Iodine Fractions in Soil and Their Determination

Iodine is an essential micronutrient for most living beings, including humans. Despite efforts through various iodine deficiency disorders elimination programs, such as salt iodization, this problem still persists. Sub-clinical deficiencies have often an endemic character, and they are characteristic to certain areas, where iodine is low or inaccessible in the geochemical environment. Thus, the monitoring of iodine speciation and fractionation—especially in soil, drinking water, and food—is needed. Therefore, the aim of this work is to review the iodine distribution in most common soil fractions which relate to its bioavailability; and briefly summarize the available methods for their identification in the environmental matrices as well.

GEOQUÍMICA E PETROGRAFIA DE DEPÓSITOS QUATERNÁRIOS DA PORÇÃO SW DA PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX E DIFRAÇÃO A LASER

Resumo: Este artigo apresenta os dados geoquímicos e petrográficos de sedimentos praiais da região SW da Praia Brava (PB) em Armação dos Búzios-RJ. Buscamos discutir os processos de intemperismo químico e proveniência, bem como, analisar o ambiente geoquímico e a sua relação com as fontes autóctones. Neste estudo foram utilizadas análises petrográficas, parâmetros texturais na distribuição de partículas, geoquímica e estatística com auxílio de Laser Difraction e Fluorescência de Raios-X com Energia Dispersiva. Os sedimentos estudados são compostos essencialmente de granadas, biotita, piroxênio (diopsídio e augita?), epidoto, monazita, hornblenda, ilmenita, zircão, rutilo, titanita, silimanita, cianita, além de quartzo. Os sedimentos investigados são reflexo dos litotipos encontrados regionalmente, indicando possivelmente uma forte correlação entre as rochas-fonte e os depósitos sedimentares. O ambiente de oxirredução é demarcado pela presença de óxidos de Fe, provavelmente hematita. O índice de alteração calculado suporta um grau moderado, onde micas são preservadas, totalmente ou em partes. Palavras-Chave: Sedimentos Inconsolidados; Depósitos Praiais; Intemperismo Químico. GEOCHEMISTRY AND PETROGRAPHY OF QUATERNARY DEPOSITS FROM SW OF PRAIA BRAVA BEACH, ARMAÇÃO DOS BÚZIOS, RJ, BRAZIL: EDFRX AND LASER DIFRACTION Abstract: This article presents the geochemical and petrographic data of beach sediments from the SW region of Praia Brava (PB) in Armação dos Búzios-RJ. We seek to discuss the processes of chemical weathering and provenance, as well as to analyze the geochemical environment and its relationship with autochthonous sources. In this study, petrographic analyzes, textural parameters in particle distribution (Laser Difraction), geochemistry (X-Ray Fluorescence with Dispersive Energy) and statistics were used. The studied sediments are essentially composed of garnets, biotite, pyroxene (diopside and augite?), epidote, monazite, hornblende, ilmenite, zircon, rutile, titanite, silimanite, kyanite, and quartz. The investigated sediments are similar to the lithotypes found regionally, thus possibly indicating a strong correlation between source rocks and sedimentary deposits. The redox environment is marked by the presence of Fe oxides, probably hematite. The alteration index supports a moderate degree, where micas are preserved, in whole or in part. Keywords: Unconsolidated Sediments, Beach Deposits; Chemical watering. GEOQUÍMICA Y PETROGRAFÍA DE DEPÓSITOS CUTERNARIOS DE LA PORCIÓN SW DE PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX Y DIFFRACCIÓN LÁSER Resumen: Este artículo presenta los datos geoquímicos y petrográficos de sedimentos de playa de la región SO de Praia Brava (PB) en Armação dos Búzios-RJ. Buscamos discutir los procesos de meteorización química y procedencia, así como analizar el entorno geoquímico y su relación con fuentes autóctonas. En este estudio se utilizaron análisis petrográficos, parámetros texturales en distribución de partículas, geoquímica y estadística con la ayuda de Difracción Láser y Fluorescencia de Rayos X con Energía Dispersiva. Los sedimentos estudiados están compuestos fundamentalmente por granate, biotita, piroxeno (¿diópsido y augita?), Epidota, monacita, hornblenda, ilmenita, circón, rutilo, titanita, silimanita, cianita, además de cuarzo. Los sedimentos investigados son un reflejo de los litotipos encontrados regionalmente, lo que posiblemente indique una fuerte correlación entre las rocas generadoras y los depósitos sedimentarios. El entorno redox está delimitado por la presencia de óxidos de Fe, probablemente hematita. El índice de cambio calculado admite un grado moderado en el que se conservan las micas, ya sea total o parcialmente. Palabras clave: Sedimentos no consolidados; Depósitos en la playa; Meteorización química.

Ancient and modern geochemical signatures in the 13,500-year sedimentary record of Lake Cadagno

Although lake sediments are globally important organic carbon sinks and therefore important habitats for deep microbial life, the deep lacustrine biosphere has thus far been little studied compared to its marine counterpart. To investigate the impact of the underexplored deep lacustrine biosphere on the sediment geochemical environment and vice versa, we performed a comprehensive microbiological and geochemical characterization of a sedimentary sequence from Lake Cadagno covering its entire environmental history since formation following glacial retreat. We found that both geochemical gradients and microbial community shifts across the ~13.5 kyr subsurface sedimentary record reflect redox changes in the lake, going from oxic to anoxic and sulfidic. Most microbial activity occurs within the top 40 cm of sediment, where millimolar sulfate concentrations diffusing in from the bottom water are completely consumed. In deeper sediment layers, organic carbon remineralization is much slower but microorganisms nonetheless subsist on fermentation, sulfur cycling, metal reduction, and methanogenesis. The most surprising finding was the presence of a deep, oxidizing groundwater source. This water source generates an inverse redox gradient at the bottom of the sedimentary sequence and could contribute to the remineralization of organic matter sequestered in the energy-limited deep subsurface.

Healing through the landscape

This study investigates the significance of landscape therapy under the impact COVID-19 pandemic. Deurbanization and social distancing drives many city dwellers to their second homes (dacha) in the countryside or stimulates house trade and construction in the rural areas. This expands the possibilities of the body’s recovery. One of the main methods is landscape therapy, along with the cultivation of their own agricultural products by the townspeople in the landscape-geochemical environment familiar to them. Of all natural components, water (natural mineral waters, mud, lakes, rivers, streams, waterfalls) has the greatest importance in the healing landscape concept. It is predicted that the COVID-19 pandemic should be perceived as a milestone in the reorientation of geography and ecology towards understanding human society in a continuous transformation.

Magnesite and bauxite ores as petrophysical objects of spectral-grade estimation based on electrometry (from the archives of oxide-metric exploration in the Ural deposits)

Research subject. Distribution of magnesite and bauxite ores in mining blocks of deposits according to electrical conductivity in connection with signals of scattered phases of Ca, Mg and Al oxides. Petrophysical objects and differentiation of the properties of oxides detected in the boundary area and at the boundary with dielectrics, the semiconductor range in the geochemical environment of metamorphic formations from carbonate sediments.Materials and methods. An approach of searching for stationary features was applied. First, a study at the elemental level (review) was undertaken. Further, the authors’ electrometric measurements of the deposits were analyzed. Results. In the review part, the analysis of the metal constants – the relative electronegativity of the OEO (Luo and Benson scale), the electronic potentials E0, and the relationship of electrical resistance and pressure in pure elements was performed. The inversion of the properties of CaO ↔ MgO was revealed (for the first time in 2002–2004); Ca was identified as a reducing agent (CaO is a solid dielectric), which contradicts the current ideas about the comparative additivity of light Mg. It was established that MgO is a separate source of semiconductor carriers. Favourable conditions for studying the conductivity during the experimental part of the work were the absolute exchange increments of ore oxides at geological contacts. The properties of ores, rocks and oxides were measured and calculated. The relationships of the varietal growth of conductivity with compaction, increased basicity and magnetic susceptibility (magnetization) were predicted. This, in turn, provides a basis for studying cores, samples from debris, shredding and recycled geo-material, including concentrates, tailings and waste.Conclusions. The spectral properties of scattered oxides with atomic numbers ≤ 20 were identified. The activation effect of MgO and Al2O3 in the ionic medium (CaCO3 = CaO+CO2) was noted. In the phenomena of the semiconductor nature (n- and psources), a version of the donor-acceptor mechanism was proposed. The established properties are a factor in the implementation of measuring identification of oxides and ore grades in the conditions of deposits, both in the estimates of carbonate chemical types of terrigenous fossils, and plagioclase-pyroxene – in igneous ones. Varietal exploration and prototype electrometry were discussed from the standpoint of high-precision interpretation in the potential and replenishment combination of various petrophysical meters.

A Review of Geochemical Modeling for the Performance Assessment of Radioactive Waste Disposal in a Subsurface System

Radionuclides are inorganic substances, and the solubility of inorganic substances is a major factor affecting the disposal of radioactive waste and the release of concentrations of radionuclides. The degree of solubility determines whether a nuclide source migrates to the far field of a radioactive waste disposal site. Therefore, the most effective method for retarding radionuclide migration is to reduce the radionuclide solubility in the aqueous geochemical environment of subsurface systems. In order to assess the performance of disposal facilities, thermodynamic data regarding nuclides in water–rock systems and minerals in geochemical environments are required; the results obtained from the analysis of these data can provide a strong scientific basis for maintaining safety performance to support nuclear waste management. The pH, Eh and time ranges in the environments of disposal sites cannot be controlled, in contrast to those under experimental conditions in laboratories. Using a hypothetical error mechanism for the safety assessment of disposal sites may engender incorrect assessment results. Studies have focused on radionuclide reactions in waste disposal, and have offered evidence suggesting that these reactions are mainly affected by the geochemical environment. However, studies have not examined the thermodynamics of chemical reactions or interactions between water and minerals, such as the surface complexation and adsorption of various nuclide-ion species. Simple coefficient models have usually been applied in order to obtain empirical formulas for deriving Kd to describe nuclide distributions in the solid or liquid phase in water–rock geochemical systems. Accordingly, this study reviewed previous research on the applications of geochemical models, including studies on the development of geochemical models, sources of thermodynamic databases (TDBs) and their applications in programs, the determination of the adequacy of TDBs in surface complexation models and case studies, and the selection and application of activity coefficient equations in geochemical models. In addition, the study conducted case studies and comparisons of the activity coefficients derived by different geochemical models. Three activity coefficient equations, namely the Davies, modified Debye–Hückel, and Pitzer equations, and four geochemical models, namely PHREEQC, MINEQL+, MINTEQA2, and EQ3/6, were used in the study. The results demonstrated that when the solution’s ionic strength was <0.5 m, the differences in the activity coefficients between the Davies and modified Debye–Hückel equations were <5%. The difference between the Pitzer and Davies equations, or between the Pitzer and modified Debye–Hückel equations in terms of the calculated activity coefficients was <8%. The effect of temperature on the activity coefficient slightly influenced the modeling outputs of the Davies and modified Debye–Hückel equations. In the future, the probability distribution and uncertainty of parameters of Kd and the equilibrium constant can be used in geochemical and reactive transport models to simulate the long-term safety of nuclear waste disposal sites. The findings of this study can provide a strong scientific basis for conducting safety assessments of nuclear waste disposal repositories and developing environmental management or remediation schemes to control sites marred by near-surface contamination.

Origin and Evolution of the Late Cretaceous Reworked Phosphorite in the Sirhan-Turayf Basin, Northern Saudi Arabia

The redeposition of pristine phosphorite plays an important role in phosphorus accumulation, which created reworked phosphorite extensively on the continental shelf. This paper, using geochemical analysis combined with data from petrology and diagenesis, focuses on the reconstruction of the formation processes of the Late Cretaceous Thaniyat phosphorite deposition in northwestern Saudi Arabia, which is a part of the famous large Neo-Tethys Ocean’s phosphorite deposit. The results of our study illustrate that the phosphorites represent the reworked products from the north, close to the edge of the Neo-Tethys Ocean’s shelf, where upwelling had accreted the pristine phosphorite. The reworked phosphatic grains were redeposited near the shore in sandstone, forming sandy phosphorite and on a carbonate platform and creating calcareous phosphorite. The microscale sedimentological and geochemical information hosted in the eroded phosphorite grains indicates that the source sediment, pristine phosphorite, occurred under a fluctuating geophysical condition and in a relatively limited geochemical environment. They were physically crushed and transported landward and deposited under oxic conditions, forming the Thaniyat phosphorites. Early diagenesis in the Thaniyat phosphorite was evidenced by recrystallization of the phosphate minerals, geochemical depletion, and C and O isotope excursion.

Team Mapping of Oxia Planum for the ExoMars 2022 Rover-Surface Platform Mission

&lt;p&gt;Oxia Planum (OP), located at the transition between the ancient terrain of Arabia Terra and the low lying basin of Chryse Planitia, will be the landing site for the ESA-Roscosmos ExoMars Programme&amp;#8217;s 2022 mission [1]. The descent module and landing platform, Kazachock, will transport the Rosalind Franklin Rover to search for signs of past and present life on Mars, and investigate the geochemical environment in the shallow subsurface over a 211-sol nominal mission.&lt;/p&gt;&lt;p&gt;OP forms a shallow basin, open to the north, characterized by clay-bearing bedrock, and episodic geological activity spans from the ~mid-Noachian to ~early Amazonian in age [2,3,4]. Building a thorough understanding of Oxia Planum prior to operations will provide testable hypotheses that facilitate interpretation of results, and hence provide an effective approach to address the mission&amp;#8217;s science objectives. To this end, we have run a detailed group mapping campaign at HiRISE-scale using the Multi-Mission Geographic Information System (MMGIS) [5], co-registered HRSC [6], CaSSIS and HiRISE mosaics [7], and 116 1km&lt;sup&gt;2&lt;/sup&gt; quads covering the 1-sigma landing ellipse envelope. Complementary CTX-scale mapping covers the wider area around the landing site and is described elsewhere [8].&lt;/p&gt;&lt;p&gt;Throughout 2020, 84 mapping volunteers associated with the mission&amp;#8217;s Rover Science Operations Working Group followed a pre-formulated programme of training, familiarisation and mapping. With the mapping phase complete, a small sub-team are focused on map reconciliation phase, comprising data cleaning and science decision making. The process will culminate in map finalisation and submission for publication, and use in activities to plan rover science activities.&lt;/p&gt;&lt;p&gt;This campaign yields important advances for overall science readiness of the ExoMars 2022 mission:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Team experience working, communicating and learning together, valuable for operations.&lt;/li&gt; &lt;li&gt;Building team knowledge of the landing site, and the main scientific interpretations.&lt;/li&gt; &lt;li&gt;Curated datasets and software available for team use in ongoing planning.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;High-resolution map data representing our geologic understanding of Oxia Planum. This is an input to ongoing RSOWG work to construct the mission strategic plan, which provides science traceability from mission objectives to rover activities.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments:&lt;/strong&gt; We thank Fred Calef and Tariq Soliman at JPL for their support regarding MMGIS.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt; [1] Vago, J. L. et al., (2017) Astrobiology 17 (6&amp;#8211;7), 471&amp;#8211;510. [2] Carter, J. et al., (2013) J. Geophys. Res. 118 (4), 831&amp;#8211;858. [3] Quantin-Nataf, C. et al., (2021) Astrobiol. 21 (3),&amp;#160; doi:10.1089/ast.2019.2191. [4] Fawdon P. et al., (2019) LPSC50 #2132. [5] Calef, F. J. et al., (2019) in 4th Planet. Data Work., Vol. 2151. [6] Gwinner, K. et al., (2016) Planet. Space Sci. 126, 93&amp;#8211;138. [7] Volat, M. et al., (2020), EPSC, #564. [8] Hauber, E. et al. (2021), LPSC52.&lt;/p&gt;

Uncertainty Estimation for Magnetic Maps

&lt;p&gt;Magnetic maps depict spatial variations in the Earth&amp;#8217;s magnetic field.&amp;#160; These variations occur at a wide range of scales and are produced via a variety of physical processes related to factors including structure and evolution of the Earth&amp;#8217;s core field and the geologic distribution of magnetic minerals in the lithosphere.&amp;#160; Mankind has produced magnetic maps for 100&amp;#8217;s of years with increasing fidelity and accuracy and there is a general understanding (particularly among the geophysicists who produce and use these maps) of the approximate level of resolution and accuracy of these maps.&amp;#160; However, few magnetic maps, or the digital grids that typically underpin these maps, have been produced with accompanying uncertainty quantification.&amp;#160; When uncertainty is addressed, it is typically a statistical representation at the grid or survey level (e.g., +- 10 nT overall uncertainty based on line crossings for a modern airborne survey) and not at the cell by cell local level.&lt;/p&gt;&lt;p&gt;As magnetic map data are increasingly used in complex inversions and in combination with other data or constraints (including in machine learning applications), it is increasingly important to have a handle on the uncertainties in these data.&amp;#160; An example of an application with need for detailed uncertainty estimation is the use of magnetic map information for alternative navigation.&amp;#160; In this application data from an onboard magnetometer is compared with previously mapped (or modeled) magnetic variations.&amp;#160; The uncertainty of this previously mapped information has immediate implications for the potential accuracy of navigation.&lt;/p&gt;&lt;p&gt;We are exploring the factors contributing to magnetic map uncertainty and producing uncertainty estimates for testing using new data collection in previously mapped (or modeled) map areas.&amp;#160; These factors include (but are likely not limited to) vintage and type of measured data, spatial distribution of measured data, expectation of magnetic variability (e.g., geologic or geochemical environment), statistics of redundant measurement, and spatial scale/resolution of the magnetic map or model.&amp;#160; The purpose of this talk is to discuss the overall issue and our initial results and solicit feedback and ideas from the interpretation community.&lt;/p&gt;

Mineralogy, aqueous history and biosignature preservation potential of bedrock deposits at Oxia Planum, ExoMars 2022 landing site - Spectral characterization of terrestrial analogues.

&lt;p&gt;In 2022, ESA/ROSCOSMOS will launch the ExoMars2022 rover mission to Mars. The selected landing site for the mission is Oxia Planum, a wide, Noachian-age, phyllosilicate-bearing plain located on the SE border of Chryse Planitia. The Fe,Mg-rich clay mineral deposits at Oxia Planum are one of the largest exposures of this type on Mars, with a thickness of more than 10 m. They clearly record complex water-rock interactions and as such are a promising target to answer scientific questions posed by the ExoMars 2022 mission pertaining to the history of water and the geochemical environment in the shallow Martian subsurface, and the ancient and present habitability of the planet.&lt;/p&gt;&lt;p&gt;From the spectral analysis by CRISM and OMEGA, bedrock deposits at Oxia appear to contain vermiculite, a hydrous 2:1 phyllosilicate. But the exact mineralogy of the deposits and their origin is not yet fully understood. To fill this gap, and to better prepare for in-situ analyses by the ExoMars2022 rover, we performed a survey of potential terrestrial analog rocks by determining their mineralogy and NIR spectra for comparison with CRISM and OMEGA spectra of bedrock deposits at Oxia. The study focused on Fe-rich, trioctahedral vermiculite.&lt;/p&gt;&lt;p&gt;Two terrestrial sites were identified and studied: Otago, New Zealand with vermiculitized chlorite-schists that underwent alteration without significant oxidation; and Granby, Massachusetts with basaltic tuffs containing Fe-rich clays of apparent hydrothermal origin filling amygdales. Both analogues have been added to a newly built Planetary Terrestrial Analogue Library (PTAL) collection. The PTAL collection aims to provide the scientific community with analogue rocks to help characterize and define the mineralogy and geochemistry of landing sites on Mars chosen for in-situ analyses (www.ptal.eu).&lt;/p&gt;&lt;p&gt;The analogue comparisons reveal that Oxia bedrock deposits consist of Fe-rich, trioctahedral vermiculite, which is well crystallized and probably mixed with minor saponite. Additionally, NIR data analysis suggests that the deposits were not oxidized, nor illitized after formation. Based on this study, Oxia&amp;#8217;s bedrock deposits may have formed from: (1) hydrothermal or magma fractionation-related origin of phyllosilicates and formation as an ash-fall deposits or (2) chlorite-rich sediment transported to a basin where chlorite was subsequently altered to vermiculite under anoxic, reducing conditions. The detailed characterization of the analogues and discussion of processes inferred for the evolution of Oxia Planum will be presented during the meeting.&lt;/p&gt;&lt;p&gt;Vermiculite, with its high surface area and exchange capacity, has great potential to store organic compounds. The mineralogy of the bedrock deposits at Oxia, along with the anoxic, reducing conditions that might have been prevalent during Noachian time would be advantageous for retaining and preserving organic matter and make it a promising site for future analysis.&lt;/p&gt;