The biogeochemistry of trace metals and their isotopes in the Mediterranean and Black Seas

The marine biogeochemistry of trace metals and their isotopes is a burgeoning field in Earth sciences. The primary interest in trace metals stems from the fact that many metals are utilized in biochemical functions of marine phytoplankton which form the base of the marine food web. Low concentrations of bioessential elements may limit primary productivity in large swaths of the global ocean, while elevated concentrations around anthropogenic sources can prove toxic to marine phytoplankton. Thus, it is important to understand the sources and sinks of metals to the ocean and the biogeochemical processes that influence their distributions. Furthermore, sedimentary records of trace metals provide important constraints on environmental change, such as the redox evolution of the ocean-atmosphere system throughout Earth’s history. In this study, the biogeochemistry of trace elements and their isotopes was investigated as part of the 2013 GEOTRACES expeditions in the Mediterranean and Black Seas. The unique oceanographic properties of these marine basins were exploited to better understand how specific processes influence the distributions of trace metals and their isotopes. The Mediterranean Sea receives the largest flux of atmospheric deposition of any modern marine basin, is strongly impacted by anthropogenic activity, and experiences overturning circulation analogous to the global ocean. The distribution of dissolved aluminum displayed high concentrations (up to 175 nM) in the Mediterranean Sea that are likely a result of the intense dust deposition. Strong correlations between dissolved aluminum and silica with salinity indicate that the general distribution of dissolved aluminum is controlled by conservative mixing, including the long recognized covariation between aluminum and silica. The distributions of dissolved iron, zinc, cadmium and lead in the Mediterranean Sea were also investigated, which reveal striking concentration gradients between the eastern and western Mediterranean basins. Atmospheric deposition of lithogenic material results in elevated concentrations of dissolved iron in Mediterranean surface waters, while anthropogenic sources of zinc, cadmium and lead within the western Mediterranean basin may support the observed concentration gradients. The Black Sea is the world’s largest anoxic marine basin and is an ideal natural laboratory for investigating the behavior of trace metals and their isotopes under variable redox conditions. The distributions of a suite of dissolved trace metals including aluminum, titanium, manganese, iron, copper, zinc, gallium, yttrium, zirconium, cadmium, lanthanum, and uranium in the Black Sea water column are reported. The distributions of trace metals in the Black Sea are primarily controlled by redox reactions that induce changes in solubility of the metals, the formation of insoluble metal-sulfides in the deep sulfidic basin, and the scavenging/regeneration of metals associated with the remineralization of sinking particles. Additionally, the iron and uranium isotope systems are investigated in the water column and sediments of the Black Sea. Iron isotope fractionation factors associated with pyrite formation, +2.75 ± 0.22‰ (2SE), and oxidation reactions, -0.19 ± 0.07‰ to -0.40 ± 0.12‰ (2SE), are calculated from the isotopic composition and concentration of iron in the water column. Similarly, the isotopic composition and concentration of U in the water column is used to calculate the uranium isotope fractionation factor associated with reduction of U(VI) to U(IV), -0.61 ± 0.08‰ to -0.84 ± 0.11‰ (2SE). Implications for the application of the iron and uranium isotope paleoredox proxies to the sedimentary record are discussed

CAFTA: Sanitary and Phytosanitary Evaluation

This report informed the USDA about the status of Sanitary and Phytosanitary (SPS) regulatory systems in five Central American countries that are participating in negotiations for a Central American Free Trade Agreement (CAFTA) with the United States. To complete the report, the Capstone team sent surveys to the appropriate in-country experts in each of the five CAFTA countries and utilized the Phytosanitary Capacity Evaluation model to measure the level of compliance with international standards

Uranium isotope fractionation by abiotic reductive precipitation

Significant uranium (U) isotope fractionation has been observed during abiotic reduction of aqueous U, counter to the expectation that uranium isotopes are only fractionated by bioassociated enzymatic reduction. In our experiments, aqueous U is removed from solution by reductive precipitation onto the surfaces of synthetic iron monosulfide. The magnitude of uranium isotopic fractionation increases with decreasing aqueous U removal rate and with increasing amounts of neutrally charged aqueous Ca-U-CO3 species. Our discovery means that abiotic U isotope fractionation likely occurs in any reducing environment with aqueous Ca ≥ 1 mM, and that the magnitude of isotopic fractionation changes in response to changes in aqueous major ion concentrations that affect U speciation. Our results have implications for the study of anoxia in the ancient oceans and other environments

Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475

The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted

Novel catalytically active pd/Ru bimetallic nanoparticles synthesized by Bacillus benzeovorans

This work was supported by a UK Commonwealth scholarship to JBO. BK was supported by the Petroleum Technology Development Funds (PTDF) of Nigeria. The project was funded by NERC grant NE/L014076/1 to LEM. The Science City Photoemission Facility used in this research was funded through the Science Cities Advanced Materials Project 1: Creating and Characterizing Next Generation of Advanced Materials with support from AWM and ERDF funds. The microscopy work was conducted in the “Laboratorio de Microscopias Avanzadas” at “Instituto de Nanociencia de Aragon - Universidad de Zaragoza” Spain. The authors acknowledge the LMA-INA for offering access to their instruments and expertise.Bacillus benzeovorans assisted and supported growth of ruthenium (bio-Ru) and palladium/ruthenium (bio-Pd@Ru) core@shell nanoparticles (NPs) as bio-derived catalysts. Characterization of the bio-NPs using various electron microscopy techniques and high-angle annular dark field (HAADF) analysis confirmed two NP populations (1–2 nm and 5–8 nm), with core@shells in the latter. The Pd/Ru NP lattice fringes, 0.231 nm, corresponded to the (110) plane of RuO2. While surface characterization using X-ray photoelectron spectroscopy (XPS) showed the presence of Pd(0), Pd(II), Ru(III) and Ru(VI), X-ray absorption (XAS) studies of the bulk material confirmed the Pd speciation (Pd(0) and Pd(II)- corresponding to PdO), and identified Ru as Ru(III) and Ru(IV). The absence of Ru–Ru or Ru–Pd peaks indicated Ru only exists in oxide forms (RuO2 and RuOH), which are surface-localized. X ray diffraction (XRD) patterns did not identify Pd-Ru alloying. Preliminary catalytic studies explored the conversion of 5-hydroxymethyl furfural (5-HMF) to the fuel precursor 2,5-dimethyl furan (2,5-DMF). Both high-loading (9.7 wt.% Pd, 6 wt.% Ru) and low-loading (2.4 wt.% Pd, 2 wt.% Ru) bio-derived catalysts demonstrated high conversion efficiencies (~95%) and selectivity of ~63% (~20% better than bio-Ru NPs) and 58%, respectively. These materials show promising future scope as efficient low-cost biofuel catalysts.Funded by NERC grant NE/L014076/

Prosocial personality traits differentially predict egalitarianism, generosity, and reciprocity in economic games

Recent research has highlighted the role of prosocial personality traits—agreeableness and honesty-humility—in egalitarian distributions of wealth in the dictator game. Expanding on these findings, we ran two studies to examine individual differences in two other forms of prosociality—generosity and reciprocity—with respect to two major models of personality, the Big Five and the HEXACO. Participants (combined N = 560) completed a series of economic games in which allocations in the dictator game were compared with those in the generosity game, a non-constant-sum wealth distribution task where proposers with fixed payoffs selected the size of their partner’s payoff (“generosity”). We further examined positive and negative reciprocity by manipulating a partner’s previous move (“reciprocity”). Results showed clear evidence of both generosity and positive reciprocity in social preferences, with allocations to a partner greater in the generosity game than in the dictator game, and greater still when a player had been previously assisted by their partner. There was also a consistent interaction with gender, whereby men were more generous when this was costless and women were more egalitarian overall. Furthermore, these distinct forms of prosociality were differentially predicted by personality traits, in line with the core features of these traits and the theoretical distinctions between them. HEXACO honesty-humility predicted dictator, but not generosity allocations, while traits capturing tendencies towards irritability and anger predicted lower generosity, but not dictator allocations. In contrast, the politeness—but not compassion—aspect of Big Five agreeableness was uniquely and broadly associated with prosociality across all games. These findings support the discriminant validity between related prosocial constructs, and have important implications for understanding the motives and mechanisms taking place within economic games

The biogeochemistry of trace metals and their isotopes in the Mediterranean and Black Seas

The marine biogeochemistry of trace metals and their isotopes is a burgeoning field in Earth sciences. The primary interest in trace metals stems from the fact that many metals are utilized in biochemical functions of marine phytoplankton which form the base of the marine food web. Low concentrations of bioessential elements may limit primary productivity in large swaths of the global ocean, while elevated concentrations around anthropogenic sources can prove toxic to marine phytoplankton. Thus, it is important to understand the sources and sinks of metals to the ocean and the biogeochemical processes that influence their distributions. Furthermore, sedimentary records of trace metals provide important constraints on environmental change, such as the redox evolution of the ocean-atmosphere system throughout Earth’s history. In this study, the biogeochemistry of trace elements and their isotopes was investigated as part of the 2013 GEOTRACES expeditions in the Mediterranean and Black Seas. The unique oceanographic properties of these marine basins were exploited to better understand how specific processes influence the distributions of trace metals and their isotopes. The Mediterranean Sea receives the largest flux of atmospheric deposition of any modern marine basin, is strongly impacted by anthropogenic activity, and experiences overturning circulation analogous to the global ocean. The distribution of dissolved aluminum displayed high concentrations (up to 175 nM) in the Mediterranean Sea that are likely a result of the intense dust deposition. Strong correlations between dissolved aluminum and silica with salinity indicate that the general distribution of dissolved aluminum is controlled by conservative mixing, including the long recognized covariation between aluminum and silica. The distributions of dissolved iron, zinc, cadmium and lead in the Mediterranean Sea were also investigated, which reveal striking concentration gradients between the eastern and western Mediterranean basins. Atmospheric deposition of lithogenic material results in elevated concentrations of dissolved iron in Mediterranean surface waters, while anthropogenic sources of zinc, cadmium and lead within the western Mediterranean basin may support the observed concentration gradients. The Black Sea is the world’s largest anoxic marine basin and is an ideal natural laboratory for investigating the behavior of trace metals and their isotopes under variable redox conditions. The distributions of a suite of dissolved trace metals including aluminum, titanium, manganese, iron, copper, zinc, gallium, yttrium, zirconium, cadmium, lanthanum, and uranium in the Black Sea water column are reported. The distributions of trace metals in the Black Sea are primarily controlled by redox reactions that induce changes in solubility of the metals, the formation of insoluble metal-sulfides in the deep sulfidic basin, and the scavenging/regeneration of metals associated with the remineralization of sinking particles. Additionally, the iron and uranium isotope systems are investigated in the water column and sediments of the Black Sea. Iron isotope fractionation factors associated with pyrite formation, +2.75 ± 0.22‰ (2SE), and oxidation reactions, -0.19 ± 0.07‰ to -0.40 ± 0.12‰ (2SE), are calculated from the isotopic composition and concentration of iron in the water column. Similarly, the isotopic composition and concentration of U in the water column is used to calculate the uranium isotope fractionation factor associated with reduction of U(VI) to U(IV), -0.61 ± 0.08‰ to -0.84 ± 0.11‰ (2SE). Implications for the application of the iron and uranium isotope paleoredox proxies to the sedimentary record are discussed

Inversion of surface composition and evolution of nanostructure in Cu/Co nanocrystals (vol 74, pg 3161, 1999)

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Inversion of surface composition and evolution of nanostructure in Cu Co nanocrystals

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder

Experimental determination of Zn isotope fractionation during evaporative loss at extreme temperatures

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