Changes In Mineral Composition Research Articles

Late Quaternary dynamics of the Lambert Glacier-Amery Ice Shelf system, East Antarctica

The Lambert Glacier-Amery Ice Shelf system (LGAISS) is the largest outlet glacier system in East Antarctica but its response to past climate variability is poorly constrained. In this study, we explore its dynamics over the last ∼520 thousand years using new high-resolution sedimentary records retrieved off Prydz Bay. Episodic occurrences of iceberg rafted debris indicate a dynamic ice sheet throughout this interval, while changes in clay mineral compositions provide detailed evidence on the waxing and waning of the LGAISS. Our data indicate that advance and retreat of the LGAISS was sensitive to oceanic forcing, but also responded to local summer insolation when insolation peaks combined with interglacial sea level high stands. Subglacial bed topography may have played an additional role in modulating the LGAISS behaviour, which could explain sectoral differences in the response of the East Antarctic Ice Sheet to climate change. Overall, our records indicate that the LGAISS advanced more extensively during previous late Quaternary glacial periods than during Marine Isotope Stages 2 and 4. Furthermore, the LGAISS retreated more significantly than present during Marine Isotope Stage 13, and only moderately during Marine Isotope Stage 7, which suggests that the duration of warm climatic states could be a key factor affecting the dynamics of the East Antarctic Ice Sheet.

Disturbance in Mineral Nutrition of Fenugreek Grown in Water Polluted with Nanosized Titanium Dioxide.

Nanoparticle (NPs) toxicity in the plant has drawn considerable attention. Fenugreek plants were cultivated for 16 days in hydroponic experiments and treated with 50 and 100mg L- 1 titanium oxide (TiO2) NPs of two sizes [23 ± 1.6nm (D1) and 83 ± 15nm. (D2)]. The level of Ti in roots was higher than that of leaves and stems of plants treated with 100mg L- 1 of TiO2 NPs (D1, D2). Ti caused a depletion of Ca and Mn compared with root control. The titane (Ti) damage to root cellular membranes could alter the plant's capacity to absorb and transport some nutrients. In our study, increasing the size of TiO2 NPs produced increases in the contents of Mg, Zn and Mn, and a decline in the contents of Fe and Cu in leaves and stems. In roots, Fe and Cu decreased after TiO2 NPs (D2) exposure. Changes in the fenugreek plant mineral composition were assessed, and physiological disturbances could be directly correlated with exposure to NPs.

Goat milk in the diet of children with gastrointestinal functional disorders

According to the Rome IV revision criteria, functional gastrointestinal disorders are defined as “disorders of the gut-brain axis interaction”. The expression of symptoms of functional gastrointestinal disorders varies from mild to extremely severe. Their presence causes anxiety of parents, can contribute to a decrease in quality of life, and lead to the formation of immediate and long-term consequences in the form of children’s health disorders. Often, mothers stop breastfeeding their babies, and numerous replacements of formulas are made. The recommendations include behavioral therapy and parental education as the first line of therapy. For correction of nutrition in children with functional gastrointestinal disorders, in the absence of data for intolerance of cow’s or goat’s milk proteins formulas based on goat’s milk may be recommended. In natural goat milk there are 14 kinds of oligosaccharides, and 5 of them are identical to breast milk oligosaccharides. The main serum protein of goat milk is α -lactalbumin. The dominating casein fraction of goat milk as well as breast milk is ß-casein. Relatively high content of albumins contributes to the formation of softer, smaller clots and small loose flakes. On the Russian market, goat milk based formulas include products that meet all standards established for infant formulas. The article contains data on goat milk mixtures with an updated formula of protein component. All the formulas of this mixture have reduced the total amount of protein and increased the content of whey protein fraction. Instead of palm oil coconut oil was added to the mixture, while the fat component has not changed its structure, maintaining 42% beta-palmitate, doubled the content of docosahexaenoic acid. The lactose content has been increased, which makes the carbohydrate profile of the mixes closer to breast milk, where the lactose content reaches 95%. In accordance with modern requirements, there were changes in vitamin and mineral composition of formulas, the content of vitamins D3, C, B6, calcium and iron was increased. The effectiveness of this mixture has been studied in young children with functional disorders of the gastrointestinal tract. By the 4th week of taking the mixture, the number of children suffering from colic decreased by 42%, and regurgitation by 30%, there was an improvement in stool consistency. The mixture can be recommended not only for healthy children, but also for children with functional gastrointestinal disorders.

When edges become centered: The ceramic social geography of early pottery communities of the American Southeast

Along the geographic edges of regional populations lies latent potential for innovation and change accruing from interactions with those beyond the edges. This arguably was the case among some of the first pottery-making communities of the American Southeast. Centuries of interactions between these mobile communities and those beyond the geographic distribution of early pottery in the Savannah River valley culminated in places of permanent residence and ritual gathering at the overlapping edges of settlement ranges. Coupled with geochemical data on clay provenance, petrographic thin sections of Stallings fiber-tempered pottery register changes in social affiliation attending the emergence of gathering places. Despite continuity in the use of fiber for temper, innovations in the decoration and form of Stallings pottery coincide with changes in clay provenance and mineral composition to suggest a reorientation away from ancestral ties downriver and towards novel connections upriver. New relationships at the overlapping edges of ancestral lands were brokered at places of settlement and mortuary activity, notably at Stallings Island, which was abandoned for as much as three centuries after pottery appeared in the region. Revealed by petrographic data on the choices potters made in either maintaining or reinventing tradition is perspective on the ceramic social geography of Classic Stallings Culture that has implications for studies of social networks worldwide.

Effect of a Boric Acid Corrosive Environment on the Microstructure and Properties of Concrete.

Boric acid, a weak acid, is often used to shield neutrons in water cooling systems in nuclear power stations. The leakage of boric acid in water cooling systems damages the concrete structure and affects the safety of nuclear power engineering. In this experiment, concrete specimens were cured with boric acid at 20, 40, and 70 °C to study the effect of boric acid on the microstructure and properties of concrete. X-ray diffraction (XRD) and thermogravimetry and differential scanning calorimetry (TG-DSC) were used to analyze the change in mineral composition. The microstructure was examined by scanning electron microscope (SEM). The porosity of the concrete was examined by mercury intrusion porosimetry (MIP). The results show that the performance of specimens was stable under the curing conditions of 20 and 40 °C. Under the curing environment of 70 °C, the performance of concrete cured with 0, 2000, and 7000 ppm concentrations was stable, but the compressive strength of the 180,000 ppm specimen was reduced by 27.8% and suffered the most serious loss of mass and surface corrosion, with the most harmful pores. The high concentration of boric acid seriously damaged the surface structure of concrete, which is the main reason for its loss of properties. This situation is extremely dangerous in nuclear power engineering, so the effect of boric acid leakage cannot be ignored.

Formation, growth and corrosion effect of sulfur oxidizing bacteria biofilm on mortar

In this paper, a protocol has been developed to evaluate the corrosion of mortar by sulfur oxidizing bacteria through formation of biofilm on mortar surface. The bacteria formed a biofilm at the air–liquid interface over time and caused mortar corrosion in liquid. The bacteria biofilm was characterized in terms of changes in composition and thickness during its formation and growth. From biofilm formation to its stabilization, the impact of the biofilm on mortar was studied in terms of the changes of mortar mass, compressive strength, mineral composition and microstructure. The results showed that: (1) The sulfur-oxidizing bacteria adhered to the mortar surface within 7 days. The biofilm formed at air–liquid interface after 15 days and entered a rapid phase starting after 45 days. The thickness of biofilm reached a maximum about 1570 μm on day 75, and then stabilized between 75 and 90 days. Similar trends were observed in microbial quantity, and the contents of polysaccharide and protein in the biofilm. (2) Corresponding to the growth of biofilm, the mass of mortar started to increase at 45 days and stabilized after 75 days. The compressive strength of mortar increased from 67.2 MPa on Day 7 to 82.9 MPa on Day 75, then declined to 68.8 MPa on Day 95. The property change correlated to the increasing amount of gypsum in the part of mortar exposed to liquid, where sulfate was accumulated by microbial oxidation. In contrast, the gypsum content in the mortar exposed to biofilm was much less, suggesting biofilm reduced gypsum formation by limiting the transportation of sulfate into mortar.

Effects of postglacial seawater intrusion on sediment geochemical characteristics in the Romanian sector of the Black Sea

Pore water and sediment geochemistry in the western Black Sea were investigated on long Calypso piston core samples. Using this type of coring device facilitates the recovery of the thick sediment record necessary to analyze transport-reaction processes in response to the postglacial sea-level rise and intrusion of Mediterranean salt water 9 ka ago, and thus, to better characterize key biogeochemical processes and process changes in response to the shift from lacustrine to marine bottom water composition. Complementary data indicate that organic matter degradation occurs in the upper 15 m of the sediment column. However, sulfate reduction coupled with Anaerobic Methane Oxidation (AOM) is the dominant electron-accepting process and characterized by a shallow Sulfate Methane Transition Zone (SMTZ). Net silica dissolution, total alkalinity (TA) maxima and carbonate peaks are found at shallow depths. Pore water profiles clearly show the uptake of K+, Mg2+ and Na + by, and release of Ca2+ and Sr2+ from the heterogeneous lacustrine sediments, which is likely controlled by chemical reactions of silicate minerals and changes in clay mineral composition. Iron (Fe2+) and manganese (Mn2+) maxima largely coincide with Ca2+ peaks and suggest a close link between Fe2+, Mn2+ and Ca2+ release. We hypothesize that the Fe2+ maxima below the SMTZ result from deep Fe3+ reduction linked to organic matter degradation, either driven by DOC escaping from the shallow sulfate reduction zone or slow degradation of recalcitrant POC. The chemical analysis of dissolved and solid iron species indicates that iron is essentially associated with clay minerals, which suggests that microbial iron reduction is influenced by clay mineral composition and bioavailability of clay mineral-bound Fe(III). Overall, our study suggests that postglacial seawater intrusion plays a major role in shaping redox zonation and geochemical profiles in the lacustrine sediments of the Late Quaternary.

CASSAVA FLOUR SUBSTITUTION AND MOISTURE CONTENT VARIATION ON SOME QUALITY CHARACTERISTICS OF HEAT PUMP DRIED EXTRUDED FISH FEED

This study examined the effect of substitution of maize with cassava flour at varying moisture contents on heat pump drying and some quality attributes including strength properties, durability index, micro-structure and floatability. The samples identified as S1- S6, were prepared from various levels of cassava flour before being extruded at steady state at 3 moisture contents (30, 35, and 40% db) in a single screw cooking extruder. Drying was done with an open loop heat pump dryer while a scanning electron microscope (FEG-SEM) was used to study the microstructure of the fish feeds. Results showed that drying rates and pellet durability were proportional to the source and concentration of starch in the samples. Some of the samples floated in water. The Coefficient of performance (COP) of the heat pump used for the drying decreased with increase in ambient temperature; the average COP being 4.77. The thermal efficiency of the heat pump dryer was 92.45%. The scanning electron microscopy indicated that cassava substituted samples lack some elements required of fish feed. Also, extrusion cooking resulted in changes in mineral composition of fish feed blends.
 
 

Changes in mineral composition of six strains of Pleurotus after substrate modifications with different share of nitrogen forms

The chemical characteristics of substrate are one the most significant factors influencing the growth and development of cultivated mushroom species. The aim of this study was to determine the mineral composition of six Pleurotus species (P. cistidiosus, P. djamor, P. ostreatus, P. ostreatus var. florida, P. pulmonarius and P. sajor-caju) growing on three wheat straw substrates with the addition of agricultural fertilizer rich in ammonium and with addition of salt solution rich in nitrates. Significant differences in the concentration of Al, Ca, Cu, Ir, Ni, Ru, Sn and Te were observed in all substrates used in this experiment. Cultivation on chemically-enriched substrates did not result in changes in yield with the exception of P. sajor-caju, which had a lower yield when grown on ammonium-rich substrate. No macroscopic alterations in fruit bodies were observed for any species regardless of the applied substrate. A higher concentration of selected elements was not correlated with their higher content in particular mushroom species, or such a relationship was present only in selected mushroom species. The efficiency of element accumulation depends on their concentration in the substrate (positive values of rs), although the mushroom species and the nitrogen form concentration may also have a significant impact (negative rs values). The obtained results show that cultivation of different Pleurotus strains on substrates enriched with a different share of ammonium and nitrate may cause changes in their mineral composition in spite of the similarity in the concentration of the majority elements in substrates.

Variations in soil water replacement levels promote changes in forage cactus mineral composition and biomass productivity

Population growth and the need to exploit natural resources to produce food and guarantee food sovereignty reduce water availability, which can influence nutrient absorption capacity and production of plants. This study evaluated whether variations in soil water replacement levels promote changes in the mineral composition and biomass productivity of forage cactus varieties. A field experiment was conducted in a randomized block design with five levels of reference evapotranspiration replacement (25, 50, 75, 100 and 125% ETo) and three replicates. Contents of the macronutrients N, P, K, Ca, Mg and S; micronutrients Cu, Fe, Mn, Zn, Cl, Na and B; and biomass productivity were quantified in two varieties of forage cactus (‘Orelha de Elefante Mexicana’ and ‘Miúda’). The data were subjected to principal component and multivariate variance analysis. The mineral composition of the forage cactus varieties ‘Miúda’ and ‘Orelha de Elefante Mexicana’ can be optimized from soil water management, so as to obtain adequate nutritional balance for higher yield. The replacement level of 75% ETo promoted greater balance between nutrients in the cladodes of the forage cactus variety ‘Miúda’, while ‘Orelha de Elefante Mexicana’ had better nutritional balance with the replacement levels of 100 and 125% ETo. Soil water replacement levels of 100 and 125% ETo promote high accumulation of Na+ and Cl- ions in the cladodes of the forage cactus varieties studied. Highest biomass productivity of the varieties ‘Orelha de Elefante Mexicana’ and ‘Miúda’ was obtained with 75 and 100% ETo replacement levels, respectively. Among the varieties, ‘Orelha de Elefante Mexicana’ had a higher capacity for nutrient accumulation and biomass productivity, followed by ‘Miúda’, under the edaphoclimatic conditions of the Brazilian semiarid region.

Study on pore evolution and diagenesis division of a Permian Longtan transitional shale in Southwest Guizhou, China

AbstractOrganic‐rich shales, deposited in marine‐continental transitional environments, are widely distributed in southern China. The pore evolution of the Late Permian Longtan Formation shale (Guizhou Province) during its diagenesis and organic matter (OM) evolution was quantitatively and qualitatively investigated through thermal simulation, mercury intrusion capillary pressure, gas adsorption, fractal dimension, and field emission‐scanning electron microscopy observation. Diagenesis and OM evolution stage were subdivided on the basis of X‐ray diffraction, rock pyrolysis, and vitrinite reflectance test; moreover, the main controlling factors of pore structure during evolution were also discussed. Shales were heated to different temperatures with their vitrinite reflectance ranged between 1.23% and 3.12%, indicating that organic matter had evolved from a low‐ to a post‐mature stage. According to the changes in clay mineral composition, hydrocarbon generation, and Tmax, we subdivided diagenesis into four parts, each of which has a good correspondence with OM evolution. Pore volume (PV) varied between 0.012162 and 0.033482 cm3/g, while the specific surface area (SSA) varied between 13.3693 and 23.0094 m2/g. Mesopores were the main contributors to the total pore volume, while mesopores and micropores were the main contributors to the total specific surface area. In this study, the evolution of pore structure was not monotonous, but intermittent: The PV and SSA of shale samples first decreased and then increased. Maturity was the most important factor affecting the evolution of pore structure. The abundance of pores in OM, associated with hydrocarbon generation, resulted in large micro‐PV and micro‐SSA; moreover, the composition of clay minerals also influenced the pore structure evolution. The transformation of kaolinite into illite increased the content of illite and illite/smectite mixed layer, hence affecting the overall meso‐PV and meso‐SSA.

Change of sandstone microstructure and mineral transformation nearby UCG channel

In order to study the evolution law of surrounding rock microstructure of underground coal gasification, and to reveal the principle from the change of mineral composition and organics in rock, the sandstone nearby the gas transmission channel was used as the tested rock. In this paper, the rock was heated at 300, 400, and 500 °C, simulating the heat convective environment of the gas transmission channel. The mineral, organic functional groups, and microstructure of sandstone transformation products were detected by XRD, FTIR, and SEM. It is concluded that the kaolin in the sandstone gradually transforms into metakaolin with the increase of temperature, meanwhile the carboxyl group and the oxygenic functional group decrease. The generation of metakaolin and the precipitation of organics increase the number of fractures in samples, which is the main reason for the compressive strength and elastic modulus for the sandstone decreases with increasing temperature for temperatures greater than 500 °C. The microscopic manifestation is the appearance of a large number of flocs on the surface. Macroscopically, the exterior appears as a grayish shell. The flow resistance and the adsorption property are weakened, and the permeability is enhanced.

Geochemical and electrical characterization of heavy metals in contaminated soils

The present work is conducted in the industrial district south of greater Cairo (ElTabbin area). Some heavy metals like Mn, Co, Ni, Cu, Zn, Pb, Cr, Ba, Cd, Mo were determined in polluted soils during May, 2018. At the study area, results displayed that average heavy metals concentrations differ considerably. They are decreased from Mn to Cd (Mn > Ba > Zn > Cr > Ni > Co > Pb > Cu > Mo > Cd). The average ranges as follows: Mn (255.8–31448.2 ppm); Ba (145.2–17545.6 ppm); Zn (53.3–1589.9 ppm); Cr (26.7–311.3 ppm); Ni (29.7–114.1 ppm); Co (13.2–39.8 ppm); Pb (5.7–77.4 ppm); Cu (7.6–35.2 ppm); Mo (0.1–15.9 ppm) and Cd (0–1.5 ppm), respectively. ElTabbin area has heavy manufacturing activity at Egypt. ElTabbin area was chosen as a model for that contamination.Electrical characteristics of some specimens from El- Tebbin area, Egypt, were taken and measured electrically at frequency range (10−3 to 100 kHz). Major and heavy elements were measured at specimens. Specimens were classified to three categories according to electrical properties. The changes were the consequence of change in minor and major mineral composition in the specimens. Electrical properties were able to recognize different specimens according to different levels of contaminants in the specimens. Texture, tortuosity and minor elements of heavy elements are the controlling factors that control electrical properties at specimens. High values concentration of Mn, Ni, and Zn heavy elements increases conductivity while the high concentration of Pb and Cu heavy elements decreases the conductivity. The mixing up of these different minor and major minerals and elements at specimen may lead to the change of conductivity values. The main controlling factors of the major elements are the Fe2O3 and SiO2, while the main controlling factors of the minor elements are the Mn and Pb. Our main objective is to study mixing up of the different minor and major minerals and elements on electrical properties of rocks.

Conditions favoring local podzolization in soils developed from flysch regolith – A case study from the Bieszczady Mountains in southeastern Poland

Podzolization occurs mainly in soils developed from highly leached and coarse-textured parent materials in areas that remain under the influence of humid climate conditions and where forest or heath vegetation supply enough organic matter to form organic horizons on the surface of mineral soils. However, in certain environmental conditions Podzol development was found also in extremely unfavorable types of parent material, e.g. ultramafic rocks or even regoliths containing carbonates. Flysch rock regolith found in many geographic regions is an example of soil parent material considered to be unfavorable for podzolization in its major part due to its high clay, Ca, and Mg contents. Areas formed of materials considered to be rather unfavorable to Podzol development but characterized by very local occurrence of podzolized soils may be helpful in assessing the factors which favor the occurrence of this process and its thresholds. The main objective of the present study was to determine an optimal combination of conditions that trigger podzolization in soils in the uppermost part of mid-mountain slopes formed of flysch rocks in the Bieszczady Mountains in southeastern Poland. At the same time, an attempt was made to determine pedogenic thresholds of local podzolization in soils in the studied area. The studied soils showed large variability in soil processes and were classified according to the WRB as four different Reference Soil Groups: Podzols, Cambisols, Umbrisols and Leptosols. Two out of the eight soil profiles exhibited well-developed spodic horizons, while the properties of the two other profiles may be explained by either cryptopodzolization and/or formation of andic properties in non-volcanic soil material. Evidence of podzolization was observable in changes in soil morphology (i. e. color and consistence of soil material), vertical distribution of labile C and Fe and Al pedogenic forms, changes in mineral composition (mainly dissolution of chlorite, formation of mixed layered clay minerals and the redistribution of various amorphous phases), and also micromorphological features (presence of monomorphic fine coatings consisting of Fe- and Al-organic compounds). However, the occurrence of Podzols was strongly limited across the study area and determined by a combination of environmental conditions such as the co-occurrence of four key factors: (1) humid and cool climate, (2) sandy texture and mineral composition of parent material dominated by quartz, (3) location on the uppermost part of consequent slopes (ridge crests) and (4) predominance of berry (Vaccinium sp.) thickets in the vegetation cover in tandem with the occurrence of mosses (Polytrichum strictum and Sphagnum sp.). Moss cover facilitated a pedogenic feedback setup by increased water storage which promoted more advanced weathering and increase in dissolved organic carbon content in the soil. In the consequence the pedogenic threshold of podzolization was crossed.

Petrophysical characteristics and log identification of lacustrine shale lithofacies: A case study of the first member of Qingshankou Formation in the Songliao Basin, Northeast China

As an unconventional resource, shale reservoirs recently have attracted considerable attention in the petroleum industry. Shale plays are highly heterogenous vertically and laterally and are characterized by rapid changes in mineral composition. Thus, identification of dominant lithofacies is a key issue in the development of shale oil and gas reservoirs. In this study, various existing lithofacies in a shale section as a target unit in the Qingshankou Formation are divided based on organic matter content, sedimentary structure, and mineral composition. To delineate the electrofacies from the log, the multiresolution graph-based clustering (MRGC) is used to optimize the conventional logs that are sensitive to the electrofacies clustering analyses. Based on the principle of lithofacies identification, the electrofacies are artificially related to the lithofacies as well. This was done by analyzing the petrophysical characteristics of various shale lithofacies, to enable obtaining the main log parameters for the facies of the lacustrine shale section understudy. The results showed that by considering the underlying geologic criterion of each lithofacies, the MRGC method is able to correlate geophysical characteristics of each identified electrofacies for an optimal selection of six lithofacies.

Blending of mining wastes from the Hammam Zriba mine (Northeast Tunisia) with the primary ingredients of clinkers: an evaluation of effects on gray Portland clinker properties

The present work focuses on the effects of the blending of mining wastes from the Hammam Zriba mine (Northeast Tunisia) with the primary ingredients of Portland clinker properties. The raw mix was composed of limestone, sand, and clay sampled from the Sidi Bouzid area in Central Tunisia. The used mining wastes are composed essentially of barium, sulfur, and strontium and associated with calcium. Results show that it is possible to use these wastes to formulate an ecological clinker with high quality. The reference clinker is composed of C3S (67.8%), C2S (7.9% β-C2S and 7.15% α-C2S), and C3A (10.3%), associated with small quantities of C4AF. The incorporation of 2% of wastes does not lead to any significant change in mineral composition. The addition of 4% of wastes promotes the decomposition of alite into α-C2S (7.1 to 13.7%) and β-C2S (7.9 to 9.6%). In contrast, the clinker melt exhibits a slight drop of ferrite (5.3 to 3.1% C4AF) and a quasi-unchanged level of cubic-C3A. Greater incorporation of wastes tends to establish the mineral distribution as the reference. The amounts of free lime low when the addition of wastes is lower than 4% (< 2.28%). Higher addition (8%) shifts the free lime levels in particular for pure C3A and C3S (15.6 and 6% respectively). For the reference, free lime levels remain low (< 1%). This result bears relevant environmental and economic aspects by limiting greenhouse gas emissions, enhancing the production of low-cost gray cement, reducing the impacts of mining wastes, and opening an alternative for mining wastes management.

Fe(II)-catalyzed transformation of Fe (oxyhydr)oxides across organic matter fractions in organically amended soils

The Fe(II)-catalyzed transformation of ferrihydrite into highly crystalline forms may represent an important pathway for soil organic matter (SOM) destabilization under moderately reducing conditions. However, the link between redox-driven changes in soil Fe mineral composition and crystallinity and SOM chemical properties in the field remains elusive. We evaluated abiotic Fe(II)-catalyzed mineralogical transformation of Fe (oxyhydr)oxides in bulk soils and two particle-size SOM fractions, namely the fine silt plus clay (<20 μm, FSi + Cl) and fine sand (50–200 μm, FSa) fractions of an agricultural soil unamended or amended with biochar, compost, or the combination of both. After spiking with Fe(II) and incubating for 7 days under anoxic and sterile conditions at neutral pH, the FSa fractions (Fe(II):Fe (III) molar ratios ≈ 3.3) showed more significant ferrihydrite transformations with respect to FSi + Cl fractions (Fe(II):Fe (III) molar ratios ≈ 0.7), with the consequent production of well-ordered Fe oxides in most soils, particularly those unamended or amended with biochar alone. Nonetheless, poorly crystalline ferrihydrite still constituted about 45% of the FSi + Cl fractions of amended soils after reaction with Fe(II), which confirms that the higher SOM and clay mineral content in this fraction may possibly inhibit atom exchange between aqueous Fe(II) and the solid phase. Building on our knowledge of abiotic Fe(II)-catalyzed mineralogical changes, the suppression of ferrihydrite transformation in FSi + Cl fractions in amended soils could ultimately lead to a slower turnover of ferrihydrite, possibly preserving the carbon sequestration potential associated with this mineral. Conversely, in both bulk soils and FSa fractions, the extent to which mineral transformation occur seemed to be contingent on the quality of the amendment used.

Formation and chemo-mechanical characteristics of weak clay interlayers between alternative mudstone and sandstone sequence of gently inclined landslides in Nanjiang, SW China

Sedimentary rocks with alternating mudstone and sandstone sequence are susceptible to landslides even under very gentle slope inclinations. Continued occurrences of such landslides in Nanjiang, South Western part of China, bring out the necessity for more understanding of their failure mechanism. In this study, we present a series of investigations on the physical, chemical, and mechanical characteristics of weak interlayers during their formation at landslide slip surfaces, both in macro- and microscales. Our field investigations at these deep-seated landslides revealed the presence of extensive weak interlayers of clay in between alternating sandstone mudstone formations. Tectonic processes combined with loading and unloading effects and strain incompatibility might lead to the argillization of rock by easing water intake, which leads to the formation of these weak layers. We studied how changes in material microstructures, mineral composition, and ionic concentrations during the formation process (argillization) might cause a fall in mechanical strength. We found that degradation of mechanical resistance takes place even at the initial stages of argillization and shear strength of the weak layers decreases proportionally to the time of saturation and argillization.

Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency

The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise well-drained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank rs = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (rs = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Fe-organic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with 13C nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Fe-organic interactions. In our incubation experiments, a doubling in short-term CO2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation.

Direct and indirect surface geochemical methods in petroleum exploration: a case study from eastern part of the Polish Outer Carpathians

The objective of this paper is to evaluate the relationship between the distributions of direct and indirect, surface geochemical indices in the selected part of the Outer Carpathians. The research included analysis of molecular composition of soil gas samples and calcite contents as well as the measurements of magnetic susceptibility and pH of soil samples. The survey contained 96 soil gas samples collected from 1.2 m depth and 96 soil samples taken from interval 0.7–0.8 m depth. The maximum concentrations of methane, total alkanes C2–C5 and total alkenes C2–C4 were: 2100, 10.43 and 0.772 ppm. The magnetic susceptibility values changed from 3.6 to 21.5 x 10–8 m3/kg. The calcium carbonate contents varied from 0.02 to 29.92 wt% and the pH values measured in soil solutions obtained changed from 4.5 to 8.3. Although the results demonstrate no correlation between the direct soil gas anomalies and the indirect geochemical indicators, the integrated profiles in Fig. 7 suggest possible haloes in the calcite/magnetic data that could be related to hydrocarbons migrating from depth. There are, however, various independent mechanisms that might control the appearance of these mineral anomalies. Secondary changes of mineral composition of soils disclosed by the indirect methods, even if controlled by hydrocarbon migration throughout geological time, might cause some closure of migration pathways, influencing the location of active hydrocarbon migration pathways. Comprehensive interpretation of the results obtained by direct and indirect methods in this paper provides another positive example helping to better understand the complicated mechanism of hydrocarbon migration and the potential usefulness of indirect methods suitable for hydrocarbon exploration.