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The Center for Environmental Molecular Science focuses
projects within two principal areas: | |||||||||
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2. Engineered Systems and Materials | |||||||||
Further, we can break this down into six groups. For detailed projects, see the following areas. | |||||||||
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a. Defect Sites in Sorption Mechanisms b. Role of Inorganic and Organic Ligands on Sequestration c. Biological and Microbially Mediated Processes d. Engineered Porous and Layered Materials e. Molecular Studies of Waste Containment and Corrosion f. Technique Development in Environmental Molecular Science | |||||||||
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- J. D. Kubicki (PSU), J. Hering (Caltech) As(III) and As(V) were modeled with molecular orbital calculations in both monodentate and bidentate bridging configurations with Al- and Fe-hydroxide dimers to approximate sites on the surfaces of amorphous Al(OH)3 and Fe(OH)3. Gibbs free energy change estimates of adsorption were consistent with the preference of As(III) for hydrous ferric oxide (HFO) over Al(OH)3. Model results were compared to results of EXAFS spectra. The bidentate bridging configuration was most consistent with EXAFS data, but the model DGads suggest that the monodentate configuration may be stable under certain conditions. | |||||||||
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[Fe2(OH)4(OH2)4AsO4 (H2O)4]1- minimum energy structure for As(V) in a bidentate bridging configuration. | ||||||||
and Multicrystalline Calcite Surfaces" -D. Strongin (Temple), V. Chada (Temple), D. Hausner (Temple), A. A. Rouff (SBU) Personnel in the Strongin and Reeder group at SUNY and Temple are collaborating on research focused on understanding the adsorption and reaction of divalent metals on cleaved and multicrystalline (i.e., powder) calcite surfaces. In the Temple University laboratory, research largely utilizes x-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS) and more recently, atomic force microscopy (AFM) to understand the adsorption of Cd(II) and Pb(II) on the 1014 cleavage surface of Calcite. Recent results using XPS and ISS have shown that these metal species under certain experimental conditions form stable solid solutions in the near surface region of calcite. The details of the adsorption behavior are highly dependent on the pH and solute concentration of the solution. The Strongin and Reeder group will be conducting EXAFS experiments at the NSLS to determine the structure of Cd in the near surface region. |
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-C. P. Grey (SBU), R. J. Reeder (SBU), M. A. A. Schoonen (SBU), B. Phillips (SBU), J. Fitts (BNL), Y. Paik (SBU), K. Cole (Fairfield Univ.), U. G. Nielsen (SBU), K. Julmius (SBU) NMR spectroscopy has been applied to examine the local and bulk structures of the manganese and iron oxide minerals found as major components in soils. These materials represent sorption sites for a wide range of toxic ions including arsenates and radioactive actinides. These materials are paramagnetic and are often considered difficult to study by NMR. We have shown, however, that the interactions between NMR spins and the unpaired electrons in these systems may be exploited to provide detailed structural information (see section 3.f.) For example, lithium-NMR has been used to show that Li+ forms an inner-sphere complex on goethite following ion-exchange at pH 7 and above. Detailed studies of a wide range of iron oxides and manganates are in progress. The sorption studies are being expanded to include phosphate, selenate anions and Pb2+ and Cd2+ cations. |
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-R. J. Reeder (SBU), E. Elzinga (SBU), D. Tait (LANL), D. Morris (LANL) Sorption experiments have been conducted in model systems to evaluate the importance of U(VI) uptake by calcite and related calcium carbonate phases, with the goal of assessing the role of carbonate solids in sequestration of mobile uranium under surface conditions. Separate experiments were conducted for adsorption (at bulk equilibrium with calcite) and coprecipitation (at low to moderate supersaturation with respect to calcite). High total solubilities of U(VI) are possible before precipitation occurs (500 mM at pH 8.3), owing to the formation of stable aqueous uranyl carbonate complexes. EXAFS and luminescence spectroscopic methods were used to assess the coordination of sorbed and coprecipitated uranium. Results of both sorption and coprecipitation studies have demonstrated the occurrence of multiple uranyl species, similar in configuration to the uranyl triscarbonato moiety, but with one or more monodentate CO3 groups. The presence of multiple species suggests that multi-phase behavior could be expected for release of U(VI) to solution. Results have been reported in two recent papers (Elzinga et al., 2004; Reeder et al., in press). |
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-A. A. Rouff (SBU), R. J. Reeder (SBU), E. Elzinga (SBU) Pb(II) exhibits strong interaction with calcite both via adsorption and co-precipitation. As part of the PhD thesis research of Ashaki Rouff, several studies have been undertaken to evaluate the relationship between adsorption and co-precipitation of this toxic metal with calcite. Recent studies have evaluated the pH dependence of Pb(II) adsorption with calcite, and the influence of ionic strength and background electrolyte. Pb-reacted sorption samples were examined using EXAFS spectroscopy to evaluate the structure of surface complexes. A maximum in sorption was observed near pH 8.2, with decreasing sorption at higher and lower pH values. Evidence of minor coprecipitation was found, with the largest fractions at pH 7.2 and 9.4 and lowest at pH 8.2 (corresponding to the PZC). The pH dependence of sorption appears to be strongly correlated with the abundance of the neutral PbCO3 aqueous complex. EXAFS results indicate that Pb(II) forms inner-sphere surface complexes with 3 or 4 nearest oxygen neighbors at 2.34 Å. This coordination number and interatomic distance are consistent with a trigonal or square pyramidal complex in which a lone electron pair is stereochemically active. Similar sorption complexes on oxides have been observed by other workers. In contrast, Pb(II) coprecipitated with calcite occurs in octahedral coordination with oxygen atoms as it substitutes in the unique Ca site of calcite. 
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-V. Alexandratos (SBU), E. Elzinga (SBU), R. J. Reeder (SBU) Arsenate (AsO43-) and its analog phosphate (PO43-) both interact strongly with calcite. Phosphate adsorption with calcite has long been recognized as inhibiting calcite growth and dissolution. Scanning-probe microscopy studies have suggested that inhibition results from formation of inner-sphere surface complexes in steps, effectively 'pinning' their movement. However, at sufficient supersaturation, we have demonstrated that arsenate is incorporated into the calcite. We have begun experiments to identify the mechanisms encompassing adsorption and coprecipitation at the calcite surface. In one set of experiments, arsenate was allowed to coprecipitate with calcite single crystals with the dominant form (1014 ). Differential interference contrast imaging revealed that growth spirals formed at this surface, with two dominant orientations of mostly straight steps. Using micro-XRF we determined that arsenate is preferentially incorporated at one set of steps relative to the other. Models of the different step types indicate differences in the arrangement of Ca atoms and the orientation of CO3 groups, thereby creating different coordination geometries. Consequently, arsenate ions apparently exhibit a preference for adsorption at a particular step type. We are presently conducting adsorption experiments (in the absence of growth) to identify the structure of surface complexes, to identify how arsenate binds at the surface. This should provide insight to the structural factors that result in the observed surface site preferences. |
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- Schoonen, M. A. A (SBU), F. M. Michel (SBU) The goal of this project is to understand how phase transformations in metal sulfides affect associated metal impurities. For example, in natural anoxic sediment iron sulfides are a host for metals (e.g., Ni, Cr, Cu, Co) and metalloids (As, Se, Te). The initial precipitate in sediments is an amorphous FeS phase, which subsequently transforms into pyrite, possibly via several intermediate Fe-S phases. The fate of the metals and metalloids associated with the initial phase is not clear. Student Marc Michel has started on this project. In the first year he has developed new laboratory protocols and installed new equipment for the synthesis and handling of metal sulfides. As part of his introduction to this area of research he developed a new protocol for the synthesis of MnS, a material of interest because of its electronic structure and possible use as a photocatalysts. While this remains to be explored, MnS may be suitable as a photocatalyst for the reduction of organic solvents. MnS has been demonstrated by collaborators at Havard to reduce CO2 (collaborators Scot Martin and Cynthia Friend, funded by NASA). Marc will participate in the NSLS EXAFS workshop this June and has already worked with Eef Elzinga on the reduction of EXAFS data collected on his MnS precipitates. These EXAFS data were collected at NSLS by Delaware University students, supervised by collaborators Drs. Donald Sparks and Mike Borda. |
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- Schoonen, M. A. A. (SBU), C. Cohn (SBU), R. Laffers (SBU), Mueller (SBU), Wimmer (SBU) It has long been known that silica or quartz particles induce the formation of hydroxyl radicals (OH-) when emerged in water or lung fluid. Quartz-water induced radical formation is thought to be one of the key steps in the development of silicosis. Given the importance of silicosis as an occupational health problem, it is not suprising that radical reactions involving quartz have been studied extensively. A recent discovery in Schoonen's research group indicates that pyrite, fool’s gold, is perhaps an even more effective producer of OH- when emerged in water. RNA and DNA, used as a proxy for biomolecules in general, are rapidly decomposed in the presence of pyrite. Pyrite-induced hydroxyl radical formation has potentially several important implications. Given that pyrite is the most abundant iron sulfide mineral on Earth, a major mineral component in coal, a host mineral for gold, and a common mine waste, exposure to pyrite dust is common in mines, power plants, ore processing facilities, and in the proximity to active and inactive (coal) mining areas. Pyrite-induced radical formation may also play a role in natural environments. Our work on pyrite-induced radical formation provides an impetus to to develop a unique, world- class effort in mineral-based radical chemistry. I currently have one student devoted to this effort. The student, Corey Cohn, a former Stony Brook undergraduate and Fullbright scholar, will work closely with me to develop a molecular-scale understanding of the reactions on the pyrite surface that lead to the formation of hydroxyl radicals. A new graduate student, Richard Laffers, will rejoin our group this summer and evaluate if other related mineral show the same ability to induce radical formation. We have initiated a new collaboration with Drs Mueller and Wimmer in the Department of Microbiology as part of this effort. Their expertise in the stability of biomacromolecules and the techniques to analyze for fragmentation of biomolecules, such as RNA and DNA, allows us to evaluate the effect of pyrite on the stability of these model compounds. Given that OH radical is also a very potent oxidant of organic solvents, we also plan to study the fate of several model organic molecules in the absence and presence of pyrite. This summer we will have a summer scholar work on a small study related to mineral-induced radical formation. An additional student may be available in the School of Medicine. Through a new collaboration with Tom O'Riordan, Department of Pulmonary Medicine, we are embarking on some limited tests to determine if pyrite exposure leads to inflammation. This work is done by studying the effect of pyrite on a line of cells available in the School of Medicine. To build up our research infrastructure to conduct research on mineral-induced radicals, I will contribute to writing a grant application to acquire an X-ray Fluorescence Analyzer (XRF) and an Electron Paramagnetic Resonance Spectrometer (EPR). To conduct some preliminary EPR experiments we have started a new collaboration with researchers at Hunter College. Ultimately, I hope to establish a research program in this area research that can attract funding not only from NASA, DOE and NSF, but also from NIH. This effort may grow to become a multidisciplinary research program that draws on expertise in Geosciences, Chemistry, and several biomedical disciplines. |
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-Schoonen, M. A. A. (SBU), M. Borda (Univ. Delaware), D. Sparks (Univ. Delaware) Collaborators Mike Borda and Donald Sparks at the University of Delaware have initiated a project to understand the surface chemistry and reactivity of Mn-oxide phases relevant to soils. Schoonen has been contributing to this effort by determining the surface charge development on these phases as well as by determining their particle size. The experiments are conducted using our light scattering instrument. This instrument was upgraded in 2003 with a combination of EPA-STAR and CEMS funds. |
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- Schoonen, M. A. A. (SBU), M. Wander, D. Strongin (Temple), J. Kubicki (PSU) Fe(II) sorbed onto Fe(III)-oxide or hydroxide phases is a much more potent reductant compared to dissolved Fe(II). This enhanced reducing potential is thought to be of importance in the reduction of various organic pollutants in anaerobic zones within aquifers. As summarized in a recent review, it is has been noted that the reactivity of sorbed Fe(II) increases upon ageing before exposure to the pollutant. We speculate in the review that this may be due to the formation of Fe(II) clusters or nano-phases on the Fe(III) surface. This summer a new graduate student, Matthew Wander, will join CEMS and start a experimental study to investigate the changes in Fe(II) sorbed onto Fe(III) phases. This work will be conducted in conjunction with Dan Strongin and may also involve a modeling component directed by Jim Kubicki. |
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-S. Cochiara (SBU), J. Feng (SBU), G. Miles (Alfred Univ.), L. Fleischer (SBU), B. Phillips (SBU), C. P. Grey (SBU) In this project we are using 19F NMR spectroscopic techniques to characterize fluoride substitution on reactive mineral surface sites, focusing on Al-oxyhydroxides and dioctahedral clay minerals. Previous work has shown that in aqueous suspension fluoride can substitute for both bridging hydroxyls and terminal water groups on Al-oxyhydroxide surfaces. These environments can be distinguished by 19F MAS-NMR techniques, possibly providing a structural probe of the labile surface sites. We are extending this work to clay minerals to determine whether fluoride can also substitute for oxygens in the silicate layers of clay minerals. Previous studies based on batch experiments showed significant sorption of fluoride to the kaolinite surface. However, in pF stat experiments we do not observe fluoride sorption isotherms, but are finding instead evidence for very rapid fluoride-promoted dissolution. 19F NMR will be used to determine which sites are being attacked by F, leading to dissolution. We are also extending the work on Al-oxyhydroxides by synthesizing crystals with distinct morphologies to determine how surface reactivity varies between neutral basal surfaces and sites on crystal edges and steps. |
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-R. Reeder (SBU), J. Parise (SBU), I. Bull (SBU), A. Celestian (SBU) A detailed knowledge of the sorption mechanism for actinyl species is a crucial first step to evaluating their uptake potential by zeolite phases and for subsequent evaluation of their role in attenuating long-term transport of radionuclides near high-level waste sites such as Yucca Mtn where large amounts of clinoptilolite and mordenite are present. A number of studies have documented uptake of highly charged actinides, occurring as dioxo cation species such as UO22+ and NpO2+, by zeolites. Both adsorption at surface sites and exchange into channel/pore sites have been proposed as important uptake mechanisms. However, direct characterization of binding mechanisms and uptake processes is lacking. Ion-exchange experiments are investigated in aqueous, melt and methanol media, with the goal to promote uranyl-exchange as the principal sorption process. It is clear at this early stage that development of protocols to carefully control the chemistry of exchange, including control of dealumination of zeolitic frameworks at low pH and exclusion of CO2 to avoid surface precipitation is required. Successful uranyl exchange will provide crystallographic models accurately defining the cation-zeolite interaction. These crystallographic models will be applied to provide a "ground truth" for interpretation of EXAFS data, collected from samples with environmentally relevant levels (ppm) of uranyl. Preliminary results include the successful occlusion of the uranyl nitrate salt into NH4-mordenite and the assessment of surface sorption as the only process involved with zeolite RHO, these samples await EXAFS analysis. |
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Salicylic and Phthalic Acids Complexed to Al3+" - C. C. Trout (PSU) and J. D. Kubicki (PSU) A method was developed for studying the carboxylic acid surface complexes using UV Raman. Carboxylic acids were adsorbed to Al2O3 and comparisons between solution and adsorbed complexes were examined. Various possible types of complexes for the acid surface complexes were modeled with hybrid molecular orbital/density functional theory calculations. The assignments acid surface complexes were based on the best fits between experimental and model vibrational frequencies. | |||||||||
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Possible surface complex of phthalic acid adsorbed onto Al2O3 based on comparison of experimental and model vibrational frequencies. | ||||||||
- G P. Halada (SBU) and C. Eng (SBU) The stability of uranium-organic complexes is extremely important in development of environmental remediation technologies and in understanding the transport and fate of contaminants in the environment. The stability of the complexes is affected by electron transfer reactions caused by bacterial activity and by redox reactions with other compounds in soil, groundwater and environmental corrosion products. Changes in pH, and hence the oxidizing or reducing character of the local environment, also have profound effects on uranium-organic complexes. An excellent way to understand the stability and bioavailability of such complexes is with electrochemical techniques, such as cyclic voltametry and potentiodynamic analysis. Though these techniques provide information on kinetics of electron transfer and reduction of complexes, they provide no information on the structure of the products formed, and, hence, interpretation of the data is extremely difficult. Through a unique in situ combination of electrochemical analysis and Raman spectroscopy with quantum mechanical molecular modeling using Density Functional Theory, the redox-driven transformation of uranium-organic complexes, primarily involving aromatic structures, is studied. |
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-G. P. Halada (SBU), A. J. Francis (BNL), C. J. Dodge (BNL), J. Gillow (BNL) This is a joint project focused on analyzing the effect of pH and environmental factors on transformation of uranium-organic complexes. It is a continuation or research begun under a joint Natural and Accelerated Bioremediation (NABIR) program. Recently, I have also begun to collaborate with Brian Phillips on this research. With him, we will perform NMR analysis on uranium-organic complexes in solution, including formulations using 13C and 17O, and compare the results to those generated through Raman spectroscopy. The results will be used to provide input for molecular modeling collaboration with James Kubicki. The graduate student working on this project is to attend the workshop on molecular modeling at Pennsylvania State University in August. |
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- G. Vazquez (BNL), C.J. Dodge (BNL), A.J. Francis (BNL) Inorganic polyphosphates (polyP) are simple linear polymers produced by a wide variety of microorganisms and are distributed throughout the bacterial cell. One of their many biological functions is to act as a chelator of metals. In this study we investigated the interaction of equimolar short chain polyP (1400-1900 Da) with uranium. U-Poly-P sample exhibited two broad inflection points at 1.0 and 1.5 mmOH-/mmH+ indicating complexation occurred at a slower rate compared to U-phosphate. Elemental analysis (U and P) of the solution at pH 3.2 (unadjusted), 4.5, 6.0, 8 and 10 showed gradual solubilization of the U-polyP complex with increasing pH. The precipitate contained varying P:U ratios as a function of pH, indicating the presence of different uranium phosphate phases. EXAFS analysis of the U-polyP complex showed a mixed-phase uranium hydroxophosphato species, in contrast to uranium phosphate resulting from the interaction of uranium with monophosphate. These results suggest that the mechanism of complexation between uranium and PolyP is different than with uranium and monophosphate. |
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- Y. J. Lee (SBU), E. Elzinga (SBU), R. J. Reeder (SBU) Previous experimental studies have demonstrated that aqueous Cu(II) sorbs strongly on calcite, forming inner-sphere Jahn-Teller-distorted octahedral surface complexes. Cu(II) is also known to bind strongly with natural organic matter (NOM) that is present in many near-surface environments. As part of the PhD thesis research of Young Lee, we carried out systematic uptake experiments to evaluate the role of NOM (specifically Suwannee River humic acid) on Cu sorption onto calcite. Previous workers have proposed that ternary surface complexes, either metal-bridged or ligand-bridged, are important in metal-NOM binding to oxides and hydroxides. Separate sorption experiments demonstrated that NOM sorbs strongly to calcite at the pH studied (8.3), with rapid uptake kinetics. Furthermore, desorption was found to be extremely limited upon resuspension in NOM-free solutions. At pH 8.3 the presence of NOM systematically decreased Cu(II) sorption onto calcite, and we attributed to formation of Cu-NOM aqueous complexes. EXAFS and XANES spectroscopies were used to evaluate the local structure of Cu surface complexes in NOM-containing and NOM-free systems. The EXAFS fit results suggest that the local coordination of sorbed Cu(II) is very similar in the systems with and without NOM. Careful analysis of XANES spectra shows subtle differences, but insufficient to suggest the formation of Cu-NOM ternary surface complexes. The results pose the interesting question of why Cu(II) exhibits a preference for CO3 ligands when sorbed at the calcite surface but a preference for NOM when dissolved in solution. The explanation may be that, when adsorbed onto calcite, the available functional groups of NOM are modified so as to have less capacity to bind with Cu. |
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- B. Phillips (SBU), Y. J. Lee (SBU), R. J. Reeder (SBU) Interaction of organic molecules with mineral surfaces during precipitation can play an important role in contaminant transport and retention processes. In addition to exerting control on the precipitating mineral phase and morphology, organic ligands can affect metal incorporation by complexing with the metal in solution and by altering the properties of the mineral/fluid interface. We are investigating the effect of organic molecules on calcite precipitation; ligands containing carboxylate groups exhibit strong sorption to the calcite surface and many significantly inhibit calcite growth. Coprecipitates of calcite with citrate were synthesized by the constant addition method and studied by NMR spectroscopic techniques. A small amount of the coprecipitate was subsequently re-dissolved in high-purity HCl solution and analyzed for citrate by ion chromatography, which show the calcite contains approximately 0.5 wt. percent citrate. The 13C{1H} CP-MAS spectra of the calcite/citrate coprecipitates at natural 13C abundance contain broad peaks at chemical shifts near 183, 78, and 47 ppm consistent with the carboxyl, central C-OH, and secondary carbons of citrate. In addition, a narrow peak of similar intensity occurs near 168.7 ppm, corresponding to carbonate that must occur in close spatial proximity to hydrogen. However, 1H-NMR spectra are dominated by signals from quasi-rigid water molecules. Comparison with samples prepared in D2O and without citrate in H2O, indicate that approximately five water molecules accompany each citrate in the structure. Detailed examination of the 13C{1H} cross polarization dynamics and 2-dimensional 13C{1H} heteronuclear correlation (HETCOR) spectra on samples prepared with 13C-enriched carbonate show unambiguously polarization transfer between the carbonate carbons and hydrogen on the citrate. In particular, the carbonate trace in the HETCOR spectra of a sample prepared in D2O contains a broad spinning sideband envelope consistent with the methylene protons on the citrate. These data indicate that the citrate is bound in the calcite structure, with citrate-carbonate distances of a few Å. Some additional data were obtained for incorporation of 13C-enriched aspartic and glutamic acids, present at concentrations about 50 times lower than observed for citrate, whereas signal from phthalic acid could not be detected. These results suggest that, in addition to metal-ligand complexation, the structural role of water and hydrogen bonding interactions may need to be considered to understand organic/calcite interactions. |
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- N. Fisher (SBU), S. Baines (SBU), B. Twining (SBU), C. Jacobsen (SBU Before metals can exert toxic effects or serve as nutrients they must first be accumulated from the environment by organisms. In aquatic systems, the greatest bioconcentration of metals occurs at the base of the food chain, that is in phytoplankton and other microorganisms, which can concentrate some metals up to one million fold out of ambient water. These organisms can then introduce metals into the food chain when herbivores consume them. Understanding the trophic transfer of metals and metalloids is necessary to understand the geochemical cycling and toxic or nutritive effects of metals, as well as understanding the link between contaminants and human health. Through radiotracer experiments, we have demonstrated a clear relationship between the cytological distribution of elements in phytoplankton cells and their assimilation in herbivores (Fig. 1). In modeling exercises, we have also demonstrated that diet can account for a substantial fraction, sometimes nearly all, of the metal accumulated by marine animals. These studies underscore the importance of quantifying the concentrations and cytological distributions of metals in phytoplankton cells. However, analyzing metal concentrations in phytoplankton in natural waters is greatly complicated by the presence of co-occurring cells of different species, as well as of abiotic particulate matter, that are of comparable size. We have therefore developed a new method to quantify the trace element composition of oceanic cells and have field tested this method in coastal and open-opean waters. This method, synchrotron-based x-ray fluorescence microscopy, is able to detect sub-attomole concentrations of metals in individual cells and can simultaneously produce 2-D maps describing their distribution in cells (Fig. 2). SXRF analyses of cells will generate valuable information on the elemental composition of phytoplankton cells in diverse natural waters that can be used to better understand the interactions of metals with aquatic organisms. | |||||||||
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Figure 1. Relationship between assimilation efficiency (%) of ingested elements in marine copepods and their cytoplasmic distribution in diatom prey. | ||||||||
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Figure 2. An example of SXRF false color element maps of 10 elements in a centric diatom from the Southern Ocean. Also included for reference are light and epifluorescence (blue excitation) micrographs of the cell. | ||||||||
Mixed Wastes: Actinide Speciation and Waste Volume Reduction (DOE) - G. P. Halada (SBU), A. J. Francis (BNL), C. J. Dodge (BNL) | |||||||||
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This new three year program will involve spectroscopic analysis and modeling of
soils contaminated by actinides and model materials containing multiple oxidation states
of Pu and other transuranics subjected to microbial activity. The first stage of this work will
involve development of an electrochemical analysis capability at BNL in the radiation laboratory
in Environmental Sciences. Molecular modeling at Stony Brook and spectroscopic analysis at BNL
will also be used to determine the mechanism of transformation of both model compounds and site-specific contaminated soils.
In addition to these, I have been performing some preliminary analyses and meeting to discuss two additional collaborations; (1) Electrochemical Studies of Corrosion Protective treatments for Pyrite Surfaces, with Martin Schoonen, and (2) Raman/IR Spectroscopic Analyses of Arsenic and EDTA Complexes in Plant Tissues, with Mark Fuhrman at BNL and graduate student Marianna Kissell. |
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- J.B.Gillow (BNL), B. Larson (SBU), M. Lerotic (SBU), S. Wirick (NSLS), C. Jacobsen (SBU), A.J. Francis (BNL) The bacterial genera Clostridia and Bacillus are being investigated using soft x-ray spectromicroscopy at the NSLS X1A beamline by a team of CEMS researchers at BNL and SBU. Both of these genera are found in the natural environment and produce spores which are resistant to heat, desiccation, and radiation. These spore forming bacteria play an important role in the biotransformation of radionuclides and toxic metals in wastes. Soft x-ray scanning transmission spectromicroscopy (STXM) at the carbon 1s-electron absorption edge using the x-ray microscope at NSLS SBU beamline X1A was used to gain spatial information (~30nm) regarding carbon speciation at the sub-cellular level i.e., the bacterial cell, in particular spores and intracellular carbon-storage compounds such as polyhydroxybutyrate. The goal is to map the molecular chemical features not detectable by conventional methods and then to perform contolled laboratory studies to determine the effect of stress and contaminants on bacterial cells. Initial results are summarized in figure 1. The strict anaerobe Clostridium sp. was grown to the late exponential growth stage and recovered by centrifugation and then examined using a wet-mount at X1A. Subtle carbon chemistry was not detectable without using the principle component (PCA) and cluster analysis method developed for application to STXM data by Lerotic and Jacobsen. These studies are continuing in a systematic manner with the next step the analysis of predominant chemical constituents of spores (dipicolinic acid and calcium dipicolinate). |
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- M. Kissell (SBU), M. Fuhrmann (BNL), R. J. Reeder (SBU) Varieties of the common fern Pteris have been identified as hyperaccumulators of arsenic. Arsenate (AsO43-) is apparently taken up by the phosphate pathway, however, it is observed that the As(V) is reduced to As(III) and sequestered in the leaves. As part of the thesis research of Marianna Kissell, experiments have been conducted to evaluate the kinetics of As(V) reduction, as well as the re-oxidation of As(III) to As(V) as plant metabolism ceases upon death. Studies have also been undertaken to identify the location and chemical form of sequestration of the As in the leaf cells. Reduction is monitored using XANES spectroscopy of living plant material. Results indicate that kinetics of reduction are very rapid. The onset of reduction can be identified within 4 hours, and >50% As(V) is reduced to As(III) within 1-2 days. A small fraction of As(V) persists in the leaves even after 8 days. Upon plant death, >90% As(III) re-oxidation to As(V) occurs within several months. EXAFS reveals that the As(III) is coordinated to 3-4 oxygen atoms in its first shell, and the re-oxidation product also has oxygen in the first shell. Ongoing studies will also assess the uptake of As(III) species and track any transformations. |
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- M. Fuhrmann (BNL), D. Singer (Stanford Univ.), T. Lanzirotti (Univ. of Chicago), L. Miller (NSLS/BNL), N. Marinkonic (NSLS/BNL) As a technique to remediate soils, uptake of Pb into plants can be greatly increased by application of EDTA to the soil. It has been unclear if the Pb-EDTA complex remains intact after uptake. We have applied synchrotron based spectroscopy techniques to examine this problem. Microbeam x-ray fluorescence tomography of plant roots showed the distribution of Pb while microbeam Fourier Transform Infrared Spectroscopy indicated the distribution of EDTA within the same root. Bulk and Attenuated Total Reflectance FTIR spectroscopy were used to fingerprint the various metal-EDTA complexes that could be present. Pb-EDTA was found in liquid pressed from plant leaves. When bare plant roots were immersed in Na-EDTA solution, leaf liquid contained Ca-EDTA indicating that the Na exchanged for Ca, probably disrupting membranes containing the Ca as a structural cross-linker. In roots, FTIR maps consistently showed EDTA in the cortex but not in the stele. Pb, however was observed in portions of the stele. This implies that some Pb-EDTA complex was dissociated and the Pb remained within the root. |
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- C P. Grey (SBU), L. Peng (SBU), H. Park (SBU), I. Bull (SBU), J. Parise (SBU) A series of NMR experiments have been used to help solve the structure of novel scandium phosphates synthesized by the Parise group. For example, 19F and 45Sc MAS NMR were used to locate the fluorine atoms that formed a part of the scandium phosphate framework. BET measurements were performed to determine the porosity of these materials before removal of the template. |
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- C P. Grey (SBU), P. Sideris (SBU), U. G. Nielsen (SBU), J. Parise (SBU), B. Phillips (SBU) In this recently commenced project, we use NMR and diffraction methods to probe the interactions responsible for selective uptake particular anions in layered materials. Our experiments are currently focussing on layered double hydroxides, Mg1-xMx(OH)2Ay, where Az- is an anion and M3+ or M4+ is cation substituent. Questions being asked are: why does the nature of the cation substituant affect sorption so strongly? What is the role of hydrogen bonding in between the layers in controlling sorption? |
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- J. Parise (SBU), I. Bull (SBU), A. Celestian (SBU), H. Park (SBU), C.P. Grey (SBU) The cation exchange capacity, selectivity and rate of porous materials can be increased by following a combination of strategies 1) decreasing the overall cationic charge on the framework 2) increasing the surface area by creating new nanostructured materials 3) increasing the anionic charge on the framework 4) a combination of the first three strategies. - J. Parise (SBU), C. P. Grey (SBU), H. Liu (SBU) S. Park (Munich) B. Toby (NIST) A new form of MFI, a framework zeolite related to ZSM-5 (silicalite) with a Li/Si ratio of 4/92, has been synthesized hydrothermally. Single crystal synchrotron X-ray diffraction data, 29Si NMR, and infrared spectroscopy indicate that the Li is randomly distributed over the frameworks sites and occluded in voids outlined by the double 5-membered-rings. Although the latter sites are not directly accessible to gas molecules, the protons formed on calcination are directly accessible. - J. Parise (SBU), A. Celestian (SBU), I. Bull (SBU) Nymann (Sandia), Belhomme (Sandia) Vaughan (ESRF) Heteropolyanions are negatively-charged clusters of corner-sharing and edge-sharing early transition metal MO6 octahedra and heteroatom XO4 tetrahedra, where the tetrahedra are usually located in the interior of the cluster. Heteropolyanions have been employed in a range of applications that include virus-binding inorganic drugs, homogeneous and heterogeneous catalysts, electro-optic and electro-chromic materials, metal and protein binding, and as building blocks for nano-structuring of materials. Our colleagues at Sandia have identified the [SiNb12O40]16- a- Keggin ion in the solid-state as either isolated clusters or as a 1-dimensional inorganic polymer. The Stony Brook group is working with Sandia to optimize the synthesis and to determine the crystal structures of these unusual materials. The infrastructure built-up in the InXS facility and at the national and international facilities is ideal for this work. To our knowledge, the [TNb12O40]16- (T =Si, Ge) Keggin ions reported in our recent manuscript have the highest negative charge observed for clusters possessing the plenary Keggin geometry; and also higher charge than the typical mono-, di- and trivacant lacunary Keggin ions. The unprecedented high charge should render these clusters unique with regard to metal binding and other applications involving anion-cation electrostatic interactions in solution or at interfaces. Recently several new and unusual “exploded” Keggin clusters have been observed and we continue to characterize these.  properties of crystalline silico-titanates (CST) - J. Parise (SBU), A. Celestian (SBU), Clearfield (Texas A&M), Tripathi (Texas A&M), Medvedev (Texas A&M) Titanium silicate (TS) with sitinakite topology and composition Na2Ti2O3SiO4 s2H2O has received considerable attention because of its high ion-exchange selectivity towards cesium and strontium. Our collaborators at A&M are working on optimizing the synthesis of this phase and understanding the origins of its selectivity. A combination of ex- and in-situ X-ray powder diffraction experiments reveal the effects of parameters such as gel composition, time, and temperature on crystallinity and composition of the final product. In situ synchrotron X-ray powder diffraction studies show that the synthesis process begins with the formation of layered sodium nonatitanate (SNT) with chemical composition of Na4Ti9O20 snH2O (also an excellent ion-exchanger) and that at high hydroxide concentration the reaction forms sodium titanium oxide silicate, Na2TiSiO5, (STOS) that has the mineral natisite structure. Time resolved in situ ion exchange experiments carried out for the H-form of CST reveal that the exchange proceeds via a 2-step process. In the case of Cs-exchange for example the exchange involves two closely spaced sites for Cs. Partial filling of the first site leads to a structural distortion opening up a second site for exchange. We now have several examples of this site selective ion exchange where exchange at one site causes structural distortion which enhances selectivity at a second site. In the case of CST this might explain its unusual selectivity for Sr and Cs even in the presence of high concentrations of Na+.  J. Parise (SBU), I. Bull (SBU), Lee (BNL), Vogt (BNL) Natrolite has been showing to superhydrate under pressure. Possible implications of this discovery included enhanced ion-exchange due to the accompanying expansion of the zeolitic channels. A series of natrolites have been synthesized with water contents from 6, 8 and 12 H2O per unit cell composition K8Ga8Si12O40.xH2O. Ion-exchange of this related family of materials should elucidate factors which influence ion-exchange. The synthetic route to the high water content material is very significant since we shall be able to test for the enhanced ion-exchange without the need for a diamond anvil cell. |
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-J. Parise (SBU), I. Bull (SBU), H. Park (SBU), Kim (Korea) Most ion exchangers and synthetic molecular sieves are synthesized in water. We are developing new routes to open materials by using water alcohol mixtures that undergo miscibility-immiscibility transitions under the hydrothermal conditions commonly used for sieve synthesis. The shortest chain alcohol immiscible with water at room P and T is 1-butanol (BuOH) at close to the BuOH:H2O ratio of 1:3. Utilizing this mixture in solvothermal reactions has yielded new classes of nanoporous materials. This far we have concentrated on one system producing unique materials, the Ni-PO4 systems with BuOH solvents and short chain amines. |
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- G. P. Halada (SBU), C. Eng (SBU), A. J. Francis (BNL), C. J. Dodge (BNL) An understanding of the association of uranium with typical steel corrosion products and with the corroding surfaces of mild steel and stainless steel is essential in order to develop and optimize efficient decontamination procedures. Through use of a broad suite of analytical techniques, including synchrotron infrared microspectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, Raman spectroscopy, and wet chemical techniques, a model for contaminant uranium interaction with metallic surfaces undergoing atmospheric corrosion has been developed and is being applied to optimization of decontamination processes which employ hydroxycarboxylic acids. The figure shows uranium association with a corroding mild steel surface following exposure to atomized uranyl nitrate solution and subsequent corrosion in a cyclic humidity chamber. Uranium was found to preferentially associate with iron hydroxide and oxyhydroxide compounds, in particular lepidocricite and ferrihydrite, and become trapped at heavily corroded, occluded sites. Islands of crystalline schoepite (a uranium oxyhydroxide mineral) also formed following repeated corrosion cycles. (Adapted from Eng, C.; Halada, G.P.; Francis, A.J.; Dodge, C.J. 2003. Surf. Interface Analysis. 35, 525-35 ). | |||||||||
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- M Fuhrmann (BNL), J. P. Fitts (BNL), J Heiser (BNL), J. Adams (BNL) Two formulations of grouts to be used as backfill materials for high level radioactive waste tanks at West Valley, NY, were tested for their ability to sorb or precipitate 22 contaminants. Isotherms were generated for these elements on the two grouts and on the components of the grout, which include portland cement, fly ash, blast furnace slag, zeolite and apatite. While the highly alkaline conditions precipitated many elements including the actinides, sorption of elements such as Cs, Sr, V, Tc, I and Cr were quantified and the active sorbing component(s) were identified. XANES indicated that the blast furnace slag effectively reduced Cr (VI) to Cr(III). In the grout some reduction took place but it was not complete. Future work will determine if the radioactive elements U, Np, Pu, Cm, and Am return to solution as the pH of the system becomes lower as the cement ages. This will be done with a set of column leaching experiments and pH titrations of the grout samples containing these elements. | |||||||||
- M. Fuhrmann (BNL), J. P. Fitts (BNL), J. Heiser (BNL), W. Wang (BNL), V. Fthenakis (BNL) A concern with photovoltaic cells is the release of toxic elements, cadmium and tellurium, during house fires. Coupons of CdTe photocells were heated in a furnace to temperatures from 400C to 1100C. Off-gas was collected and analyzed for Cd and Te. Cross-section of the cells were made and distribution of Cd was determined through the glass layers of the cell. Untreated and low temperature samples showed no Cd in the glass, and only a very thin layer of Cd was present where it was originally deposited. As the glass softened at higher temperatures, Cd was observed in the off-gas. It also was redistributed inhomogeneously within the glass. At the highest temperature Cd was well distributed in the glass, dissolving into it as an oxide, with a maximum of 30% loss of Cd to the vapor. Much less Te was released. | |||||||||
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- C. Jacobsen (SBU), M. Lerotic (SBU), B. Hornberger (SBU), M. Kissell (SBU), B. Larson (SBU), J. Gillow (BNL) The x-ray microscopy group in physics is involved in the development of x-ray microscopy techniques and instrumentation, and the application of these techniques to problems in environmental science and biology. Example ongoing activities include the development of improved instrumentation and analysis methods for soft x-ray spectromicroscopy (for example, work by Mirna Lerotic on cluster analysis methods as applied to several studies with several CEMS collaborators, and work by Bjorg Larson on bacterial sporulation with Jeff Gillow of BNL), and for phase contrast imaging in hard x-ray microprobe experiments to correlate elemental distributions with hyperaccumulating plant ultrastructure (Benjamin Hornberger, with geosciences student Marianna Kissell). Instrumentation activies include a modification of the X1A beamline to provide improved spectral resolution in the 600-800 eV energy range (project now completed), and upgrade of the room temperature STXMs to incorporate laser interferometer feedback for improved scan data registration (first tests are to be carried out summer 2004). | In a collaboration with CEMS scientists, Dr. Thorsten Schafer and colleagues at the Institute for Nuclear Waste Research in Karlsruhe, Germany, have been studying fundamental science issues associated with the transport of nuclear wastes in groundwater. A particular question has involved the incorporation of americium into colloidal particles that travel with groundwater flows. Using lutetium as a homologue for americium, oxygen-absorption-edge scanning transmission x-ray microscope (STXM) images were obtained of lutetium that had been allowed to react with ferrihydrite. Such measurements contain considerable information but it can be difficult to recognize the key themes due to complexity. By using cluster analysis methods developed by CEMS student Mirna Lerotic (working in the lab of Chris Jacobsen), one can simplify this information into an image shown in the top left panel. The red areas correspond to lutetium enrichment and indicate that the crystallization process excludes lutetium from the hematite structure. These results suggest that lutetium-substituted hematite might not be thermodynamically stable, and therefore, the abundance of iron oxides in soils and sediments may not protect against long-term actinide mobility. The cluster analysis methods used to obtain these results are described in a publication that has been submitted to Ultramicroscopy: "Cluster analysis of soft x-ray spectromicroscopy data", by M. Lerotic, C. Jacobsen, T. Schafer, and S. Vogt.  STXM images and oxygen near-edge spectra showing regions of lutetium enrichment in hematite. Work conducted at the NSLS beamline X1A2. |
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-C. P. Grey (SBU), Y. Paik (SBU), K. Cole (Fairfield Univ.), U. G. Nielsen (SBU) | |||||||||
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Please send correspondance and questions to: Andrea Illausky, Administrative Assistant Center for Environmental Molecular Science ESS 255 Stony Brook University Stony Brook, NY 11794-2100 TEL: (631) 632-1924 FAX: (631) 632-1937 aillausky@notes.cc.sunysb.edu |
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Last modified January 2006
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