of the degradation of carbon nanoparticles, are known. For instance, conversion of C60 fullerenes to hydroxylated or carboxylated analogs will shift the manner in which they partition between soils and sediments and water as well as how they interact with cell membranes. This paper combines our findings on the microbial activity of C60 fullerenes, one of the most common types of manufactured carbon nanoparticles, along with recent literature to develop potential chemical decay trajectories in oxidative environmental settings. We show what is known about the environmental fate of this type of nanomaterial and also areas where further research is needed.
B33C-1436
Photocatalytic properties of Small Sized TiO2 Supported on Clays for the Degradation of Indoor Pollutants: Toluene and Limonene.
Novel materials for the degradation of hydrophobic organic pollutants by photocatalytic oxidation were developed. Intercalation of TiO2 on clays provide favorable properties to the photocatalyst due to the adsorption properties of the clay, its content of mesopores that enables pollutant trapping and its further interaction with TiO2, leading to mineralization. Particularly, we are interested in hydrophobic pollutants for which bare TiO2 had been shown less effective than for polar species. Synthesis was carried out by the sol-gel method using titanium isopropoxide (Ti(OC3H7)4 ) as precursor; the formation of anatase phase was achieved by hydrothermal treatment. Clays used were Hectorite [SHCa-1, Na0.4Mg2.7Li0.3Si4O10(OH)2 ] from San Bernardino Country, California, USA and Kaolinite [KGa-1b, Al2Si2O5(OH)4 ] from Washington Country, Georgia, USA. Samples characterization was conducted using XRD, SEM, XPS, ICP-OES. Our results showed a strong intercalation of TiO2 on hectorite and a poor one on kaolinite. Nanoparticle size obtained on hectorite was of 9.6 nm compared to 17.39 nm of commercial TiO2 (Degussa P25). Photocatalytic experiments were realized by the FTIR-ATR technique monitoring the concentration of the organic compound on the surface of the material. Results were compared with commercial TiO2 (Degussa P25). For limonene bare TiO2 showed better degradation rates, while for toluene, degradation rates using TiO2 supported on clays were higher.
B33C-1437
Bacterial Physiology and Viability in the Presence of Quantum Dot Nanoparticles: Towards an Environmental Perspective
Quantum dot nanoparticles represent a broad class of engineered semiconductor nanomaterials under intensive development for multiple applications in the device and biomedical industries. Quantum dots have been studied in biological systems, particularly for bioimaging applications. Nevertheless, biological interactions with these materials in a more environmental context remain mostly unexplored. Understanding the long-term abiotic and biotic fate of this class of nanomaterials is necessary to forsee their potential environmental impact. Towards this goal, we present our initial studies of the effects of polymer-coated ZnS/CdSe core-shell nanoparticles (quantum dots) upon Pseudomonas aeruginosa, a bacterial species common throughout the environment. Along with viability measurements, we discuss the results of physiological fitness measurements, which may be more indicative of long-term environmental impacts. The effect of bacteria upon the physical and chemical state of the quantum dots is also examined.
B33C-1438
Surface Energetics of Calcite {10-14} Faces upon the Adsorption of succinic Acid
Interactions of calcite with carboxylic acids occur widely and play an important role in many natural processes such as biomineralization and metal ion sequestration. The main contributor to the adsorption energy is the electrostatic interaction between the deprotonated carboxylic group of the organic acid and Ca2+ ions on the mineral surface. Although a number of experimental studies have identified the distribution of adsorption sites on calcite, the energetics of the surfaces of this mineral and the orientation of the organic molecules after the adsorption is still poorly understood. We have used empirical-potential methods to calculate calcite step energies for different step directions on {10-14} surfaces. In the presence of succinic acid (SUC), the less common and polar [421] and [010] directions develop and are shown to be more stable than the periodic bond chain directions. Three different adsorption cases were tested for each step: (i) one SUC molecule in the center of the step, (ii)a neutral SUC molecules chain along the step, (iii) a deprotonated SUC molecules chain along the step. These results indicate that SUC stabilizes steps in the directions parallel to [421] and [010] by lowering the step free energies. Adsorption energies of SUC were calculated along different kinds of steps with decreasing numbers of SUC molecules. The results showed a positive correlation between the number of SUC molecules and the stability of steps along [421] and [010] directions, and an insignificant dependence of step stability upon the amount of SUC molecules for cleavage directions.
B33C-1439
Isolation of Strain MLTeJB From Mono Lake, California, a Dissimilatory Tellurite Respiring Prokaryote.
Previous investigations on the dissimilatory reduction of Te-oxyanions have been constrained by the inhibtory effects of circa 1.0 mM concentrations of either Te(IV) or Te(VI) upon growth of established cultures. Therefore we initiated new enrichments using anoxic Mono Lake mud supplemented with 10 mM Te(IV) as the electron acceptor and lactate as the electron donor. Sediments turned black with time owing to the formation of Te(0), microscopic examination of which confirmed the presence of both shards, rosettes, and nanospheres of Te(0). The enrichment was subcultured several times in liquid medium and then streaked onto solid medium and incubated in an anaerobic chamber. Isolated black colonies were re-streaked several times, and thence inoculated into liquid medium. However, growth in liquid medium required the presence of a small amount of solid phase, which included a plug of either agar, phytagel, or glass beads. Growth resulted in oxidation of lactate to acetate, formate and CO2 with the reduction of Te(IV) to Te(0). The isolate, strain MLTeJB was a non-motile rod that stained Gram positive, and formed copious exogenous deposits of Te(0) nano-shards and rosettes. Further details on the physiology of this organism will be presented.
B33C-1440
Preliminary non-invasive measurement of magnetic susceptibility of the frontal lobe: a possible antecedent marker for Alzheimer's disease.
It is generally recognized that the amount of iron in the brain increases with age. Magnetic work on post mortem tissue from Alzheimer's patients has indicated the presence of magnetite and there seems to be a direct relation between magnetite and Alzheimer's disease. We measured the magnetic susceptibility of the frontal lobe of subjects using a sensitive susceptibility meter SM30 placed against the forehead. This is a very simple and speedy observation normally made by geologists to investigate rock outcrops. Preliminary measurements were performed on 53 persons, whose ages ranged from 3 to 92 and included several Alzheimer's patients. The magnetic susceptibiIity is negative, reflecting the dominant diamagnetism of brain tissue. The positive susceptibility of ferrimagnetic material present therefore reduces this negative number. Interestingly the magnetic susceptibility of 3 of the Alzheimer patients was among the 5 lowest negative susceptibilities measured. The mean value of magnetic susceptibility of the population is close to -6e-6 SI units. Alzheimer patients show slightly higher values, closer to -5e-6 SI units. The susceptibilities of the Alzheimer's patients can be distinguished at one standard deviation from the whole population tested. The mean susceptibility of the Alzheimer's patients is also greater than the mean value from patients of the same age group, but it cannot be distinguished at one standard deviation. We speculate that the source of the positive susceptibility contribution may be magnetite. We suggest that extensions of this observation may serve as an antecedent marker of the onset of Alzheimer's disease.