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Geochem Trans 2019 Mar 22;20(1). Epub 2019 Mar 22.

Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600, Duebendorf, Switzerland.

Iron(III)-precipitates formed by the oxidation of dissolved Fe(II) are important sorbents for major and trace elements in aquatic and terrestrial systems. Their reductive dissolution in turn may result in the release of associated elements. We examined the reductive dissolution kinetics of an environmentally relevant set of Fe(II)-derived arsenate-containing Fe(III)-precipitates whose structure as function of phosphate (P) and silicate (Si) content varied between poorly-crystalline lepidocrocite, amorphous Fe(III)-phosphate, and Si-containing ferrihydrite. Read More

Geochem Trans 2019 Mar 13;20(1). Epub 2019 Mar 13.

Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA.

Mineralogical studies of contaminated soils affected by smelter emission and dust from mining activities indicate that minerals of the spinel group are one of the common hosts of metal-bearing contaminants. Spinel group minerals typically originate from high temperature processes, but an increasing number of studies indicate that metal-bearing spinel group minerals can also form under ambient Earth surface conditions in surficial soils. In this contribution to honor Donald Sparks, we show that the spinels Zn-bearing magnetite (ZnFeO) and minium (PbO) form during low temperature alteration of Pb-bearing silica glass in surficial organic rich soils in proximity to a former Cu-smelter in Timmins, Ontario, Canada. Read More

Geochem Trans 2018 Dec 6;19(1):15. Epub 2018 Dec 6.

Marine Environment Section, Center for Regional Environmental Research, National Institute for Environmental Studies (NIES), 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan.

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. Read More

Geochem Trans 2018 Aug 14;19(1):14. Epub 2018 Aug 14.

Delaware Environmental Institute (DENIN), University of Delaware, Newark, DE, 19716, USA.

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. Read More

Geochem Trans 2018 Jun 26;19(1):13. Epub 2018 Jun 26.

Geochemistry Department, Sandia National Laboratories, 1515 Eubank Blvd SE, Albuquerque, NM, 87123, USA.

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. Read More

Geochem Trans 2018 Jun 22;19(1):12. Epub 2018 Jun 22.

Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China.

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. Read More

Geochem Trans 2018 May 2;19(1):11. Epub 2018 May 2.

Department of Geology, Mining and Environmental Science, University of Bamenda, P.O Box 39, Bambili, Cameroon.

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 (HClO + HF + HCl) and analyzed for trace metals using a combination of ICP-MS and AAS analytical methods. Read More

Geochem Trans 2018 Apr 2;19(1):10. Epub 2018 Apr 2.

Department of Soil and Water Systems, University of Idaho, Moscow, ID, 83844-2340, USA.

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. Read More

Geochem Trans 2018 Mar 27;19(1). Epub 2018 Mar 27.

Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China.

Trace metals (e.g. Ni, Zn) leached from industrial and agricultural processes are often simultaneously present in contaminated soils and sediments. Read More

Geochem Trans 2018 Mar 1;19(1). Epub 2018 Mar 1.

Civil and Environmental Engineering Department, University of Connecticut, Storrs, CT, USA.

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. Read More

Geochem Trans 2018 Feb 21;19(1). Epub 2018 Feb 21.

Poultry Production and Product Safety Research Unit, Plant Science 115, USDA-ARS, University of Arkansas, Fayetteville, AR, 72701, USA.

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. Read More

Geochem Trans 2018 Feb 13;19(1). Epub 2018 Feb 13.

Department of Plant & Soil Sciences and Delaware Environmental Institute, University of Delaware, Newark, DE, 19716, USA.

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. Read More

Geochem Trans 2018 Feb 13;19(1). Epub 2018 Feb 13.

Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.

Background: The coexistence of Cd and Zn 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 Cd and Zn, few studies can be found in the literature focused on the interaction of Cd and Zn on soil clay fractions especially in terms of energy relationship.

Results: The binding energies of Cd on boggy soil (Histosols) particles and Zn on yellow brown soil (Haplic Luvisols) particles were the highest, while those of Cd and Zn on paddy soil (Inceptisols) particles were the lowest. Read More

Geochem Trans 2018 Feb 3;19(1). Epub 2018 Feb 3.

Department of Plant and Soil Sciences and Delaware Environmental Institute, University of Delaware, 221 Academy Street, ISE Lab, Newark, DE, 19711, USA.

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. Read More

Geochem Trans 2018 Jan 25;19(1). Epub 2018 Jan 25.

Department of Earth & Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ, 07102, USA.

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). Read More

Geochem Trans 2018 Jan 16;19(1). Epub 2018 Jan 16.

Geosciences Department, Fort Lewis College, Durango, CO, 81301, USA.

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. Read More

Geochem Trans 2018 Jan 8;19(1). Epub 2018 Jan 8.

Department of Soil Science, University of Saskatchewan, Saskatoon, SK, S7N 5A8, Canada.

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. Read More

Geochem Trans 2017 Dec 5;18(1). Epub 2017 Dec 5.

Civil and Environmental Engineering, University of Iowa, Iowa City, IA, 52242, USA.

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-MnO) using electron microscopy, X-ray diffraction, aqueous Fe and Mn analyses, and Fe Mössbauer spectroscopy. We reacted pyrolusite solids repeatedly with 3 mM Fe(II) at pH 7. Read More

Geochem Trans 2017 Oct 19;18(1). Epub 2017 Oct 19.

Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076, Tuebingen, Germany.

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 (FeO) 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. Read More

Geochem Trans 2017 Mar 31;18(1). Epub 2017 Mar 31.

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA.

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). Read More

Geochem Trans 2017 Sep 11;18(1). Epub 2017 Sep 11.

Department of Earth & Environmental Sciences, Vanderbilt University, Nashville, TN, 37240, USA.

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. Read More

Geochem Trans 2017 Mar 20;18(1). Epub 2017 Mar 20.

School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UE, UK.

Background: Hydrogen is known to occur in the groundwaters of some ancient cratons. Where associated gases have been dated, their age extends up to a billion years, and the hydrogen is assumed also to be very old. These observations are interpreted to represent the radiolysis of water and hydration reactions and migration of hydrogen into fracture systems. Read More

Geochem Trans 2017 Sep 20;18(1). Epub 2017 Sep 20.

College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361005, China.

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 on N-isotope pairing incubations, we estimated denitrification rates ranging from 1. Read More

Geochem Trans 2016 6;17. Epub 2016 Oct 6.

Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA 19122 USA.

The effect of simulated solar radiation on the oxidation of arsenite [As(III)] to arsenate [As(V)] on the layered manganese oxide, birnessite, was investigated. Experiments were conducted where birnessite suspensions, under both anoxic and oxic conditions, were irradiated with simulated solar radiation in the presence of As(III) at pH 5, 7, and 9. X-ray absorption spectroscopy (XAS) was used to determine the nature of the adsorbed product on the surface of the birnessite. Read More

Geochem Trans 2017 10;18. Epub 2017 Feb 10.

Department of Land, Air and Water Resources, University of California, Davis, Davis, CA 95616-5270 USA.

The participation of sunlight in the natural chemistry of the earth is presented as a unique field of study, from historical observations to prospects for future inquiry. A compilation of known reactions shows the extent of light-driven interactions between naturally occurring components of land, air, and water, and provides the backdrop for an outline of the mechanisms of these phenomena. Catalyzed reactions, uncatalyzed reactions, direct processes, and indirect processes all operate in natural photochemical transformations, many of which are analogous to well-known biological reactions. Read More

Geochem Trans 2016 11;17. Epub 2016 Jul 11.

Environmental Science Discipline, Khulna University, Khulna, 9208 Bangladesh.

Background: High salinity and arsenic (As) concentrations in groundwater are widespread problems in the tidal deltaplain of southwest Bangladesh. To identify the sources of dissolved salts and As, groundwater samples from the regional shallow Holocene aquifer were collected from tubewells during the dry (May) and wet (October) seasons in 2012-2013. Thirteen drill cores were logged and 27 radiocarbon ages measured on wood fragments to characterize subsurface stratigraphy. Read More

Geochem Trans 2016 13;17. Epub 2016 Jun 13.

Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo km 4.5, C.P. 42081 Mineral de la Reforma, Hgo. México.

Background: The presence of natural and industrial jarosite type-compounds in the environment could have important implications in the mobility of potentially toxic elements such as lead, mercury, arsenic, chromium, among others. Understanding the dissolution reactions of jarosite-type compounds is notably important for an environmental assessment (for water and soil), since some of these elements could either return to the environment or work as temporary deposits of these species, thus would reduce their immediate environmental impact.

Results: This work reports the effects of temperature, pH, particle diameter and Cr(VI) content on the initial dissolution rates of K-Cr(VI)-jarosites (KFe3[(SO4)2 - X(CrO4)X](OH)6). Read More

Geochem Trans 2016 6;17. Epub 2016 May 6.

College of Environmental Science and Engineering, Guilin University of Technology, Guilin, 541004 People's Republic of China.

Background: The interaction between Ca-HAP and Pb(2+) solution can result in the formation of a hydroxyapatite-hydroxypyromorphite solid solution [(PbxCa1-x)5(PO4)3(OH)], which can greatly affect the transport and distribution of toxic Pb in water, rock and soil. Therefore, it's necessary to know the physicochemical properties of (PbxCa1-x)5(PO4)3(OH), predominantly its thermodynamic solubility and stability in aqueous solution. Nevertheless, no experiment on the dissolution and related thermodynamic data has been reported. Read More

Geochem Trans 2016 29;17. Epub 2016 Apr 29.

Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA.

Background: Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (Read More

Geochem Trans 2015 19;16:17. Epub 2015 Nov 19.

School of Earth and Environmental Sciences, Schmid College of Science & Technology, Chapman University, Orange, CA 92866 USA.

[This corrects the article DOI: 10.1186/1467-4866-15-6.]. Read More

Geochem Trans 2015 Dec 22;16(1):16. Epub 2015 Sep 22.

Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070 People's Republic of China.

Background: In soils and sediments, manganese oxides and oxygen usually participate in the oxidation of ferrous ions. There is limited information concerning the interaction process and mechanisms of ferrous ions and manganese oxides. The influence of air (oxygen) on reaction process and kinetics has been seldom studied. Read More

Geochem Trans 2015 16;16:15. Epub 2015 Sep 16.

Department of Plant and Soil Sciences, Delaware Environmental Institute, University of Delaware, 221 Academy Street, 250A ISE Lab, Newark, DE 19711 USA.

Background: Manganese-oxides are one of the most important minerals in soil due to their widespread distribution and high reactivity. Despite their invaluable role in cycling many redox sensitive elements, numerous unknowns remain about the reactivity of different manganese-oxide minerals under varying conditions in natural systems. By altering temperature, pH, and concentration of arsenite we were able to determine how manganese-oxide reactivity changes with simulated environmental conditions. Read More

Geochem Trans 2015 15;16:14. Epub 2015 Sep 15.

Department of Geosciences, Penn State Astrobiology Research Center, 220 Deike Building, University Park, PA 16802 USA.

Background: Due to the biogeochemical fractionation of isotopes, organic material can be heterogeneous at the microscale. Because this heterogentiy preserves in the rock record, the microscale measurement of carbon isotopes is an important frontier of geobiology. Such analyses via secondary ion mass spectrometry (SIMS) have been, however, held back by the lack of an appropriate homogeneous synthetic standard that can be shared between laboratories. Read More

Geochem Trans 2015 3;16:13. Epub 2015 Sep 3.

Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany ; Department of Earth Sciences, Freie Universität Berlin, 12249 Berlin, Germany ; Water and Environment Division, French Geological Survey (BRGM), Orléans, France.

Background: In geochemically perturbed systems where porewater and mineral assemblages are unequilibrated the processes of mineral precipitation and dissolution may change important transport properties such as porosity and pore diffusion coefficients. These reactions might alter the sealing capabilities of the rock by complete pore-scale precipitation (cementation) of the system or by opening new migration pathways through mineral dissolution. In actual 1D continuum reactive transport codes the coupling of transport and porosity is generally accomplished through the empirical Archie's law. Read More

Geochem Trans 2015 2;16:12. Epub 2015 Sep 2.

Univ. Grenoble Alpes, ISTerre, 38041 Grenoble, France ; CNRS, ISTerre, 38041 Grenoble, France.

Background: Vernadite is a nanocrystalline and turbostratic phyllomanganate which is ubiquitous in the environment. Its layers are built of (MnO6)(8-) octahedra connected through their edges and frequently contain vacancies and  (or) isomorphic substitutions. Both create a layer charge deficit that can exceed 1 valence unit per layer octahedron and thus induces a strong chemical reactivity. Read More

Geochem Trans 2015 8;16:11. Epub 2015 Aug 8.

The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, 100871 People's Republic of China.

Background: Mn oxides occur in a wide variety of geological settings and exert considerable influences on the components and chemical behaviors of sediments and soils. Microbial reduction of Mn oxides is an important process found in many different environments including marine and freshwater sediments, lakes, anoxic basins, as well as oxic-anoxic transition zone of ocean. Although the pathway of Mn anaerobic reduction by two model bacteria, Geobacter and Shewanella, has been intensively studied, Mn bio-reduction is still the least well-explored process in nature. Read More

Geochem Trans 2015 25;16:10. Epub 2015 Jul 25.

Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021 China.

Background: Organic dye pollution in water has become a major source of environmental pollution. Mn(III/IV) oxides have attracted a great deal of attention to remove organic dye pollutants due to their unique structures and physicochemical properties. Numerous studies have reported the removal of dye by various Mn(III/IV) oxides through catalytic degradation and adsorption. Read More

Geochem Trans 2015 18;16. Epub 2015 Jul 18.

College of Environmental Science and Engineering, Guilin University of Technology, Guilin, 541004 People's Republic of China.

Background: The substitution of Ca(2+) in Ca-hydroxylapatite by toxic Cd(2+) can cause the forming of Cd-hydroxylapatite and is a significant issue in a great variety of research areas, which hence needs an understanding of the essential physicochemical characteristics. Unfortunately, the solubility product and thermodynamic data for Cd-hydroxylapatite in water under a variety of conditions now are lacking. Little information has been reported by previous researchers. Read More

Geochem Trans 2015 15;16. Epub 2015 Jul 15.

Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070 China.

Background: Todorokite, a 3 × 3 tectomanganate, is one of three main manganese oxide minerals in marine nodules and can be used as an active MnO6 octahedral molecular sieve. The formation of todorokite is closely associated with the poorly crystalline phyllomanganates in nature. However, the effect of the preparative parameters on the transformation of "c-disordered" H(+)-birnessites, analogue to natural phyllomanganates, into todorokite has not yet been explored. Read More

Geochem Trans 2015 2;16. Epub 2015 Jul 2.

Department of Geological and Environmental Sciences, Faculty of Natural Sciences, Ben-Gurion University of the Negev, P.O. Box 653, 84105 Beer Sheva, Israel.

Background: We studied the annual variability of the concentration and isotopic composition of main sulfur species and sulfide oxidation intermediates in the water column of monomictic fresh-water Lake Kinneret. Sulfate concentrations in the lake are <1 mM and similar to concentrations that are proposed to have existed in the Paleoproterozoic ocean. The main goal of this research was to explore biogeochemical constrains of sulfur cycling in the modern low-sulfate fresh-water lake and to identify which processes may be responsible for the isotopic composition of sulfur species in the Precambrian sedimentary rocks. Read More

Geochem Trans 2015 26;16. Epub 2015 Jun 26.

Department of Civil and Environmental Engineering, Carnegie Mellon University, PH 118L, Pittsburgh, PA 15213 USA.

In this work, the geochemistry of the rare earth elements (REE) was studied in eleven outcrop samples and six, depth-interval samples of a core from the Marcellus Shale. The REE are classically applied analytes for investigating depositional environments and inferring geochemical processes, making them of interest as potential, naturally occurring indicators of fluid sources as well as indicators of geochemical processes in solid waste disposal. However, little is known of the REE occurrence in the Marcellus Shale or its produced waters, and this study represents one of the first, thorough characterizations of the REE in the Marcellus Shale. Read More

Geochem Trans 2015;16. Epub 2015 Apr 28.

Soil Research Centre, Department of Geography and Environmental Science, School of Archaeology, Geography and Environmental Science, University of Reading, Wokingham, RG6 6DW UK ; NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 USA.

Background: Many biominerals form from amorphous calcium carbonate (ACC), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete calcium carbonate granules which contain highly stable ACC. We analysed the milky fluid from which granules form and solid granules for amino acid (by liquid chromatography) and functional group (by Fourier transform infrared (FTIR) spectroscopy) compositions. Read More

Geochem Trans 2015 13;16. Epub 2015 May 13.

Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070 China.

Background: Although most reported biogenic Mn oxides are hexagonal birnessites, other types of biogenic Mn oxides also commonly occur in the environment. However, sorption characteristics and underlying mechanisms of the adsorption of heavy-metal ions on these biogenic Mn oxides are still rarely addressed. In this study, the sorption mechanisms of Cu(II) on a low valence biogenic Mn oxide, poorly crystallized bixbyite-like Mn2O3 (α-Mn2O3), were investigated. Read More

Geochem Trans 2015 10;16. Epub 2015 Apr 10.

Department of Environmental Analytical Chemistry, Goethe-University, Institute of Atmospheric and Environmental Sciences, Altenhoeferallee 1, 60438 Frankfurt am Main, Germany.

Background: On Late Cretaceous Tethyan upwelling sediments from the Mishash/Ghareb Formation (Negev, Israel), bulk geochemical and biomarker analyses were performed to explain the high proportion of phosphates in the lower part and of organic matter (OM) preserved in upper parts of the studied section. The profile is composed of three facies types; the underlying Phosphate Member (PM), the Oil Shale Member (OSM) and the overlying Marl Member (MM).

Results: Total organic carbon (TOC) contents are highly variable over the whole profile reaching from 0. Read More

Geochem Trans 2015 16;16. Epub 2015 Apr 16.

GET/OMP, UMR 5563 CNRS, Université Paul Sabatier-CNRS-IRD, 14 avenue Edouard Belin, 31400 Toulouse, France.

Stable Zn isotopes fractionation was studied in main biogeochemical compartments of a pristine larch forest of Central Siberia developed over continuous permafrost basalt rocks. Two north- and south-oriented watershed slopes having distinctly different vegetation biomass and active layer depth were used as natural proxy for predicting possible future climate changes occurring in this region. In addition, peat bog zone exhibiting totally different vegetation, hydrology and soil temperature regime has been studied. Read More

Geochem Trans 2015 12;16. Epub 2015 Feb 12.

Center for Marine and Environmental Research, Ruđer Bošković Institute, Bijenička 54, 10 000 Zagreb, Croatia.

Background: Elemental sulfur (S) persists in natural aquatic environment in a variety of forms with different size distributions from dissolved to particulate. Determination of S speciation mainly consists of the application of chromatographic and electrochemical techniques while its size determination is limited only to the application of microscopic and light scattering techniques. S biological and geochemical importance together with recent increases of S industrial applications requires the development of different analytical tools for S sizing and quantification. Read More

Geochem Trans 2014 16;15(1):15. Epub 2014 Dec 16.

MARUM, University of Bremen, Leobener Str., Bremen, 28359 Germany.

Background: Integrated Ocean Drilling Program Expedition 338 was the second scientific expedition with D/V Chikyu during which riser drilling was conducted as part of the Nankai Trough Seismogenic Zone Experiment. Riser drilling enabled sampling and real-time monitoring of drilling mud gas with an onboard scientific drilling mud gas monitoring system ("SciGas"). A second, independent system was provided by Geoservices, a commercial mud logging service. Read More

Geochem Trans 2014 Dec 11;15(1):14. Epub 2014 Oct 11.

Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 USA.

Background: The oxidative dissolution of sulfide minerals, such as arsenopyrite (FeAsS), is of critical importance in many geochemical systems. A comprehensive understanding of their dissolution rates entails careful preparation of the mineral surface. Measurements of dissolution rates of arsenic from arsenopyrite are dependent on the size and degree of oxidation of its particles, among other factors. Read More

Geochem Trans 2014 Dec 12;15(1):10. Epub 2014 Aug 12.

Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, 76100 Israel.

Background: Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, the microbiological processes involved, and the effects of pyrite on human health. Elemental sulfur (S) is a common product of incomplete pyrite oxidation. Read More

Geochem Trans 2014 12;15:12. Epub 2014 Aug 12.

Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA ; Department of Biological Sciences, University of Southern California, Los Angeles, USA.

Shallow-sea (5 m depth) hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction. Seafloor vent features include large (>1 m(2)) white patches containing hydrothermal minerals (elemental sulfur and orange/yellow patches of arsenic-sulfides) and cells of sulfur oxidizing and reducing microorganisms. Sulfide-sensitive film deployed in the vent and non-vent sediments captured strong geochemical spatial patterns that varied from advective to diffusive sulfide transport from the subsurface. Read More