A nitrogen isotopic shift in fish otolith-bound organic matter during the Late Cretaceous.

The nitrogen isotopes of the organic matter preserved in fossil fish otoliths (ear stones) are a promising tool for reconstructing past environmental changes. We analyzed the N/N ratio (δN) of fossil otolith-bound organic matter in Late Cretaceous fish otoliths (of , and sp.) from three deposits along the US east coast, with two of Campanian (83.

Nanoscale Transforming Mineral Phases in Fresh Nacre.

Nacre, or mother-of-pearl, the iridescent inner layer of many mollusk shells, is a biomineral lamellar composite of aragonite (CaCO3) and organic sheets. Biomineralization frequently occurs via transient amorphous precursor phases, crystallizing into the final stable biomineral. In nacre, despite extensive attempts, amorphous calcium carbonate (ACC) precursors have remained elusive.

Novel apatite-based sorbent for defluoridation: synthesis and sorption characteristics of nano-micro-crystalline hydroxyapatite-coated-limestone.

Elevated levels of fluoride (F(-)) in groundwaters of granitic and basaltic terrains pose a major environmental problem and are affecting millions of people all over the world. Hydroxyapatite (HA) has been shown to be a strong sorbent for F(-); however, low permeability of synthetic HA results in poor sorption efficiency. Here we provide a novel method of synthesizing nano- to micrometer sized HA on the surfaces of granular limestone to improve the sorption efficiency of the HA-based filter.

Estimation of reactive thiol concentrations in dissolved organic matter and bacterial cell membranes in aquatic systems.

Organic thiols are highly reactive ligands and play an important role in the speciation of several metals and organic pollutants in the environment. Although small thiols can be isolated and their concentrations can be estimated using chromatographic and derivatization techniques, estimating concentrations of thiols associated with biomacromolecules and humic substances has been difficult. Here we present a fluorescence-spectroscopy-based method for estimating thiol concentrations in biomacromolecules and cell membranes using one of the soluble bromobimanes, monobromo(trimethylammonio)bimane (qBBr).

Natural niche for organohalide-respiring Chloroflexi.

The phylum Chloroflexi contains several isolated bacteria that have been found to respire a diverse array of halogenated anthropogenic chemicals. The distribution and role of these Chloroflexi in uncontaminated terrestrial environments, where abundant natural organohalogens could function as potential electron acceptors, have not been studied. Soil samples (116 total, including 6 sectioned cores) from a range of uncontaminated sites were analyzed for the number of Dehalococcoides-like Chloroflexi 16S rRNA genes present.

X-ray absorption spectroscopy of aqueous aluminum-organic complexes.

Aqueous-phase X-ray absorption near-edge structure (XANES) spectra were collected on dissolved Al complexes with organic ligands, including desferrioxamine B, EDTA, acetohydroxamate, malate, oxalate, and salicylate. Spectral interpretations were made using the density functional theory-based modeling package StoBe. The goals of this work were to study the geometric and electronic structural characteristics of these complexes relative to Al(H(2)O)(6)(3+) and to examine the utility of the aqueous Al XANES technique as a tool for probing Al speciation and structure.

Geometric and electronic structure of the aqueous Al(H2O)6(3+) complex.

The bonding environment of the aqueous Al(H2O)6(3+) complex was studied using X-ray absorption near-edge structure (XANES) spectroscopy at the Al K-edge, with spectral interpretations based on density functional theory (DFT). Calculations for a highly symmetric complex (T(h) symmetry) indicate electron transitions into Al3 p-O 2s and Al3 p-O 2p antibonding orbitals, with a split O 2p contribution that appears to be due to a weak pi-interaction of the Al 3p orbitals with water ligands off-axis (equatorial) with respect to the Al 3p axis. Calculations were performed with several hypothetical structures to assess the effects of Al-O bond length, orientation of water ligands in the first coordination shell, and the presence of a second solvation shell on the XANES spectrum.

Complexation of oxoanions and cationic metals by the biscatecholate siderophore azotochelin.

Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II), Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV-vis and X-ray spectroscopy. Azotochelin forms a strong 1:1 complex with molybdate (log K=7.

Near edge X-ray absorption fine structure spectroscopy of bacterial hydroxamate siderophores in aqueous solutions.

X-ray absorption spectroscopy (XAS) is widely used to explore the coordination environments and structures of metal complexes in aqueous solutions and disordered phases. Although soft-XAS studies on gaseous phases, solid phases and their interfaces have shown that XAS is a versatile tool in studying the functional group composition of organic molecules, the application of XAS to studying aqueous solutions is seriously limited because of experimental difficulties. In this report, using a modified synchrotron endstation geometry, we show how soft-XAS was used to study the changes in electronic states of reactive functional groups in a bacterial macromolecule, desferrioxamine B (desB, a hydroxamate siderophore) and its structural analogue (acetohydroxamic acid (aHa)).

Quantitative determination of absolute organohalogen concentrations in environmental samples by X-ray absorption spectroscopy.

An in situ procedure for quantifying total organic and inorganic Cl concentrations in environmental samples based on X-ray absorption near-edge structure (XANES) spectroscopy has been developed. Cl 1s XANES spectra reflect contributions from all Cl species present in a sample, providing a definitive measure of total Cl concentration in chemically heterogeneous samples. Spectral features near the Cl K-absorption edge provide detailed information about the bonding state of Cl, whereas the absolute fluorescence intensity of the spectra is directly proportional to total Cl concentration, allowing for simultaneous determination of Cl speciation and concentration in plant, soil, and natural water samples.

Hard and soft X-ray absorption spectroscopic investigation of aqueous Fe(III)-hydroxamate siderophore complexes.

Microorganisms release organic macromolecules, such as siderophores, to obtain Fe(III) from natural systems. While the relative stabilities of Fe(III)-siderophore complexes are well-studied, the structural environments of Fe(III) and ligands in the complex are not well-understood. Using the X-ray absorption spectroscopy (XAS) at the Fe- and N-K absorption edges, we characterized the nature of Fe(III) interactions with a hydroxamate siderophore, desferrioxamine B (desB), and its small structural analogue, acetohydroxamic acid (aHa), as a function of pH (1.

Effect of soil fulvic acid on nickel(II) sorption and bonding at the aqueous-boehmite (gamma-AIOOH) interface.

The influence of soil-derived fulvic acid (SFA) on Ni(II) sorption and speciation in aqueous boehmite (gamma-AIOOH) suspensions was evaluated using a combination of sorption experiments and Ni K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy measurements. Co-sorption of SFA at the aqueous-boehmite interface modifies both the extent of Ni(II) sorption as well as the local structure of the sorbing Ni(II) ions. In SFA-free suspensions, Ni(II) sorbs by forming inner-sphere bidentate mononuclear complexes with surface aluminol groups.

Speciation of iron and sulfate in acid waters: aqueous clusters to mineral precipitates.

Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, FeIII, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy.

Elucidation of functional groups on gram-positive and gram-negative bacterial surfaces using infrared spectroscopy.

Surface functional group chemistry of intact Gram-positive and Gram-negative bacterial cells and their isolated cell walls was examined as a function of pH, growth phase, and growth media (for intact cells only) using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Infrared spectra of aqueous model organic molecules, representatives of the common functional groups found in bacterial cell walls (i.e.

Organic aerosol growth mechanisms and their climate-forcing implications.

Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.

Uptake of bromide by two wetland plants (Typha latifolia L. and Phragmites australis (Cav.) Trin. ex Steud).

The successful use of bromide (Br-) as a conservative tracer for hydrological tests in wetland systems requires minimal Br- loss due to plant uptake. The uptake of Br- by two wetland plants, cattail (Typha latifolia L.) and reed grass (Phragmites australis (Cav.

Cl K-edge X-ray spectroscopic investigation of enzymatic formation of organochlorines in weathering plant material.

The contribution of halocarbons from plant weathering to the total organohalogen budget of terrestrial systems is gaining recognition. To evaluate the formation of such halocarbons, speciation of chlorine in Sequoia sempervirens (redwood) needles was examined in the presence of an external chloroperoxidase (CPO) enzyme using Cl K-edge X-ray absorption spectroscopy. The Cl forms in fresh and naturally weathered needles and in model laboratory reactions were compared.

Formation of stable chlorinated hydrocarbons in weathering plant material.

Though several chlorinated organic compounds produced by humans are carcinogenic and toxic, some are also produced by the biotic and abiotic processes in the environment. In situ x-ray spectroscopy data indicate that natural organic matter in soils, sediments, and natural waters contain stable, less volatile organic compounds with chlorinated phenolic and aliphatic groups as the principal Cl forms. These compounds are formed at rapid rates from the transformation of inorganic Cl during humification of plant material and, thus, play a critical role in the cycling of Cl and of several major and trace elements in the environment and may influence human health.