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In this study, the immobilization of the laccase enzyme, which has a wide application area in the industry, was examined. For this purpose, commercially obtained laccase enzyme was immobilized on various clays using the physical adsorption method. The effects of pH, temperature, substrate concentration, and storage time on the activity of free and immobilized laccase were examined. As a result of the studies, the optimum pH and temperature for free laccase were obtained as 5.5 and 40 °C respectively and the optimum pH and temperature for all immobilized enzymes (bentonite, diatomite, and Bardakçı) were 5.5-6.0 and 40 °C respectively. The effects of pH and temperature on the activity of the immobilized laccase showed that the properties of the immobilized enzyme were the same as those of the free enzyme. The resulting kinetic constant values turned out to be quite close to each other. In addition, it was shown that adsorption did not significantly affect the kinetic properties of the enzyme. Only 20%-30% of immobilized laccase activity disappeared in 2 months. KM values for free enzyme and immobilized enzymes were found as 0.0700 mM, 0.0724 mM, 0.0831 mM, and 0.0935 mM and Vmax values were 0.0695, 0.0216, 0.0236, and 0.0233 mM-1, respectively. The KM value of the immobilized enzyme is greater than that of the free enzyme and the Vmax value is smaller. The increase in resistance of the immobilized enzyme to temperature change and storage time indicates that laccase immobilization on clay is beneficial for enzyme immobilization.

International audience; Abrupt and large-scale climate changes have occurred repeatedly and within decades during the last glaciation. These events, where dramatic warming occurs over decades, are well represented in both Greenland ice core mineral dust and temperature records, suggesting a causal link. However, the feedbacks between atmospheric dust and climate change during these Dansgaard-Oeschger events are poorly known and the processes driving changes in atmospheric dust emission and transport remain elusive. Constraining dust provenance is key to resolving these gaps. Here, we present a multi-technique analysis of Greenland dust provenance using novel and established, source diagnostic isotopic tracers as well as results from a regional climate model including dust cycle simulations. We show that the existing dominant model for the provenance of Greenland dust as sourced from combined East Asian dust and Pacific volcanics is not supported. Rather, our clay mineralogical and Hf-Sr-Nd and D/H isotopic analyses from last glacial Greenland dust and an extensive range of Northern Hemisphere potential dust sources reveal three most likely scenarios (in order of probability): direct dust sourcing from the Taklimakan Desert in western China, direct sourcing from European glacial sources, or a mix of dust originating from Europe and North Africa. Furthermore, our regional climate modeling demonstrates the plausibility of European or mixed European/North African sources for the first time. We suggest that the origin of dust to Greenland is potentially more complex than previously recognized, demonstrating more uncertainty in our understanding dust climate feedbacks during abrupt events than previously understood.

WOS: 000483769900004, Calcretes are widespread in Adana and Mersin provinces and form under different morphologies. Most calcrete profiles comprise a hard laminated crust/hardpan at the top, gradually intergrading into the nodular and/or tubular/columnar horizon with depth. This study compares the delta O-18 and delta C-13 values of calcretes from both provinces and discusses the controlling factors and environmental conditions. The delta O-18 and delta C-13 values are characteristic for the pedogenic calcretes. The Adana calcrete mean delta O-18 values of the hardpan, nodules and tubes, and fractures-infills are 0.69 parts per thousand, 0.77 parts per thousand, and 1.04 parts per thousand PDB heavier than those of the Mersin calcretes, respectively. The overall difference between the two groups is 0.78 parts per thousand PDB. The differences are related to the high evaporation rate in Adana province in respect to Mersin province under similar climatic conditions, except for the evaporation rate. The high evaporation rate in Adana province is due to higher ventilation. The delta C-13 values of both provinces are ahnost the same, reflecting calcrete formation in soil with abundant C-3 vegetation similar to contemporary vegetation. In addition, the mean delta C-18 and delta(1)3C values of the hardpan calcretes slightly differ from those of the columnar horizon, showing a depletion in heavy isotopes. The depletion in the mean delta C-18 values of hard laminated crust in respect to the columnar horizon is 0.09 parts per thousand PDB for Adana calcretes and 0.12 parts per thousand PDB for Mersin calcretes. This is related to the relatively thick water film from which the calcretes formed by precipitation and displacive replacement processes. The difference in the mean delta C-13 values is 0.32 parts per thousand PDB for the Adana calcretes and 0.11 parts per thousand PDB for the Mersin calcretes, and the depletion in delta C-13 values of the hard laminated crust reflects proximity of the bioactive horizon in the soil.

© 2019 Elsevier Ltd The role of organic matter (OM) in antimonate (further denoted as Sb(OH) 6 ) mobility in soil is unclear. The objective of this study was to evaluate Sb(OH) 6 –OM interaction. Antimonate solid:liquid distribution coefficients (K D ) were measured at low Sb concentrations in soil samples with a natural gradient in soil organic carbon (OC) that were collected from different depths of up to 3 m in two excavated soil profiles and in a subset of four soil samples with experimentally increased OM concentration from addition of Suwannee River OM. The K D values were related to soil properties by multiple linear regression and described with the CD–MUSIC model of ferrihydrite. The K D values ranged from 12 to 2800 L kg −1 and decreased strongly with increasing OC concentrations, when normalized to the amount of iron (Fe) and aluminium (Al) in acid oxalate extracts (r = −0.69; p < 0.0001). Experimentally increasing OC by ∼1.5 g kg −1 increased soluble Sb and decreased Sb(OH) 6 K D values by up to a factor of 8. The multiple regression model reveals that sorption of Sb(OH) 6 to Fe and Al hydroxides decreases with increasing pH and increasing dissolved organic carbon concentration. This effect could be explained with geochemical modelling by the competitive and electrostatic effects of adsorbed humic substances on Sb(OH) 6 surface complexation to the reactive surface sites of the Fe and Al hydroxides. Finally, both models could predict the in situ pore water Sb concentrations of unspiked samples, with a RMSE of 0.35 for the regression model and 0.43 for the geochemical model on the log 10 Sb concentrations. For these predictions, the 0.1 M Na 2 HPO 4 –extractable Sb concentration was measured and used to estimate the reversibly sorbed Sb pool. This study shows that increasing soil OM increases Sb(OH) 6 mobility at low soil Sb concentration, likely due to competitive sorption on Fe and Al hydroxides and a process based, geochemical model was calibrated to describe Sb(OH) 6 mobility in soil. ispartof: APPLIED GEOCHEMISTRY vol:104 pages:1-45 status: Published online

The Anadarko Basin of Oklahoma represents a major Paleozoic depocenter that existed along the rifted margins of southwestern Laurentia. In its infancy it accumulated a thick series of Cambrian through Mississippian detritus while further subsidence caused by inversion of the Cambrian Southern Oklahoma Aulacogen resulted in voluminous Pennsylvanian to Permian sediment. This contribution reports new data on K-Ar ages and trace-element geochemistry of detrital illite from middle and upper Pennsylvanian shale used to reconstruct sediment origins at the peak period of subsidence of the Anadarko Basin. X-ray diffraction was used to unveil mineral compositions and abundances of illite polytypes in two size fractions of separated illite (˂1 and 2-1 μm). K-Ar isotopic analyses were completed for both fine fractions, while the laser ablation inductively coupled plasma mass spectrometry was done for the latter. All illite separates consisted of mixtures of authigenic (1Md) and detrital (2M1) illite. The Illite Age Analyses showed that the detrital age of Desmoinesian (Moscovian) shale is the late Ediacaran (584 Ma), while the age of Missourian (Kasimovian) shale is the middle Cambrian (512.5 Ma). Trace-element abundances of all analyzed illite, irrespectively of stratigraphic age, are consistent with those of mica from metamorphic rocks. Based on illite detrital age and geochemistry it was inferred that Desmoinesian (Moscovian) shale represents a mixture of Neoproterozoic and Cambrian detritus sourced locally, whereas Missourian (Kasimovian) shale records a provenance shift toward more distal easterly sources from the Ouachita-(Marathon) foreland. This study has proposed a sediment source transition between the middle and upper Pennsylvanian that likely reflected major changes in the basin paleogeography and progressive development of the east-west (transcontinental) fluvial systems., Financial support for this study was received from the AAPG-Grants-in-Aid program and Geological Society of America. Any findings and conclusions expressed in this contribution are those of the authors and do not necessarily reflect the views of mentioned societies. Further support was obtained from the Geosciences Clay Laboratory of Texas Tech University. We are especially grateful to the core depository of the Oklahoma Geological Survey in Norman, OK, for granting us access to the core samples. We extend our appreciation to Drs. Calvin Barnes and Kevin Werts for their guidance in the GeoAnalytical Laboratory of Texas Tech University. Further on, we are in debt to James Browning and Rufino Lozano for their valuable help with sample preparation for LA-ICP-MS analyses and the acquisition of KAr ages, respectively. Critical comments and constructive reviews by two anonymous reviewers, as well as the editorial handling by Dan Sturmer and Thomas Algeo contribut

Recent robotic missions to Mars have offered new insights into the extent, diversity and habitability of the Martian sedimentary rock record. Since the Curiosity rover landed in Gale crater in August 2012, the Mars Science Laboratory Science Team has explored the origins and habitability of ancient fluvial, deltaic, lacustrine and aeolian deposits preserved within the crater. This study describes the sedimentology of a ca 13 m thick succession named the Pahrump Hills member of the Murray formation, the first thick fine‐grained deposit discovered in situ on Mars. This work evaluates the depositional processes responsible for its formation and reconstructs its palaeoenvironmental setting. The Pahrump Hills succession can be sub‐divided into four distinct sedimentary facies: (i) thinly laminated mudstone; (ii) low‐angle cross‐stratified mudstone; (iii) cross‐stratified sandstone; and (iv) thickly laminated mudstone–sandstone. The very fine grain size of the mudstone facies and abundant millimetre‐scale and sub‐millimetre‐scale laminations exhibiting quasi‐uniform thickness throughout the Pahrump Hills succession are most consistent with lacustrine deposition. Low‐angle geometric discordances in the mudstone facies are interpreted as ‘scour and drape’ structures and suggest the action of currents, such as those associated with hyperpycnal river‐generated plumes plunging into a lake. Observation of an overall upward coarsening in grain size and thickening of laminae throughout the Pahrump Hills succession is consistent with deposition from basinward progradation of a fluvial‐deltaic system derived from the northern crater rim into the Gale crater lake. Palaeohydraulic modelling constrains the salinity of the ancient lake in Gale crater: assuming river sediment concentrations typical of floods on Earth, plunging river plumes and sedimentary structures like those observed at Pahrump Hills would have required lake densities near freshwater to form. The depositional model for the Pahrump Hills member presented here implies the presence of an ancient sustained, habitable freshwater lake in Gale crater for at least ca 10^3 to 10^7 Earth years.

Low salinity waterflooding is a low-cost method of enhancing oil recovery although, no consistent concept has been established explaining why some oil-fields show an increase in oil production when the salinity of the injected brine is reduced, while others do not. Various studies were conducted investigating the underlying mechanisms of the ‘low salinity effect’ using different crude oil, brine and rock compositions. Core floods of sandstone rock and analyses of molecular interactions using model systems indicate that clay content may play a dominant role. However, the spatial configuration of the sheet-like clay particles, which may vary from rock to rock, complicate comparisons of these model scenarios with reality. In the present study, we report the development of a pre-screening method using Atomic Force Microscopy (AFM) to assess rock-fluid interactions, which has previously only been used either on artificial model systems or minerals from crushed rock, by exploring the capability to operate in-situ in complex rock without crushing. The orientation of clay particles within a pore of an outcrop sandstone, Bandera Brown, was investigated with AFM and these particles were further assessed for changes in adhesion in brines of differing salinity. The results show a decrease in adhesions between CH3-functionalised AFM tips and the rock surface in low salinity brine, predominantly at the clay edges. This demonstrates that the edges of the clay particles, which may pin the oil phase after wettability alteration and therewith prevent oil from getting produced, lose this capacity when exposed to low salinity brine.

Sheared sedimentary clay was found in a faulted fracture in crystalline bedrock in a tunnelling site at 60 m depth in southern Finland. Brittle faults are numerous in the Fennoscandian Palaeoproterozoic bedrock, but only some of them have relative age constraints, while absolute ages are nearly lacking. Sedimentary rocks altogether are uncommon in Finland and only sparsely dated by micropaleontological studies. This study reports K-Ar data of fresh, non-weathered authigenic illite and constrains a time framework for the local faulting and sedimentation. The Neoproterozoic Tonian to Cryogenian ages derived from the grains in diminishing grain-size order are c. 967, 947, 809 and 697 Ma. Results indicate that the formation of the extension fracture is related to the collapse of Sveconorwegian orogeny c. 1000 Ma; clay and mature quartz sand were deposited in this extension fracture in shallow water in an intracratonic basin followed by early diagenetic processes and neocrystallization of illite around 967-947 Ma. The Neoproterozoic 1000-700 Ma sedimentation documented in this study is rare in the Fennoscandian shield as a whole. Neocrystallization of authigenic illite in the finest 0.4 and

This study determined the geochemical properties of phyllosilicates in the Upper Palaeozoic-Lower Mesozoic metamorphic units outcropping from west to east in the vicinities of Göksun, Afşin and Ekinözü towns in the north of Kahramanmaraş province in the westerly part of the Eastern Taurus mountains. Geochemical examination of phyllosilicates (major and trace elements, stable isotope) was carried out on pure K-micas and illite/K-micas separated from low-medium grade metamorphic samples. According to the main oxide composition of the phyllosilicates, illite/K-micas from the areas of Afşin and Göksun contain higher SiO2 and Al2O3 and lower MgO, Fe2O3, MnO and Na2O compared to those in the area of Ekinözü. The minerals represented by schists in the Ekinözü K-micas are close to having a biotite-celadonite composition while those with phyllites in Afşin and Ekinözü are close to muscovite composition. Chlorites have a trioctahedral composition between chamosite and clinochlor. Illite/K-micas with both trioctahedral and dioctahedral characteristics show a composition between muscovite and biotite (biotite-celadonite, muscovite-phlogopite, muscovite-ferriphengite, muscovite-ferrobiotite, Al-phlogopite-Al-annite) in general. In the trace element content of phyllosilicate minerals, transition metals and granitoid elements are at high concentrations while other elements, especially elements with low (LFSE) and high field strength (HFSE), display low concentrations. In the chondrite-normalized trace element content of phyllosilicate minerals, chlorites have higher values compared to K-micas and trioctahedral K-micas show lower values compared to dioctahedral K-micas. Rare earth element (REE) distribution of chlorite and sericite/K-mica minerals is normalised to chondrite and North American Shale Composition (NASC); the dioctahedral K-mica of Afşin region has the highest depletion, while the trioctahedral mica of Ekinözü has the highest enrichment. The oxygen and hydrogen isotope composition of the phyllosilicate minerals show that they are in the hypogene region, which represents high temperature and deep environment conditions. The oxygen and hydrogen isotope values of sericite/K-mica and chlorites indicate that the formation temperatures of these minerals varied between 375 and 500 °C. 40Ar/39Ar radiometric age data for the metamorphic rocks show that the metamorphism developed during the Upper Cretaceous (Santonian-Campanian) in the Afşin and Göksun regions and the Lower-Middle Eocene (Ypresian-Bartonian) periods in the Ekinözü region., Bu çalışmada, Doğu Toroslar’ın batı kesiminde Kahramanmaraş ili kuzeyinde batıdan doğuya doğru Göksun, Afşin ve Ekinözü ilçeleri çevresinde yüzeyleyen Üst Paleozoyik-Alt Mesozoyik yaşlı metamorfik birimlerindeki fillosilikatların jeokimyasal özellikleri incelenmiştir. Bu kapsamda düşük-orta dereceli metamorfik örneklerden elde edilen saf K-mika ve illit/K-mikalarda jeokimyasal (ana ve iz/eser element, duraylı ve radyojenik izotop) incelemeler yapılmıştır. Fillosilikatların ana oksit bileşimlerine göre; Afşin ve Göksun bölgelerine ait illit/K-mikalar Ekinözü bölgesindekilere göre daha yüksek SiO2 ve Al2O3, buna karşın daha düşük MgO, Fe2O3, MnO ve Na2O içermektedir. Fillosilikat minerallerinin ana oksit bileşimlerine göre; şistlerle temsil edilen Ekinözü bölgesindeki K-mikalar biyotit-seladonit, fillitlerle temsil edilen Afşin ve Göksun bölgesindekiler ise muskovit bileşimlerine daha yakındır. Kloritler; şamozit ve klinoklor arasında trioktahedral bileşime sahiptir. Hem trioktahedral, hem de dioktahedral özelliğindeki illit/K-mikalar; genel anlamda muskovit ile biyotit arasında (biyotit-seladonit, muskovit-filogopit, muskovit-ferrifenjit, muskovit-ferrobiyotit, Al-flogopit-Al-annit) bir bileşim sergilemektedir. Fillosilikat minerallerinin eser element içerikleri; geçiş metalleri ve granitoyid elementler bakımından yüksek; buna karşın diğer elementler, özellikle kalıcılığı düşük (LFSE) ve yüksek (HFSE) elementler açısından düşük derişim göstermektedir. Fillosilikat minerallerinin kondrit-normalize iz element desenlerinde; kloritler K-mikalara, benzer biçimde trioktahedral K-mikalar dioktahedral olanlara göre daha düşük değerler sunmaktadır. Klorit ve illit/K-mikaların kondrit ve Kuzey Amerika Şeyl Bileşimi’ne (NASC) göre normalize edilmiş nadir toprak element (NTE) dağılımlarında; Afşin bölgesine ait dioktahedral K-mikalar en fazla fakirleşmeye, Ekinözü bölgesine ait trioktahedral mikalar ise en yüksek zenginleşmeye sahiptirler. Oksijen ve hidrojen izotop bileşimlerine göre; fillosilikatları incelenen tüm örnekler yüksek sıcaklık ve derin ortam koşullarını temsil eden hipojen bölgede yer almaktadır. Serizit/K-mika ve kloritlerin oksijen ve hidrojen izotop değerleri; bu minerallerin oluşum sıcaklıklarının 375-500 °C arasında değiştiğine işaret etmektedir. İllit/K-mikaların 40Ar/39Ar radyometrik yaş verileri; Afşin ve Göksun bölgelerindeki metamorfik kayaçlar için Üst Kretase (Santoniyen-Kampaniyen), Ekinözü bölgesindekiler için Alt-Orta Eosen (İpresiyen-Bartoniyen) döneminde gelişen metamorfizmayı göstermektedir.

In this work, modified halloysite was successfully prepared and its adsorptive capacity was studied using methyl orange dye solution. The adsorption behavior was systematically performed as a function of initial dye concentration and time. The halloysite-mineral (Al2O3 center dot 2SiO(2)center dot 4H(2)O) used in this study was an aqueous alumino silicate mineral consisting of layers with similar structural composition and was gathered from the Biga Peninsula, Western Anatolia. Characterization of the prepared material was examined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Differential Thermal Analyzer (DTA). The adsorptive capacity of the modified halloysite in methyl orange was increased by increasing the contact time and initial dye concentration. Lagergren pseudo first-order and pseudo second-order kinetics were performed and pseudo second-order model was found to be the best fit model for the adsorption kinetic. Langmuir, Freundlich, Sips and Dubinin-Radushkewich isotherm models were applied to the experimental data to find the suitable model for describing the adsorption equilibrium. Unmodified-clay was also used in the adsorption process of methyl orange to compare the adsorptive property of the modified-clay. It was found that modified halloysite performed better as an adsorbent than untreated clay for the adsorption of methyl orange. Scientific Research Projects (BAP), coordination unit of Istanbul UniversityIstanbul University [49703] This work was supported by the Scientific Research Projects (BAP), coordination unit of Istanbul University, Project ID, 49703.

The role of eroding landscapes in organic carbon stabilization operating as C sinks or sources has been frequently discussed, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC) stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are generally abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14C ages for aggregated and non-aggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14C ages of buried soil indicate that C in aggregated fractions seems to be preserved more efficiently while C in non-aggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14C ages and at the same time high contents of microbial residues in aggregates suggest either that microorganisms feed on old carbon to build up microbial biomass or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of protection mechanisms, a potential C sink through soil burial is finally temporally limited.

Eurosoil Meeting, WOS: 000437053000004, This paper describes beta-fabric features and their distribution in the calcretes, and emphasizes the role of soil organisms in the formation of the calcrete profiles. Quaternary calcretes are common in the Mersin and Adana provinces occurring as powdery, nodular, tubular, fracture-infill and various forms of crusts. The stable isotope values indicate calcrete development under semi-arid climatic conditions and a pedogenic origin. Biogenic or beta-fabric constituents are abundant in the hard laminated crust. These are the rhizoliths, alveolar septal structures, needle-fiber calcites, calcified filaments, spherical calcite bodies, microcodium and vadose (calcrete) pisoliths. Rhizoliths have mainly formed by the petrification of roots, and often contain cellular cortex structures. The alveolar septal structure comprises root-voids separated by a micritic wall or a bundle of tangentially oriented calcite needles. Needle-fiber calcite is common in the hard laminated crust as monocrystalline rods and polycrystalline needles. Monocrystalline rods are smooth and small (< 1 mu m in length), whereas polycrystalline needles consist of a chain of calcite rhombs stacked as parallel c-axes. The elongated crystals generally form interwoven masses. The calcified filaments are straight to slightly curved tubular microstructures with a central hollow. Microcodiums are rosette-like aggregates composed of slightly curved radial-fibrous calcite crystals extending from a central cavity. Vadose pisoliths consist of irregularly coated microbial laminae around a nucleus, and often show a downward elongation indicating an in-situ formation. All these biogenic features indicate a pedogenic origin for calcretes. Their abundance in the hard laminated crust points to calcification in a biologically active zone and maturation in calcrete formation with a thin soil cover., Eurosoil

For more than two decades, research groups in hydrology, ecology, soil science, and biogeochemistry have performed cryogenic water extractions (CWEs) for the analysis of δ2H and δ18O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soil water isotope composition. Here we present results from the first worldwide round robin laboratory intercomparison. We test the null hypothesis that, with identical soils, standards, extraction protocols, and isotope analyses, cryogenic extractions across all laboratories are identical. Two standard soils with different physicochemical characteristics along with deionized (DI) reference water of known isotopic composition were shipped to 16 participating laboratories. Participants oven-dried and rewetted the soils to 8 and 20 % gravimetric water content (WC), using the deionized reference water. One batch of soil samples was extracted via predefined extraction conditions (time, temperature, and vacuum) identical to all laboratories; the second batch was extracted via conditions considered routine in the respective laboratory. All extracted water samples were analyzed for δ18O and δ2H by the lead laboratory (Global Institute for Water Security, GIWS, Saskatoon, Canada) using both a laser and an isotope ratio mass spectrometer (OA-ICOS and IRMS, respectively). We rejected the null hypothesis. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to soil type and soil water content with mean differences compared to the reference water ranging from +18.1 to −108.4 ‰ for δ2H and +11.8 to −14.9 ‰ for δ18O across all laboratories. In addition, differences were observed between OA-ICOS and IRMS isotope data. These were related to spectral interferences during OA-ICOS analysis that are especially problematic for the clayey loam soils used. While the types of cryogenic extraction lab construction varied from manifold systems to single chambers, no clear trends between system construction, applied extraction conditions, and extraction results were found. Rather, observed differences in the isotope data were influenced by interactions between multiple factors (soil type and properties, soil water content, system setup, extraction efficiency, extraction system leaks, and each lab's internal accuracy). Our results question the usefulness of cryogenic extraction as a standard for water extraction since results are not comparable across laboratories. This suggests that defining any sort of standard extraction procedure applicable across laboratories is challenging. Laboratories might have to establish calibration functions for their specific extraction system for each natural soil type, individually.

In soils goethite and kaolinite are often cemented together as a binary association, which has a significant influence on the physical and chemical properties of soils. In this study, the surface properties and phosphate adsorption of goethite, kaolinite, goethite-kaolinite association (GKA) and goethite-kaolinite mixture (GKM) were investigated. Compared to the average simple sum values of goethite and kaolinite, the pore volume and specific surface area (SSA) of GKA increased, and those of GKM remained almost unchanged. Goethite, kaolinite, GKM and GKA have a pH of point of zero charge (PZC) at around 8.2, 4.1, 6.1, and 7.0, respectively; and their surface charge is 0561, -0.092, 0.041, and 0.097 mmol/g at pH 5.0, respectively. The phosphate adsorption data of goethite and kaolinite could be fitted by one-site Langmuir model (R-2 = 0.963 and 0.956, respectively). Two-site Langmuir model described the phosphate adsorption by GKM and GKA well (R-2 = 0.985 and 0.982, respectively); and the Freundlich correlation coefficients of GKM and GKA were 0.967 and 0.924, respectively. This indicated that GKM and GKA possessed the surface with two types of reactive sites, and the surface heterogeneity of GKM was higher than that of GKA. Compared to the average value of goethite and kaolinite, the adsorption capacities of GKM (q(max) = 198.17 and q(t) = 226.11 mmol/g) increased slightly and those of GKA (q(max) = 230.24 and q(t) = 235.96 mmol/g) significantly increased, indicating that GKA was a highly effective adsorbent for phosphate. (C) 2013 Elsevier B.V. All rights reserved.

The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (−1.0, −0.66 and −0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the selfdiffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.

International audience; In acidic soils, the fixation of Al in the interlayer spaces of 2:1 clay minerals and the subsequent formation of hydroxyl interlayer minerals (HIMs) are known to reduce soil fertility. The resulting crystal structure of HIMs consist of complex mixed-layer minerals (MLMs) with contrasting relative proportions of expandable, hydroxy-interlayers (HI) and illite layers. The present study aims to experimentally assess the influence of particle size on the formation of such complex HIMs for vermiculite saturated with potassium (K). Based on chemical and structural data, this study reports the dissolution and Al-interlayer occupancy of three size fractions (0.1–0.2, 1–2 and 10–20 μm) of K-vermiculite, which were obtained at pH = 3 by using stirred flow-through reactors. The Al-interlayer occupancies were ordered 0.1–0.2 μm < 10–20 μm < 1–2 μm even though the dissolution rate (in molvermiculite g−1 s−1) increases with decreasing particle size. For fine particles (0.1–0.2 μm), a rapid but low Al-interlayer occupancy during the transitory state and a null rate in the steady-state were evidenced and interpreted as indicating (i) a rapid but limited K+ interlayer exchange during the first step of the overall reactions and (ii) a stoichiometric dissolution of the crystal (TOT layer + interlayer) in the steady-state. By contrast, although the stoichiometric dissolution of the TOT layer is reached in the steady-state for the coarsest fractions (10–20 and 1–2 μm), the Al-interlayer occupancies continue to evolve due to the exchange of interlayer K+, which continues to progress for a longer duration.The mechanism of auto-aluminization is interpreted in the present study as multiple processes that involve (i) the dissolution of the mineral under acidic conditions, (ii) the interlayer diffusion of initial interlayer cations and their exchange with those from the aqueous phase and (iii) the fixation of interlayer aluminum. Competition between the kinetics of ion-exchange reactions and that of mineral dissolution is responsible for the above Al-interlayer occupancy order among the particle sizes (i.e., 0.1–0.2 μm < 10–20 μm < 1–2 μm). Moreover, this mechanism may be the cause of complex mineralogical structures such as mixed-layer minerals, which are commonly found in the clay-size fraction of acidic soils.

Aluminium (Al) and iron (Fe) play a key role in pedogenetic processes; however, short-term changes in Al- and Fe-bearing secondary minerals are little documented. In this study, Al and Fe dynamics in the solid phase have been evaluated in three soil compartments (bulk, ‘rhizosphere outer’, corresponding to soil volume detached from fresh roots, and ‘rhizosphere inner’, corresponding to soil volume detached from dried roots) and during 4 months (November, February, May and August) in an acid soil with podzolic features at its surface. Soil samples were collected from under Norway spruce (Picea abies (L.) Karst.) at three depths (0–3, 3–10 and 10–23 cm) and were sieved at 200 µm. The Al and Fe forms were extracted with different solutions: potassium chloride (AlKCl and FeKCl), oxalate (Alo and Feo), tri-citrate (Alc) and dithionite-citrate-bicarbonate (Fed). The influence of spruce roots and seasons on the dynamics of Al and Fe (precipitation and dissolution reactions) was observed. The rhizosphere effect on Fed varied with sampling dates. Thus, Fed-Feo decreased between winter and spring in the rhizosphere inner soil only (decrease of 40%). In contrast, Alc was greater in the bulk soil than in both rhizosphere soils for all seasons. The strongest variations in Al were observed at depth, especially in the bulk and the rhizosphere outer soil, where Alc-Alo decreased drastically between winter and spring (from 50 to 60%). The seasonal dynamics of the podzolization process are discussed. This study shows that Al- and Fe-bearing secondary minerals can quickly react to environmental changes, suggesting that these minerals could be markers of currently active functioning of soils.

Goethite and kaolinite are ubiquitous in natural environments. In soils they are often cemented together as a binary association, which has a significant influence on the structure and properties of soils. In this study, the mineralogy (using X-ray diffraction [XRD], thermal analyses, and infrared analysis), interactions, and stability of a goethite-kaolinite association (GKA) and a goethite-kaolinite mixture (GKM) were investigated. In GKA, goethite almost completely coated the surface of kaolinite, whereas for GKM the coating was partial. Infrared (IR) spectra showed that the vibrational frequencies of Fe-OH in GKM and GKA shifted to higher wave numbers and those of Al-OH, O-Al-O, Al-O-Si, and Fe-O shifted to lower wave numbers. Magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy demonstrated that interactions between goethite and kaolinite increased the chemical shifts of Si-29 and Al-27. The shifts of both the IR and the MAS NMR parameters were larger for GKA than for GKM. In addition, the IR bands of Al-OH and the XRD peaks of goethite were weaker with GKA than with GKM. As expected, particle size distributions showed that GKA had a higher mechanical stability than GKM. The thermal stability of the kaolinite in GKA was higher than that of GKM, but that of goethite in GKA was lower than that in GKM. These results imply that: (i) kaolinite and goethite interact by electrostatic attraction, anion ligand exchange, surface coordination, and hydrogen bonds; (ii) the interaction strength was much stronger for GKA than for GKM; (iii) a cation exchange reaction and isomorphous substitution of Fe by Al for goethite occurred in GKA.

Diverse analytical techniques are available to determine the particle size distribution of potentially toxic elements in matrices of environmental interest such as soil, sediments, freshwater and groundwater. However, a single technique is often not exhaustive enough to determine both particle size distribution and element concentration. In the present work, the investigation of mercury in soil samples collected from a polluted industrial site was performed by using a new analytical approach which makes use of sedimentation field-flow fractionation (SdFFF) coupled to cold vapour generation electrothermal atomic absorption spectroscopy (CV-ETAAS). The Hg concentration in the SdFFF fractions revealed a broad distribution from about 0.1 to 1 ?m, roughly following the particle size distributions, presenting a maximum at about 400-700 nm in diameter. A correlation between the concentration of Hg in the colloidal fraction and organic matter (O.M.) content in the soil samples was also found. However, this correlation is less likely to be related to Hg sorption to soil O.M. but rather to the presence of colloidal mercuric sulfide particles whose size is probably controlled by the occurrence of dissolved O.M. The presence of O.M. could have prevented the aggregation of smaller particles, leading to an accumulation of mercuric sulfides in the colloidal fraction. In this respect, particle size distribution of soil samples can help to understand the role played by colloidal particles in mobilising mercury (also as insoluble compounds) and provide a significant contribution in determining the environmental impact of this toxic element.

Iron oxide-kaolinite associations are important components of tropical and subtropical soils and have significant influence on the physical and chemical properties of soils. In this study, the formation and transformation of Fe oxide-kaolinite associations as a function of pH, temperature, and time were investigated at different Fe(II)/ Fe(III) molar ratios (R). Results show that the formation of crystalline Fe oxides was significantly inhibited due to the presence of kaolinite, while accelerated by Fe(II). The formation of lepidocrocite- and goethite-kaolinite associations were accelerated by Fe(II) at R = 0.04 to 0.06, an initial pH (pHi) of 5 to 8, and a temperature (T) of 50 to 70°C; the formation of hematite-kaolinite association was accelerated by Fe(II) at R = 0.06, pHi 7 to 8, and T= 60 to 80°C; magnetite-kaolinite association was obtained at R = 0.06, pHi 9, and T = 60°C or at R = 0.1 to 0.5, pHi 7, and T = 60°C. The pH as a function of time (pHt) decreased sharply when crystalline Fe oxides were formed in the presence of Fe(II), Fe(III), and kaolinite. The decrease in pHt was slow, however, in the system with Fe(III) and kaolinite but without Fe(II) and in the system with Fe(II) and kaolinite but without Fe(III). The morphologies of lepidocrocite, goethite, hematite, and magnetite in associations are strip shaped, nanorod like, pseudo-cubic shaped, and nanosphere like, respectively. In a system with Fe(II), Fe(III), and kaolin

Fundamental properties such as cation exchange capacity (CEC), permanent charge, pH(PZC), and metal uptake of a Zn-containing montmorillonite are modified, in a predictable manner, by a mild chemical treatment using acetate. Acetate treatment allows a controllable increase of the CEC of montmorillonite up to 180 mequiv/100 g. The CEC of the clay is increasing for decreasing Zn content, with a slope of Delta[Zn]/Delta[CEC] approximately -2. X-ray powder diffraction analysis shows that the lamellar structure of the clay remains unaltered by the acetate treatment, while XPS substantiates the removal of Zn. H(+) uptake data show that the intrinsic protonation pK values and concentration of the variable charge sites ( identical with SOH) are not modified by the acetate treatment. In contrast, the concentration of the permanent charge sites ( identical with X(-)) increased linearly with Zn removal by acetate, leading to a significant H(+) and Cd(2+) uptake enhancement. A physical model is suggested where acetate removes Zn ions strongly bound in the clay, and this in turn modulates the permanent charge and the CEC of the clay.

Clay minerals are used in variety of applications ranging from composites to electronic devices. For their efficient use in such areas, understanding the effect of surface-active agents on interfacial properties is essential. We investigated the role of surface ions in the adsorption of water molecules by using a muscovite mica surface populated with two different, He and K+, surface ions. A series of grand canonical Monte Carlo (GCMG) simulations at various relative vapor pressures (p/p(0)) were performed to obtain the water structure and adsorption isotherm on the He-exposed mica (H-mica) surface. The obtained results were compared to the recent simulation data of water adsorption on the Kt-exposed mica (K-mica) surface reported by Malani and Ayyappa (Malani, A.; Ayappa, K. G. J. Phys. Chem. B 2009, 113, 1058-1067). Water molecules formed two prominent layers adjacent to the H-mica surface, whereas molecular layering was observed adjacent to the K-mica surface. The adsorption isotherm of water on the K-mica surface was characterized by three stages that corresponded to rapid adsorption in the initial regime below p/p(0) = 0.1, followed by a linear development regime for p/p(0) = 0.1-0.7 and rapid film thickening for p/p(0) >= 0.7, whereas only latter two regimes were observed in the H-mica system. In addition, the film thickness of adsorbed water molecules for p/p(0) < 0.7 was lower as compared to that for the K-mica surface and comparable beyond. The film thickness obtained from the MC simulations was in excellent agreement with the interferometry experimental data of Balmer et al. (Balmer, T. E.; Christenson, H. K.; Spencer, N. D.; Heuberger, M. Langmuir 2008, 24, 1566-1569). It was observed that the hydration behaviors of the two ions were completely different and depended on the size of their hydration shell and their ability to form hydrogen bonds. The behavior of water adsorption between these two cases was illustrated using the water density distribution, orientational distributions, hydrogen bonding, and isosteric heats of adsorption.

Adsorption, electrokinetic properties and the interactions between polymer and clay minerals have recently received much attention, owing to the physicochemical properties of these materials. In this study, surface properties of poly(vinylimidazole)-adsorbed expanded perlite such as adsorption, adsorption kinetics and electrokinetic properties have been investigated as a function of temperature, ionic strength and pH. The zeta potential measurements have been performed to determine the isoelectric point (iep) and potential determining ions (pdi). Although pH strongly altered the zeta potential of expanded perlite sample, expanded perlite does not yield any isoelectric point in the pH ranges of 2–11, poly(vinylimidazole) (PVI) changes the interface charge from negative to positive for expanded perlite when adsorbed on its surface. Adsorbed amounts ( q e ) showed a great dependence on pH. The adsorption of PVI increases with increasing pH, ionic strength and temperature. The pH values where the maximum adsorbed mass occurred might be considered as the conditions where electrostatic attraction is the most favourable. Experimental adsorption data were investigated using Langmuir and Freundlich isotherm models and found that Langmuir isotherm model gave the best representation of the adsorption equilibrium. In order to investigate the mechanism of adsorption and potential rate controlling step, pseudo-first- and second-order kinetic equations, and intraparticle diffusion model have been used to test the experimental data. The rate constants and the related correlation coefficients were determined in order to assess which model provides the best-fit predicted data with experimental results. Pseudo-first-order kinetic equation provided the best fit to experimental data.

The adsorption of humic acids (HA) to goethite (at pH 3-11) and the proton co-adsorption (at pH 4.0, 5.5, and 7.0) were measured, and the results were compared to those of fulvic acids (FA). Compared to FA, the adsorption of HA is stronger and more ionic strength dependent. The adsorption of both HA and FA decreases with increasing pH. The relative change of the adsorption with pH is bigger for HA than for FA at relatively low pH. At relatively high pH, it is the opposite. Protons are released at pH 4.0 and co-adsorbed at pH 5.5 and 7.0 upon the adsorption of both HA and FA. The observed pH dependency of HA and FA adsorption is in agreement with the proton co-adsorption data. Model calculations show that the adsorbed FA particles are on average located in the Stern layer, whereas the adsorbed HA particles protrude beyond the Stern layer. The closer location to the surface of the adsorbed FA leads to stronger electrostatic interactions between the FA particles and the surface, which explains the larger amount of protons released at low pH and co-adsorbed at high pH with each mass unit of FA adsorbed than that with HA adsorbed. The model also reveals that for FA a mean-field (smeared-out) approximation is reasonable, but for HA a patchwise approach is more appropriate at relatively low loading.

The adsorption of thiram and disulfiram onto alpha-Al2O3 and montmorillonite clay has been studied in the presence of small carboxylate anions, bicarbonate, formate, and oxalate. At natural concentrations, HCO3- enhances dramatically the adsorption of both pesticides on alpha-Al2O3 and clay. An analogous significant enhancement of pesticide adsorption is also observed in the presence of formate and oxalate. Density functional theory calculations demonstrate that in solution a stable molecular complex between one molecule of thiram and one molecule of HCO3- is formed with interaction energy -35.6 kcal/mol. In addition, two H2O molecules further stabilize it by an interaction energy of -3.6 kcal/mol. This clustering [thiram-HCO3--2H(2)O] leads to a change of the electronic structure and the ultraviolet-visible spectrum of thiram that is observed experimentally. Surface complexation modeling shows that the molecular cluster [thiram-HCO3-2H(2)O], which bears a total net charge of -1, is responsible for the observed enhanced adsorption on the charged surface of alumina and clay at pH below their points of zero surface charge. The results reveal a novel pervasive role of carboxylate anions and particularly HCO3- on the adsorption of dithiocarbamate pesticides in natural waters. Environ Sci Technol

Adsorption of trace amounts of radiocaesium on NH4-, K-, and Na-saturated Fithian illite and subsequent desorption by 1 M NH4 showed that a substantial amount of radiocaesium (44%, 46%, and 91% for NH4-, K-, and Na-illite, respectively) cannot be desorbed after only 5 min of adsorption. Our results suggest that this instantaneous fixation is caused by the collapse of the frayed edges of the clay mineral and the relatively high concentration of radiocaesium building up in solution in the batch desorption experiments. Consequently, commonly applied high-NH4 extractions underestimate truly exchangeable amounts of radiocaesium in soils and sediments containing illitic clay minerals. The rate of desorption of trace amounts of radiocaesium from the solids using high NH4 or Cs concentrations has a half-life of about 2 yr, reflecting radiocaesium desorption from (partially) collapsed interlayers. Extraction of radiocaesium from illite after 5 min of contact time with a Cs-selective adsorbent or a 1 × 10-6 M CsCl solution shows that 100% of the bound radiocaesium is readily available. The desorption rate in the presence of a Cs-selective adsorbent has a half-life of about 0.2 yr. Desorption of radiocaesium from illite using different ammonium concentrations shows that radiocaesium partitioning follows reversible ion-exchange theory if the NH4 concentration is below 1 × 10-4 M, and sufficient time (weeks) is allowed for the reaction to proceed. Thus, radiocaesium sorption reversibility in the natural environment is much higher than generally assumed, and equilibrium solid/liquid partitioning may be assumed for the long-term modelling of radiocaesium mobility in the natural environment. In the particular case of anoxic freshwater sediments with very high NH4 concentrations in the pore waters (up to several mmol.L-1), collapse of the frayed edges of illite may occur, influencing radiocaesium partitioning. If collapse occurs before radiocaesium adsorbs to illite, high caesium sorption reversibility as measured by high-NH4 extraction can be expected because further collapse of the frayed edges during the extraction procedure will be limited. This effect has indeed been observed earlier in the extraction of radiocaesium from anoxic freshwater sediments with high-NH4 solutions and was as yet unexplained.

The aim of this study was to characterize 27 feed additives marketed as mycotoxin binders and to screen them for their in vitro zearalenone (ZEN) adsorption. Firstly, 27 mycotoxin binders, commercially available in Belgium and The Netherlands, were selected and characterized. Characterization was comprised of X-ray diffraction (XRD) profiling of the mineral content and d-spacing, determination of the cation exchange capacity (CEC) and the exchangeable base cations, acidity, mineral fraction, relative humidity (RH) and swelling volume. Secondly, an in vitro screening experiment was performed to evaluate the adsorption of a single concentration of ZEN in a ZEN:binder ratio of 1:20,000. The free concentration of ZEN was measured after 4 h of incubation with each of the 27 mycotoxin binders at a pH of 2.5, 6.5 and 8.0. A significant correlation between the free concentration of ZEN and both the d-spacing and mineral fraction of the mycotoxin binders was seen at the three pH levels. A low free concentration of ZEN was demonstrated using binders containing mixed-layered smectites and binders containing humic acids.

Different grain-size fractions of samples collected from shales were investigated to determine the role of late diagenetic grade and mineralogy on the rare earth elements (REE) distribution. The samples were collected from Upper Cretaceous varicoloured shales of the Sicilide Unit near the Corleto Perticara villages, Southern Apennines (Italy). The mineralogical and chemical composition of the sample’s five fractions (>63, 32–63, 2–32, 0.1–2, and µm) was studied. The data indicate that certain accessory minerals are more important than clay minerals in controlling the REE distribution. In particular, zircon controls the distribution of earth elements in the 0.1–2 µm fraction and is an efficient mechanism in determining the concentration and distribution of REEs in the studied shales.

International audience; Minerals in soils evolve through contact with water and other weathering agents (protons, organic acids and ligands) from the atmosphere or released by the surrounding vegetation and associated fauna. Determining the respective contribution of these agents to weathering budgets and the mechanisms by which they interact with soil minerals is a key step toward obtaining refined models of soil development, plant/mineral interactions and, ultimately, soil sustainability. To test the influence of different chemical agents on the processes of mica weathering (dissolution and transformation), we conducted a series of laboratory flow-through experiments on biotite using three chemical groups of reactants found in forest soils: protons (HCl), organic acids (citric acid) and ligands (siderophores). These experiments were performed at two different pH values (pH 3 and pH 4.5) for 37 days at 20 degrees C. Biotite was chosen as a test-mineral because it is reactive with acids and water and because it is commonly found in granite soils. To investigate the weathering reactions, the chemical and isotopic compositions of B (delta B-11) and the concentrations of predominant cation (Si, Al, Mg, K and Fe) were monitored in the out-flowing solutions. The choice of B as a proxy for weathering processes is based on the fact that B is located in different crystallographic sites in biotite (interlayers and structural sites, named I- and S-sites, respectively). We observed a large delta B-11 contrast between these sites (Delta B-11(S-I) (sites)similar to 80 parts per thousand), which allows for a precise quantification of the respective contribution of I- and S-sites to B released during biotite weathering. The individual reaction rates for these crystallographic sites were inferred from the B chemical and isotopic compositions of the outflowing solutions. A comparison with the major elements reveals that B is preferentially released to solution under all tested experimental conditions (up to 4 times more), particularly in the presence of siderophores. A major finding of the present work is that the dissolution of delta B-11 is shown to be highly dependent on the nature of the weathering agent: the presence of citric acid leads to a near-stoichiometric contribution of I-and S-sites to dissolved B, whereas the presence of siderophores results in an almost exclusive release of B from the I-sites, which indicates a mineral transformation without significant dissolution. The presence of HCl leads to an intermediate situation that shows a higher B reactivity from the I-sites than from the S-sites, indicating that biotite minerals transform faster than they dissolve. Because the dissolution reactions imply the destruction of the mineral structure, whereas transformation reactions are non-destructive, assessing the proportions in which minerals evolve by dissolution and transformation reactions has important implications for predicting plant/mineral interactions and soil sustainability. (C) 2013 Elsevier Ltd. All rights reserved.

Mono-amide cross-linked alkyl-siloxane hybrids synthesized through the sol-gel process and the self-directed assembly have been doped with variable concentrations of monomethinecyanines SSCH2(C6H5)I, SSCH3Cl and SSC2H5ClO4. The host matrix m-A(14) is a lamellar structured hybrid composed of short methyl-capped alkyl chains grafted to the siliceous framework through amide groups. The doped mono-amidosil hybrid materials were obtained as solid powders. The bulky SSCH2(C6H5)I dye inhibited the condensation of the silica network. In the SSCH3Cl- and SSC2H5ClO4-doped m-A(14)-based materials the original lamellar structure coexists with a new lamellar ordered phase with a lower interlamellar distance in which the alkyl chains adopt essentially all-trans conformations. The efficient encapsulation of these two dyes by m-A(14), which ensures their complete dissolution, is due to the coordination of the S atoms of SSCH3Cl and SSC2H5ClO4 to the carbonyl oxygen atoms of the amide cross-links. This process leads to a major breakdown of the disordered and ordered hydrogen-bonded aggregates of m-A(14), but does not affect globally the strength of the hydrogen-bonded array. The most dilute SSC2H5ClO4-doped mono-amidosil studied displays room temperature emission in the visible spectral region (380-680 nm) due to the convolution of the intrinsic emission (blue spectral region) of m-A(14) with that of the SSC2H5ClO4 dye (green and red spectral regions) due to the formation of fluorescent J-dimers. The excitation spectra (monitored along the emission spectra) reveal the occurrence of host-to-monomethinecyanine energy transfer.

Processes that operate at planetary surfaces have the potential to record a history of planetary evolution in the form of sedimentary rocks. This is important because our experience on Earth shows that sediments and sedimentary rocks are the dominant archive of high-resolution proxies of present and past tectonic, climatic, and biological processes. Our understanding of the evolution of Earth’s very ancient climate and paleobiological records derives from detailed examination of the mineralogical, textural, and geochemical signatures preserved in the sedimentary rock record. Sedimentary rocks were first recognized on Mars less than a decade ago (Malin and Edgett, 2000). Recent interpretations of data collected by the Mars Express and Mars Reconnaissance Orbiter spacecraft have confirmed the surprising abundance of these sedimentary rocks, the past role of water on the martian surface, and the similarity—in some cases—to sedimentary rocks formed on Earth. Thick sulfaterich deposits invite comparison to terrestrial evaporites (Grotzinger et al., 2005). In other cases, clay-rich strata are interpreted as the terminal deposits of source-to-sink systems with well-developed fluvial networks in the upper reaches of watersheds that date back to a much wetter period in Mars’ earliest history (Ehlmann et al., 2008; Metz et al., 2009). However, these Earth-like depositional systems contrast with other deposits that may be unique in the Solar System: for example, vast terrains as large as Earth’s continents covered by thick veneers of strata that may derive entirely from settling out of wind-transported dust (Bridges et al., 2010). Whatever their origin, it is now clear that the sedimentary rocks of Mars represent a new frontier for research. Mars science is in its golden era of exploration—the past decade of orbiter and landed missions has produced an extraordinary amount of new data relevant to the analysis of sediments and sedimentary rocks, and robust international programs exist for future missions. To help stimulate discussion of these data, the First International Conference on Mars Sedimentology and Stratigraphy was convened in El Paso, Texas, in April 2010. The contents of this white paper represent the most significant findings of the conference, with additional information provided by the coauthors, and focus on seven key questions for future investigation by the sedimentary geology community.

Soils derived from the Loess Plateau of China are regionally important and expression of the soil properties along the soil profile may be directly related to climate changes. The objective of this research was to analyze the clay mineral transformation of loess from the southernmost Loess Plateau, in relation to the pedogenesis and the regional climate changes. The mineralogy of the soil profile at the site was studied by using X-ray diffraction. The results showed that 2:1 layer type minerals dominated with the illite in the majority throughout the profile. The changes of the soil minerals were consistent with the soil genetic horizons and with the variable CaCO3 content, particle size distribution, and variations of magnetic susceptibility. A relatively high vermiculite content and the presence of hydroxyl-interlayered mineral (HIM) occurred in the most weathered horizon (50–150 cm) corresponding to the buried palaeosol (S0) formed during the ‘optimum’ Holocene (8400–3100 B.P. yr) which indicated the acidic conditions with low organic matter in this period. During the formation of palaeosol, the expected transformation of illite and chlorite into vermiculite through the formation of mixed layers has occurred. The distribution of kaolinite was uniform with depth in the palaeosol suggesting inheritance from the original eolian deposition materials. Generally, the depotassication of illite and the degradation of chlorite were the major mineral transformation processes that occurred with soil-formation. Calculation of the total amount of carbonate leaching of the palaeosol suggested that the annual precipitation during the ‘optimum’ Holocene was probably approximately to 880 mm. The regional climate during the ‘optimum’ Holocene on the southernmost Loess Plateau was analogous with the modern climate conditions in the northern subtropical zone (the southern slope of Qingling Mountains) for the formation of Udic Luvisols (Brown Soil). However, as a result of its specific pedogenic pattern, the pedogenic strength of the palaeosol did not reached the level of Udic Luvisols (Brown Soil). The hydroxyl-interlayered mineral presence in the 50–150 cm horizon only, also illuminated that the palaeosol was buried rapidly by post depositional loess during the abrupt cold-dry climate in the late Holocene. The contradiction between the type clay minerals present and the measured alkaline soil pH values in the palaeosol could be understood by the recalcification caused by the post-pedogenic leaching from the overlying loess.

International audience; We used of a set of mechanistic adsorption models (1-pK TPM, ion exchange and Nica-Donnan) within the framework of the component additive (CA) approach in an attempt to determine the effect of repeated massive application of inorganic P fertilizer on the processes and mechanisms controlling the concentration of dissolved inorganic phosphorus (DIP) in soils. We studied the surface layer of a Luvisol with markedly different total concentrations of inorganic P as the result of different P fertilizer history (i.e. massive or no application for 40 years). Soil pH was made to vary from acid to alkaline. Soil solutions were extracted with water and CaCl2 (0.01 M). The occurrence of montmorillonite led us to determine the binding properties of P and Ca ions for this clay mineral. Satisfactory results were obtained using generic values for model parameters and soil-specific ones, which were either determined directly by measurements or estimated from the literature. We showed that adsorption largely controlled the variations of DIP concentration and that, because of kinetic constrains, only little Ca-phosphates may be precipitated under alkaline conditions, particularly in the P fertilized treatment. The mineral-P pool initially present in both P treatments did not dissolve significantly during the course of the experiments. The adsorption of Ca ions onto soil minerals also promoted adsorption of P ions through electrostatic interactions. The intensity of the mechanism was high under neutral to alkaline conditions. Changes in DIP concentration as a function of these environmental variables can be related to changes in the contribution of the various soil minerals to P adsorption. The extra P adsorbed in the fertilized treatment compared with the control treatment was mainly adsorbed onto illite. This clay mineral was the major P-fixing constituent from neutral to alkaline pH conditions, because the repulsion interactions between deprotonated hydroxyl surface sites and P ions were sufficiently counterbalanced by Ca ions. The drastic increase of DIP observed at acid pH was due to the effect of the lower concentration of surface sites of Fe oxides and kaolinite. In addition to confirming the validity of our approach to model DIP concentrations in soils, the present investigation showed that adsorption was the predominant geochemical process even in the P fertilized soil, and that Ca ions can have an important promoting effect on P adsorption. However the influence of the dissolution of the mineral-P pool under field conditions remained questionable.

International audience; The field of astrobiology lacks a universal marker with which to indicate the presence of life. This study supports the proposal to use nucleic acids, specifically DNA, as a signature of life (biosignature). In addition to its specificity to living organisms, DNA is a functional molecule that can confer new activities and characteristics to other organisms, following the molecular biology dogma, that is, DNA is transcribed to RNA, which is translated into proteins. Previous criticisms of the use of DNA as a biosignature have asserted that DNA molecules would be destroyed by UV radiation in space. To address this concern, DNA in plasmid form was deposited onto different surfaces and exposed to UVC radiation. The surviving DNA was quantified via the quantitative polymerase chain reaction (qPCR). Results demonstrate increased survivability of DNA attached to surfaces versus non-adsorbed DNA. The DNA was also tested for biological activity via transformation into the bacterium Acinetobacter sp. and assaying for antibiotic resistance conferred by genes encoded by the plasmid. The success of these methods to detect DNA and its gene products after UV exposure (254 nm, 3.5 J/m(2)s) not only supports the use of the DNA molecule as a biosignature on mineral surfaces but also demonstrates that the DNA retained biological activity.

Fe-Co bimetallic catalysts supported on MgO were studied for the catalytic chemical vapor deposition growth of carbon nanotubes (CNTs). Different wt.% metal loadings were investigated at various deposition temperatures and times. Characterization of the products involved thermal analysis (DTA-TGA), X-ray diffraction, spectroscopy (Raman, UPS, EELS and STS) and microscopy (SEM, TEM and STM) techniques. It was found that the metal content is critical, not only to the yield and the structural quality of the synthesized carbon nanotubes, but it can be also used to tune the desired type of synthesized nanotubes. Lower (2 wt.%) loadings of Fe-Co catalysts favor the formation of single- and/or double-wall CNTs for deposition time and temperature 30 min and 800 degrees C, respectively. Thermal analysis and Raman measurements showed that these thin CNTs were synthesized at high amounts (CNT-per-catalyst wt.% of more than 100%), exhibiting high graphitization degree with only traces of by-products (mainly amorphous carbon) among them. Microscopy results revealed the formation of CNTs bundles, consisting of individual nanotubes with less than 2 nm outer diameter, while additional energy loss measurements pointed out that the deposited CNTs are mainly single wall. Higher (10 wt.%) Fe-Co loadings resulted to the formation of multi-wall CNTs. (C) 2010 Elsevier Ltd. All rights reserved. Carbon

Studies have shown that viruses are frequently attached onto or enmeshed within suspended particles in natural water and wastewater and that this viral–particle association can impede disinfection processes in some circumstances. This article summarizes the current state of knowledge of the occurrence of particle-associated viruses in the aquatic environment and the reported subsequent impacts on disinfection processes. The intention is that this article will help guide future research and aid regulators attempting to address the disinfection of particle-laden waters.

Aims: To investigate the impact of iron particles in groundwater on the inactivation of two model viruses, bacteriophages MS2 and T4, by 254-nm ultraviolet (UV) light. Methods and Results: One-litre samples of groundwater with high iron content (from the Indianapolis Water Company, mean dissolved iron concentration 1·3 mg l−1) were stirred vigorously while exposed to air, which oxidized and precipitated the dissolved iron. In parallel samples, ethylenediaminetetra-acetic acid (EDTA) was added to chelate the iron and prevent formation of iron precipitate. The average turbidity in the samples without EDTA (called the ‘raw’ samples) after 210 min of stirring was 2·7 ± 0·1 NTU while the average turbidity of the samples containing EDTA (called the ‘preserved’ samples) was 1·0 ± 0·1 NTU. ‘Raw’ and ‘preserved’ samples containing bacteriophage MS2 were exposed to 254-nm UV light at doses of 20, 40, or 60 mJ (cm2)−1, while samples containing bacteriophage T4 were exposed to 2 or 5 mJ (cm2)−1, using a low pressure UV collimated beam. The UV inactivation of both phages in the ‘raw’ groundwater was lower than in the EDTA-‘preserved’ groundwater to a statistically significant degree (α = 0·05), due to the association of phage with the UV-absorbing iron precipitate particles. A phage elution technique confirmed that a large fraction of the phage that survived the UV exposures were particle-associated. Conclusions: Phages that are associated with iron oxide particles in groundwater are shielded from UV light to a measurable and statistically significant degree at a turbidity level of 2·7 NTU when the phage particle association is induced under experimental conditions. Significance and Impact of the Study: While the particle association of the phage in this study was induced experimentally, the findings provide further evidence that certain particles in natural waters and wastewaters (e.g. iron oxide particles) may have the potential to shield viruses from UV light.

This study investigated whether colloid-sized particles can enmesh and protect viruses from 254-nm ultraviolet (UV) light and sought to determine the particle characteristics (e.g. size, chemical composition) that are most relevant in causing a protective effect. Two viral surrogates (MS2 coliphage and bacteriophage T4), three types of particles (kaolin clay, humic acid powder, and activated sludge), two coagulants (alum and ferric chloride), two filtration conditions (none and 0.45 microm), and two UV doses (40 and 80 mJ/cm2 for MS2 coliphage; 2 and 7 mJ/cm2 for bacteriophage T4) were considered in a series of bench-scale UV collimated beam experiments. Transmission electron microscopy was used to qualitatively confirm the phage particle-association after coagulation. Humic acid and activated sludge floc particles shielded both viral surrogates to a statistically significant degree (with99% confidence) relative to particle-free control conditions, while the kaolin clay particles provided no significant protection. The results of the study suggest that particles2 microm in diameter are large enough to protect viruses from UV light and that particulate chemical composition (e.g. UV-absorbing organic content) may be a critical factor in the survival of particle-associated viruses during UV disinfection.

Soils under intensive livestock farming and heavily fertilized with animal manure may have elevated soil phosphorus (P) contents. We determined P desorption kinetics in batch experiments using soils from a pot experiment where grass was cropped on a P-rich noncalcareous sandy soil without P addition, to lower the soil P content. A diffusion model was used to describe P desorption kinetics from a spherical aggregate. The model was calibrated with data from the batch experiments. Simulation results show that in the pot experiment, P desorption from the solid phase of the inner layers was initially far from equilibrium with the rest of the aggregate, but desorption came closer to equilibrium as the soil P content decreased further. A simple tool is presented, referred to as the dynamic bioavailability index (DBI), to determine whether kinetics of P desorption limits plant uptake. This tool is the dimensionless ratio of the modeled maximal diffusive flux from soil aggregates to solution and the plant uptake rate measured in the pot experiment. The DBI was initially much larger than one; the maximal possible P desorption rate exceeded the uptake rate, so uptake was not limited by desorption. The DBI stabilized at a value somewhat larger than one after a while, due to soil transport limitations. This decrease coincided with a large decrease of the P content in the grass to a value (far) below what is considered as optimal; the supply rate of P from soil to the root cannot meet the demand needed for optimal P uptake. The DBI could be seen as a promising onset to a new dynamic approach of bioavailability.

The zeolitization of basanite lava flows in the Plateau des Coirons, Ardèche, France, is controlled by the initial location of the flows in paleorivers and by the thermal evolution of the flows during cooling. It predates the development of a well-defined columnar jointing. The zeolites (phillipsite and chabazite) are associated with ferro-magnesian or aluminous smectites (and sometimes carbonates) and crystallize in basalt vesicles and veinlets, showing chemical variations between the top and the deeply altered base of the flow. Their distribution is accounted for by hydrothermal mass transfer driven by the temperature variations within the flow during cooling : — The centre of the flow is at first hotter than the base. Ferro-magnesian smectites crystallize in the median part and aluminous smectites crystallize at the base of the flow. — Then, the base of the flow becomes the hotter zone. Phillipsite crystallizes in the median part and ferro-magnesian smectites in the lower part of the flow. — The end of cooling leads to a more general development of phillipsite and chabazite crystallization at the base., Les coulées de laves du Plateau des Coirons (Ardèche, France) sont affectées antérieurement à leur prismation d'une zéolitisation dépendant de la situation originelle des coulées dans les paléorivières et de leur évolution thermique durant le refroidissement. Les zéolites (phillipsite et chabazite) associées à des smectites ferro-magnésiennes ou alumineuses et parfois des carbonates, cristallisent dans les amygdales et les veines du basalte. La répartition de ces minéraux entre le sommet et la base de la coulée et leur évolution chimique en fonction du degré d'altération sont expliquées par un transport de matière en milieu hydrothermal contrôlé par les variations de la température dans la coulée en cours de refroidissement : — Dans un premier temps, la partie centrale de la coulée est plus chaude que sa base. Les smectites ferro-magnésiennes cristallisent dans les amygdales de la zone médiane tandis que les smectites alumineuses cristallisent dans celles de la base. — Secondairement, la partie basale devient la zone la plus chaude. La phillipsite cristallise alors dans la partie médiane tandis que les smectites ferro-magnésiennes cristallisent dans la partie la plus basse de la coulée. — Enfin, le refroidissement général de la coulée conduit à un développement généralisé de la phillipsite et à la cristallisation finale de chabazite à sa base., Robert Christian, Goffé Bruno, Saliot Pierre. Zeolitization of a basaltic flow in a continental environment : an example of mass transfer under thermal control. In: Bulletin de Minéralogie, volume 111, 2, 1988. pp. 207-223.