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Geochemical Transactions

Shigeshi Fuchida, Jun-Ichiro Ishibashi, Kazuhiko Shimada, Tatsuo Nozaki, Hidenori Kumagai, Masanobu Kawachi, Yoshitaka Matsushita, Hiroshi Koshikawa
We observed the initial release rate of metals from four fresh (i.e., without long time exposure to the atmosphere) hydrothermal sulfide cores into artificial seawater. The sulfide samples were collected by seafloor drilling from the Okinawa Trough by D/V Chikyu, powdered under inert gas, and immediately subjected to onboard metal-leaching experiments at different temperatures (5 °C and 20 °C), and under different redox conditions (oxic and anoxic), for 1-30 h. Zinc and Pb were preferentially released from sulfide samples containing various metals (i...
December 6, 2018: Geochemical Transactions
Matthew G Siebecker, Rufus L Chaney, Donald L Sparks
Serpentine soils and ultramafic laterites develop over ultramafic bedrock and are important geological materials from environmental, geochemical, and industrial standpoints. They have naturally elevated concentrations of trace metals, such as Ni, Cr, and Co, and also high levels of Fe and Mg. Minerals host these trace metals and influence metal mobility. Ni in particular is an important trace metal in these soils, and the objective of this research was to use microscale (µ) techniques to identify naturally occurring minerals that contain Ni and Ni correlations with other trace metals, such as Fe, Mn, and Cr...
August 14, 2018: Geochemical Transactions
Andrew W Knight, Austen B Tigges, Anastasia G Ilgen
Nano-scale spatial confinement can alter chemistry at mineral-water interfaces. These nano-scale confinement effects can lead to anomalous fate and transport behavior of aqueous metal species. When a fluid resides in a nanoporous environments (pore size under 100 nm), the observed density, surface tension, and dielectric constant diverge from those measured in the bulk. To evaluate the impact of nano-scale confinement on the adsorption of copper (Cu2+ ), we performed batch adsorption studies using mesoporous silica...
June 26, 2018: Geochemical Transactions
Lingqun Zeng, Biao Wan, Rixiang Huang, Yupeng Yan, Xiaoming Wang, Wenfeng Tan, Fan Liu, Xionghan Feng
Recently, the wide application of CuO nanoparticles (NPs) in engineering field inevitably leads to its release into various geologic settings, which has aroused great concern about the geochemical behaviors of CuO NPs due to its high surface reactivity and impact on the fate of co-existing contaminants. However, the redox transformation of pollutants mediated by CuO NPs and the underlying mechanism still remain poorly understood. Here, we studied the interaction of CuO NPs with As(III), and explored the reaction pathways using batch experiments and multiple spectroscopic techniques...
June 22, 2018: Geochemical Transactions
Mumbfu Ernestine Mimba, Takeshi Ohba, Salomon César Nguemhe Fils, Melvin Tamnta Nforba, Nozomi Numanami, Tasin Godlove Bafon, Festus Tongwa Aka, Cheo Emmanuel Suh
The distribution of trace metals in active stream sediments from the mineralized Lom Basin has been evaluated. Fifty-five bottom sediments were collected and the mineralogical composition of six pulverized samples determined by XRD. The fine fraction (< 150 µm) was subjected to total digestion (HClO4  + HF + HCl) and analyzed for trace metals using a combination of ICP-MS and AAS analytical methods. Results show that the mineralogy of stream sediments is dominated by quartz (39-86%), phyllosilicates (0-45%) and feldspars (0-27%)...
May 2, 2018: Geochemical Transactions
Daniel G Strawn
Arsenic is a non-essential element that poses risks in many environments, including soil, groundwater, and surface water. Insights into the environmental biogeochemistry of As can be gained by comparing As and P reaction processes. Arsenic and P are chemical analogues, and it is proposed that they have similar chemical behaviors in environmental systems. However some chemical properties of As and P are distinct, such as redox reactions, causing the biogeochemical behavior of the two elements to differ. In the environment, As occurs as either As(V) or As(III) oxyanions (e...
April 2, 2018: Geochemical Transactions
Wenxian Gou, Matthew G Siebecker, Zimeng Wang, Wei Li
Trace metals (e.g. Ni, Zn) leached from industrial and agricultural processes are often simultaneously present in contaminated soils and sediments. Their mobility, bioavailability, and ecotoxicity are affected by sorption and cosorption at mineral/solution interfaces. Cosorption of trace metals has been investigated at the macroscopic level, but there is not a clear understanding of the molecular-scale cosorption processes due to lack of spectroscopic information. In this study, Ni and Zn cosorption to aluminum oxides (γ-Al2 O3 ) in binary-sorbate systems were compared to their sorption in single-sorbate systems as a function of pH using both macroscopic batch experiments and synchrotron-based X-ray absorption fine structure spectroscopy...
March 27, 2018: Geochemical Transactions
James D Kubicki, Nadine Kabengi, Maria Chrysochoou, Nefeli Bompoti
Density functional theory (DFT) calculations were performed on a model of a ferrihydrite nanoparticle interacting with chromate ([Formula: see text]) in water. Two configurations each of monodentate and bidentate adsorbed chromate as well as an outer-sphere and a dissolved bichromate ([Formula: see text]) were simulated. In addition to the 3-D periodic planewave DFT models, molecular clusters were extracted from the energy-minimized structures. Calculated interatomic distances from the periodic and cluster models compare favorably with Extended X-ray Absorption Fine Structure spectroscopy values, with larger discrepancies seen for the clusters due to over-relaxation of the model substrate...
March 1, 2018: Geochemical Transactions
Barbara J Cade-Menun, Kyle R Elkin, Corey W Liu, Ray B Bryant, Peter J A Kleinman, Philip A Moore
Phosphorus (P) can limit crop production in many soils, and soil testing is used to guide fertilizer recommendations. The Mehlich III (M3) soil test is widely used in North America, followed by colorimetric analysis for P, or by inductively coupled plasma-based spectrometry (ICP) for P and cations. However, differences have been observed in M3 P concentrations measured by these methods. Using 31 P nuclear magnetic resonance (P-NMR) and mass spectrometry (MS), we characterized P forms in M3 extracts. In addition to the orthophosphate that would be detected during colorimetric analysis, several organic P forms were present in M3 extracts that would be unreactive colorimetrically but measured by ICP (molybdate unreactive P, MUP)...
February 21, 2018: Geochemical Transactions
Jason W Stuckey, Christopher Goodwin, Jian Wang, Louis A Kaplan, Prian Vidal-Esquivel, Thomas P Beebe, Donald L Sparks
Minerals constitute a primary ecosystem control on organic C decomposition in soils, and therefore on greenhouse gas fluxes to the atmosphere. Secondary minerals, in particular, Fe and Al (oxyhydr)oxides-collectively referred to as "oxides" hereafter-are prominent protectors of organic C against microbial decomposition through sorption and complexation reactions. However, the impacts of Mn oxides on organic C retention and lability in soils are poorly understood. Here we show that hydrous Mn oxide (HMO), a poorly crystalline δ-MnO2 , has a greater maximum sorption capacity for dissolved organic matter (DOM) derived from a deciduous forest composite Oi , Oe , and Oa horizon leachate ("O horizon leachate" hereafter) than does goethite under acidic (pH 5) conditions...
February 13, 2018: Geochemical Transactions
Tingting Fan, Chengbao Li, Juan Gao, Dongmei Zhou, Marcelo Eduardo Alves, Yujun Wang
BACKGROUND: The coexistence of Cd2+ and Zn2+ ions in nature has a significant influence on their environmental behaviors in soils and bioavailability for plants. While many studies have been done on the mutual toxicity of Cd2+ and Zn2+ , few studies can be found in the literature focused on the interaction of Cd2+ and Zn2+ on soil clay fractions especially in terms of energy relationship. RESULTS: The binding energies of Cd2+ on boggy soil (Histosols) particles and Zn2+ on yellow brown soil (Haplic Luvisols) particles were the highest, while those of Cd2+ and Zn2+ on paddy soil (Inceptisols) particles were the lowest...
February 13, 2018: Geochemical Transactions
Tyler D Sowers, Jason W Stuckey, Donald L Sparks
Sequestration of organic carbon (OC) in environmental systems is critical to mitigating climate change. Organo-mineral associations, especially those with iron (Fe) oxides, drive the chemistry of OC sequestration and stability in soils. Short-range-ordered Fe oxides, such as ferrihydrite, demonstrate a high affinity for OC in binary systems. Calcium commonly co-associates with OC and Fe oxides in soils, though the bonding mechanism (e.g., cation bridging) and implications of the co-association for OC sequestration remain unresolved...
February 3, 2018: Geochemical Transactions
Ying Zhu, Jingjing Liu, Omanjana Goswami, Ashaki A Rouff, Evert J Elzinga
We studied the effects of humic substances (HS) on the sorption of Fe(II) onto Al-oxide and clay sorbents at pH 7.5 with a combination of batch kinetic experiments and synchrotron Fe K-edge EXAFS analyses. Fe(II) sorption was monitored over the course of 4 months in anoxic clay and Al-oxide suspensions amended with variable HS types (humic acid, HA; or fulvic acid, FA) and levels (0, 1, and 4 wt%), and with differing Fe(II) and HS addition sequences (co-sorption and pre-coated experiments, where Fe(II) sorbate was added alongside and after HS addition, respectively)...
January 25, 2018: Geochemical Transactions
Ray Kenny
The upper carbonate member of the Kaibab Formation in northern Arizona (USA) was subaerially exposed during the end Permian and contains fractured and zoned chert rubble lag deposits typical of karst topography. The karst chert rubble has secondary (authigenic) silica precipitates suitable for estimating continental weathering temperatures during the end Permian karst event. New oxygen and hydrogen isotope ratios of secondary silica precipitates in the residual rubble breccia: (1) yield continental palaeotemperature estimates between 17 and 22 °C; and, (2) indicate that meteoric water played a role in the crystallization history of the secondary silica...
January 16, 2018: Geochemical Transactions
Jordan G Hamilton, Jay Grosskleg, David Hilger, Kris Bradshaw, Trevor Carlson, Steven D Siciliano, Derek Peak
Adsorption and precipitation reactions often dictate the availability of phosphorus in soil environments. Tripolyphosphate (TPP) is considered a form of slow release P fertilizer in P limited soils, however, investigations of the chemical fate of TPP in soils are limited. It has been proposed that TPP rapidly hydrolyzes in the soil solution before adsorbing or precipitating with soil surfaces, but in model systems, TPP also adsorbs rapidly onto mineral surfaces. To study the adsorption behavior of TPP in calcareous soils, a short-term (48 h) TPP spike was performed under laboratory conditions...
January 8, 2018: Geochemical Transactions
Michael V Schaefer, Robert M Handler, Michelle M Scherer
Iron (Fe) and manganese (Mn) are the two most common redox-active elements in the Earth's crust and are well known to influence mineral formation and dissolution, trace metal sequestration, and contaminant transformations in soils and sediments. Here, we characterized the reaction of aqueous Fe(II) with pyrolusite (β-MnO2 ) using electron microscopy, X-ray diffraction, aqueous Fe and Mn analyses, and 57 Fe Mössbauer spectroscopy. We reacted pyrolusite solids repeatedly with 3 mM Fe(II) at pH 7.5 to evaluate whether electron transfer occurs and to track the evolving reactivity of the Mn/Fe solids...
December 5, 2017: Geochemical Transactions
Anneli Sundman, James M Byrne, Iris Bauer, Nicolas Menguy, Andreas Kappler
Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe3 O4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry...
October 19, 2017: Geochemical Transactions
Jian Zeng, Min Chen, Minfang Zheng, Wangjiang Hu, Yusheng Qiu
The western Arctic Shelf has long been considered as an important sink of nitrogen because high primary productivity of the shelf water fuels active denitrification within the sediments, which has been recognized to account for all the nitrogen (N) removal of the Pacific water inflow. However, potentially high denitrifying activity was discovered within the oxygenated Chukchi Shelf water during our summer expedition. Based on15 N-isotope pairing incubations, we estimated denitrification rates ranging from 1...
September 20, 2017: Geochemical Transactions
John C Ayers, Gregory George, David Fry, Laura Benneyworth, Carol Wilson, Leslie Auerbach, Kushal Roy, Md Rezaul Karim, Farjana Akter, Steven Goodbred
To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012-2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0...
September 11, 2017: Geochemical Transactions
Ying Chen, Eric J Bylaska, John H Weare
BACKGROUND: Many important geochemical and biogeochemical reactions occur in the mineral/formation water interface of the highly abundant mineral, goethite [α-Fe(OOH)]. Ab initio molecular dynamics (AIMD) simulations of the goethite α-FeOOH (100) surface and the structure, water bond formation and dynamics of water molecules in the mineral/aqueous interface are presented. Several exchange correlation functionals were employed (PBE96, PBE96 + Grimme, and PBE0) in the simulations of a (3 × 2) goethite surface with 65 absorbed water molecules in a 3D-periodic supercell (a = 30 Å, FeOOH slab ~12 Å thick, solvation layer ~18 Å thick)...
March 31, 2017: Geochemical Transactions
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