Silt Content Research Articles

Environmental risk assessment, spatial distribution, and abundance of heavy metals in surface sediments of Dal Lake-Kashmir, India

This study assesses the pollution levels of Dal Lake in Kashmir, India, focusing on the spatial distribution, abundance, and risk of heavy metals in surface sediments. Granulometric analysis revealed a complex interplay of sedimentation processes, characterized by a wide range of sand (1.25% to 47.03%), silt (2.65% to 58.21%), and clay (38.35% to 94.48%) contents across sediment samples. The average CaCO3 content of 18.65% is notably higher than observed in other regional and global lakes, indicating higher production or preservation of carbonates. The organic matter (OM) content within the sediment samples varied significantly, ranging from 3.9% to 25.01%, reflecting complex sedimentary dynamics. Utilizing environmental assessment indices (Contamination Factor, degree of contamination, Pollution Load Index, Potential ecological risk index, Enrichment Factor, and Geo-accumulation Index) and multivariate statistical analyses (Pearson's Correlation, Principal Component Analysis, Cluster Analysis), it examines the contamination by Iron, Manganese, Cobalt, Chromium, Copper, Nickel, Lead, and Zinc across 32 samples. Results indicate spatial variability in metal concentrations, with Cobalt ranging from 24.1178 ppm to 52.95 ppm and Iron from 25,800.99 ppm to 164,747.82 ppm, highlighting areas of significant contamination and potential ecological risks, especially from Nickel, which exceeds safe levels for benthic invertebrates. The Pollution Load Index suggests moderate contamination of the lake. These findings emphasize the urgent need for continuous monitoring and effective management to protect Dal Lake's ecological integrity.

Testing turbidite conceptual models with the Kaikōura Earthquake co-seismic event bed, Aotearoa New Zealand

ABSTRACT The 2016 Mw7.8 Kaikōura Earthquake in Aotearoa New Zealand provides an opportunity to test widely applied turbidite sedimentation models because it triggered a co-seismic turbidity current. The resultant Kaikōura event bed (KEB), interpreted as a turbidite, is sampled for ∼ 1300-km down-flow along the depositional system. Sediment core lithologies, computed tomography (CT), and particle-size data are used to test event-bed thickness, silt content, facies distribution, and stacking patterns against the foundations of the turbidite conceptual model of Bouma (1962). KEB thickness is variable to ∼ 100 km down-flow distance and attains a maximum thickness at ∼ 700 km down-flow distance before thinning distally, similar to the predicted bell-shaped proximal to distal trend. Silt content is high throughout the KEB from canyon to fan. The KEB is dominated by laminated Td facies and Te facies that evolve down-system from laminated, then graded, to homogeneous muds. CT and granulometry data are key to differentiating subtle density and textural variations in fine-grained deposits and reveal that KEB Td and Te facies in the KEB that are often not preserved or readily observed in older deposits. The KEB highlights a fine-grained sedimentary system that contrasts with more widely studied sandy turbidite basins. In particular, the KEB example reveals that Td and Te facies are ubiquitous in this fine-grained, silt-rich system. A varied conceptual model developed from the KEB may be applicable to many modern deep-sea turbidite systems and crucial for understanding present-day particulate transport to the deep sea and interpreting evidence from the stratigraphic record.

Effect of Soil Texture on Soil Nutrient Status and Rice Nutrient Absorption in Paddy Soils

Soil texture affects rice nutrient uptake and yield formation by influencing soil structure, microbial activity, and soil nutrient supply capacity. Analyzing the relationship between soil texture, nutrient content, and rice agronomic traits is of great significance for precise and efficient fertilizer application. The tillage layer (0–20 cm) of 31 paddy fields in China’s main rice-producing areas was collected to perform rice pot experiments, and soil texture characteristics, physicochemical properties, microbial-related indicators, and rice agronomic traits were measured and analyzed. The results showed that these soils could be classified into four types of soil texture: loamy sandy soil, sandy loam soil, silty loam soil, and silty soil. Analysis of variance showed that the available nitrogen (AN), available potassium (AK), and available phosphorus (AP) contents were the highest in silty loam, silty, and sandy loam soils, respectively, and silt loamy soil had the highest CEC. Principal component analysis (PCA) also showed that soil physicochemical properties can be distinguished to a certain extent according to soil texture types. For the relationship of soil texture parameters and soil physicochemical properties, soil organic matter (OM), total nitrogen (TN), AN, ammonium nitrogen (NH4+-N), and microbial carbon (MBC) contents were positively correlated with soil clay content, AK was positively correlated with silt content, and soil phosphorus status was significantly related to pH. Mantel’s test revealed significant correlations between rice N, P, and K nutrient status, dry matter accumulation, and yield, and soil available nutrient content, MBC, pH, and soil texture parameters. Structural equation modeling (SEM) indicated that sand affected soil available nutrients by regulating pH, while clay can positively influence soil available nutrients by affecting soil organic matter mineralization and microbial activity, thus influencing nutrient absorption and yield formation in rice. Overall, in rice production, the silty and silty loam paddy soil with fine texture and higher clay content facilitates the mineralization of soil organic matter and the activity of soil microbes, resulting in more available soil nutrients, which benefits the rice absorption and accumulation of nutrients. Furthermore, a higher content of clay also promotes the distribution of dry matter to the panicle, thereby promoting rice yield formation.

Investigating soil properties on the north and south slopes at different elevations in Al-Jabal Al-Akhdar, Libya

This scholarly study investigated the physicochemical characteristics of soil in the Al-Jabal Al-Akhdar forest, Libya, with a specific focus on the influence of elevation and slope aspects. Fifty-six sample plots were established across varying elevations, each subdivided into four subplots, totaling 224. Soil samples were collected from each subplot at 0-15 cm depth. Results demonstrate significant variations in clay, silt, and sand content with elevation, indicating lower clay and higher sand content at higher elevations. Available water capacity (AWC) increased with altitude on the northern slope, while consistently lower values were observed on the southern slope. Bulk density (BD) decreased with increasing altitude, suggesting less compacted soils at higher elevations. Available phosphorus (Pav), available potassium (Kav), and pH values decreased with increasing altitude on both slopes. Cation exchange capacity (CEC) values varied at altitudes on the northern slope, with higher values observed at mid to high altitudes. Calcium carbonate (CaCO3) decreased with increasing altitude on the northern slope while showing inconsistent trends on the southern slope. Soil organic matter (SOM) content increased with altitude on both slopes. Pearson's correlation and Principal Component Analysis (PCA) examined relationships among soil properties, elevations, and aspects. Elevation positively correlated with AWC and SOM and negatively correlated with clay content, Kav, BD, and pH. PCA identified elevation, aspect, silt content, CaCO3, and electrical conductivity (EC) as primary influencers. SOM exhibited positive correlations with AWC and negative correlations with BD. Soil pH showed a negative correlation with SOM and a positive correlation with CaCO3. Additionally, CaCO3 content was positively correlated with the cation exchange capacity (CEC). These findings contribute to understanding soil property relationships, elevation, and aspect, emphasizing their role in shaping soil ecosystems and nutrient dynamics. Further research is warranted to explore additional factors influencing soil properties and to develop effective nutrient management strategies.

Assessment of Soil Particle Distribution and Primary Nutrient Status in the Groundnut-Producing Areas of Nalgonda, Telangana, India

The current research involved a thorough field survey to assess particle size distribution and the availability of primary nutrients in rabi-grown groundnut soils (2022-2023) across three productivity regions: high (2497.15-3006.47 kg ha-1), medium (1987.82-2497.15 kg ha-1), and low (up to 1987.82 kg ha-1) in Nalgonda district, Telangana. A total of 150 surface soil samples (0 - 15 cm depth), with 50 samples from each productivity region, were collected before the sowing of rabi groundnut crop using a stratified random sampling method. These collected soil samples are further processed and analysed for soil texture, available nitrogen (N), phosphorus (P) and potassium (K). The objective of this research is to know the status of texture and primary nutrients in groundnut growing areas of Nalgonda district. The sand, silt and clay content in high, medium and low productivity regions averaged 72.90%, 71.29%, 67.56%; 6.82%, 8.35%, 10.16% and 20.27%, 20.36%, 22.27% respectively. The respective available N, P and K showed mean values of 257.29 kg ha-1, 189.40 kg ha-1 and 138.99 kg ha-1; 48.025 kg h IJPSS_116978a-1, 44.512 kg ha-1, 27.09 kg ha-1 and 251.91 kg ha-1, 236.48 kg ha-1, 174.86 kg ha-1 in high, medium and low productivity regions. In regions characterized by high productivity, there was a pronounced prevalence of sand content, significantly influencing soil particle aggregation. Notably, silt content exhibited considerable variation, particularly within areas of medium and low productivity, whereas clay content displayed the most variability in regions of low productivity. The availability of nitrogen decreased sequentially from high to medium productivity areas, and further from medium to low productivity regions. This same pattern was observed for available phosphorus and potassium, with substantial variations across the three productivity categories, declining consistently from high productivity regions to low productivity ones. Variations in available phosphorus (P) and potassium (K) exhibited extensive dispersion within every productivity category, as evidenced by the significant standard deviation and coefficient of variation values across these regions. This is particularly notable for potassium, highlighting the necessity of considering diverse soil conditions and factors affecting potassium availability when formulating fertilization plans.

Amphioxus (Branchiostoma lanceolatum) in the North Adriatic Sea: ecological observations and spawning behavior.

The European amphioxus (Branchiostoma lanceolatum) is a member of the chordate subphylum Cephalochordata, and, as such, a key model organism for providing insights into the origin and evolution of vertebrates. Despite its significance and global distribution, detailed characterizations of natural populations of cephalochordates are still very limited. This study investigates the abundance, habitat, and spawning behavior of amphioxus in the North Adriatic Sea. Across 32 sampled sites, adult amphioxus were consistently present, reaching densities exceeding 300 individualsm- 2. DNA barcoding confirmed the species as B. lanceolatum, and environmental analyses revealed an amphioxus preference for slightly gravelly sand with low silt content and a correlation between amphioxus density and the presence of specific macroinvertebrate taxa. Remarkably, the amphioxus population was breeding in early spring and possibly late fall, in contrast to the typical late spring/early summer spawning season described for other populations of European amphioxus. Amphioxus adults kept in captivity maintained the spawning seasonality of their place of origin, suggesting the possibility of extending the overall spawning season of European amphioxus in laboratory settings by exploiting populations from diverse geographic origins. This study thus expands our understanding of B. lanceolatum ecology and reproduction in the Mediterranean Sea, emphasizing the role of the North Adriatic Sea as a substantial reservoir.

Recycling of contaminated waste glass in ultra-high performance concrete: Impurities impact

The feasibility of recycling clean waste glass in construction products has been demonstrated. However, the direct utilization of contaminated waste glass from consumed beverage glass bottles may negatively affect the performance of concrete. This study aimed to investigate the effect of impurities in waste glass on the properties of ultra-high-performance concrete (UHPC). Washed and unwashed waste glass powder and sand were used as cement and river sand substitutes, respectively. Light particles, clay and fine silt, organic impurities and aluminium content in waste glass were determined. The results showed that the use of washed waste glass powder (W-WGP), washed waste glass sand (W-WGS) and unwashed waste glass powder (U-WGP) had a limited negative effect on the compressive strength of UHPC. In contrast, the use of unwashed U-WGS significantly decreased the compressive strength of UHPC due to the presence of impurities (e.g., paper and metallic aluminium). However, the impurities in the unwashed waste glass could positively reduce the autogenous and drying shrinkages of UHPC. The metallic impurities reacted with an alkaline solution to generate gases, resulting in the expansion of the matrix and reduction of autogenous shrinkage at the early stage. X-ray CT and microstructural images indicated that expansion resulting from the U-WGS caused cracks in the matrix and degraded the interfacial zone between the U-WGS and the paste. However, the incorporation of waste glass did not induce any alkali-silica reaction expansion in UHPC due to its low water-cement ratio and dense structure. The UHPC prepared with 30 % U-WGP as a replacement for cement was found to achieve satisfactory performance and lower carbon emissions.

Influence of operating parameters on the silt erosion performance of bare and coated SS304 steel

Purpose The purpose of this paper is to investigate the silt erosion performance of Bare, 75%Cr2O3 + 25%Al2O3 and 85%Cr2O3 + 15Al2O3-coated SS304 under various control parameters such as rotation speed, concentration of silt and particle size of silt used for making slurry. This can provide insight for using chromia and alumina-based coatings for hydro-turbines. Design/methodology/approach Taguchi approach was used to identify the effect of three input parameters on the bare and coated alloys. L16 orthogonal array is used for determining the signal-to-noise (S/N) ratio for each process parameter. For each level of parameters taken into consideration about the erosion wear, the arithmetic mean of the S/N ratio is calculated. On the essence of the results of S/N ratios, it is possible to determine the effect of the most dominating parameters of the erosion wear. Findings Results show that the erosion increases with an increase in silt concentration (Wt.%). It has been analyzed that the rotational speed has the most significant effect followed by the particle size and concentration on erosion wear for all uncoated and coated SS-304 samples. Maximum resistance to erosion is provided by 85%Cr2O3 + 15%Al2O3. The least erosion wear for process parameters has occurred at the optimal parametric combination of rotational speed (N) = 415 rev/min, concentration (C) = 15 Wt.% and particle size range as <53 µm for uncoated and coated stainless steel. Originality/value The study clearly shows the silt erosion performance of chromia and alumina coatings of different compositions at different input parameters. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0028/

The limited effect of deforestation on stabilized subsoil organic carbon in a subtropical catchment

Abstract. Predicting the quantity of soil organic carbon (SOC) requires understanding how different factors control the amount of SOC. Land use has a major influence on the function of the soil as a carbon sink, as shown by substantial organic carbon (OC) losses from the soil upon deforestation. However, predicting the degree to which land use change affects the OC content in soils and the depth down to which this occurs requires context-specific information related to, for example, climate, geochemistry, and land use history. In this study, 266 samples from forests and agricultural fields were collected from 94 soil profiles down to 300 cm depth in a subtropical region (Arvorezinha, southern Brazil) to study the impact of land use on the amount of stabilized OC along the soil profile. We found that the stabilized OC content was not affected by land use below a depth of 90 cm. Along the soil profile, the amount of stabilized OC was predominantly controlled by land use and depth in addition to the silt and clay content and aluminium ion concentrations. Below 100 cm, none of the soil profiles reached a concentration of stabilized OC above 50 % of the stabilized OC saturation point (i.e. the maximum OC concentration that can physically be stabilized in these soils). Based on these results, we argue that it is unlikely that deeper soil layers can serve as an OC sink over a timescale relevant to global climate change due to the limited OC input in these deeper layers. Furthermore, we found that the soil weathering degree was not a relevant control on the amount of stabilized OC in our profiles because of the high weathering degree of the studied soils. It is therefore suggested that, while the soil weathering degree might be an effective controlling factor of OC stabilization over a large spatial scale, it is not an informative measure for this process at regional and local scales (with similar climate, bedrock, and weathering history) in highly weathered soils.

Assessment of Deposited Red Clay Soil in Kirkuk City Using Remote Sensing Data and GIS Techniques

This study investigates the physical characteristics of red clay using the IDW approach and linear regression modeling in an area of 268.12 km2, focusing on Kirkuk, Bor, and Jambor structures. Through the analysis of 52 soil samples and the integration of laboratory data with IDW and regression results, several significant findings have emerged. The IDW method combined with linear regression proves to be a cost-effective and efficient approach for obtaining soil property data and generating accurate digital maps of red clay’s physical features. The Silt concentration exhibits a wide range, while the gravel content remains relatively low, indicating the predominance of silt in the soil composition. Analysis of Atterberg limits reveals the soil’s behavior and consistency in response to moisture, with the plasticity index generally falling within the low to medium range due to the considerable silt content in most soil samples. The linear regression model highlights positive correlations between the liquid limit, plastic limit, and plasticity index. Moderately positive relationships exist between the liquid limit and clay content, as well as a weak positive association between the liquid limit and specific gravity. Dry density, on the other hand, shows no significant correlation with other physical variables, suggesting its independence from the measured parameters. The plastic limit demonstrates a stronger relationship with the clay content compared to the liquid limit. Additionally, weak positive correlations are found between the liquid limit, plastic limit, and specific gravity and water content, indicating the influence of moisture on these parameters. Furthermore, gravel exhibits a moderate positive correlation with sand and silt concentrations, while a strong positive correlation is observed between sand and silt contents, underscoring their close association with the soil composition.

Fire-Induced Changes in Soil Properties and Bacterial Communities in Rotational Shifting Cultivation Fields in Northern Thailand.

Fire is a common practice in rotational shifting cultivation (RSC), but little is known about the dynamics of bacterial populations and the impact of fire disturbance in northern Thailand. To fill the research gap, this study aims to investigate the dynamics of soil bacterial communities and examine how the soil's physicochemical properties influence the bacterial communities in RSC fields over a period of one year following a fire. Surface soil samples (0-2 cm depth) were collected from sites with 6 (RSC-6Y) and 12 (RSC-12Y) years of fallow in Chiang Mai Province, northern Thailand at six different time points: before burning, 5 min after burning (summer), 3 months after burning (rainy season), 6 months after burning (rainy season), 9 months after burning (winter), and 12 months after burning (summer). The results revealed a reduction in the soil bacterial communities' diversity and an increase in soil nutrient levels immediately after the fire. The fire significantly influenced the abundance of Firmicutes, Proteobacteria, Acidobacteria, and Planctomycetes, but not that of Actinobacteria. At the genus level, Bacillus, Conexibacter, and Chthoniobacter showed increased abundance following the fire. During the rainy season, a recovery in the abundance of the soil bacterial communities was observed, although soil nutrient availability declined. Soil physicochemical properties such as pH, organic matter, organic carbon, electrical conductivity, cation exchange capacity, nitrate-nitrogen, available phosphorus, exchangeable potassium, total nitrogen, bulk density, sand, and silt contents significantly influenced the composition of bacterial communities. Alpha diversity indices indicated a decrease in diversity immediately after burning, followed by an increase from the early rainy season until the summer season, indicating that seasonal variation affected the composition of the soil bacterial communities. After one year of burning, an increase in bacterial richness was observed, while the diversity of the bacterial communities reverted to pre-burning levels.

Potential toxic elements distribution and phytoextraction status of Avicennia marina in eastern coast of Sri Lanka

This research sought to evaluate the phytoextraction capability of Avicennia marina plants for potentially toxic elements (Cr, Ni, Co, Cu, As, Cd and Pb) in Batticaloa and Uppar lagoons along the east coast of Sri Lanka, thereby investigating its potential application in ecological restoration and coastal management. An experiment was conducted to identify the elemental concentration in roots above and below water level, stem and leaves of well grown Aicennia marina plants and sediment samples obtained along a transect from the plant to the deeper levels of the lagoon in six selected locations. The grain size distribution of sediments and organic geochemical proxies of sediments and plants were correlated with elemental distributions to identify their effect on the mobility. The average clay and silt contents of these lagoons are <1.03% with high contents of fine to medium size sands (about 66%). The pollution load indices (PLI) for both lagoons are low to moderate, however, Ni concentration exceeds Effect Range-median limit for some locations. The ecological risk indices and toxicity response of the sediments are in low risk levels may be due to the low development state of the region and sedimentary distributions. The elemental concentration in roots are high for Cr, Ni, Co, Cu and As compared to the stem and leaves of Avicennia marina whereas, Cd and Pb shows high values in stem parts regardless of the C/S and C/N ratios. The average bio concentration factor for Cr, As, Co, Ni, Cu, Pb and Cd are 31.77, 19.98, 17.33, 15.38, 4.57, 3.53 and 2.77 respectively indicating significant values compared to the most other studies which might be controlled by the climate.

Experimental Study on the Effect of Fine-Grained Soil Content on the Freezing Strength of Aeolian Sand-Cement Interface

In cold regions, understanding the freezing strength of the interface between soil and structure is crucial for designing frost-resistant foundations. To investigate how the content of cement powder in aeolian sand affects this strength, we conducted direct shear tests under various conditions such as different fine-grained soil content, normal stress, and initial moisture content of the soil. By analyzing parameters like soil properties, and volume of ice content, and using the Mohr-Coulomb strength theory to define interface strength, we aimed to indirectly measure the cementation strength of the interface. Our findings revealed that as the particle content increased, the interface stress-strain curves became noticeably stiffer. We also observed a positive linear relationship between freezing strength and silt content, while the initial moisture content of the soil did not significantly impact the strengthening effect of fine-grained soil on freezing strength. Moreover, we discovered that as the powder content increased, the force binding the ice to the interface decreased, while the friction angle at the interface increased. However, the cohesion force at the interface remained relatively unchanged. Overall, our analysis suggests that the increase in freezing strength due to fine-grained soil content is primarily due to the heightened friction between aeolian sand and the interface.

Ecological risk and spatial distribution, sources of heavy metals in typical purple soils, southwest China

The identification and quantification of the ecological risks, sources and distribution of heavy metals in purple soils are essential for regional pollution control and management. In this study, geo-accumulation index (Igeo), enrichment factor (EF), pollution index (PI), potential ecological risk index (RI), principal component analysis (PCA) model and geographical detector (GD) were combined to evaluate the status, ecological risk, and sources of heavy metals (HMs) in soils from a typical purple soil areas of Sichuan province. The results showed that the average contents of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in purple soil were 7.77, 0.19, 69.5, 27.9, 0.077, 30.9, 26.5 mg/kg and 76.8 mg/kg, and the Igeo, EF and RI of topsoil Hg and Cd in designated area was the highest, and the average contents of Hg and Cd in topsoil were obviously greater than respective soil background value in Sichuan province and purple soil. The hot spots for the spatial distribution of 8 HMs were mainly focused in the southwest and northeast of the designated area, and there were also significant differences for 8 HMs distribution characteristics in the profile soil. Cu comes from both anthropogenic and natural sources, Zn, Ni and Cr mainly come from natural sources, but As, Pb, Hg and Cd mainly derived from human activities. GD results showed that soil texture (X18), altitude (X4), total nitrogen (TN), clay content (X3), sand content (X2) and silt content (X1) had the greatest explanatory power to 8 HMs spatial differentiation.This study provides a reference for understanding the status and influencing factors of HM pollution in typical purple soil, and lays a theoretical foundation for the environmental treatment of purple soil in China.

Assessment of Soil Particle Distribution, Primary Nutrient Status and Their Response to Environmental Factors Across the Bengal Gram Productive Regions of Sangareddy, Telangana

The present study was carried out to know the fertility status of rabi grown bengal gram soils of Sanga Reddy district, Telangana state by thorough field survey during the year 2022-2023. Total of 150 soil samples (50 samples from each productivity regions) from soil surface (0 - 15 cm depth) across three productivity regions high (592-613 kg acre-1), medium (571-592 kg/acre) and low (&lt;571 kg acre-1) were collected from the study area before sowing of the crop and analyzed for the soil particle size distribution, available Nitrogen(N), Phosphorous(P) and Potassium(K). Their status was quantified and analytical data was interpreted and statistical parameters like range, mean, standard deviation and coefficient of variation were calculated. The sand, silt and clay content in high, medium and low productivity regions averaged 32.1 %, 26.7%, 41.1 %; 33.7 %, 26.1 %, 40.1 % and 37.4 %, 25.1 %, 37.2 % respectively. The soil available N, P and K showed mean values of 224.3 kg ha-1, 209.4 kg ha-1 and 204.0 kg ha-1; 32.0 kg ha-1, 28.4 kg ha-1, 24.8 kg ha-1 and 316.4 kg ha-1, 311.0 kg ha-1, 306.1 kg ha-1 in high, medium and low productivity regions. Low productivity areas had the largest mean sand concentration, which influenced soil particle aggregation. Silt content varied greatly, particularly in medium and low productivity zones, whereas clay content varied the most in high productivity regions. Available N decreased from high to medium and medium to low production areas. Fluctuations in available P and K showed a wide distribution within each category, as evidenced by large standard deviation and coefficient of variation values across productivity regions, particularly for potassium, emphasising the importance of considering diverse soil conditions and factors influencing potassium availability when developing fertilisation strategies.

Millennial to orbital scale Indian summer monsoon evolution inferred from grain size end-members in Tengchongbeihai wetland, southwestern China

Understanding the Indian summer monsoon (ISM) variabilities under different climatic constraints on various timescales is crucial for socio-economic stabilization within the ongoing warming globe. However, aside from stalagmite records, very few terrestrial paleoclimate archives have been used to explore the last glacial ISM characteristic, which limits our understanding of the ISM natural behaviors and their underlying mechanisms on longer timescales. Here, we present a grain size end-member analysis for Tengchongbeihai wetland sediments from southwestern China to investigate the paleo-hydroclimate changes since the late MIS3. The overall low fine silt content before ∼19 cal ka BP resulted from weak catchment erosion indicating weak ISM during cold glacial while the increasing trend thereafter indicates the ISM strengthened during the last deglaciation and Holocene. Such an orbital ISM evolution resembles to the insolation gradient between 25°N and 25°S during the boreal summer periods, which implies that the transequatorial insolation difference could be an alternative explanation for the orbital scale low latitude hydroclimate changes. The remarkable peaks of coarse component around ∼9, 12, 19, 26, 32, 37 and 42 cal ka BP were related to significant water level descending indicating the millennial ISM collapse corresponding to the YD and Heinrich events. However, the absence of sawtooth feature as the NGRIP δ18O and the well correspondence to the Indian Ocean sea surface temperatures (SSTs) of the ISM collapses evidence the modulation of low latitude forcing on the North Atlantic climate effects on the millennial scale hydroclimate variabilities.

Assessing Soil Prediction Distributions for Forest Management Using Digital Soil Mapping

Texture, soil organic matter (SOM), and soil depth (SoD) are crucial properties in forest management because they can supply spatial information on forest site productivity and guide fertilizer applications. However, soil properties possess an inherent uncertainty that must be mapped to enhance decision making in management applications. Most digital soil mapping predictions primarily concentrate on the mean of the distribution, often neglecting the estimation of local uncertainty in soil properties. Additionally, there is a noticeable scarcity of practical soil examples to demonstrate the prediction uncertainty for the benefit of forest managers. In this study, following a digital soil mapping (DSM) approach, a Quantile Regression Forest (QRF) model was developed to generate high-resolution maps and their uncertainty regarding the texture, SoD, and SOM, which were expressed as standard deviation (Sd) values. The results showed that the SOM (R2 = 0.61, RMSE = 2.03% and with an average Sd = 50%), SoD (R2 = 0.74 and RMSE = 19.4 cm), clay (R2 = 0.63, RMSE = 10.5% and average Sd = 29%), silt (R2 = 0.59, RMSE = 6.26% and average Sd = 33%), and sand content (R2 = 0.55, RMSE = 9.49% and average Sd = 35%) were accurately estimated for forest plantations in central south Chile. A practical demonstration of precision fertilizer application, utilizing the predictive distribution of SOM, effectively showcased how uncertainty in soil attributes can be leveraged to benefit forest managers. This approach holds potential for optimizing resource allocation and maximizing economic benefits.

1 g shake table study on seismic strengthening of low-cost rammed earthen houses built of silt enriched soil using natural fiber reinforcement

Earthen houses are practiced as a traditional and low-cost housing in many countries around the globe. These houses were exposed to unacceptable earthquake (EQ) risks despite their environmental benefits. Past earthquakes including the recent past 2017 Tripura EQ has evidenced significant damages mostly in earthen/masonry houses which are built in a non-engineered manner. In this context, the current study aims to investigate the seismic behavior and failure patterns of both unreinforced and using proposed retrofitted rammed earth model houses (with and without openings) built using typical Tripura soils having higher silt content using unidirectional shake table experiments on total 26 physical models. Besides, both seismic strength and structural stability are also examined for retrofitted earthen houses. The study indicates that, proposed novel low-cost natural fiber made textile encasing reinforcement technique has exhibited promising seismic performance of such houses from the view point of structural strength and ductile behavior as compared to traditional cementitious additives and fiber blended stabilized retrofitted houses as well untreated houses. The fundamental lateral period of model unreinforced and reinforced houses found within the range of 0.08 to 0.15 s respectively which indicates increased stiffness of walls due to strengthening may decrease the lateral period maximum up to 46.67%. On the other hand, the maximum increase in seismic strength was observed in order of 4.50 to 6.31 times in the case of bitumen treated bamboo fiber textile based encased houses with L-shaped bamboo splint corner reinforcement whereas traditional cementitious stabilized method has offered maximum 1.13 to 1.83 times increment in lateral strength. Further, the effect of different parametric variations such as area of openings (doors and windows), thickness to height ratio, variation in compaction methodologies on seismic performances of unreinforced rammed earthen houses were also studied in detail. Finally, regression based closed form predictive expressions for seismic strength of rammed earthen houses and without retrofitting are proposed herein. The performed cost analysis study will also help to assess the effectiveness of proposed strengthening techniques.

Vegetation degradation alters soil physicochemical properties and potentially affects ecosystem services in green spaces of a tropical megacity (Lubumbashi, DR Congo)

Urban soils are degraded by various human pressures, including vegetation degradation, leading to changes in physical and chemical characteristics and affecting important ecosystem services. Soil physical properties are an important fertility control parameter, providing the basis for sustainable soil use in urban conditions; however, they do not receive sufficient attention in work on tropical cities. We assessed the impact of vegetation degradation in six urban green spaces (bare soils versus vegetated soils) on the physical (texture, soil bulk density and structure) and chemical (pH, cation exchange capacity (CEC), organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K), copper (Cu) and manganese (Mn)) qualities of soils in a tropical megacity (Lubumbashi, DR Congo). Vegetated soils presented better physical and chemical qualities than bare soils. Vegetated soils were characterized by a high clay and silt content and a good consistency (soil structure), while bare soils were characterized by a high sand content and high bulk density. Vegetated soils were characterized by higher pH, OC, N, C/N ratio, CEC, P, and K. There was no significant difference in Mn or Cu between bare and vegetated soils. Cu was highly variable between sites (from 99 ± 61 mg.kg−1 in VS to 8559 ± 151 mg.kg−1 in BS). Our results demonstrate that the destruction of vegetation, leading to bare soil, negatively affects soil properties and may interfere with ecosystem services provided by urban soils in tropical climates. The physical properties observed in bare soils in this study, including silt, clay, and sand content, soil structure, and soil bulk density, along with chemical properties such as soil pH, cation exchange capacity, and soil organic carbon, can influence the ecosystem services provided by urban soils. These services include regulating water flow and nutrient cycling, enhancing nutrient availability, and supporting ecosystem functions through the cycling of water and nutrients.

Knowledge, Ability and Motivation for the Practice of Checking Mud Content in Sand on Learning Outcomes of Concrete Specifications and Characteristics

Sand mining in the area around Sumber Ringin Village, Sri Gading Village, Jati Dukuh Village and around the coast of the Rantas River is a blessing for the people around Mojokerto City and Regency. Mining activities in this area cannot be separated from the attention of many parties and the community, so researchers want to know how much silt content is in the sand and apply it to the basic competencies of concrete specifications and characteristics. This study aims to determine the knowledge, abilities and learning motivation of students in carrying out the practice of silt content in sand on the learning outcomes of basic competency specifications and characteristics of concrete. including research ex post facto. The research design used path analysis. The prerequisite test used is the homogeneity of the F test and the normality test of the Chi Square distribution. Instrument validation was analyzed using the Rasch Model. The research was conducted in class X Modeling Design and Building Information (DPIB) for State Vocational High School (SMK) 1 Mojokerto with a total of 100 students. The results of the research: (1) there is an effect of knowledge on learning outcomes, (2) there is an effect of ability on learning outcomes, (3) there is an effect of knowledge on student learning motivation, (4) there is an influence of ability on student learning motivation, (5) there is an effect of student learning motivation on learning outcomes, (6) there is an influence of knowledge on learning outcomes through learning motivation, (7) there is an effect of ability on learning outcomes through learning motivation.