Total Clay Research Articles

Soil Water Retention in the Semiarid Region of Brazil

From the physics point of view, soil structure is a dynamic attribute that is affected by genetic conditions and anthropogenic changes and requires an integrated approach. Soil water retention curve is one of the main tools used in soil structure evaluations. The objective of this work was to evaluate the structural and chemical attributes of soils of different classes and agroecosystems in the Terra de Esperança Settlement (Governador Dix Sept Rosado, Rio Grande do Norte, Brazil) to distinguish these environments. Disturbed and undisturbed soil samples were collected in horizons of 10 soil profiles of the soil classes: Cambissolo Háplico (Haplustepts), Latossolo Vermelho-Amarelo (Eutrustox), Chernossolo Rêndzico (Calciustolls), and Neossolo Flúvico (Usticfluvents). The soil physical attributes evaluated were granulometry, soil density, total porosity, aeration porosity, macroporosity, microporosity, field capacity, permanent wilting point, available water, and water retention curve. The results were expressed in averages of four replicates per horizon (in laboratory) by multivariate analysis, which detected the most sensitive attributes for the distinction of the environments. The soil physical attributes of the different classes and its inorganic fractions, especially silt and clay, were determinant to distinguish the environments; they affected the microporosity; aeration porosity; and available water. The source material of the Chernossolo Rêndzico, which is rich in calcium and magnesium, affected its physical attributes, characterized by the predominance of the silt fraction. Clay was the determinant fraction of the Cambissolo Háplico, and Neossolo Flúvico; and the sand fraction on the surface layer, and clay fraction in the Bw horizon were determinant of the Latossolo Vermelho-Amarelo. The more expressive physical attributes were soil density, sand content, macroporosity (Latossolo Vermelho-Amarelo), microporosity, field capacity, available water, permanent wilting point, total organic carbon, mass-based moisture, volume-based moisture, clay, aeration porosity (Cambissolo Háplico, and Neossolo Flúvico), and silt (Chernossolo Rêndzico).

Soil physical indicators of management systems in traditional agricultural areas under manure application

ABSTRACT Studies of the successive application of manure as fertilizer and its combined effect with long-term soil management systems are important to the identification of the interdependence of physical attributes. The aim of this study was to evaluate changes in the physical properties of a Rhodic Kandiudox under management systems employing successive applications of pig slurry and poultry litter, and select physical indicators that distinguish these systems using canonical discriminant analysis (CDA). The systems consisting of treatments including land use, management and the application time of organic fertilizers are described as follows: silage maize under no-tillage (NT-M7 years); silage maize under conventional tillage (CT-M20 years); annual pasture with chisel plowing (CP-P3 years); annual pasture with chisel plowing (CP-P15 years); perennial pasture without tillage (NT-PP20 years); and no-tillage yerba mate (NT-YM20 years) and were compared with native forest (NF) and native pasture (NP). Soil samples were collected from the layers at the following depths: 0.0-0.05, 0.05-0.10, and 0.10-0.20 m, and were analyzed for bulk density, porosity, aggregation, flocculation, penetration resistance, water availability and total clay content. Canonical discriminant analysis was an important tool in the study of physical indicators of soil quality. Organic fertilization, along with soil management, influences soil structure and its porosity. Total porosity was the most important physical property in the distinction of areas with management systems and application times of manure for the 0.0-0.05 and 0.10-0.20 m layers. Soil aeration and micropores differentiated areas in the 0.05-0.10 m layer. Animal trampling and machinery traffic were the main factors inducing compaction of this clayey soil.

Effects of boron distribution on sugar beet crop yield in two Tunisian soils

Boron is an important micronutrient required for the growth of various types of plants. Both a deficiency in boron and its toxicity may lead to marked yield reduction and quality loss of many crop species. The range between these extremes is quite narrow. Therefore, the management of boron in soil has become a worldwide agricultural problem in the recent years. Facing this situation, the present research was undertaken in order to better understand boron distribution effect on sugar beet crop yield in two soils of Dour Ismail irrigated perimeter (North Tunisia). Two pits P1 and P2 were dug in field plots that had not received any boron fertilization. We followed the dynamic of the available boron and its depth distribution according to the three sugar beet cycle stages. Soil samples were taken from different horizons of the profile and analyzed for the main physicochemical properties. Both studied soils are Stagnic Fluvisols (Clayic) and the water used for irrigation comes from Oued Medjerda River. Our results showed that the highest boron values were recorded in surface horizons of the two studied soils. These amounts decreased with depth following different patterns according to the sugar beet cycle stages. The boron vertical distribution was similar to the total organic carbon and clay contents but was greatly affected by some soil properties such as pH, carbonate calcium content, and salinity. Sugar beet yield in P2 (100 t ha−1) was less than that of P1 (114 t ha−1) indicating a problem of boron availability.

Comparative study of three methods of determining cation exchange capacity of three major soils in the rainforest region of Southwestern Nigeria

ABSTRACT The cation exchange capacity (CEC) of three benchmark soils in the rain forest region of Southwestern Nigeria, were measured by three standard CEC methods. Results obtained were compared with a view to selecting the best suited CEC method for the soils. The study sites were the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, and Itagunmodi settlement. Two representative soil profile pits each were established in soils developed in coarse-grained granite and gneiss, fine-grained biotite gneiss and schist, and the amphibolite. The three methods gave different CEC values in the order of CEC-pH 8.2 > CEC-pH 7 > ECEC. There was a significant correlation between soil organic matter (SOM) and the CEC obtained by each of the three methods (P ≤ 0.05), meanwhile, total clay showed no significant correlation. ECEC provided the best estimate of the CEC for the soils and adequate SOM management is crucial to enhance sustainable productivity of the soils.

The influence of nanostructure on the mechanical properties of 3D printed polylactide/nanoclay composites

An obstacle for wider application of 3D printed parts is their inferior mechanical performance compared with those from conventional fabrication. This research aims to overcome this deficiency by developing nanostructured PLA/clay composite filaments that are 3D printable by the FFF technique, investigating the effect of filament composition on mechanical properties, and correlating it with the extent of intercalation of different types of clay. The results showed the addition of 5 wt% organomodified clay to PLA raised the elastic and flexural modulus by 10% and 14% respectively. Einstein’s composite theory did not hold for the PLA/organoclay composites but the Halpin-Tsai model was successful in interpreting the measured moduli of the organoclays. The model also showed that increasing the clay intercalation was much more effective than raising the total clay content.

Modeling cation exchange capacity in multi geochronological-derived alluvium soils: An approach based on soil depth intervals

Knowledge of soil chemical properties is indispensable to conduct sustainable land use management in alluvial areas. In this study we developed specific pedotransfer functions for cation exchange capacity (CEC-PTFs) in alluvial soils based on soil depth intervals. A soil data set (n = 1094 samples) at different depths from three different Nile River terraces (lower, middle, and upper) and the lower and upper Blue Nile terraces in Sudan was randomly collected and divided into a training data set (n1 = 900 samples) and a testing data set (n2 = 194 samples) for validation. Soil pH, texture, and organic matter were used as predictor variables to estimate CEC. PTF performance was evaluated with the coefficient of determination (R2), root mean square error (RMSE), and standard error for the estimate (SEE) between the observed and predicted values. Fourteen predictive equations were developed. Results revealed that the CEC of topsoil layers of the lower Nile River terrace were the most difficult to predict (r2 = 0.29 for training) while the deep soil layers (60–120 cm) of the Blue Nile terraces were predicted well (r2 = 0.99 for training). Sixty to 76% of CEC variation of the subsoil of the Nile River terraces could be explained by clay alone. From 85 to 90% of the CEC variation in the deep soils could be explained by organic matter, total silt, and total clay. Validated results indicate that the predictive models based on total clay were less reliable at predicting CEC in the top soil layers. Overall, the CEC-PTFs generated by multiple linear regression models (MLR) provided a reasonable estimate of CEC for most soils investigated.

Correlation between macrobenthic structure (biotic) and water-sediment characteristics (abiotic) adjacent aquaculture areas at Tembelas Island, indonesia

Macrobenthic community play important role in sedimentary habitats as a part of food chain. Their structure may be influenced by environmental characteristic spatially and temporally. The purpose of this study is to access the correlation between macrobenthic structure (biotic) and water-sediment characteristics (abiotic) adjacent aquaculture areas at Tembelas Island, Indonesia. Water and sediments samples were taken twice, where the first and second sampling time were taken in June and October 2016, respectively. Samples were taken in the area of fish farming at coastal area of policulture/IMTA (as Location I), site of 1 km away from fish farming area as a reference site (as Location II), and monoculture sites (as Location III), with three stations for each location. Data of abiotic parameters included the composition of sediment substrate and DO, pH, salinity, temperature, and. Sediment samples were taken using Ekman grab. The organisms were 1 mm -size sieved and fixed using 10% formalin for further analysis, i.e. sorting, preserving, enumerating, identifying, and grouping. The relationship between biotics (macrobentos) and abiotics (physical-chemical factors) was assessed using a non-parametric multivariate procedure (BIOENV). This study found 61 species consisting of 46 families and 5 classes of macrobenthos. The most common classes were member of Mollusca and Polychaeta. Total nitrogen, silt, and clay were the abiotic factors most influencing macrobenthic structure (BIO-ENV; r = 0.46; R2 = 21.16%).

Historical records, distributions and sources of mercury and zinc in sediments of East China sea: Implication from stable isotopic compositions

The distribution and source of mercury (Hg) and zinc (Zn) in surface sediments from East China Sea (ECS) were studied using stable isotopes. Hg concentrations in surface sediments varied from 12.6 to 133.2 ng g−1. Zn concentrations ranged between 45.9 and 133.6 ng g−1. Hydrodynamic circulation and sedimentary process within the ECS were the dominant factors controlling the distribution and fate of heavy metals, referring from relationships of Hg and Zn concentrations and total organic carbon (TOC) and clay contents. Spatial variations in Hg isotopic compositions (δ202Hg) were observed in the ECS, with δ202Hg ranging from −1.86 to −0.83‰ and Δ199Hg ranging from −0.07 to +0.26‰. The high δ202Hg values and relatively negative Δ199Hg values in estuarine and inner shelf sites indicated that the riverine inputs from Yangtze River played an important role in delivering Hg to ECS. In contrast, Hg isotopic signatures in outer shelf sediments had relatively low δ202Hg and positive Δ199Hg, implying that atmospheric Hg deposition could be relatively dominant source for Hg. Moreover, application of zinc isotopes to trace anthropogenic sources has been tested, with δ66Zn ranging from 0.20 to 0.67‰. The results showed significant variations of δ66Zn in the ECS, implying that Zn isotope compositions can be tracers of anthropogenic sources. Using these Hg isotope compositions, the source attributions of sediments in ECS were estimated based on a mixing model, suggesting that river-dominated inputs, discharging pollutants from industrial sources, and atmospheric deposition could dominate in the occurrence and fate of Hg in sediments of ECS.

Efeitos no solo e nas culturas após vinte anos de cultivo convencional e semeadura direta

The aim of this research was to evaluate soil properties and performance of crops after 20 years of cultivation in two management systems in a Humic Cambisol in the south of Brazil. No-tillage (NT) and conventional tillage (CT) were evaluated during the cultivation of maize (Zea mays), bean (Phaseolus vulgaris) and soybean (Glycine max), in two years. Soil samples were collected in three layers at the end of the second year, while the determinations of agronomic traits were carried at the end of each year. NT decreased soil bulk density and increased total porosity, aggregate stability and clay flocculation degree, however it decreased macroporosity at the soil surface. In NT higher accumulations of phosphorus occurred up to 0.05 m, calcium and mag­nesium up to 0.1 m and potassium and organic carbon up to 0.2 m depth compared to CT, and it had a gradient of soil acidification from the surface. Differences in the performance of crops occurred in the second year, being verified in CT a reduction of grain yield of soybean and corn and lower thousand-grain mass of beans compared to NT. Bean and soybean produced low amount of above-ground biomass, independent of soil management, while maize produced high amount and higher biomass in NT than CT.

Relationship between geosorbent properties and field-based partition coefficients for pesticides in surface water and sediments of selected agrarian catchments: Implications for risk assessment

Studies on pesticide behavior, adsorption-likelihood, and bioavailability vis-a-vis geosorbent properties and seasons, are critical for understanding pesticide-fate and risks in pesticide-prone environments. We examined the relationship between geosorbent profiles of sediments (percentage sand, silt, clay, organic carbon content) across seasons and occurrence of pesticide residues in surface water and sediment of agricultural catchments at Owan, Ogbesse and Illushi communities of Edo State, Nigeria. Pesticide concentrations were measured monthly in samples of surface water and sediments across the selected sites for 18-months. Pesticide behavior and sorption-likelihoods were examined using partition coefficients Kd (sediment-water coefficient), Koc (sediment-water coefficient normalized for organic carbon) and Log Kow (octane-water coefficient); the relationship between Kd and Koc was also examined. Results of the principal component analysis (PCA) indicated that pesticide levels in sediment and surface water were positively associated with the rainy season, total organic content (TOC), percentage silt and clay in sediment. Field-derived pesticide partition coefficients (Kd < 100 and log Koc < 3) indicated that pesticide species were largely mobile and less likely to be retained in sediments by adsorption. As such, pesticides irrespective of solubility would end up in surface water, increasing risks for pelagic biota and humans sourcing river water for domestic use. Values of Log Kow indicate that organochlorines including DDT, dieldrin, endrin and heptachlor epoxide portend significant bioaccumulation risks to humans and biota across sites. The relationship between Kd and Koc for each site fitted into a quadratic model; it depicted a biphasic behavior of pesticide adsorption and desorption to sediments revealing that concentration of organic carbon across study sites was a limiting factor determining the extent of pesticide adsorption. This study demonstrates that understanding pesticide mobility using field-based partition coefficients could give a clearer picture of pesticide risks to biota and human populations.

Pore geometrical complexity and fractal facets of Permian shales and coals from Auranga Basin, Jharkhand, India

The pore system is a significant factor for the hydrocarbon generation, storage and production. Several studies had been carried earlier by distinguished researchers on pore system characterization, where little information regarding a thermally immature basin has been discussed so far. To understand these, total fifty-one samples including 41-shales and 10-coals are taken for study from Barakar (L.Sakmarian-Kungurian) Formation of Auranga basin to investigate the pore characteristics of a low mature substance. This work provides information regarding a low mature basin having oil generation potential. For this, authors have carried low pressure N2 sorption, FE-SEM/EDX with rock eval pyrolysis, total organic carbon (TOC), ash yield, vitrinite reflectance and clay content. The low-pressure N2 sorption: BET (Brunauer-Emmett-Teller) and BJH (Barrett-Joyner-Halenda) are employed to analyze the pore size, area, geometry and its distribution. Shale samples have shown variation in the specific surface areas (BET) and pore volume from 7.43 to 30.36 m2/g and 0.019–0.069 cm3/g respectively; whereas coal samples exhibits these properties ranging from 3.13 to 17.2 m2/g and 0.08–0.31 cm3/g respectively. Here, two kinds of desorption curve have been observed: (a) sub-hysteresis types H2′ where rapid desorption (lacking a plateau at high pressure) indicating pipette shaped pore (b) hysteresis type H3 having slow rate of desorption suggesting slit shaped pore. The subtype H2′ i.e. lacking the plateau at high pressure has been distinguished under H2 hysteresis. The dominance of mesopores to macropores are deduced from BJH and presence of micropores were also observed in few samples from t-plot method. The Type II isotherms are observed dominantly in shales and few coal samples (27-shales; 3-coals) whereas Type IV isotherms (13 shales; 7 coals) are mainly noticed in coals and in limited number of shales. Moreover, the total organic carbon (TOC) content of the shale and coal samples ranges from 1.35 to 29.42 wt% and 32.38–63.46 wt% respectively. Tmax [temperature under S2 to release maximum amount of pyrolyzate from the kerogen under rock eval pyrolysis (REP)] range from 409 to 468 °C and 420–426 °C of shales and coals respectively indicating of immature to early mature stage of the sample. The TOC normalized-BET (BET*) in relation to ash yield exhibits the significance of mineral matter in the shales for pore formation. The relation of pyrolysis parameters (S1and S2) with BET* gives the indication of bitumen retention in the pore spaces of organic matter, which reduces their surface area in coals. Fractal geometry of the samples were also studied. The surface fractal dimensions viz. D1 (P/Po = 0.0–0.5) and D2 (P/Po = 0.5–1.0) both are calculated for the basin. The D1 (pore surface) varies from 1.9888 to 2.5530 and 1.8190–2.4430 for shales and coals respectively pointing towards surface heterogeneity and ruggedness of the surface favorable for increasing the adsorption capability. However, D2 (pore structure) for the shales and coals are placed in the range of 2.570–2.759 and 2.6150–2.7530 respectively indicating large heterogeneity of the pore structure causing high capillary condensation that reduces the adsorption ability. The FE-SEM with EDX study supports the analysis of pore structure, characteristics and fractal behaviour of shales and coals.

Spatial Analysis of Granulometry and Humic Substances of an Ecological Restoration Area in the Brazilian Atlantic Forest

The present study aimed at spatially analyzing granulometry and humic substances (HS) of an ecological restoration area in the Brazilian Atlantic Forest. In the study area, 49 points were systematically distributed, and soil was collected at each point, at a depth of 0-10 cm. The soil attributes evaluated were: total clay, total sand, silt, and organic carbon in the fulvic acid fraction (C-FAF), humic acid fraction (C-HAF), and humic fraction (C-HUM). Semivariogram analysis was performed for each variable, with spherical, exponential, and Gaussian semivariogram models tested. In order to choose the best model, the following parameters were used: Akaike Information Criterion (AIC), determination coefficient (R²), root mean square error (RMSE), Willmott concordance index (d), and degree of spatial dependence (DSD %). Mapping was performed using the Ordinary Kriging method. The attributes showed spatial dependence. The spherical model was adjusted for all variables. From spatialization, the attributes, except clay, showed a heterogeneous distribution, which may be due to the high range value. The distribution of soil texture depended mainly on soil class and relief. A correlation was observed in the distribution of the silt and C-HUM attributes. The ecological restoration area had HS content values close to those reported in studies conducted under conditions similar to those in the present study. Therefore, it appears that the study area is probably undergoing recovery; however, a thorough and continuous study of the area is essential for confirmation.

Reclamation of used green sand in small scale foundries

Disposal of Used Foundry Green Sand (UFGS) remains one of the significant challenges faced by foundry industry nowadays. Experiments were performed to reduce the total clay content from 12% to as low as 2.2% in waste foundry sand. Three prototypes were developed during the course of this work. They include vertical fluidized bed, horizontal fluidized bed and a novel ball-mill type attrition and sieving unit. The cost per ton of reclaimed sand is higher in case of fluidized bed based prototypes while in case of attrition and sieving based prototype, it is less than half of the cost of the fresh sand. The experimental data generated on the two-stage attrition and sieving unit under different conditions is further used to arrive at a semi-empirical correlation and the optimum set of design and operating parameters to get the best performance.

Porosity and genesis of clay in gneiss saprolites: The relevance of saprolithology to whole regolith pedology

Weakening of the rock texture in a saprolite by weathering and further pedoplasmation results in the formation of a porous network and neoformed clays, which are the initial stages of pedogenesis, but the saprolite is likely the least studied compartment of the regolith. In this paper, the genesis of clays and their associated pore system was studied in gneiss saprolites. We investigated the saprolites of three regoliths in the Atlantic Forest Biome in northeast Brazil and used optical and electron microscopy to depict the clay–pore morphology. To assess the mobility of clays, we also determined the amounts of water–dispersible and total clay. The total chemical composition (SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, TiO2 and P2O5), exchangeable cations (Al+3, Ca+2, Mg+2, K+ and Na+), available P, capacity for saprolites to exchange cations and secondary forms of iron (Fed and Feo) were also measured. Micromorphological analyses showed that the most frequent pore types were channels and fissures. Channels occurred in the more weathered saprolite layers, which were identified according to the weathering indexes, and the clay–sized minerals found in the saprolite were illite, kaolinite, iron oxides, feldspar and quartz. The weathering of biotite and green hornblende formed an Fe–rich clay, and the weathering of feldspars formed an Al–rich clay. Secondary clays were accumulated at the mineral surfaces, pseudomorphs, clay infillings and clay coatings. The clay coatings are formed by two layers, i.e., the first clay layer was formed by an Fe–rich clay, and the second layer was formed by an Al–rich clay. Peculiar features named “doughnut–shaped holdfasts” were described in the clay cutans. The capacity for saprolites to exchange cations was similar to that in the shallower soils, which was environmentally relevant to the adsorption of plant nutrients, e.g., Ca+2, Mg+2 and K+, and potentially toxic elements, e.g., Al+3.

Micromorphology, clay mineralogy, and geochemistry of calcic-soils from western Thar Desert: Implications for origin of palygorskite and southwestern monsoonal fluctuations over the last 30 ka

The Thar desert with intense aeolian activity and calcrete formation is one of the hottest arid regions of the world. Little is known about the formation of calcic soils with a large amount of palygorskite in the western Thar. In this study, we have used microscopy, sub-microscopy, clay mineralogy, and geochemistry of three calcic soils from western Thar to understand the pedogenesis in response to fluctuating southwestern monsoon over the last 30ka. Thin sections of the soils show a dominance of weakly developed pedofeatures with powdery to well-indurated pedogenic calcium carbonate that influenced weathering of primary mineral grains. Sub-microscopy of the calcretes shows a large amount of fibrous palygorskite in pore spaces of micritic and sparitic nodules. XRD of the total clay (<2μm) and fine clay (<0.2μm) fractions of the soils shows the dominance of smectite, palygorskite, chlorite, mica, kaolinite, and small amounts of quartz and feldspar. Palygorskite occurring in Bw, Bss, Bwk, and BC horizons of these calcic-soils is related to non-pedogenic processes. Presence of only weak pedogenesis, lithological discontinuities, varying geochemical composition, and silt size palygorskite suggest its inheritance from marine sedimentary rocks of the area. It is attributed to rapid aggradation of palygorskite bearing aeolian sedimentary flux during increased aridity and weakening of the southwestern monsoon over the last 30ka. A decrease or complete absence of palygorskite in Btk horizon and sediments is related to intervening wetter conditions during MIS3-MIS1 stages. The present study of the palygorskite bearing calcic soils from western Thar could be useful to explain the possible mechanism for ongoing desertification and formation of calcrete in other arid tracts of the world.

Quantitative prediction of fractures using the finite element method: A case study of the lower Silurian Longmaxi Formation in northern Guizhou, South China

Natural fractures have long been considered important factors in the production of gas from shale reservoirs because they can connect pore spaces and enlarge transport channels, thereby influencing the migration, accumulation and preservation of shale gas. Industrial-level shale gas production has been initiated in the lower Silurian Longmaxi Formation in northern Guizhou, South China. However, it is important to quantitatively predict the distribution of natural fractures in the lower Silurian shale reservoirs to locate additional ‘sweet spots’ in northern Guizhou. In this study, data obtained from outcrops, cores, thin sections, field-emission scanning electron microscope (FE-SEM) images and X-ray diffraction (XRD) were used to determine the developmental characteristics and controlling factors of these fractures. Correlation analysis indicated that the mechanical parameters of the Longmaxi shale are mainly related to the total organic carbon (TOC), quartz, clay, calcite and dolomite contents. The spatial variations in the mechanical parameters of the Longmaxi shale were determined based on the spatial variations in the TOC and mineral contents. Then, a heterogeneous geomechanical model of the study area was established based on interpretations of the fault systems derived from seismic data and acoustic emission (AE) experiments performed on samples of the relevant rocks. The paleotectonic stress fields during the Yanshanian period were obtained using the finite element method (FEM). Finally, a fracture density calculation model was established to analyze the quantitative development of fractures, and the effects of faults and mechanical parameters on the development of fractures were determined. The results suggest that the main developmental period of tectonic fractures in the Longmaxi Formation was the Early Yanshanian period. During this time, the horizontal principal stress conditions were dominated by a SE-NW-trending (135–315°) compressional stress field, and the Longmaxi Formation experienced a maximum tectonic stress of 110–120 MPa. This simulated paleotectonic stress field was mainly controlled by faults and the contents of TOC, quartz, clay, calcite and dolomite; at different positions along the same fault, the degree of fracture development varies significantly. Overall, the distribution of fractures in the Longmaxi Formation can be used to optimize well deployment and provides a basis for the future exploration of shale gas.

Comparison of soil physicochemical properties and mineralogical compositions between noncollapsible soils and collapsed gullies

This study aimed to compare soil physicochemical properties and mineralogical compositions, including the cohesive force and internal friction angle, using direct shear tests with designed water contents and temperatures, between noncollapsible soil and collapsed gullies. Two pedons were collected from Longmen Town (Anxi County, Fujian Province) with severely collapsed gullies that developed from granitic rocks, and another two pedons were collected from metamorphic regions (Gande Town) without soil erosion. The samples were subjected to X-ray diffraction (XRD) analysis, and their soil physicochemical properties were compared. Noncollapsible soils had superior physicochemical characteristics, e.g., these soils contained higher amounts of cations, especially total iron oxides (Fet). Furthermore noncollapsible soils were able to resist shearing due to their greater cohesive force, and the internal friction angle did not differ considerably from that of the collapsed soils. Kaolinite, illite, hydroxy-interlayered vermiculite (HIV) and gibbsite were the dominant clay minerals in the noncollapsible soils. However, in the collapsed soils, kaolinite accounted for >85% of the total clay mineral composition. The cohesive force and internal friction angle were significantly correlated with sesquioxides of all non-collapsible and collapsed pedons, such as Fed (free Fe-oxides, 0.762**, 0.637**) and total iron (Fet, 0.783**, 0.708**), as well as magnetic susceptibility (0.650**, 0.740**) (P<0.01). In stepwise regression analysis, some of these factors did not exhibit dominance, which merits further in-depth research.

Identifying the phyllosilicate minerals of hypogene ore deposits in lateritic saprolites using the near-IR spectroscopy second derivative methodology

Infrared field-based reflectance spectroscopy in the Visible - Near-Infrared - Short-wave Infrared (VIS-NIR-SWIR) domain is a useful tool in mining geology particularly efficient for investigating the clay mineralogy of alteration haloes around ore deposits. It is used as a routine technique for the basic identification, mapping and semi-quantification of clay mineral species. However, the use of this technique for prospecting in hypogene deposits at depth in intertropical areas is strongly limited because of the presence of a thick, kaolinite-rich lateritic cover. Due to the strong IR absorption of kaolinite and the overlapping of its IR bands with those of most of the phyllosilicates in the SWIR domain, the use of field based near-infrared spectroscopy does not permit efficient identification and mapping of the phyllosilicates inherited from hypogene alteration that persist in the saprolite of lateritic profiles.In this paper, we propose a methodology to enhance the detection and semi-quantification of hypogene phyllosilicate minerals in kaolinite-rich lateritic saprolites using calibration curves. Those curves are built from the NIR spectra of binary admixtures of kaolinite or smectite with muscovite, Fe-Mg chlorite, clinochlore or talc in different known proportions.For each admixture series, calibration curves were established, based on investigation of two regions of interest within the NIR domain (1350–1470nm and 2080–2500nm) using a field-based spectrometer. For each binary mixture series of phyllosilicates, the second derivative of the NIR spectra was used to enhance the detection of the diagnostic absorption bands of each type of phyllosilicate, and hence to optimize the calculation of the intensity ratios between the diagnostic bands of the phyllosilicate components as a function of their percentage in the mixture. In presence of large amounts of lateritic kaolinite, the detection limit of the major types of hypogene phyllosilicates has been found at ranges from 5 to 10wt% of the total clay content using the second derivative of the NIR spectra acquired with a field-based spectrometer. Above these aforementioned limits of detection, the semi-quantitative data obtained by comparing the NIR reflectance spectra of natural samples with those of the calibration curves could permit to map hypogene alteration haloes directly from the lateritic saprolite.Finally the described approach has been successfully tested on natural samples from the skarn deposits of the Ity gold mine (Ivory Coast).

Classification of Serwan river Levee&amp;#39;s Soils in Kurdistan Region- Iraq

The study was conducted in order to classify Levee's Soil of Serwan river and to knowthe dominant soil units in the study area, as well as to determine the dominant pedogenicprocesses in the study area. Four pedons were selected along Sirwan River and describedmorphologically. Soil samples were taken from each soil horizon to determine somephysical and chemical properties. The results showed that all pedons are developed withA-B-C horizon sequences. All pedons have a Mollic epipedons with Agrillic and Calcicendopedons. The The increase of fine and total clay are due to the activity of Eluviationand illuviation pedogenic processes and to some extent to the new formation of clayminerals. According to the morphological, physical and chemical properties of thestudied pedons, soils were classified as Typic Argixerolls as they have Mollic surfacehorizons with more than 50% base saturation for more than 175 cm depth. They haveArgillic and Calcic subsurface horizons. The results indicated that the dominantpedogenic processes affecting soil development are eluviation, illuviation,decalcification and calcification.

Pore characteristics of Damodar valley shale and their effect on gas storage potential

The current global interest in fine grained sedimentary shale rock is driven by its ability to store gas in the pore spaces in them. The current study focuses on the understanding of the gas storage capacity of less explored Damodar Valley shales of India, in light of pore characteristics of organic matter and clay minerals. In this study, four samples were collected from different parts of Damodar valley basin and their geochemical composition, pore structure and adsorption capacity were investigated by XRD studies, rock-eval analyses, low-pressure N2-CO2 adsorption analyses and high-pressure methane adsorption experiment. The samples were also studied to know their hydrocarbon potential. The relationship between mineralogy, organic matter, and pore-structure was analyzed and finally, their effect on methane sorption capacity was discussed. The shale samples are found to be clay rich. The average clay content of the shale samples is 50.69% and average quartz content is 31.65%. Presence of excellent TOC content (4.8%–37.36%) with a predominance of type III organic matter and Tmax varying from 440 °C to 465 °C suggests a very good to excellent hydrocarbon generation potential in all the samples. The correlation between the TOC and VL was found to be positive indicating a positive influence of organic matter on methane sorption capacity of the studied samples. However, a lack of correlation between total clay and CH4-VL indicates that the role of clay minerals on methane sorption behavior of these shales are inconclusive. A positive correlation between CO2 micropore volume, CH4-VL and TOC suggest microporous nature of organic matter within the shale samples and their positive control on methane sorption potential. The negative correlation of clay mineral with CO2 micropore volume suggests a lack of microporosity in the clay minerals of the collected shale samples. It was also observed that thermally mature shale samples have higher micropore volume and surface area, and are prone to higher methane sorption capacity compared to that of less mature shales.