Sand Fraction Research Articles

Study of Light and Heavy Minerals and Their Effect on Oil Aggregation in the Zubair Formation for the Rumaila Oil Field in Southern Iraq

Zubair Formation is the most productive reservoir in southern Iraq, which is comprised of sandstones, interbedded with shale sequences and sometimes carbonate rock. It is an important formation in the lower Cretaceous cycle in Iraq. Rumaila oil field is the largest oil field in Iraq and the 6th in the world. Two wells were studied for three depths, one in the southern Rumaila and the other in the north. The study focused on light and heavy minerals in sand fractions and their relationship with hydrocarbon assemblages. For the survey to be complete, the sedimentological study of the cores was also conducted. This research aims to determine the effect of the amount of heavy and light minerals on the generation and production of oil in the reservoir layers. The sedimentological results were the prevalence of sand for all depths, especially in Southern Rumaila. The sand ratio ranged from 62% to 98%. The rate of heavy minerals in southern Rumaila was greater than in Northern on average at 1.17%. Light minerals were the most in Northern Rumaila up to 99.3% represented in quartz with a high percentage and a little part of feldspar represented in orthoclase. Heavy minerals were represented in Opaque (24%), zircon (27.6%), tourmaline (18%), rutile (11%), biotite (3%), chlorite (3.6%), muscovite (3.6%), staurolite (2%) and hornblende (3.6%). The proportion of quartz was the most in light minerals. The average of minerals is ultra-stable, and Opaque is the most dominant over the other minerals. Ultra-stable minerals in the sand that contain hydrocarbon assemblage are an index to mineralogical maturity for sandstone rocks. The SEM images showed deformations in quartz grains due to the high energy; on the other hand, the roundness and sphericity of the grains were evident, especially in Southern Rumaila sands.

Geochemical characteristics of surface aeolian sand in the Badain Jaran Desert, northwestern China: Implications for weathering, sedimentary processes and provenance

Knowledge of the provenance of the aeolian sand in deserts is crucial for revealing their development and the corresponding driving mechanisms. As the second-largest desert in China, the Badain Jaran Desert (BJD) has developed the tallest megadunes on Earth. However, the material source of these dunes, especially the provenance of different particle size fractions, is debated. Here, we address these issues using new geochemical data, consisting of the major, trace, and rare earth elemental signatures of different particle-size fractions of dune sands in the BJD and sediments from potential source areas. The source area sediments are from the rivers originating in the Qilian Mts., the Gobi regions between the Heihe River and the BJD, the piedmont of the Gobi-Altay Mts., and the alluvial fan of the Beida Mts. The results show that the dune sands of the BJD are mainly derived from felsic source rocks subjected to weak chemical weathering in the source area. The fine fraction (<63 μm) of the aeolian sand in the BJD has experienced some degree of sedimentary sorting and recycling, despite its mineralogical immaturity. Furthermore, comparison of the immobile trace elements and rare earth element (REE) ratios of the samples from the BJD with those from the potential source regions, together with the results of multidimensional scaling and principal component analysis, shows that the coarse fraction (63–250 μm) of the dune sand in the BJD originated mainly from fluvial and Gobi deposits eroded from the Qilian Mts.; whereas the fine fraction has a mixture of provenances, including the Qilian Mts. and the Gobi-Altay Mts., although the latter contribution is of limited significance.

Sedimentary response to the contrasting provenance and oceanographic conditions on the continental shelf of India

The present study sets out to elucidate how magnetic minerals derived from wide array of source regions respond to shelfal sedimentary processes in a complex shelf system. Bulk sediment magnetic mineralogy comprised of detrital magnetic (magnetite, titanomagnetite, titanohematite) particles with variable concentrations and grain sizes. A prominent change in magnetic mineral contribution from mafic to felsic dominated sediment province is clearly evident through a trend of decline in magnetite content manifested by fining of magnetic crystal size. Elevated magnetite content followed by the presence of fine and coarse-grained magnetic particles, and mere variations interms of mineralogy can be attributed with the enhanced magnetic contribution from the Deccan basalt (DcB) in the shelf sediments off Narmada, Tapti, Mahi, and Sabarmati (NTMS) River system, Arabian Sea. A distinct shift in magnetite content accompanied by abrupt fluctuations in clastic grain size in the sediment core off Ganga-Brahmaputra (G-B) shelf, Bay of Bengal indicate the major change in detrital sedimentation. A major change in the magnetic mineralogy linked with enhanced supply of titanomagnetite particles marks the onset of mafic sourced material in the sediments off Pennar – Swarnamukhi (P–S) shelf, Bay of Bengal. Magnetogranulometry data revealed that magnetic crystal size is independent of physical grain size above >40 μm in NTMS and G-B, and >20 μm in P–S samples. Decoupling is largely due to polycrystalline nature, where fine-grained magnetic particles occurred as inclusions within silt and sand fractions. We demonstrate that multi-proxy approach presented in this study can be effectively used to assess the influence of the contrasting provenance and oceanographic conditions on the shelfal sediment dynamics.

SUITABILITY EVALUATION OF RAINFED RICE (ORYZA SATIVA) IN FLOOD PLAIN OF SOUTHERN GUINEA SAVANNAH ZONE OF NIGERIA

The flood plain of Awe in Southern Guinea Savannah Zone of Nigeria was studied for rice production. The physical, morphological and chemical properties of the soils were matched with the requirements of the rice production and the overall suitability rating of the soils was obtained using limitation method. The soils were deep (101cm – 170cm) and well drained, poorly to very poorly drained. The soils were fine textured and strongly to moderately acidic and slightly alkaline in reaction (pH 5.10 – 7.15). The percentage sand fraction ranged from 44.8% to 83.1%; silt 5.4% to 9.4% and clay 9.4% to 46.7%. They had low to moderate organic carbon (0.41% to 3.52%); total N (0.04% to 0.11%); available P (1.64mglkg-1 to 3.72mg/kg-1), total exchangeable bases (2.85cmol/kg-1 to 7.97cmol/kg-1), CEC (4.10cmol/kg-1 to 7.98cmol/kg-1), base saturation (65% to 97.5%) and Fe2+ (1.10 to 2.11). Soils of the three flood levels (toeslope or deep swamp, medium or lower slope, levee or shallow swamp) were rated highly to suitable (S1) because of the soils ability to retain water during the growth period with the favourable physical and chemical characteristics such as climate, slope, water levels, pH and texture. Management practices such as organic matter incorporation, liming to increase soil pH, fertilizer application and appropriate time of planting are hereby recommended for increased rice production in the mapping units that are not highly suitable for rice production in the study area.

Quantification of soil textural and hydraulic properties in a complex conductivity imaging framework: Results from the Wolfsegg slope

We present an approach that permits to predict hydraulic conductivity from extensive, multi-methodical geophysical data collected on a hillslope affected by landslides in Austria. The objective of the investigation is the spatial characterization of a slope affected by mass movements to derive hydrogeological structures and preferential flow paths. The geophysical data sets presented in this study consists of 24 densely distributed complex conductivity (CC) imaging profiles, collocated to these profiles we also collected 517 transient electromagnetic (TEM) soundings and 10 refraction seismic tomography (RST) profiles. Additionally, we also present well-logging data (namely electrical resistivity, natural gamma logs) collected in five boreholes. Cores recovered during the drilling of the boreholes are used to aid in the interpretation of the geophysical units, while analysis of the sediments was conducted to obtain grain size distributions, cation exchange capacity and mineralogy of the subsurface materials. While all geophysical data was processed initially independently, the final complex conductivity imaging results are based on the incorporation of structural constraints about the electrical units obtained from the TEM soundings. The interpretation of the resolved CC units is then sustained by the RST images and the lithological information from the boreholes. We estimate then the hydraulic conductivity of the subsurface derived from the CC images using a two-step approach. In a first step, we investigated the link between the complex conductivity and the different soil volume fractions of gravel, sand, silt and clay. In a second step, we applied a pedo-transfer function, namely the well-known Rosetta model, that permits to predict the hydraulic conductivity from the estimated grain size volumes. This approach allowed a quantitative interpretation of the geophysical data and thus a 3-dimensional (3D) representation of the grain size distribution and hydraulic conductivity in the investigated slope section. Thereby, we observed well-determined site-specific relationships (R2 &amp;gt; 0.7) from the comparison of the complex resistivity images and grain size analysis. The obtained hydrogeophysical 3D model permits to delineate the geometry of an aquiclude, and, thus, the analysis of preferential water-flow paths. In particular, we can identify a spatial correlation between the aquiclude interface and morphological features.

Preliminary mineralogical and geotechnical characterization of kaolin from Abeokuta area, southwestern Nigeria

Kaolin of sedimentary origin in the Abeokuta area, southwestern Nigeria was studied to determine its mineralogy and geotechnical properties as well as possible industrial applications. Samples of kaolin were collected from different mine sites in the Abeokuta area. Geotechnical test was also performed to determine the grain size parameters and plasticity of the kaolin samples. Samples were also subjected to mineralogical and morphological analysis using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Results revealed that kaolin samples have clay, silt and sand fraction ranging from 7.3 -53.93%, 29.56 – 53.72% and 1.8 to 29.56% respectively. XRD and SEM results revealed that minerals in kaolin are kaolin, quartz, rutile and anatase. Industrial and geotechnical appraisal revealed that some of the samples with high content and low quartz content can be used in production of ceramics and paper while cannot be used in some industrial application such as pottery and production of ceramics due to the grain size geotechnical properties and mineralogy.

Richness and distribution of endangered orchid species under different climate scenarios on the Qinghai-Tibetan Plateau.

Predicting the potential influences of climate change on the richness and distribution is essential for the protection of endangered species. Most orchid species are narrowly distributed in specific habitats and are very vulnerable to habitat disturbance, especially for endangered orchid species on the Qinghai-Tibetan Plateau (QTP). In this study, we simulated the potential influences of climate change on the richness and distribution of 17 endangered orchid species on the QTP using the MaxEnt model based on the shared socioeconomic pathways scenarios (SSPs) in the 2050s and 2070s. The results showed that aspect, annual precipitation, elevation, mean temperature of driest quarter, topsoil pH (H2O), and topsoil sand fraction had a large influence on the potential distribution of endangered orchid species on the QTP. The area of potential distribution for orchid species richness ranging from 6 to 11 under the current climate scenario was 14,462 km2 (accounting for 0.56% of QTP), and it was mostly distributed in the southeastern part of QTP. The area of orchid species richness ranging from 6 to 11 under SSP370 in the 2070s was the smallest (9,370 km2: only accounting for 0.36% of QTP). The largest area of potential distribution for orchid species richness ranging from 6 to 11 was 45,394 km2 (accounting for 1.77% of QTP) under SSP585 in the 2070s. The total potential distribution area of 17 orchid species richness all increased from the 2050s to the 2070s under SSP126, SSP245, SSP370, and SSP585. The orchid species richness basically declined with the increasing elevation under current and future climate scenarios. The mean elevation of potential distribution for orchid species richness ranging from 6 to 11 under different climate scenarios was between 3,267 and 3,463 m. The mean elevation of potential distribution for orchid species richness ranging from 6 to 11 decreased from SSP126 (3,457 m) to SSP585 (3,267 m) in the 2070s. Based on these findings, future conservation plans should be concentrated on the selection of protected areas in the southeastern part of QTP to protect the endangered orchid species.

Effects of Geologic Setting on Contaminant Transport in Deltaic Aquifers

AbstractCoastal deltaic aquifers are vulnerable to degradation from seawater intrusion, geogenic and anthropogenic contamination, and groundwater abstraction. The distribution and transport of contaminants are highly dependent on the subsurface sedimentary architecture, such as the presence of channelized features that preferentially conduct flow. Surface deposition changes in response to sea‐level rise (SLR) and sediment supply, but it remains unclear how these surface changes affect the distribution and transport of groundwater solutes in aquifers. Here, we explore the influence of SLR and sediment supply on aquifer heterogeneity and resulting effects on contaminant transport. We use realizations of subsurface heterogeneity generated by a process‐based numerical model, DeltaRCM, which simulates the evolution of a deltaic aquifer with different input sand fractions and rates of SLR. We simulate groundwater flow and solute transport through these deposits in three contamination scenarios: (a) vertical transport from widespread contamination at the land surface, (b) vertical transport from river water infiltration, and (c) lateral seawater intrusion. The simulations show that the vulnerability of deltaic aquifers to seawater intrusion correlates to sand fraction, while vertical transport of contaminants, such as widespread shallow contamination and river water infiltration, is influenced by channel stacking patterns. This analysis provides new insights into the connection between the depositional system properties and vulnerability to different modes of groundwater contamination. It also illustrates how vulnerability may vary locally within a delta due to depositional differences. Results suggest that groundwater management strategies may be improved by considering surface features, location within the delta, and the external forcings during aquifer deposition.

THE BEHAVIOUR OF PHOSPHORUS IN AN OLD PARALLEL CHANNEL SLAŇÁKY IN THE POODŘÍ (CZECH REPUBLIC)

Within the Poodří nature reserve and the Odra River old parallel channel, Slaňáky, various forms of phosphorus were investigated due to increased high concentrations of total phosphorus (Ptot) in the surface water. Surface water samples were subjected to chemical analyses using absorption spectrophotometry (Ptot and P-PO43- ) and accompanying parameters (t, O2, pH, Cond, TSS ) were measured. Next, grain size analysis of the sediment and sediment analyses using X-ray fluorescence were carried out (P, Fe, Al, Ca, Si, K, Mn, S, etc.). The seasonality of Ptot concentrations in the water was not confirmed, the reservoir behaved as a pool. The concentrations of the dissolved inorganic form P- PO43- were low when compared to Ptot, thus suspended phosphorus prevailed. This may be related to the low depth of the given water body, where stratification does not occur in contrast to deep water bodies. However, sediment resuspension is frequent, and phosphorus largely accumulates. The concentrations of Ptot in the sediment ranged around 4900 mg/kg, where the inorganic form prevailed (87.24 – 93.73 %) over the organic (6.27 – 12.76 %). At the same time, the sediment samples were abundant for sand fractions (2 – 0.03 mm), 47.86 – 60.89 %, and finest silt and clay (&lt; 0.063 mm), 33.07 – 44.60 %.

Influence of Lateglacial meltwater influx from alpine glaciers on the aquatic ecosystem of Kanas Lake in the Altai Mountains, China

Glacier retreat in high altitude areas triggered by anthropogenic warming exerts a profound impact on the ecology of glacier-fed lakes. In this paper, we report on the results of a multi-proxy analysis of a Lateglacial (13.3–11.3 cal kyr B.P.) core obtained from the glacier-fed Kanas Lake in the Altai Mountains, China, to understand the responses of aquatic ecosystems to meltwater influxes. Core intervals with high sand fractions and enriched silicon dioxide and zirconium (~11.5, 11.7, 11.8, 12.2 and 13.0 cal kyrs B.P.) reflect intense meltwater pulses from alpine glaciers. In the core, these pulses generally coincide with low abundance of littoral cladocerans, high abundance of planktonic Pediastrum, and high phosphorus concentrations. Our results suggest that intense meltwater influxes not only brought nutrients (nitrogen and phosphorus) into the lake and promoted phytoplankton growth, they also generated cold, turbid water masses and restricted the growth of benthic algae and invertebrates. Therefore, we infer that future anthropogenic warming may lead to significant changes in the structure and function of aquatic ecosystems in glacier-fed lakes worldwide.

Effect of the Microsand Fraction on the Ballistic Resistance of UHP-SFRC

This work investigates the effect of various sand fractions on the ballistic resistance of ultra-high-performance steel-fibre-reinforced concrete (UHP-SFRC) samples. We specifically investigated replacing expensive and generally inaccessible microsands with commonly available sands. The tests and the measured values show that replacing part of the microsand with the more commonly and economically acceptable 0/2 mm aggregate fraction minimises the resulting mechanical properties and ballistic resistance. The most common type of ammunition was used to test all sample bodies, which is a 7.62 × 39 mm calibre with an all-metal jacket and a mild steel core. The damage’s extent and mode were determined using a 3D scanner operating on photogrammetry.

Effect of Particle Character and Calcite Dissolution on the Hydraulic Conductivity and Longevity of Biosand Filters Treating Winery and Other Acidic Effluents

Acidic effluent such as winery wastewater is challenging to remediate. Biological sand reactors can simultaneously remove organics and neutralize winery wastewater via biotic and abiotic mechanisms. The systems have been shown to be suitable for treating the intermittent flow of wastewater at small wineries. It has been shown that dissolution of calcite is the most important abiotic mechanism for increasing the pH of the influent. In this study, sand column experiments were used to determine the effects of (i) sand particle size distribution on calcite dissolution kinetics, and (ii) the effects of calcite particle dissolution on the hydraulic conductivity. The results were then used to calculate the theoretical temporal abiotic neutralization capacity of biological sand reactors with differently sized sand fractions, including unfractionated (raw) sand. The results were compared with those determined from a pilot system treating winery wastewater over a period of 3 years. Sand fractions with larger particles contained lower amounts of calcite (using Ca as a proxy), but exhibited higher hydraulic conductivities (3.0 ± 0.05 %Ca and 2.57 to 2.75 mm·s−1, respectively) than those containing smaller particles and/or raw sand (4.8 ± 0.04 to 6.8 ± 0.03 %Ca and 0.19 to 1.25 mm·s−1, respectively). The theoretical abiotic neutralization capacity of biological sand reactors was compared with a pilot system with the same flow rates, and a temporal abiotic neutralization capacity of 37 years was calculated for biological sand reactors, which compared favorably with the theoretical results obtained for wastewater with pH values between 2 (8.2 years) and 3 (82 years). It was concluded that biological sand filters with around 10% calcite will be able to abiotically neutralize winery wastewater and other wastewaters with similar acidities for the projected life span of the system. Future work should focus on determining the effect of sand grain size on the bioremediation capacity, as well as the use of biological sand reactors for treating other acidic organic wastewaters such as fruit processing, food production and distillery wastewater.

A partial least squares-path model of environmental degradation in the Paraopeba River, for rainy seasons after the rupture of B1 tailings dam, Brumadinho, Brazil

The present study aimed to investigate the rupture of B1 tailings dam of Córrego do Feijão mine, which drastically affected the region of Brumadinho (Minas Gerais, Brazil). The contamination of water resources reached 155.3 km from the dam site. In the river channel, high concentrations of Mn, Al, As and Fe were detected and correlated to the spillage of the tailings in the river. The presence of the tailings also affected the chlorophyll-a content in the water, as well as the reflectance of riparian forests. With the increase of metal(oid) concentrations above permitted levels, water management authorities suspended the use of Paraopeba River as resource in the impacted areas, namely the drinking water supply to the Metropolitan region of Belo Horizonte. This study aimed to evaluate possible links between tailings distribution, river water quality, and environmental degradation, which worked as latent variables in partial least squares regression models. The latent variables were represented by numerous physical and chemical parameters of water and sediment, measured four times in 22 locations during the rainy season of 2019, in addition to stream flow and to NDVI evaluated in satellite images processed daily. The modeling results suggested a relationship between river flow turbulence and increased arsenic release from sand fractions, as well as desorption of Mn from metal oxides, both representing causes of water quality reduction. They also revealed increasing iron concentrations affecting the forest NDVI (greening), which was interpreted as environmental degradation. The increase of chlorophyll-a concentrations (related with turbidity decreases), as well as the increase of river flows (responsible for dilution effects), seemed to work out as attenuators of degradation. Although applied to a specific site, our modeling approach can be transposed to equivalent dam failures and climate contexts, helping water resource management authorities to decide upon appropriate recovery solutions.

Unraveling the Deep‐Sea Sedimentary Record of Ice Sheet History

AbstractIce rafted debris (IRD) is a proxy used to interpret the deep‐sea sedimentary record of ice sheet history. McKay et al. (2022, https://doi.org/10.1029/2021PA004404) focused on methods used to reconstruct past iceberg presence around Antarctica using IRD from deep‐sea sediment cores and address the efficacy of the following three common methodologies of IRD quantification: counting clasts &gt;2 mm in x‐radiographs; the sieved weight percent of the medium‐to‐coarse sand fraction (250 μm–2 mm); and volumetric estimates of the &gt;125 μm sand fraction using laser particle size analysis. A high correlation occurred between IRD percentage determined by sieve analysis and visual clast counts using radiograph analysis. Although each method has pros and cons that are considered by the authors, the separation of coarse sand (&gt;250 μm–2 mm) from fine‐grained sediment by sieving provided the cleanest signal. In addition, IRD grains can be used for paleoenvironment or provenance analyses providing more complete marine ice sheet paleorecords. This thorough analysis highlights a topic that has been previously overlooked and has become increasingly important in understanding the response of marine ice sheets to a warming atmosphere and ocean.

The FastCarb project: Taking advantage of the accelerated carbonation of recycled concrete aggregates

Recycled concrete aggregates (RCA) incorporate hydrates that can be carbonated. The FastCarb project aims to mineralize CO2 within RCA, improving the quality of these aggregates by the clogging of the porosity and finally decreasing the CO2 impact of concrete in structures. It has two main objectives: to optimize in laboratory conditions the accelerated carbonation process which can be transposed at an industrial scale at a suitable cost and to show that the process could be used in industrial conditions. This paper presents firstly the results obtained in laboratory conditions: it confirms that it is possible to store between 10 and 50 kg of CO2/t of RCA depending on several factors (natural carbonation, water content, temperature, size of RCA…) and that the treatment allows an improvement of the properties like the water absorption. The feasibility of accelerated carbonation has been also demonstrated by setting up two industrial-scale demonstrators. The first results without optimization showed a CO2 capture rate in the order of 3–4 %, i.e. 30 kg of CO2 per ton of crushed concrete. 80 t of carbonated RCA were produced and used to produce C25/30 and C45/55 concretes. The measurement of the main properties (performance in the fresh state, mechanical performance, and durability) shows that the use of the carbonated RCA doesn’t affect these properties. A variety of precast products (blocks, curbs, stairs) and parts of cast-in-situ structures (construction of walls) were fabricated showing the feasibility of using these aggregates in real situations. Finally, our project considers whether the accelerated carbonation process is environmentally acceptable and economically viable. The first results show that the distance of transport (by trucks) is a major factor and that transportation should be limited to maintain a positive impact of the accelerated carbonation (i.e. local sources of CO2 should be used). The LCA and the economic study confirm that the sand fraction of RCA is the most interesting material for the uptake of CO2. This is also interesting for a circular economy objective because recycled concrete sand is not easily used in concrete made with RCA.

The Sustainable Future of Carbon Farming with Virginia Fanpetals, a Carbon-Negative Species

In 2016–2018, an experiment with Sida hermaphrodita L. Rusby (Virginia fanpetals) called Sida was conducted in the system of random blocks on sandy and sandy loam soil. Each year, the yields of dry aboveground mass and dried mass of roots were determined. Before sowing Sida and after the end of the research, the composition of earthy fractions in the soils was determined. In the stalks and roots of Sida, the percentage content was determined, and the mass of carbon was calculated. When Sida was grown in sandy soil, the average dry mass yield (stalks and roots) in the third year of cultivation (2018), was slightly above 13 t∙ha−1, and in the sandy loam soil it was three times higher (36 t∙ha−1). In the third year of cultivation, the carbon sequestration in the stems and roots exceeded 5 t∙ha−1 (sandy soil), and 15 t∙ha−1 (sandy loam). The carbon content in the stems was 46.25%, and in the roots–42.67%. The results were statistically processed using ANOVA. It was found that the cultivation of Sida caused a percent decrease in the sand fraction, an increase in the floatable (fine) fraction in sandy soil, and an increase in humus content; the opposite changes were noted in the sandy-loam soil.

The USLE soil erodibility nomograph revisited

The nomograph by Wischmeier et al. (1971) for calculating the K-factor in the USLE was extremely useful when there was low access to calculators. However, the generalised calculation of this factor requires the development of analytic procedures. This paper presents a detailed analysis of the nomograph and its underlying equation, which is applicable only when the silt plus very find sand fraction does not exceed 70%. We also examined the quality of fit on the nomograph of the adaptations to the equation that have been proposed, as a means of dealing with those areas where the original equation is not applicable. All models are shown to have areas where the fit is deficient or even unacceptable. Besides, the family of curves on the nomograph for the various values taken by the organic matter are not coincident with the mathematical function from which they presumably derive. The study also identifies those areas of the textural triangle in which the soils originally used in developing the USLE are located, with a view to according a lower predictive value to the contrasting areas in which calculations of the K-factor will necessarily be extrapolations. Finally, a new equation for calculating the K-factor is presented, which accurately reproduces the different sections of the nomograph, and allows the poorly functioning graph to be dispensed with. The paper ends with a link to a tool in R for simplifying the procedure for calculating the K-factor, taking into account varying situations of data availability.

How much raindrop energy is used for transportation of the two-phase splashed material?

The ejection of a mixture of solid (soil) and liquid (water) phases is one of the aspects of the energy dissipation of the impacting drop during the soil splash phenomenon. All calculations to date have only been taking into account the ejection of solid phase material and were based on significant simplifications of the measured quantities. Therefore, the aim of the study was an improved calculation of the falling drop energy transferred to the ejected material, while considering that such material was a mixture of solid soil particles and water droplets and therefore, “two-phase”. Experimental variants included combinations of soils with different textures and initial moisture contents as well as various falling water-drop energies. Two complementary methods of i)splash cup measurements and ii) image analysis based on high-speed cameras were used for the calculation of quantities i.e. the number of ejected particles, their mass, and their ejection velocity. Based on the obtained results, it was stated that the kinetic energy of ejected particles, expressed as a percentage of falling drop energy, ranged from 1 % to 14 %. This percentage depended strongly on soil texture as well as initial moisture content. The highest values were obtained for soil with the largest amount of sand fraction and the lowest for the soil with the largest amount of finer fractions. All tested soils showed a trend of a higher drop energy transferred to the splashed particles with increasing initial soil moisture content. Taking into account the varied energy of the falling drop variants, the amount of energy transferred to ejected particles was constant.

C:N ratios of bulk soils and particle-size fractions: Global trends and major drivers

C:N ratios are the most ancillary and available proxy for soil organic matter (SOM) chemical composition and quality in the literature, but there is surprising little information on how it is affected by environmental factors. To address this knowledge gap, we searched the global literature and gathered information from 74 studies conducted between 1980 and 2019, covering 29 countries and a wide range of variation environmental settings. We compiled data on soil organic carbon (SOC), total N (TN) and C:N ratios in bulk soil and, for the first time, within soil particle-size fractions – sand, silt, and clay. Correlation and random forest statistical analyses showed that SOC and TN contents were mostly controlled by macroscale, climatic drivers, namely temperature and precipitation, whereas soil C:N ratios were more responsive to microscale drivers, e.g. soil particle-size distribution. Specifically, C:N ratios in bulk soil were most strongly correlated with sand contents (r = 0.52; p < 0.001), consistent with the high C:N of sand-sized SOM (median 16.7). Otherwise, clay-sized SOM showed much less variation in C:N ratios (5.0–17.6, median 9.6), regardless of sampling depth and land use. Clay C:N ratios were only consistently lower under arid climate types. Silt-sized SOM showed intermediate C:N ratios (median 13.1) relative to sand and clay-sized fractions. Hence, our results suggest a preferential immobilization of N-enriched SOM onto clay-sized particles coupled to a segregation of N-depleted SOM in sand-sized fractions. Although bulk soil C:N increased with sand contents, the accumulation of N-depleted SOM within sand-sized fractions increased with clay content. Overall, by identifying the complementarity of macro- and microscale factors underpinning soil C and N pools and their C:N ratios, our results contribute to reduce the inherent complexity to model SOM cycling across global to local scales.

Selective Grain Size Fractionation, CO2-Enhanced Aqueous Extraction and Characterization of Trona, a Non-marine Evaporite Mineral, Originating from Semi-arid Soil Sediments

Abstract Beneficiation of white-powdery mineral, from selective grain size (63 – 200 µm) sand fractions and its characterization as trona, a non-marine evaporite, exudates as efflorescent crust, originated from the semi-arid region soil sediments, occurring at Siddhamalli, Tamil Nadu, India is described, by a five-stage process. Aqueous extraction of selective sand fractions, in CO2-enhanced medium, resulted in white crystalline powder, is chemically characterized as sodium sesquicarbonate dihydrate, [Na3H(CO3)2.2H2O]. The % yield of trona is directly proportional to the % fine and very fine sand fractions and inversely proportional to the % coarse fractions (0.5 – 1.0 mm), as revealed by grain-size analysis. CO2-enhanced medium significantly increases the yield, additionally by 20 %.PXRD data revealed the presence of trona with traces of nahcolite and natrite phases. FT-Raman spectrum revealed the characteristic bands correspond to carbonate group. The hydroxyl stretching of water is observed at 3400 cm-1 inferred from FT-IR spectral studies.The content of sodium and trace elements analysed by ICP-OES and water of hydration by TGA, are found to be good agreement with the calculated values of Na (30.58 %) and dihydrate (15.97 %) respectively. SEM images revealed the less agglomerated particles of sizes ranging from 0.093 - 0.44 µM. Geologically, soil sediments fall in tractive current, from talus of Bouldery sandstone and shale of Talchir formation, Lower Gondwana of Upper Carboniferous to Lower Permian Age. Trona is popularly known as “Po¯neeru” in Indian traditional Siddha system of medicine finds its application in most of the drug formulations.