Goldschmidt Abstracts 2010 – E

Goldschmidt Conference Abstracts 2010

Proportionate crystal growth 1

D.D. EBERL * AND D.E. KILE

Electronmicroscopic individual particle analysis of ice nuclei

2

1

U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303 USA (*correspondence: [email protected]) 2 5176 Black Bear Run, Littleton, CO 80125 USA ([email protected]) It is often assumed that crystals grow at a rate that is independent of their size (constant growth). However, it is readily shown that most crystals grow at a rate that is proportional to their diameter. This effect is demonstrated in the figure below, which depicts the result of growing initially large- and small-diameter crystals side-by-side in a flowing, supersaturated, K-alum solution. The crystal growth law for this system is: Xfinal = Xinitial + kXinitial, where X is the crystal’s diameter and k is a constant (k = 0.3 for the experiment depicted).

K-alum crystal growth experiments

Diameter at time T - initial diameter (mm)

0.20 Big crystal (0.75 mm)

0.15

R^2 = 0.99

Small crystal (0.47 mm)

0.10

0.05

R^2 = 0.96

0.00

-0.05

-0.10

0

5

10

15

20

25

30

35

A257

40

Time interval (min.)

At very small diameters (nanometer scale), a crystal experiences a heterogeneous solution during growth, and k is a random number that varies from 0 to 1. The growth equation then is termed the Law of Proportionate Effect (LPE). When iterated several times for many crystals, LPE yields the commonly observed lognormal crystal size distribution (CSD). The lognormal CSD shape then is preserved as crystals grow larger and k becomes constant. Generally, the shapes of CSDs formed at the nanometer scale are preserved by proportionate growth as crystals grow larger. The common CSD shapes, formed during and immediately after nucleation, are the lognormal, discussed above, the asymptotic, formed by simultaneous nucleation and growth, and the universal steady-state shape (reverse skew) formed by Ostwald ripening. These three mechanisms prevail at different levels of supersaturation; therefore, CSD shapes often yield information on the initial conditions of crystallization.

M. EBERT, A. WORRINGEN AND S. WEINBRUCH Environmental Mineralogy, Institute of Applied Geosciences, Technical University Darmstadt, Schnittspahnstr. 9, 64287 Darmstadt, Germany The effects of aerosol particles on heterogeneous ice formation are currently insufficiently understood. Therefore, the physicochemical identification of ice nuclei (IN) is crucial for a better understanding of formation, life cycles, and the optical properties of clouds. During the CLACE 5 campaign in 2006 at the high alpine research station Jungfraujoch (3580 m asl), Switzerland, the single particle composition of IN and the interstitial aerosol within mixed-phase clouds was studied. The size, morphology, elemental composition and mixing state of more than 7000 particles were analyzed by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDX). Pb bearing particles (up to 24% by number), aluminium oxide particles and different complex internal mixtures (main components: soot, silicates and metal oxides) were identified to act as IN. The high abundance of Pb-bearing particles in the INsamples was an unexpected finding. A smaller number of these particles are Pb-dominated (PbO and PbCl2). However, the majority of these particles are sea salt, soot or silicates, while Pb is present as small (50 – 500 nm) heterogeneous Pb or PbS inclusions. As the component with best IN capability present in an individual particle determines its IN behaviour, the determination of the main-component of a particle is not sufficient for the prediction of its IN-capability.

A258

Goldschmidt Conference Abstracts 2010

Reductive dissolution of hematite nanoparticles with ascorbic acid T. ECHIGO1, D.M. ARUGUETE1, M. MURAYAMA2 1,2 AND M.F. HOCHELLA JR.

Southern US Cordillera pre-magmatic zircons: Sounding a Cordilleran source region RITA ECONOMOS1, ANDREW BARTH1 AND JOE WOODEN2

1

Department of Geosciences, Virginia Tech, Blacksburg, VA 24061-0420, USA ([email protected]) 2 Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech, Blacksburg, VA, 24061, USA Iron oxides and oxyhydroxides, hereafter referred to as iron oxides, are commonly found in surface water, soils and sediments. Their dissolution behaviour is important because it influences the bioavailability of nutrients for plant growth and migration of pollutant metals and substances. In natural environments, reductive dissolution is the most important dissolution mechanism [1]. While the reductive dissolution of iron oxides has been an area of intensive study, little attention has been paid to the impact of mineral size upon this process. Nanoscale iron oxides are omnipresent in nature [2], and initial studies have found their size can influence chemical reactivity. To further investigate the effect of iron oxide particle size upon chemical reactivity, we have studied the reductive dissolution of hematite by ascorbate using two types of nanoparticles with average diameters of 7 nm and 25 nm. Synthesized nanoparticles were characterized with powderXRD, TEM, and BET surface area measurements. Reductive dissolution experiments were carried out in continuously stirred Nalgene bottles at 25 °C in the absence of light under approximately 1 atm nitrogen gas. Aqueous [Fe (II)] was measured by the ferrozine assay. The evolution of crystal morphology by reductive dissolution was examined by highresolution TEM (FEI Titan 300). HRTEM revealed that the 7 nm hematite crystals are pseudo-hexagonal plates, and the 25 nm hematite crystals have diamond and rectangular shapes before dissolution. The relationship between dissolution rate determined from bulk solution chemistry and morphological evolution observed by HRTEM will be discussed. [1] Sulzberger et al. (1989) Marine Chemistry 28, 127–144. [2] Hochella et al. (2008) Science 319, 1631–1635.

1

Department of Earth Sciences, IUPUI, 46202 [email protected] ([email protected]) 2 Department of Geological and Environmental Sciences, Stanford University, 94305 ([email protected])

The western Mojave preserves a periodic Mesozoic arc built into a full thickness of continental crust with a protracted Proterozoic history. Plutons there contain abundant premagmatic (inherited) zircons from magma source rocks which preserve age and compositional information, measurable by SIMS. We utilize whole rock parameters such as SiO2, Sr and Nd isotopic ratios, and geochronology as a guide in the exploration of this pre-magmatic zircon geochemical dataset in an attempt to elucidate variations in source age, rock composition, and processes, and how they are mirrored in upper crustal intrusions. In the Mojave, the Cadiz Valley Batholith (77 – 73 Ma) is underlain by intermediate sized plutons and a compositionally heterogeneous mid-crustal sheeted complex of identical age. This structural framework is exposed in a tilted crustal section. Whole rock compositions indicate the upper crustal batholith and underlying intrusions are similar but larger volume intrusions were derived from relatively deeper, garnet-bearing crustal sources. Such dynamic source region processes may be elucidated through comparison of whole rock isotopic and premagmatic zircon chemistry. Geochronology of pre-magmatic zircons revealed their ages correlate with known Proterozoic magmatic events but lack older framework rock zircons. Crustal melting would be unlikely to ubiquitously discriminate between these rocks, therefore we suggest a source of basaltic under-plates generated during Proterozoic magmatism. To investigate the magmatic compositions of source rocks, REE concentrations were calculated from pre-magmatic zircons using best known partition coefficients. Source rocks had dominantly flat MREE to HREE patterns suggestive of a basaltic composition, while some were HREE depleted, possibly indicating garnet in the original source for the underplated basalts. Whole rock isotopes suggest isotopically distinct crustal components, which contain zircon populations with distinctive REE signatures.

Goldschmidt Conference Abstracts 2010

Microbial community analyzis and connection to Iron chemistry in a former uranium mine — Lake Tranebärssjön F. EDBERG1*, A.F. ANDERSSON2 3 AND S.J. M. HOLMSTRÖM 1

Department of Applied Environmental Science, Stockholm University, S-106 91, Stockholm, Sweden (*correspondence: [email protected]) 2 Swedish Institute for Infectious Disease Control, Solna, Sweden and Department of Ecology and Evolution, Limnology, BMC, Uppsala University, Uppsala, Sweden 3 Department of Geological Sciences, Stockholm University, S-106 91, Stockholm, Sweden

Aim, site description and sampling The aim of this study was to investigate the connection between biogeochemical functions and bacterial community composition in lakes with focus on the consequences for metal mobilization and transport in mining areas. As study site we used Lake Tranebärssjön, the now water filled open-pit at the closed uranium mining site at Ranstad, Sweden. The water column was sampled at stratified conditions in late summer at the deepest part of the lake. Samples were analyzed for chemistry, dissolved organic carbon (DOC) and metals. The bacterial communities of the samples were monitored by 454-pyrosequensing of 16SrRNA genes and cloning of the full 16SrRNA gene.

Results and discussion The water inflow is dominated by groundwater and the surrounding bedrock is mainly alum-shale and limestone resulting in high alkalinity, sulphate (1.3 gL-1) as well as Fe (50 mgL-1) and other metals in the anoxic bottom water while pH is lower (6.9) compared to oxygenated surface water (7.9). The microbial community of the anoxic bottom water differs completely from the surface water and is dominated by a Chlorobium sp. (20-40% of population), an anoxic phototrophic oxidizer of inorganic sulphur or iron compounds, and Delta-proteobacteria (12-15% of population) represented by sulphate and iron reducing bacteria. The results imply that the hydrogeochemical environment controls the composition of the microbial populations and suggest close interactions between microbial community and chemistry in the iron and sulfate rich bottom water. With the results from the cloning of the total 16SrRNA gene we hope to shed more light on these interactions and the consequences for the environment.

A259

Chinese cave climate records R.L. EDWARDS1, H. CHENG1, Y.J. WANG2, Z.S. AN3, D.X. YUAN4 AND P.Z. ZHANG5 1

Dept. Geology & Geophysics, U. Minnesota, Minneapolis, MN 55455, [email protected] 2 College of Geography Science, Nanjing Normal University, Nanjing 210097, China 3 Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710075, China 4 Karst Dynamics Laboratory, Ministry of Land and Resources 40 Qixing Road, Guilin 541004, China 5 College of Earth & Environment Sciences, Lanzhou U., Lanzhou 730000, China Using refined multi-collector inductively-coupled plasma mass spectrometric techniques, we have determined precise 230 Th ages for cave calcite sequences at key sites in China. In total, we have established more than 300, 000 years of record, with resolution in terms of oxygen isotope values of several decades or better. The sites span the region affected by the East Asian Monsoon, in SE China, to the region affected by both the Indian and East Asian Monsoons in SW China, to high altitude regions of central Tibet, to areas of NW China at the fringes of summer monsoon precipitation, and beyond, to the semi-arid NW where climate is dominated by the westerlies. Patterns of oxygen isotope variation are broadly similar thoughout this region, particularly at the orbital scale; however, clear differences are evident at the millennial scale. These observations are broadly consistent with the idea that the cave oxygen isotope variations are caused by temperature anomalies in the North Atlantic, which modulate seasonal atmospheric circulation patterns by controlling the seasonal position of the sub-tropical jet, and therefore, the degree to which the jet impinges on the Tibetal Plateau seasonally. Whereas the Chinese records contribute inherently to our understanding of climate change, they are also invaluable in setting the timing of climate change worldwide. These records are among the most precisely dated climate records. Equally important, they can be correlated with other cave records as well as some marine and ice core records. Thus, they can be used to establish the timing of a wide-range of records worldwide. These correlations are particularly valuable in establishing the sequence of events and plausible causes of events during ice age terminations.

A260

Goldschmidt Conference Abstracts 2010

High Cd concentrations in Bajocian carbonates in the Swiss Jura Mountains: Evidences for hydrothermal input N. EFIMENKO1*, J.E. SPANGENBERG1, J. SCHNEIDER2, M. CHIARADIA3, T. ADATTE1, V. MATERA4 1 AND K.B. FÖLLMI 1

Université de Lausanne, 1015 Lausanne, Switzerland (*correspondence: [email protected]) 2 TU Bergakademie Freiberg, D-09596 Freiberg, Germany 3 Université de Genève, 1205 Genève, Switzerland 4 INRS, 54500 Vandoeuvre Les Nancy, France Anomalous high Cd concentrations (up to 16 mg/kg) in certain soils of the Swiss and French Jura Mts. are related to underlying Cd-enriched (up to 21.4 ppm) carbonate rocks of Middle-Late Jurassic age. The aim of this study is to understand the processes controlling Cd incorporation into carbonate rocks of Bajocian age and to develop a predictive tool to identify potentially contaminated top soils of Cdenriched carbonate rocks. The geochemical approach includes thin-section microscopy, ICP-MS, ion microprobing, sulphur isotope analysis, and Rb-Sr/Pb-Pb isotopic dating and tracing. Cd distribution in the carbonate rocks is heterogeneous, ranging from 0.03 to 12 ppm within few centimeters. Cd does not correlate with other trace elements, excepting Zn. High Cd concentrations in carbonate rocks are commonly related to the presence of subordinate, Cd-rich (up to 2%) sphalerite mineralization. !34S values of sphalerites (–22.3 to –5.3‰) suggest that intraformational bacterial sulfate reduction was the main source of reduced sulfur, with S-contributions from the degradation of diagenetic Fe sulfides and organo-Scompounds. Sphalerite Pb isotope signatures are uniform, indicating isotopically well-homogenized fluid systems. Comparative isotope patterns may point to extraformational lead sources located in the crystalline basement. Rb-Sr dating of sphalerites indicates a Middle-Late Jurassic, post-Bajocian mineralization event at c. 162 Ma. We argue that sphalerite mineralization and Cd enrichment in the Bajocian carbonate rocks reflects multistage tectonic and hydrothermal periods in the region related to the opening of the Atlantic and Alpine Tethys oceans, which led to the reactivation of Variscan basement faults. Tertiary (Oligocene) tectonic activity related to the opening of the Rhine graben may have triggered some remobilisation of sulfides and redistribution of Cd.

Fractionation of Cl isotopes during precipitation of NaCl from a nearly pure NaCl brine H.G.M. EGGENKAMP1*, J.M. MARQUES1 2 AND H. GRAÇA 1

Centro de Petrologia e Geoquímica, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal (*correspondence: [email protected]) 2 Centro Hospitalar das Caldas da Rainha, R. Diário de Notícias, 2500-176 Caldas da Rainha, Portugal

The natural spring ‘Fonte da Pipa’ in Rio Maior (Central Portugal) is unique as it contains about 137 grams of dissolved NaCl per litre and this salt is extracted and marketed as table salt by a local Cooperative. The salt content from this spring probably originates from dissolving salt from a shallow diapier in this area. Water extracted from the spring is preconcentrated in large basins until it contains about 250 grams NaCl per litre. It is then transferred to shallow concrete basins and left until all water is evaporated. This latter procedure takes place at air temperatures above 25 °C and requires about one week to complete. In a first approach to study the saline spring we sampled water from the spring and several evaporation basins to study the Cl isotope compositions of the brine and the precipitated NaCl. As the springwater is a nearly pure (98%) NaCl brine we expected it to have a large (potential) Cl isotope variation. This is unlike fractionation of Cl isotopes precipitating from seawater. As the Cl isotope fractionation factor for NaCl is much larger than for KCl and MgCl2, in seawater a minimum !37Cl of about -0.5‰ is expected [1]. Indeed we found values regularly decreasing from -0.2‰ for the saline spring to as low as 1.1‰ in the most evaporated brine. The NaCl precipitate in all cases had more positive !37Cl values compared to the coexisting brine, and decreased from 0.0‰ in the first precipitate to -0.5‰ in the last stage. We believe it is important that this unique saline spring and its hydrological environment be studied in detail as the spring is located in an area heavily used for agricultural purposes. The extraction of freshwater from wells as close as 100 meters from the saline spring implies that a sharp boundary exists between the saline and fresh groundwater; pumping of freshwater for agricultural purposes may therefore disturb the equilibrium between these two water systems and cause an unwanted rise in salinity of this valuable freshwater resource. [1] Eggenkamp, Kreulen & Koster van Groos (1995) Geochimica et Cosmochimica Acta 59, 5169–5175.

Goldschmidt Conference Abstracts 2010

1

A261

The hematite-pyrite tandem cell: Avenue to understanding Mars photochemical water oxidation?

Carbonate clumped isotope thermometry as a tool for paleoceanography

C.M. EGGLESTON1*, B.A. PARKINSON2 1 AND E.S. BRAMLETT

JOHN EILER1, KRISTIN BERGMANN1, MAGALI BONIFACI3, ROB EAGLE1, SETH FINNEGAN1, WOODWARD FISCHER1, BEN PASSEY2, DANIEL STOLPER1 4 AND ARADHNA TRIPATI

Dept. of Geology and Geophysics and 2Dept. of Chemistry, University of Wyoming, Laramie, WY 82071 (*correspondence: [email protected])

1

California Institute of Technology ([email protected]) Johns Hopkins University ([email protected]) 3 IPG, Paris ([email protected]) 4 UCLA, ([email protected]) 2

The oxidized Mars surface has been explained as a product of atmospheric photochemistry. Rarely have Mars surface materials been considered a cause of oxidation. For example, hematite must have resulted from oxidation of Fe (II) in Mars rocks. Photooxidation has been invoked in this process. Hematite is under study as a photocatalyst for water oxidation in solar energy research. Thus, once hematite has formed, it may play a role in subsequent water oxidation. Hematite (bandgap ~ 2.0 eV) absorbs in the visible and UV. While photogenerated valence band holes are highly oxidizing, the conduction band would not be able to reduce H+ to H2. However, ferric coatings are an expected part of pyrite oxidation. Pyrite has a smaller bandgap than hematite, and could absorb light transmitted by a hematite coating. Thus, we examined the properties of a hematite-pyrite tandem cell from the point of view of water oxidation on Mars. Si-doped nanocrystalline hemtite photoanodes were grown on F-doped SnO2 by atmospheric pressure chemical vapor deposition. Natural pyrite was sliced and used as a photocathode. Current passing from hematite to pyrite was monitored. Various electrolyte solutions were used, including solutions made based on Mars Phoenix lander aqueous chemistry results. Photovoltage was also measured periodically. Experiments were run at Mars-like light intensities as well as higher light intensities using both a Xe lamp as well as a data projector emitting white light. Photocurrents of up to 1 microamp per square centimeter were observed, depending on conditions, as shown in the figure in chopped light and accompanied by substantial photocurrent transients. Given billions of years, such current densities are capable of oxidizing substantial amounts of water and producing both O2 and H2. Photooxidation of pyrite would eventually lead to sulfate and perhaps formation of ferric sulfate sediments.

Carbonate clumped isotope thermometry is based on the temperature-dependent formation of 13C18O16O2-2 ion groups in carbonate minerals. Paleotemperatures based on this technique do not depend on the isotopic composition of water from which carbonate grows, and thus can be combined with conventional O isotope analyses to reconstruct the !18O of past waters with relatively few assumptions. At least five laboratories currently make carbonate clumped isotope analyses (Caltech, Harvard, Yale, ETH and Johns Hopkins), all with broadly similar methods and limits of precision. Interlaboratory comparisons of reference carbonates are encouraging but reveal discrepancies that will require coordination to establish a basis for absolute accuracy. This method has been calibrated for inorganic calcite, diverse biogenic Ca-carbonates, natural and synthetic dolomite, carbonate-bearing bioapatite (Eagle et al. this meeting) and inorganic aragonite (Kim et al. this meeting). Several of these calibrations conform to a single relationship between T and clumped isotope composition of carbonate ions. However, experimental determinations of this relationship for synthetic calcite and aragonite differ from each other, and only a sub-set of them agree with the relatively uniform calibrations of various biogenic carbonates. These discrepancies are not yet understood and could reflect some combination of interlaboratory analytical artifacts, kinetic isotope effects during experimental carbonate synthesis and/or unrecognized and counter-intuitive vital effects in biogenic carbonates. The capabilities of this method will be illustrated through three recent applications : reconstruction of the body temperatures of mesozoic land vertebrates; a high-latitude terrestrial Cenezoic climate record; and a determination of the variation in ice volume across the end-Ordovician glaciation and extinction. Finally, we will discuss new insights into the imprint of burial and metamorphic processes on clumped isotope compositions of carbonate-bearing minerals.

A262

Goldschmidt Conference Abstracts 2010

A ‘mass-anomalous’ vapor-pressure isotope effect for SF6 JOHN EILER1, AMY HOFMANN1 AND PIERRE CARTIGNY2 1 2

Structural evolution and fluid flow in the Wealden and Hampshire basins, southern England, U.K SALAH ELDIN M. ELGARMADI *, GRAHAM POTTS AND RICHARD WORDEN

California Institute of Technology ([email protected]) Stable Isotope Laboratory of IPG-Paris, France 1

Large mass-anomalous isotope fractionations of O and S are commonly attributed to photochemical reactions. It is unclear whether more subtle mass-anomalous fractionations of O and S can arise from exchange equilibria or other nonphotochemical reactions. Statistical thermodynamic models of a simple harmonic oscillator may [1] or may not [2] predict mass-anomalous equilibrium fractionations of light elements. Experimental devolatilization of carbonate [3] and sulfate [4] reveal mass-anomalous net fractionations of O and S, respectively, but have unconstrained reaction mechanisms and may reflect mixing and/or distillation rather than novel chemical isotope effects. We present experimental observations of the vapor pressure isotope effect (VPIE) for solid, liquid, and adsorbed SF6 between temperatures of 300 and 141 K. SF6 exhibits a reversed (for ice and sorbate) or negligible (for liquid) VPIE under all studied conditions. In this respect, it resembles the VPIEs for 13CO2/12CO2 and other cases in which mass substitution involves a central atom in a non-polar molecule. The size of the VPIE for solid SF6 is approximately -2.5 ‰ for 34 32 S/ S (solid/vapor) at 150 K. The mass exponent, "3/4 = ln#33/ln#34, averages 0.56 ± 0.01 and is nearly constant across all explored temperatures. Time series experiments suggest these results reflect equilibrium VPIEs; bracketing the ice/vapor equilibrium through reversal experiments is challenging, presumably due to slow solid-state diffusion in SF6 at these temperatures, but has been achieved for longduration, ice-dominated experiments. The mass exponent we observe is significantly higher than those for canonical equilibrium or kinetic fractionations ("3/4 = 0.515 or 0.508, respectively). Its value, occurrence at low temperatures, and lack of variation with T differ from predictions of the harmonic-oscillator model that yields noncanonical mass laws for sorption1. "6/4 = ln#36/ln#34 varies more complexly than "3/4 but is also generally ~10 % higher than canonical mass-dependent values. We suggest our results are explained by the interplay between isotope effects on intermolecular and intramolecular vibrational and rotational energies. Support for this conjecture can be found in prior observations of the mass laws of vapor pressure isotope effects for H-D-T and 12C-13C-14C. Potential relevance for S-bearing molecules of natural significance will be discussed. [1] Lasaga et al. (2008) EPSL. [2] Balan et al. (2009) EPSL. [3] Miller et al. (2002) PNAS. [4] Watanabe et al. (2009) Science.

Departmental of Earth and Ocean Sciences, University of Liverpool, L69 3GP, UK (*correspondence: [email protected])

From Permian to late Cenozoic southern England went through a complex structural evolution. A tensional stress regime during the Permian and Mesozoic produced a pattern of subsidence dominated by E-W striking normal faults. This tectonic regime was followed by a reversal of the subsidence pattern and inversion of the Wealden sedimentary basin in response to compressive tectonic stresses that converted the Mesozoic depocentres into structural highs during late Cretaceous and early Cenozoic times. Also during the Cenozoic the Hampshire basin formed as a direct result of crustal flexure. These events have produced a wide range of large- and small-scale structures that provide valuable record of structural evolution The migration of petroleum and solute bearing fluids may have been controlled by the tectonic features such as faults. The timing and migration paths of these fluid movement events remain poorly constrained. Understanding the present day distribution of hydrocarbons and cements relies on understanding both the structure and fluid movement in these basins. The complex structural history of the Wealden and Hampshire basins provides an excellent opportunity to investigate links between structural evolution, petroleum migration and water movement. Structures in outcrop and displayed on published geological maps have been examined in order to determine the geometries, relative ages and stratigraphic ages of faults, veins systems and folds throughout Wealden and Hampshire basins. Samples of cemented faults and veins have been collected from a wide range of stratigraphic units (Early Cretaceous to late Tertiary) in different structural positions. The faults and veins are concentrated in four locations, two on the Isle of Wight around the zones of flexure, Eastbourne and Dover. Petrographical analysis indicates that these samples are dominantly calcite with minor amounts of pyrite and barite and the veins in different orientations share the same mineralogy. The validity of this apparently simple pattern is examined using fluid inclusion studies. By integrating these results with the chemistry of the source rocks and hydrocarbons found within the basins a model of fluid flow and the evolution will be established.

Goldschmidt Conference Abstracts 2010

Can direct extracellular electron transfer occur in the absence of outer membrane cytochromes in Desulfovibrio vulgaris? D.A. ELIAS1*, G.M. ZANE2, M.A. AUER3, M.W. FIELDS4, J.D. WALL2 AND Y.A. GORBY5 1

Oak Ridge National Lab, P.O. Box 2008, MS-6036, Oak Ridge, TN, USA (*correspondence: [email protected]) 2 University of Missouri, 117 Schweitzer Hall, Columbia, MO, USA 65211 ([email protected], [email protected]) 3 Lawrence Berkeley National Lab, One Cyclotron Road MS: Donner, Berkeley, CA, USA 94720 ([email protected]) 4 Montana State University, PO Box 173980 ,Bozeman, MT, USA, 59717 ([email protected]) 5 J. Craig Venter Institute, 10355 Science Center Dr., San Diego, CA, USA 92121 ([email protected]) Extracellular electron transfer has been investigated over several decades via forms of soluble electron transfer proteins that are exported for extracellular reoxidation. More recently, several organisms have been shown to reduce extracellular metals via the direct transfer of electron through appendages; also known as nanowires. They have been reported most predominantly in Shewanella and Geobacter. While the relevancy and composition of these structures in each genus has been debated, both possess outer membrane cytochrome complexes that could theoretically come into direct contact with solid phase oxidized metals. Members of the genus Desulfovibrio apparently have no such cytochromes although similar appendages are present, are electrically conductive, and are different from flagella. Upon U (VI)-reduction, the structures in Desulfovibrio become coated with U (IV). Deletion of flagellar genes did not alter soluble or amorphous Fe (III) or U (VI) reduction, or appendage appearance. Removal of the chromosomal pilA gene hampered amorphous Fe (III)-reduction by ca. 25%, but cells lacking the native plasmid, pDV1, reduced soluble Fe (III) and U (VI) at ca. 50% of the wild type rate while amorphous Fe (III)-reduction slowed to ca. 20% of the wild type rate. Appendages were present in all deletions as well as $pDV1, except $pilA. Gene complementation restored all activities and morphologies to wild type levels. This suggests that pilA encodes the structural component, whereas genes within pDV1 may provide the reactive members. How such appendages function without outer membrane cytochromes is under investigation.

A263

Arsenic distribution in laterites of the Balkan Peninsula and its environmental significance D.G. ELIOPOULOS1, M. ECONOMOU-ELIOPOULOS2 2 AND G. TSOUPAS 1

Institute of Geology and Mineral Exploration (IGME), Olympic Village, GR-13677, Acharnai, Greece 2 Department of Geology and Geoenvironment, University of Athens, GR-15784 Athens

Arsenic contents in large laterite deposits are <2 to a few decades ppm. However, As contents in bauxitic-laterites from Larymna, lying on karstified Jurassic limestone, vary significantly from <2 ppm to 2600 ppm, and are accompanied by elevated Co, Ni, Th, U and REE as well. Also, As contents in the yellow-grey colored bauxite ores of the ParnassosGhiona deposit, characterized by abundant pyrite and microorganisms, reach values up to 1000 ppm The latter bauxite type is common along faults, closed to overlain U. Cretaceous limestone, accompanied by thin layers of coal, which is considered to be the source As in laterites. Arsenic ranging between 0.5 to 1.6 wt% As2O3 is mainly hosted by Fe- and Al-oxides, cross-cutting matrix of an earlier stage. Sorption of both As (III) and As (V) form inner-sphere complexes on Fe-oxides, while As (III) forms outer-sphere sorption mechanisms on Al-oxides [1]. The calculated ° negative free energy (!G ) values for arsenite and arsenate ° sorption onto Fe-oxides, positive entropy (!S ) and positive enthalpy (!H°) values suggest favourable sorption of arsenic onto laterite concretions [1]. Thus, although high As content in Ni-laterites may be unacceptable for the quality of the coming products, any influence of As-bearing laterites on the groundwater aquifer would be inconsistent with the sorption of arsenic in Fe- and Al-oxides. Instead both bauxites and Nilaterites could be used to remove As from water. [1] Partey (2008) Ph.D. New Mexico IMT, Dept of Earth & Environ. Science, p.177.

A264

Goldschmidt Conference Abstracts 2010

Observations on the distribution of high 3He/4He in OIB R.M. ELLAM AND F.M. STUART Scottish Universities Environmental Research Centre, East Kilbride, G75 8DZ, Scotland, UK Picritic lavas from the ancestral Iceland plume have the highest 3He/4He yet recorded. About 30 lavas from Baffin Island and West Greenland have 3He/4He (35 - 50 Ra [1, 2]) significantly higher than the highest OIB. Contrary to established mantle models, these picrites are dominantly MORB-like but span a significant range of %Nd. While the lowest %Nd are consistent with small degrees of crustal contamination, a significant range of %Nd60 (+10 to +6.8) is best attributed to mantle heterogeneity. Thus, in the North Atlantic Palaeogene province, any putative high 3He/4He component shows Nd isotope heterogeneity that is comparable to that which in many OIBs would be attributed to multiple discrete sources. A similar picture emerges from the global OIB database. Even excluding extreme 143Nd/144Nd samples from Hawaii and Samoa, the higher 3He/4He (20-32 Ra) OIB are dominantly depleted, but still span about 4 %Nd units [3]. Thus, any depleted high 3He/4He component is not an ‘end-member’ in the sense that it can be defined within the anaytical uncertainty of the data used to define it. Rather, there is a general tendency of the highest 3He/4He OIB to be associated with a relatively depleted %Nd composition. However, there are some notable exceptions because some of the lowest %Nd OIB have high 3He/4He while OIB with MORB-like 3He/4He also show a wide range of %Nd. A single high 3He/4He mantle reservoir with a discrete Sr, Nd, Pb etc. isotopic composition does not seem consistent with the data. We suggest that the apparent association between high 3He/4He and elevated %Nd is simply a volumetric consequence of mantle heterogeneity; most of the mantle sampled by OIB is depleted, so most high 3He/4He mantle is depleted. Whatever the cause of high 3He/4He in OIB, it does not exert a strong influence on the lithophile isotopes and readily overprints the He isotope composition of all OIB sources encountered. A component whose high [He] exerts such influence on mixtures with other mantle sources is inconsistent with the generation of high 3He/4He by melt extraction irrespective of the relative partition coefficients of U, Th and He. [1] Starkey et al. (2009) Earth Planet. Sci. Lett. 277, 91–100. [2] Stuart et al. (2003) Nature 424, 57–59. [3] Class & Goldstein (2005) Nature 436, 1107–1112.

Diagenesis of jarosite and hematite: A low temperature path to nanophase iron oxides and ‘specular’ c-axis aligned hematite on Mars M.E. ELWOOD MADDEN1, A.S. MADDEN1, V.E. HAMILTON2, J.D. RIMSTIDT3, S.K. ZAHRAI1 1 AND M.A. MILLER 1

School of Geology and Geophysics, University of Oklahoma, Norman OK 73019 ([email protected]) 2 Southwest Research Institute, Boulder CO 80302 ([email protected]) 3 Dept. Geosciences, Virginia Tech, Blacksburg VA 24060 ([email protected]) The association of c-axis aligned ‘specular’ hematite with low temperature mineral assemblages, including clays, sulphates, and evaporites on Mars does not fit previous models of specular hematite formation which require hydrothermal alteration of iron hydroxide precursors or dry oxidation of mafic glass. Laboratory experiments examining the rate of jarosite dissolution over temperatures from 277- 323K and a range of aqueous compositions (pH 2-6, varying ionic strength) demonstrate that jarosite converts dominantly to hematite at rates of 10-7- 10-9 mol m-2 s-1, resulting in abundant nanophase hematite platelets. Based on transmission electron microscopy observations, these hematite platelets replace jarosite within the original particles, nucleate on the surface of jarosite particles, and may also nucleate from the bulk solution at pH"3. At pH 2, no secondary hematite was observed in short term experiments. In separate experiments, c-axis aligned ‘specular’ hematite was synthesized through freeze-thaw treatment of synthetic hematite nanoparticles, similar to those produced by jarosite dissolution. Freezing followed by desiccation also produced specular hematite with thermal emission spectra indicative of c-axis aligned particles nearly identical to thermal emission spectra of Meridiani Planum. Scanning and transmission electron microscopy (SEM and TEM) images suggest that aqueous suspensions of hematite nanoparticles crystallographically align parallel to the basal surfaces during confined freezing to form larger domains. Stacking of the aligned domains leads to mm-scale particles with specular reflectance. These results suggest that aqueous alteration of jarosite to hematite followed by freezing of porewaters may produce c-axis oriented hematite similar to that observed on Mars. While this process alone does not generate spherules, freezing may align particles prior to spherule formation or alter spherules of disordered nanophase iron oxides to form c-axis aligned hematite.

Goldschmidt Conference Abstracts 2010

Adsorption of Mn(II) at the surface of birnessite: Characterization of sorption products by XRD and EXAFS analyses

A265

Emerging patterns in deep-sea microbial iron mats D. EMERSON1*, S.M. MCALLISTER2, C. CHAN3, E. FLEMING1 AND C. MOYER2 1

EVERT J. ELZINGA Rutgers University, Department of Earth & Environmental Sciences, Newark, NJ 07102 Manganese oxides are among the most reactive mineral phases found in the environment and exert a strong control on the chemistry of soil and sediments through adsorption and redox reactions [1]. Here, results from experiments characterizing the interaction between Mn2+ and hexagonal birnessite, which typifies the phyllomanganates found in natural aquatic systems, are presented for a variety of reaction conditions. Experiments were performed at varying pH (3.0-7.0) and Mn2+ concentrations (0.5 – 4 mM) under both oxic and anoxic conditions. Reacted solids were washed and dried, and characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Under all conditions studied, the XAS results indicate an increase in MnIII content of the reacted solids relative to non-reacted birnessite, consistent with electron transfer between surface sorbed Mn2+ and structural MnIV. For samples reacted at pH 7.0, XAS and XRD results show that reaction with Mn2+ results in transformation of birnessite into manganite (#-MnOOH), a tunnel-structured MnIII phase. No differences in reaction products were observed between samples reacted under oxic and anoxic conditions, suggesting that oxidation of Mn2+ by O2 is of secondary importance in these systems. The results of this study indicate that Mn2+ acts as a reductant of birnessite under the conditions applied. Transformation of birnessite into #-MnOOH during interaction with Mn2+ resembles the transformation of bacteriogenic vernadite ($-MnO2) into feitknechtite (%MnOOH) resulting from reaction with Mn2+ at concentrations > 0.5 mM observed by Bargar et al. [2], and can be explained in terms of a thermodynamic driving force resulting from lowering Eh by introduction of Mn2+ facilitating transformation. The kinetics and pathway (s) of transformation, and the effects of and consequences for adsorbed trace impurities are the subject on ongoing research. [1] Post (1999) Proceedings of the National Academy of Science of the USA 96, 3447–3454. [2] Bargar et al. (2005) American Mineralogist 90, 143–154.

Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, ME, 04538, USA 2 Western Washington University, Bellingham WA 3 Univ. of Delaware, Newark, DE There is growing evidence that Fe-oxidizing bacteria (FeOB) are the primary mediators of Fe-oxyhydroxide deposition at Fe (II)-rich marine hydrothermal vents. One clade of bacteria in particular, the candidatus class ‘Zetaproteobacteria’ has been found consistently in iron-rich microbial mats. Thus far, this class is represented by only one cultivated genus, Mariprofundus an obligately lithotrophic FeOB that is a microaerophile. Mariprofundus forms a helical stalked comprised primarily of Fe-oxydroxide. We have investigated Fe-mats at Loihi Seamount, an active undersea volcano (950 mbsl) in the Pacific for over five years. These studies reveal total numbers of bacteria remain quite constant in active mats at Loihi, as does population structure as revealed by tRFLP. Both tRFLP and SSU rRNA gene clone libraries indicate Zetaproteobacteria are consistently present, and dominant features of tRFLP profiles, or numerically dominate clone libraries. Phylogenetic analysis indicates that the cultured Mariprofundus strains are relatively rare compared to other uncultivated members of the Zetaproteobacteria. Colonization of microslides by FeOB at different vents consistently show that stalk-forming FeOB initiate colonization. Gross morphological characterization of the mats reveal at least four morphotypes, Mariprofundus-like helical stalks, a Y-shaped tubular oxide, long tubular sheaths, and particulate oxides. The stalks, Y-structures, and particulate oxides are most common, while the sheaths are rare and sporadic. Specific cell types have been linked to stalks, Y-structures, and sheaths. Bulk analysis suggests that the vast majority of these structures are devoid of cells, suggesting active growth is restricted to specific zones within the mats. Overall, these results suggest that Fe-mats are stable communities dependent upon a continuous source of Fe (II) with internal structure composed of unique populations of FeOB, most of which remain a mystery.

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Goldschmidt Conference Abstracts 2010

Geochemical parameters and age of U ores related to sodium metasomatism in the Ukrainian Shield ALEXANDER EMETZ1, MICHEL CUNEY2, JULIEN MERKADIER2 AND NATALIA NAZARCHUK1

Vanadium: A new biomarker of ancient life JULIENNE RUTH EMRY, ALISON OLCOTT MARSHALL AND CRAIG MARSHALL* Department of Geology, University of Kansas, Lawrence Kansas, 66049, USA ([email protected], [email protected], *correspondance: [email protected])

1

IGMOF of NAS of Ukraine, Kiev-142, 34 Palladina Av. ([email protected]) 2 B.P. 23., 54501 Vandoeuvre-Les-Nancy, France ([email protected]_nancy.fr) The first U deposits related to sodium metasomatism in Ukraine were discovered in 1946 in the Kryvy RigKremenchug syncline zone filled with iron metasedimentary formations. Since that time around 20 deposits with actual resources over 200 000 t of U were discovered westward in the gneiss-migmatite-granite formations of the Ingul megablock of the Ukrainian Shield. Albitite bodies were developed along with crystallization of aegirine and Na-amphyboles as major femic minerals but U mineralization is predominantly represented by uraninite and brannerite. Albitization was supported by dequartzification of the host rocks (silica ejection) with formation of episiyenites around albitites when in the host granites or aegirinites and reibeckitites when in the iron formations. Ca metasomatism is also widely spread in the deposits and is the major factor controlling U ore position. U-bearing albitites are enriched in Na, Ca, Sr, P, F, Be and Zr but dramatically depleted in Si and K in comparison with the host rocks. Hondrite-normalised REE distribution in the host rocks and U ore bodies is in general similar although depletion in LREE connected with the hydrothermal alterations is often detected. Uraninite and brannerite irregularly contain isomorphic Th but Th content in the host rocks and in the ores scatters similarly in low amount from 0.6 to 70 ppm. La/Yb index varies from 1 to 105, progressively decreases with increasing Th content in the host rocks of the Kirovograd megablock whereas both in the metamorphic rocks of the Kryvy Rig-Kremenchug syncline and in all ore samples positive correlation between Th content and La/Yb ratio is observed. This effect suggests synchronous leaching of La and Th during albitization and U ore deposition. U/Pb dating was performed for uraninite crystals of the Zhovta Richka U deposit using CAMECA 3F SIMS (CNRS, Nancy). Uraninite contains impurities of non-radiogenic 204Pb but corrected for the corresponding radiogenic lead U/Pb isochronic age is 1760±22 Ma (10 points solution).

Carbonaceous microstructures from the 3.5 billion year old Apex Chert have been proposed as the oldest evidence of life on Earth [1, 2]. However, they have also been described as abiotic material formed by Fischer-Tropsch-style reactions within a hydrothermal depositional environment [3, 4]. Several analytical techniques have been applied to these microstructures [5, 6], but it is still unclear if abiotic or biotic processes were the dominant mechanism of formation [7].

New Data for an Old Problem To obtain a new perspective on the issue, we isolated carbonaceous microstructures from the Apex Chert and analyzed them with synchrotron-based x-ray flourescence. The data collected reveal that the concentration of vanadium is significantly greater in the carbonaceous microstructures than in the host cherts. Vanadium is a biologically important element, and is used by many organisms, including nitrogenfixing bacteria [8]. Proxy data, including the concentration of vanadium found within Archean shales, indicate that the Archean oceans were depleted in vanadium [9, 10]. Additionally, as vanadium is not adsorbed by organic material [11], its enrichment in these carbonaceous microstructures is best explained by biological concentration. Thus, these new data indicate that these controversial carbonaceous microstrucutres are of biological origin, and that vanadium, therefore, is a good biosignature for prospecting for signs of life in the Archean Apex chert, as well as in other ancient deposits. [1] Schopf & Packer (1987) Nature 237, 70–73. [2] Schopf (1993) Science 260, 640–646. [3] Brasier et al. (2005) Prec. Res. 140, 55–102. [4] Lindsay et al. (2005) Prec. Res. 143, 1– 22. [5] Schopf et al. (2002) Nature 416, 73–76. [6] Pini et al. (2009) Nature Geosciences 2 640–643. [7] Marshall et al. (in press) Astrobiology [8] Rehder (2008) Org. Biomol. Chem. 6, 957–964. [9]. Siebert et al. (2005) GCA 69, 1787–1801. [10] Lyon et al. (2009) Annu. Rev. Earth Planet. Sci. 3, 507– 534 [11] Krauskopf (1956) GCA 9, 1–32.

Goldschmidt Conference Abstracts 2010

Microbial organoarsenical production in geothermal systems ANNETTE SUMMERS ENGEL1, LINDSEY R. JOHNSON1, AMITAVA ROY2 AND GREGORY MERCHAN2

A267

The stability of phlogopite in the sub-continental lithospheric mantle: KCMASH±CO2 vs. KMASH-CO2 A. ENGGIST* AND R.W. LUTH

1

Department of Geology & Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803 USA 2 J. Bennett Johnston, Sr., LSU Center for Advanced Microstructures and Devices, Baton Rouge, LA 70806

Microbial As cycling from non-sulfidic, circumneutral pH fluids above 50 °C is poorly understood because few natural systems exist. El Tatio Geyser Field, Chile, is one example where geothermal fluids discharge at local boiling (~86 °C) and As (III) progressively oxidizes to As (V) downstream. Although removal of As (III) from solution may be occurring through sorption onto organic matter or by photooxidation to As (V), changes in As speciation due to microbial metabolism were investigated, with a focus on the occurrence of organoarsenical compounds. There has been limited research on the presence, origin, or possible role of organoarsenicals in geothermal systems. Arsenic in mats and sediments was in the As (V) valence state, and XANES and EXAFS confirmed that As was not bound to S or occurred as an oxide mineral, but instead existed as inorganic As (V) weakly complexed to Fe oxyhydroxides and at least two organoarsenicals, dimethylarsinic acid (DMA), which signified methylated metabolites, and roxarsone, which was a proxy for other complex biological arsenicals like arsenobetaine. XANES spectra from the furthest downstream mats fit best with DMA, whereas upstream fits were best with roxarsone and comprised almost 50% of the mat As species. Methylated As is usually produced through detoxification, but complex As species could indicate novel pathways. From 16S rRNA gene sequences, Chloroflexi were the most prevalent in the mats, especially downstream. Phylogenies of arsenic oxidase (aroA)-like genes identified potential homologues from Chloroflexi genomes and fewer homologues affiliated with the Proteobacteria. No Aquificales, Deinococci, or Chlorobi aroA-like genes were retrieved. Chloroflexi are considered anoxygenic phototrophs, and have not been previously linked to phototrophic or even heterotrophic As (III) oxidation, and no known Chloroflexilike aroA-like genes have been found from other geothermal or As-enriched environments. With some indication that aroA is used for detoxification by some Proteobacteria, the Chloroflexi communities downstream could be responsible for the identified methylated organo-arsenicals in the mats. This work provides an important perspective into the role of microbes in producing organoarsenical compounds in geothermal systems.

C. M. Scarfe Laboratory of Experimental Petrology, Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada (*correspondence: [email protected]) Previously, we reported that in the phlogopite + magnesite system, phlogopite can be stable to a depth of 200 km in the presence of carbonate at a cooler lithospheric mantle geotherm of 40 mWm-2. At the base of a hotter sub-continental lithospheric mantle (SCLM), phlogopite and magnesite will react to form enstatite, olivine, garnet and hydrous, potassiumand CO2-rich melt [1, 2]. Here we present first results of phlogopite + diopside + enstatite ± carbonate.

KCMASH In the presence of pyroxenes, phlogopite is stable to 1300°C and 5.5 GPa and starts to break down at 6 GPa; amphibole becomes stable and coexists with remaining phlogopite to higher pressures, which is in agreement with [3]. The solidus is located at 1400 and 1350°C at 5 and 4 GPa, respectively, where phlogopite reacts out over a temperature range of about 50°C and garnet, enstatite, diopside, olivine and melt is in equilibrium.

KCMASH-CO2 Adding carbonate to the pyroxene-bearing system lowers the thermal stability of phlogopite considerably: Phlogopite starts to react out at 4 GPa and ~950°C. An experiment at 6 GPa and 1000°C still contains phlogopite, which may reflect the sluggish kinetics of the breakdown reaction. Above the solidus, melt coexists with garnet, enstatite, diopside, and olivine. Melt quenches to amphibole and phlogopite of around 10 &m in size.

KCMASH±CO2 vs. KMASH-CO2 No hydrous solution was seen escaping from the capsules upon breach. Amphibole is the new phase occurring, either primary, to higher pressures, or, above solidus, as an additional quench product. First results indicate that in KCMASH-CO2 and at SCLM conditions, phlogopite is stable to about 4.5 and < 4 GPa with a 40 and 44 mWm-2 geotherm, respectively. [1] Enggist et al. (2009) Eos Trans. AGU 90(52) Abstract V51B-1669. [2] Enggist & Luth (2010) GeoCanada2010, expanded Abstract, 4p. [3] Sudo & Tatsumi (1990) Geophys. Res. Lett. 17(1), 29–32.

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Goldschmidt Conference Abstracts 2010

Tracking solutes and water from subsurface drip irrigation application of coalbed methane produced waters

Groundwater composition of a rock waste pile of the uranium mine of Poços de Caldas, Brazil

MARK A. ENGLE1, CARLETON R. BERN2, RICHARD W. HEALY2, JAMES I. SAMS3, JOHN W. ZUPANCIC4 AND KARL T. SCHROEDER3

J. ENZWEILER*, S.Y. PEREIRA, J.A. BARROS AND A.J.B COTTA

1

U.S. Geological Survey, Reston, VA, 20192 ([email protected]) 2 U.S. Geological Survey, Denver, Colorado 80225 3 National Energy Technology Lab, U.S. Dept. of Energy, Pittsburgh, PA 15236 4 BeneTerra, LLC., Sheridan, WY 82801 Coalbed methane (CBM) currently accounts for ~7% of US natural gas production. Compared to traditional sources, CBM co-produces large volumes of water. Subsurface drip irrigation (SDI) is an emerging technology that beneficially uses pre-treated CBM waters (injectate) by emitting them into the root zone of agricultural fields to aid in irrigation. The method is designed to minimize impacts by storing salts in the vadose zone. Research objectives include tracking the injectate-derived water and salts at an SDI site on an alluvial terrace, adjacent to the Powder River, Wyoming. This research utilizes soil science, geochemical, and geophysical methods. Initial results from pre-SDI data collection and the first year of post-SDI operation will be presented. Over the first year of the study, soil moisture significantly increased in the SDI areas and groundwater elevations in wells below the SDI fields increased by ~15cm (~45% of total SDI irrigation). The injectate is dilute with respect to most constituents (except, most notably, sodium adsorption ratio [SAR]) relative to the site groundwater. Large variations in soil water salinity (some samples much greater than groundwater) and SAR within the SDI fields suggest that, in general, SAR is buffered in the vadose zone by calcite and gypsum dissolution and that some readily soluble Na-rich salts may also be present in small portions of the site. Changes in chemical composition and specific conductivity along surface water transects adjacent to the site are minimal, suggesting that discharge to the Powder River from groundwater underlying the SDI fields is negligible. Findings from this research provide a critical understanding of water and salt dynamics associated with SDI systems using CBM produced water. Information obtained from different parts of this heterogeneous site can be used to improve SDI and other CBM produced water use/disposal technologies in a variety of environmental settings of the PRB to minimize adverse impacts.

Institute of Gesociences, Universty of Campinas - UNICAMP Campinas, SP, Brazil, P.O. Box 6152 (*correspondence: [email protected]) While the decommission strategies of the former uranium production centre of Poços de Caldas (Brazil) are being discussed and elaborated, several studies performed at the area [1-3] help to give insight about the geochemical processes inside the rock waste piles, which are basically related to the oxidative dissolution of pyrite. For instance, the chemical composition of the groundwater collected at the monitoring wells of waste rock pile 4 show that the oxidation inside the pile is not uniform. In the present study, we looked at the geochemistry of the underground water of three monitoring wells (PM-01, PM-03 and PM-04) and also from an artificial pond (BNF) which receives the drainage of the pile before neutralization. PM-03 has the shallowest water level (~-25 m), pH 4.4 and chemical composition dominated by sulphate, fluoride, calcium, iron, aluminum, potassium and magnesium. PM-01 and PM-04 (> -46 m and -41 m, respectively) water samples were alkaline and near neutral and contained low quantities of dissolved ions. The behavior of rare earth elements (REE) was compared with previous data of the acid drainage of the Osamu Utsumi mine [4]. The &REE=452 µmoL/L of PM-03 is more than twice that measured in the above mentioned study, suggesting an intense weathering rate at the upper part of the waste pile. Furthermore the NASC (North American Shale Composite) REE normalized patterns of water samples show enrichment in LREE compared to the HREE. Negative and positive anomalies for Ce and Eu, respectively, were observed for the acidic PM-03 and BNF waters. The Eu positive anomaly was not previously observed [4] and is probably related to the complexation of Eu2+ by sulphate and fluoride, after its release from the host minerals. This suggestion will be further checked by modeling with a speciation code, considering the whole chemistry of the water samples. [1] Fernandes et al. (1998) Waste Manage. 18, 169–181. [2] Fernandes et al. (2008) J. Environ. Manage. 87, 59–72. [3] Franklin (2007) Doctorate Thesis, COPPE/UFRJ II. [4] Serrano et al. (2000) Chem. Geol. 165, 167–180.

Goldschmidt Conference Abstracts 2010

Reactivity of Ferrihydrite 1

2

JASMINE J. ERBS , THELMA BERQUØ , SUBIR K. BANERJEE3, GEGORY V. LOWRY4, BRIAN C. REINSCH4, BEN GILBERT5AND R. LEE PENN6 1

University of Minnesota, Department of Chemistry 207 Pleasant St. SE, Minneapolis, MN 55455 ([email protected]) 2 University of Minnesota, Institute for Rock Magnetism, 100 Union Street SE, Minneapolis, MN 55455 ([email protected]) 3 University of Minnesota, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455 ([email protected]) 4 Civil & Environmental Engineering, Carnegie Mellon University, 119 Porter Hall, Pitsburgh, PA 15213 ([email protected], [email protected]) 5 Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Rd., MS 90-1116, Berkeley, CA 94720 ([email protected]) 6 University of Minnesota, Department of Chemistry 207 Pleasant St. SE, Minneapolis, MN 55455 ([email protected]) Iron oxide nanoparticles are a major source of reactive surface in many natural systems. Ferrihydrite is a naturallyoccurring iron oxide that typically occurs as nanoparticles in the 3-10 nm size range. This material is dynamic from the perspectives of size, phase, morphology, reactivity, and aggregation-state. Quantitative results tracking reactivity as a function of particle size, arsenic loading, and storage method will be presented. One major result is that dried ferrihydrites are substantially less reactive than never-dried materials. A second result is that the method of arsenic incorporation (e.g. co-precipitated or adsorbed to pre-existing ferrihydrite nanoparticles) is a strong predictor of arsenic release during reductive dissolution. Results from characrerization by transmission electron microscopy, X-ray diffraction, small angle X-ray scattering, X-ray absorption, and magnetic methods will be presented.

A269

A conceptual model for foraminiferal proxy incorporation based on their biomineralization mechanism JONATHAN EREZ Institute of Earth Sciences, the Hebrew University of Jerusalem 91904, Israel ([email protected]) Based on recent observations it has been demonstrated that the fluid from which perforate foraminifera precipitate their secondary calcite is modified seawater. The seawater is supplied by endocytosis of large vacuoles which are modified within the cell and then are exocytosed into a privileged space where biomineralization occurs. Based on the dynamics of vacuole supply the residence time of the fluids in the biomineralization site is estimated to be short (few to tenths of minutes). Both trace elements and isotopes are incorporated into the secondary calcite by Rayleigh type fractionation processes. The main factor which controls the degree depletion of the calcification reservoir is the supply of CO32ion to the privileged space. A carbon concentrating mechanism (CCM) can be demonstrated both in the vacuoles and in the privileged space. The CCM is based on the diffusion and accumulation of CO2 (aq) originating in acidic seawater vesicles and from respiration into the alkaline seawater vacuoles which eventually arrive to the privileged space. Environmental parameters in the original seawater such as DIC, pH and/or CO32- may influence the CCM and thus control the Rayleigh processes involved in the proxies incorporation into the shell. However, different ions and isotopes need to be examined individually to be explained with this mechanism. New confocal microscope observations and experiments of these processes leading to this conceptual model will be demonstrated and discussed.

A270

Goldschmidt Conference Abstracts 2010

Lead isotopes in marine barite: An intermediate water mass tracer A.M. ERHARDT1,2* AND A. PAYTAN2

Distal transport (>650 km) of detrital shocked zircon in a cratonic fluvial system: The Vaal River, South Africa TIMMONS M. ERICKSON1*, AARON J. CAVOSIE1, HENRI A. RADOVAN2 AND DESMOND E. MOSER3

1

Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 (*correspondence: [email protected]) 2 Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 95064 ([email protected]) Changes in the chemistry of intermediate water provides insight into formation and movement of this water mass. These intermediate water dynamics are attributed to the redistribution of heat and freshwater, making it an important driver and archive of climate change. This study investigates the utility of lead isotopic ratios incorporated into marine barite to address changes in intermediate water provenance. Lead and its isotopes are introduced into the ocean primarily through the weathering of continental rock. These rocks may have distinct isotopic signatures, depending on the age of the eroded material. As a result, the source regions of a water mass and climate related weathering processes can be reconstructed [1]. Marine barite is known to precipitate directly from seawater in micro-environments containing decaying organic mater. It has been shown to record seawater chemistry for a variety of trace elements. Marine barite forms predominantly at intermediate water depths and does not exchange with seawater or porewater after formation. This work reports the first application of stable lead isotopes in marine barite. To determine the integrity of the method, marine barite was precipitated in seawater with varying concentrations and ratios of lead isotopes. These experiments show a linear relationship between lead concentration in the marine barite and seawater. In addition, the lead incorporated into the barite crystal faithfully recorded the seawater isotopic composition. Marine barite from core top sediments demonstrate a near contemporaneous regional record consistent with expected intermediate water signatures. Down core records show large scale shifts in the lead isotopic signature. These changes generally correspond to global glaciation events, potentially reflecting changes in ocean circulation and source waters during these times. The trends exhibited in this marine barite lead record are consistent with records from iron-manganese nodules, though the magnitude of the shifts are greatly increased. Potential water source regions and their implications for global circulation will be discussed. [1] Foster & Vance (2006) Nature 444, 918–921.

1

Univ. of Puerto Rico, Dept. of Geology, Mayagüez, PR 00681 (*correspondence: [email protected]) 2 Univ. of Puerto Rico, Dept. of Physics, Mayagüez, PR 00681 3 University of Western Ontario, Dept. of Earth Sciences, London, ONT N6A 5B7, CA No evidence of meteorite impacts has been recognized from the Hadean. A new approach to discover the early impact history is through identification of detrital shocked minerals. Shocked minerals eroded from an impact crater express unique microstructures. The 2.02 Ga Vredefort Dome is the largest and oldest identified impact structure on Earth. The Vredefort structure is 90 km wide and is the remnant of the central uplift of a 300 km wide multi-ring basin. The Vaal River cross cuts the Vredefort Dome and flows 750 km further to its confluence with the Orange River. Cavosie et al. [1] identified detrital shocked zircons from sediments in the channel of the Vaal River and its tributaries within the Vredefort Dome, including grains with multiple sets of Planar Fractures (PFs). We have extended the occurrence of shocked zircons in the Vaal River in channel sediments ~675km downstream from the Vredefort Dome. Zircons were analyzed by SEM in sediments from several localities. Shocked zircons were identified in 5 of 6 samples, including the furthest downriver sample near Sydney-on-Vaal, approximately, 675 km from Parys, a location on the Vaal River chosen to represent the center of the Vredefort Dome. PFs were recognized in euhedral, subhedral and rounded zircons that show severe sedimentary abrasion. Multiple grains with PFs have been identified, with 90% of the identified shocked zircons exhibiting at least two sets of PFs and 45% displaying 3 sets. This study demonstrates that shocked zircons survive sedimentary transport to distal locations (~700 km of fluvial transport) and are therefore a robust record of eroded impact structures. Shocked zircons will likely remain within detrital systems long after erosion and tectonics has destroyed the original impact structure. An impact record from the early Earth may therefore exist as shocked zircons in Archean siliciclastic deposits containing Hadean detritus. [1] Cavosie et al. (2010) GSA Bulletin, in press.

Goldschmidt Conference Abstracts 2010

Montmorillonite catalysis and potential of charge density in proposing the target sites on Mars for search of organics G. ERTEM1,2*, R. SCHUHMANN3, A. STEUDEL3, K. EMMERICH3 AND R.M. HAZEN4 1

Carl Sagan Center, SETI Institute, Mountain View, CA 94043, USA 2 National Institutes of Health, Bethesda, MD 20892, USA (*correspondence: [email protected], [email protected]) 3 Karlsruhe Institute of Technology, Germany 4 Geophysical Laboratory, Carnegie Institution, Washington DC 200015, USA Montmorillonite, a member of phyllosilicate group minerals, which have been identified on martian soil, serves as catalyst for the non-enzymatic formation of RNA-like oligomers in aqueous solution [1]. Extent of catalysis widely varies with the region where montmorillonite is mined [2, 3]. While oxide composition of montmorillonites varies within narrow limits, their charge densities resulting from isomorphous substitutions fluctuate to a larger extent. Research designed to investigate whether there exists a relation between the layer charge density of montmorillonites mined in different regions, and the extent of their catalytic activity demonstrates that montmorillonites with low charge density exhibit higher catalytic activity, Table 1. Table 1. Mean layer charge of montmorillonites per formula unit, ', length of the longest oligomers, and their % yields. Charge density of montmorillonites can be determined by measuring the d(001) spacing of [mineral- alkyl ammoniummineral] complexes by XRD) [4]. Charge density can also be calculated from the chemical analysis results [5] During NASA’s next rover mission to Mars, CheMin (CHEmistry and MINeralogy) will provide information on the mineralogical, and elemental analysis of the samples by combined application of XRD and XRF. Therefore, results obtained in this work may play a significant role in determining the target sites on Mars in future missions for the search of organic compounds, and extinct or extant life. [1] Ertem et al. (2007) Astrobiology 7, 715–722. [2] Kawamura & Ferris (1994) J. Am. Chem. Soc. 116, 7564– 7572. [3] Ertem (2004) Origins Life Evol. Biosphere 34, 549– 570. [4] Lagaly & Weiss (1970) Kolloid Z. und Z. Polymere 237, 266–273, 364–368. [5] Köster, H.M. (1977) Clay Minerals 12, 45–54.

A271

Insights from comparisons of two Lau Back-arc Spreading Centers S. ESCRIG1, C. LANGMUIR1, A. BEZOS2, P.J. MICHAEL3 4 AND R. ARCULUS 1

Harvard University, Cambridge, MA 02138, USA Lab de Planet Géodyn. de Nantes, 44322 Nantes, France 3 Dept. Geosciences, Univ. Tulsa, Tulsa, OK 74104, USA 4 Research School of Earth Sciences, ANU, Australia 2

Eastern Lau Spreading Center (ELSC) and Fonualei Spreading Center (FSC) are two independent systems in the southern and northern Lau Basin, respectively. Both spreading centers are closest to the Tonga arc front at their southern extremity, and increase in distance northwards. The distance from the arc with latitude increases twice as fast for the FSC for a similar latitude interval. Trace element and Pb-Sr-Nd isotope data for >110 samples from ELSC and >60 from FSC permit a comparison of how back-arcs vary along strike and with distance from the arc. While to first order the subduction input to back-arc lavas decreases with distance from the arc front, the back-arc composition and flux also oscillates along-strike in tandem with the arc front. Directly behind volcanoes of the arc front, the back-arc is shallower and contains more subduction input that corresponds with the particular composition of the arc front volcano. This observation precludes major along-strike flow of the mantle wedge to influence the mantle that feeds the back-arc. Differences in subduction input in north and '

Length

% Yield

Otay 0.37 4 0.05 Vol 0.29 10 0.07 Japan 0.29 9 0.04 Swy-2 0.29 9 0.11 south also influence both arc and back-arc, and back-arc lavas at similar distances vary in composition accordingly. The FSC also has less decrease in subduction input with distance than the ELSC, and a general ‘pollution’ of subduction influence. For the two spreading centers, this leads to trends with distance from the arc with slopes of the same sign but different values for analogue element ratios such as Nb/U, Ce/Pb, or Th/Nb. As a further contrast, for the FSC, the background mantle becomes progressively enriched northwards, a feature not observed in the south. As a consequence, trends with distance for the two spreading centers have opposite slope for Pb isotope ratios, La/Sm and Th/La. These complexities show that global relationships of backarc composition with distance to the arc do not exist. Subduction input varies along strike and the back-arc chemical composition does not change linearly with distance, but fluctuates at the same length scale as arc volcanoes; mantle wedge composition is an important factor; and some back-arcs are polluted by an arc component owing to their tectonic history.

A272

Goldschmidt Conference Abstracts 2010

Evolution of H2O and CO2 contents in silicate melt inclusions during postentrapment crystallization

Geochemical modeling of speciation and the prediction of bioaccessibility: Can the former lead to the latter?

R. ESPOSITO, M.J. STEELE-MACINNIS, L. FEDELE AND R.J. BODNAR

M.E. ESSINGTON*

Department of Geosciences, Virginia Tech, Blacksburg, VA 24061 USA ([email protected], [email protected], [email protected]) Concentrations of H2O and CO2 in silicate melt inclusions are often interpreted to represent magmatic ‘degassing paths, ’ in which depressurization of the magma during ascent leads to volatile saturation and release of CO2 and H2O from the melt [1]. This interpretation explicitly assumes that melt inclusions are trapped under conditions of volatile saturation. If the trapped melt is saturated in volatiles, then the melt must exsolve a volatile phase if any post-entrapment crystallization occurs on the walls of the inclusion (which happens to greater or lesser extent in all melt inclusions). As a result, the pressure inside the MI may differ from the confining pressure during post-entrapment cooling, and the PT path of the MI may be calculated knowing the solubility of H2O and CO2 in the melt as a function of temperature and pressure, as well as the PVT properties of the of H2O-CO2 volatile phase and the partial molar volumes of H2O and CO2 in the melt. Using PVTX data for the systems NaAlSi3O8-H2O and NaAlSi3O8-H2O-CO2 [3, 4], we investigate the effect of small fractions of post-entrapment crystallization on the dissolved volatile content in an albitic melt inclusion entrapped under conditions of volatile saturation. The model is constrained to be a closed, isochoric system. As small amounts of albite crystallize on the inclusion walls, nucleation and growth of an H2O or H2O-CO2 vapor bubble occurs and the pressure inside the MI is estimated from the difference between the molar volume of the volatile phase and the partial molar volume of the volatile in the melt using the EOS for H2O-CO2. Model results show that dissolved volatile contents in the melt vary in a systematic manner during low degrees of postentrapment crystallization. More importantly, the H2O and CO2 contents of the melt (glass) in the inclusion define trends that are similar to those produced during open system degassing. Thus, melt inclusions that all trap a volatilesaturated melt, but experience varying degrees of postentrapment crystallization on the walls, will define an H2OCO2 volatile trend similar to a open-system degassing path. [1] Lowenstern (1994) Geology 22, 893–896. [2] Roedder (1984) Rev. Mineral. 12. [3] Burnham & Davis (1974) Am. J. Science 274, 902–940. [4] Holloway & Blank (1994) Rev. Mineral. 30, 187–225.

Biosystems Engineering and Soil Science, University of Tennessee, USA (*correspondence: [email protected]) It has long been recognized that the chemical speciation of an element in the terrestrial environment is an important determinant of bioavailability. Valence (redox status), aqueous speciation, solid-phase speciation (mineralogy), and adsorbed phase speciation (exchangeable vs. non-exchangeable) all play a role in dictating the ability of an organism to assimilate a potentially toxic element. Mechanisms to predict the distribution of an element between and within the various phases of soil and other environments are commonly based on the Laws of Thermodynamics through the application of the ion associate model. This model, which is executed by various geochemical computer codes, requires two generally distinct datasets: (1) the chemical characteristics of the environment in question, and (2) the thermodynamic data that described elemental distribution. As the Laws of Thermodynamics are assumed immutable, the quality of the ion speciation computations is due to the quality and completeness of the two datasets. For natural systems, the determination of the salient chemical characteristics of an environment that affect elemental fate and behavior can be a daunting, if not impractical (or impossible) exercise. Also implicit to the model predictions are the robustness and accuracy of the accompanying thermodynamic database. The satisfactory determination of aqueous phase speciation is required for the prediction of mineral solubility and adsorption equilibria. Although geochemical models are meagerly equipped to predict the stability a small number of pure and macrocystalline minerals, and to consider the surface complexation of a limited number of metals and ligand, the coupling of geochemical model predictions to bioaccessibility remains a challenge. This presentation will examine the requirements for predicting the fate and behavior of the emerging contaminant antimony. The information necessary to delineate aqueous, solid, and adsorbed phase speciation of antimony will be identified. Mechanisms to translate geochemical modeling results to predictions of bioaccessibility will be discussed.

Goldschmidt Conference Abstracts 2010

A273

The Zn-Pb-(Ag) epithermal mineralization of Mazarrón (Spain): A preliminary isotope study

Interaction between Aluminium ion and poly(acrylic acid) in aqueous solution

I. ESTEBAN1*, J. CARRILLO2,3, S. MORALES1,3, F. VELASCO4, I. YUSTA4 AND A.J. BOYCE5

MAYUMI ETO1, YUKA MASAKI1, SHUQIN BAI2, YUTAKA TSUJI3, YOSHIHIRO OKAUE1 1 AND TAKUSHI YOKOYAMA

1

Min. & Petr. Dep., U. of Granada (*correspondence: [email protected]) 2 Scie. Educ. Dpt., U. of Granada, Spain 3 IACT, U. of Granada-CSIC. Spain 4 Min. & Petr. Dep., U. of Pais Vasco, Spain 5 SUERC, Scotland, UK The Volcanic Field of SE Spain hosts several precious/base-metal epithermal volcanic-hosted deposits [1]. Among them, Mazarron comprises several volcanic centers of !"#!$%& '()'$()*()"+,/shoshonitic composition which show pervasive hydrothermal alteration and related Zn-Pb-Ag mineralization. Deposits occur as stockworks and vein systems of sphalerite, silver-rich galena, pyrite and marcasite with quartz and carbonates. Common Fe-Al sulfates are found in a thick net of decimeter to submillimeter size veins. Barite veins are also present. Preliminary sulfur isotope study for the base-metal sulfides show a $34S range between 5 and 13‰. In contrast, pyrite-marcasite values show a wider $34S range: between -3 to 29‰, with depleted sulfur in earlier crystals. Barite exhibits a bimodal $34S distribution: from +14 to +18‰ and around +54‰. $18Obarite is more homogeneous: between +12 to +17‰); Fe-Al sulfates, show significant variations in isotopic signature of S (2-14‰), O (3 to 13‰ in SO4 and 1 to 11‰ in OH group) and D (-54 to -115‰). O isotope equilibrium between SO4 and OH in these minerals is only established in one case, yielding a temperature of 150°C and pointing to a typical low-temperature hydrothermal environment. The range in sulfide sulfur isotopic is suggestive of thermochemical sulfate reduction of sea water. The extremely enriched sulfur signatures (pyrite-marcasite and barite) indicating closed system conditions. Isotopic (e.g. depleted deuterium values) and geological evidence also support a magmatic fluid input. The Fe-Al sulfate mineralizing event may represent the waning stage of the hydrothermal system, rather than a supergene event as is invoked in other epithermal deposits with similar sulfur signatures [1]. These data therefore suggest a marine-magmatic origin for the Mazarrón ore-fluids. Mazarron in an unusual and tantalising deposit, the origin of which involved complex mineralizing processes, not typical of epithermal volcanic-hosted deposits. [1] Arribas et al. (1995) Econ. Geol. 90, 795–822.

1

Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 812-8581, Japan ([email protected]) 2 College of Environment and resources, Inner Mongolia, University ([email protected]) 3 Kurume National College of Technology, Komorino, Kurume 830-8555, Japan ([email protected])

In nature, aqua aluminium ion ([Al (H2O)6]3+, Al ion) and its hydrolytic species have toxic effect for plants. However, aluminium complexes with organic compounds are less toxic. In natural organic materials that complex with Al ions, the main functional group is carboxylic group and some of them are macromolecules such as fulvic acid and humic acid. Therefore, it is important to examine the interaction between Al ion and macromolecule with carboxylic groups. Therefore, we studied the interaction between Al ion and poly carboxylic acid in solution. We used poly (acrylic acid) (PAA) as a model compound of natural organic compounds.
When Al solution and PAA solution were mixed at various molar ratio ((COOH in PAA)/Al) in the pH range 3 to 8. Precipitate was formed below the limiting ratio. For precipitate at pH 3 one Al ion combined with 4 to 7 carboxylic groups at pH 3. In contrast, for precipitate at pH 8, one Al ion combined with one carboxylic group. It is suggested that the interaction between Al ion and PAA varies by pH: the variation of chemical state of Al ion and PAA by pH strongly affects. In conclusion, it is suggested that Al ion can interact with natural macromolecule with carboxylic groups in the wide pH range.

Goldschmidt Conference Abstracts 2010

A274

A comparative study of rare earth element concentration in coppersulfides from different hydrothermal sites on the MAR 1

2

C. EVRARD *, J.A. BARRAT AND Y. FOUQUET

1

1

Ifremer, BP70, 29280 Plouzané, France (*correspondence: [email protected]) 2 IUEM, Place N. Copernic, 29280 Plouzané, France Rare earth elements (REE) are good tracers of the evolution of geochemical systems. Their geochemistry is classically studied in hydrothermal fluids [1, 2], mid-ocean ridge basalts and seawater [3]. Because of their low concentration, few studies exist on the REE geochemistry in hydrothermal sulfides. The aim of this study is to determine the REE concentrations and their evolutions in sulfides close to equilibrium with the endmember fluid. At the core of the chimney, Cu-sulfides (chalcopyrite, isocubanite…) are generally dominant. Minerals were sampled from three site associated with ultramafic rocks: Rainbow (36°14'N), Logatchev (14°45’N), Ashadze (12°58’N), and one site associated to basalt: Snake Pit (23°22’N). All sulfides were collected on active black smokers (fluids at 250-350 °C) or in massive sulfide from the internal part of large spires. The differences in the REE concentrations will be discussed in term of basement rock settings and in term of zonation across the sulfides precipitation. We will also discuss how the fluid evolves during the growth of the chimney. The normalisation by REE concentration of hydrothermal fluids from the same area [4] is a way to trace the relationship between the precipitated chalcopyrite and the endmember black smoker fluid. [1] Douville et al. (2002) Chemical Geology 184(1-2), 37–48. [2] Schmidt et al. (2007) Chemical Geology 242(1-2), 1–21. [3] Elderfield (1988) 325(1583), 105–126. [4] Mills & Elderfield (1995) GCA 59(17), 3511–3524.

Critical processes in the release and transport of radionuclides in the near-field RODNEY C. EWING* Geological Sciences, Univ. of Michigan, Ann Arbor, MI 48109, USA (*correspondence: [email protected]) A total system analysis of the performance of a geologic repository generally involves the simulation of a connected series of processes, beginning with radionuclide release from the waste form and ending with a calculation of dose to an exposed individual. The simulation consists of a series of cascading models, and the uncertainty in the analysis increases with increasing spatial and temporal scales. When the point of compliance is tens of kilometers from the source and the time of compliance extends for hundreds of thousands of years, a positive judgement of the veracity of the analysis requires a remarkable level of credulity. Although the limitations of such analyses have been discussed in detail [1, 2], this begs of question of whether there is not a better approach. An alternative may be to break the analysis into ‘parts’ that are focused on specific barriers. I will argue that the barrier most amenable to analysis is the waste form and its interactions with the near-field. To the extent that the mechanisms of release and transport of specific radionuclides can be understood and the uncertainties decreased, the subsequent analysis of the far-field barriers becomes less important. Radionuclide release will be critically sensitive to variations in the temperature, the radiation field, redox conditions, pH, pCO2, surface area to solution volume and the presence and type of near-field materials. Among the important processes are: 1.) the kinetics of waste form corrosion; 2.) the mechanisms of waste form corrosion; 3.) the formation of secondary, alteration phases; 4.) the sorption/reduction reactions at the surfaces of near-field materials; 5.) the formation and mobility of colloids; 6.) microbial interactions with radionuclides and materials in the near-field. Each of these processes are complicated and are expected to vary in importance with changing conditions over time. One approach may be to consider the radionuclide inventory as it changes with time and to identify the critical processes within each time frame that hold the promise or potential for reducing the mobility of specific radionuclides. Such an approach may reduce the complexity of safety assessments. [1] Ewing et al. (1999) Risk Analysis 19, 933–958. [2] Ewing (2006) In Uncertainty Underground–Yucca Mountain & the Nations’s High-Level Nuclear Waste. MIT Press, pp.71–83.

Goldschmidt Conference Abstracts 2010

A275

Biogeochemistry of Weeks Bay during bottom water hypoxic and norm-oxic events

Marine SOA: Gas-to-particle conversion and oxidation of primary organic aerosol

JOHN E. EZELL AND KAREN S. MCNEAL*

M.C. FACCHINI1*, S. DECESARI1, M. RINALDI1, E. FINESSI1, D. CEBURNIS2, C.D. O’DOWD2 3 AND E.G. STEPHANOU

([email protected], *correspondence: [email protected]) Weeks Bay (WB), as well as many other estuaries, faces the threat of hypoxia. WB is used by many people for both recreation and commercial practices, which could be seriously affected if a sustained major hypoxic event occurs. While several studies have been conducted in WB, very little is known about the biogeochemistry of the bay or its response to hypoxic conditions. During the project, ten sediment cores were taken from sampling locales in WB, and O2 and H2S microelectrode profiles were conducted. Porewater was extracted from cross sections and analysed, and water column data was recorded using a sonde. Combining this information, a hypoxia likihood index (HLI) was formed indicating sites likely to experience hypoxia. The results provided an understanding of the sediment and water column geochemistry. H2S levels rose in the absence of O2, and the HLI indicated some sites were more likely to go hypoxic than others.

1

Institute of Atmospheric Sciences and Climate, National Research Council, Bologna, Italy (*correspondence: [email protected]) 2 Department of Experimental Physics & Environmental Change Institute, National University of Ireland Galway, Galway, Ireland 3 Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Greece&

A multi-technique approach was exploited to characterize organic marine aerosol collected during high biological activity period over North-East Atlantic, outside continental pollution plumes onboard the research vessel Celtic Explorer, in the frame of the EU project MAP (Marine Aerosol Production) Elemental analysis, nuclear magnetic resonance spectroscopy (NMR), liquid chromatography-mass spectrometry (LC-MS) and ion chromatography provided a unique characterization of the complex mixture of water soluble (WSOC) and water insoluble (WIOC) organic matter in the sub micron aerosol. Beside MSA and amine salts, which constitute the main gas to particle SOA single species, WSOC showed the occurrence of two main fractions: one more hydrophilic, rich of sulphonates and hydroxy-carboxylic acids, likely derived by gas to particle conversion processes, and another one, less hydrophilic, likely forned by oxidation products of hydrophobic sea-sray organic matter. This last observation is is supported by PMF- NMR analysis indicating that a fraction up to 30% of WSOC can be accounted for by C7-C9 aliphatic carboxylic acids, plausibly produced by the degradation of lipids in primary marine organic particles. Moreover NMR analysis of water insoluble fraction, indicated that submicron particles contain a relevant fraction of long chain fatty acid, the likely precursors of the less- hydrophilic WSOC fraction. This picture shows that WSOC is mainly of secondary origin not only due to gas-to-particle conversion, but also, and for a relevant fraction, is originated from oxidation of sea spray organic particles.