Soil Particle Size Distribution Research Articles

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 (<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.

Multifractal characteristics of soil particle size distribution of abandoned homestead reclamation under different forest management modes

In this study, fast-growing poplar reclaimed from abandoned homestead in Xixian New District, Xi’an City, Shaanxi Province, was used as the research object to explore the multi-fractal characteristics of soil particle size distribution under different management modes of abandoned land (control), irrigation, fertilizer irrigation and mixed fertilizer irrigation. The results showed that the mean values of soil clay, silt and sand in abandoned land were 14.58%, 81.21% and 4.22% respectively, 14.08%, 79.92% and 5.99% under irrigation, 15.17%, 81.19% and 3.64% under fertilizer irrigation, and 16.75%, 80.20% and 3.05% in mixed fertilizer treatment. From 40 cm, with increasing soil depth, soil clay particles increase under irrigation, fertilizer irrigation, and mixed fertilizer irrigation modes. The single fractal dimension of soil particle size distribution (D) in each treatment ranges from 2.721 to 2.808. At 60–100 cm, D shows fertilizer irrigation > mixed fertilizer irrigation > irrigation > abandoned land, indicating that fertilization and irrigation can increase the fine-grained matter of deep soil particles and reduce soil roughness. Compared with abandoned land, under irrigation, fertilizer irrigation and mixed fertilizer modes the capacity dimension (D0), entropy dimension (D1), correlation dimension(D2), shape characteristics of the multifractal spectrum (Δf) and overall inhomogeneity of the soil particle size distribution (D0–D10) indicate an uneven distribution of soil particle size; fractal structure characteristics of soil (D−10–D0) indicate a simplified soil structure, and degree of dispersion of soil particle size distribution (D1/D0) indicates that soil particle size is distributed in dense areas. Pearson correlation analysis showed that D was significantly correlated with clay, sand, D0–D10, soil organic matter (SOM) and soil available phosphorus (SAP) (P < 0.05). Stepwise regression analysis showed that clay was the main controlling factor of D and D0–D10 changes. The research results can provide some potential indicators for the quality evaluation of abandoned homestead reclamation.

Experimental study on the interface characteristics of geogrid-reinforced gravelly soil based on pull-out tests

The factors influencing geogrid–soil interface characteristics are critical design parameters in some geotechnical designs. This study describes pull-out tests performed on gravelly soils commonly encountered in the Xinjiang region and reinforced with two types of geogrids. The factors affecting the geogrid–gravelly soil interface properties are investigated with different experimental loading methods (pull-out velocity, normal stress), geogrid types, and soil particle size distributions and water contents. The ultimate pull-out force increases with the normal stress and pull-out velocity. Furthermore, with increasing coarse particle content and water content, the ultimate pull-out force increases and then decreases sharply. Based on these research results, this paper provides reasonable parameters and recommendations for the design and pull-out testing of reinforced soil in engineering structures. In reinforced soil structure design, the grid depth should be increased appropriately, and the coarse particle content of the overlying soil should be between 30 and 40%. During construction, the gravelly soil should be compacted to the maximum compaction at the optimal water content, and the structure should have a reasonable waterproofing system. According to the calculation results of the interface strength parameters, the uniaxial geogrid–gravelly soil interface has a high cohesive force csg, which should not be ignored in reinforced soil structure design.

Assessment of Saturated Hydraulic Conductivity with Using Soil Particle Size Distribution: A Comparative Study of Constant Head and Falling Head Methods

&lt;p&gt;The purpose of soil hydraulic conductivity is to retain soil water contents, and soil water pressure. In this study investigates two different methods to understand the soil hydraulic conductivity of loam and clay soils. The present research conducted a laboratory experiment to measure the saturated hydraulic conductivity (Ksat) using two different methods: the constant head and falling head methods. The constant head method utilized a soil column with a length of 8.5 cm, and three soil columns were occupied with various soil texture classes (%). The study results demonstrate that the classification of soil texture was predominantly sandy loam with porosity varying between 35%, 43%, and 50% within the clay soil category. Furthermore, the average value of Ksat for the soil samples using the constant head method was 0.00142 cm/sec, while the falling head method provides average values of 0.00123, 0.00172, and 0.00144 for sandy loam and 0.0000146 cm/sec for clay soil. It is concluded that the falling head method indicates greater accuracy, particularly evident in the concurrent analysis of three samples. This study suggested that determination of Ksat through laboratory method is suitable due to cost effectiveness and simplicity.&lt;/p&gt;&#x0D;

Effects of hillslope aspect on erosion rate of alpine meadows in the Three-River Headwater Region, China

Soil erosion causes serious grassland degradation in the Three-River Headwater Region (TRHR) of the Qinghai-Tibet Plateau. Identifying source areas of erosion is important, including understanding the influences of hillslope aspect on soil erosion. However, the effect of hillslope aspect on soil erosion is a much-debated process, wherein contrasting results were previously reported. We hypothesized that aspect-induced differences in environmental variables will be related to differences in erosion magnitude and spatial pattern, and that these differences will impact soil physiochemical characteristics as well. To test this hypothesis, soil samples were collected at conjoined south- and north-facing hillslopes along elevational profiles in a small watershed in Yushu County, with measurements of soil water content (SWC), soil organic carbon (SOC), soil organic matter (SOM), soil particle size distribution, soil total nitrogen (STN) and phosphorus (STP). Soil erosion rate was estimated using 137Cs technology. The results showed that soil erosion rates of the two hillslopes ranged from 0.073 to 10.83 t ha-1 yr-1, and were 3 times greater on the south-facing hillslope. Soil water content ranged from 7.6% to 76.8% on the two hillslopes with lower values on the south-facing hillslope due to the greater solar radiation. By Spearman correlation analysis and path analysis, we concluded that lower soil water content on the south-facing hillslope restricts vegetation growth, and hence resulting in greater soil erosion under the case where vegetation growth is dominantly controlled by water availability. Greater soil erosion on the south-facing hillslope caused greater surficial accumulation of coarser materials and greater loss of soil nutrients, which are expected to complicate the hydrological erosion process. Moreover, the downslope increased soil erosion rate should be fully considered in conservation practices. These results will improve our understanding of the interaction and feedback mechanisms between soil characteristics, vegetation function, and soil erosion in the TRHR.

Sediment sorting and transport mechanism controlled by both soil properties and hydraulic parameters on hillslopes

Understanding the sediment sorting and transport processes is is crucial for enhancing the understanding of soil erosion mechanisms and improving soil erosion prediction. However, quantitative studies based on the coupling effects of both hydraulic parameters and soil properties are still lacking. In this study, five loessial soils with varying physicochemical properties were collected in the Loess Plateau of China, and simulated rainfall experiments were carried out in a metal box with a slope of 20 degrees under rainfall intensities of 1, 1.5, and 2 mm min−1. Runoff samples were collected to analyze the variation in erosion rates and effective particle size distribution of eroded sediments during the rainfall process. The results showed that the stream power was the optimal parameter to model the erosion rate, and a power function incorporating the clay content and stream power could well predict the erosion rate of different soils. The enrichment ratio indicated the enrichment of fine particles and depletion of coarse particles. And the sediment sorting degree increased with increasing soil clay content. The critical particle size for distinguishing different transport mechanisms varied among soils, with more than 55.46 % of the total sediment transported by suspension/saltation. A linear function and power function including the original soil particle size distribution and stream power were developed to quantify the sediment clay content and the relative contribution of different transport mechanisms. This study could be helpful to improve the soil erosion prediction model and provide basic guidelines for regional soil and water conservation.

Statistical Evaluation of Sleeve Friction to Cone Resistance Ratio in Coarse-Grained Soils

The investigation of soil is a particularly important stage of structural design. Cone penetration tests (CPTs) are the most common soil investigation techniques. The results of these tests provide information about the values of cone resistance (qc) and sleeve friction (fs), which correspond to depth. Previous studies have shown that the ratio of sleeve friction to cone resistance depends on the particle size distribution in soil and its use for soil classification. Unfortunately, as an analysis of the literature shows, there is no such classification for coarse-grained soils. This paper presents statistically significant differences in the ratio of fs to qc in coarse-grained soils. Based on the research performed, the proposed coefficients depend on the classification of coarse-grained soils with respect to the size of the soil particles. The data investigated were obtained from study reports on 35 sites (5934 tests) at which the main type of soil was coarse-grained and contained different sizes of particles. Following a statistical analysis, five groups of tested coarse-grained soils, silty fine sand, clayey fine sand, fine sand, medium sand and gravelly coarse sand together with gravel, are derived. The analysed data show statistically significant differences in the ratio of fs to qc considering this particular type of soil. A ratio of fs to qc with a probability of 95% is proposed for sandy soils. The values for silty fine sand, clayey fine sand, fine sand, medium sand and gravelly coarse sand mixed with gravel are 0.009459, 0.010982, 0.009268, 0.008001 and 0.006741, respectively. A linear relationship between the fs and qc indexes is also suggested.

Can the shrink-swell index be predicted in the Wagga Wagga region based on Atterberg limits?

Relationships between the shrink-swell index and other clay tests, such as Atterberg limits have been investigated by others however, there is not any available information for the Wagga Wagga region in NSW Australia. This study’s objective is to establish some relationships between the shrink-swell index and Atterberg limits of the soils in the Wagga Wagga region. A total of 27 samples at different locations and depths was tested for shrink-swell index, linear shrinkage, liquid limit, plastic limit, plasticity index and soil particle size distribution, using Australian Standard test methods. The results and data analysis indicated that shrink-swell index correlated with Atterberg limits. The shrink-swell index can be estimated based on a single Atterberg limit test or the combination of linear shrinkage + liquid limit and linear shrinkage + plasticity index. In conclusion, linear shrinkage and liquid limit are the reasonable prediction factors for the estimation of shrink-swell index for the soils in the Wagga Wagga region.

Prediction of hysteretic soil and water characteristic curve of loess based on multifractal theory and improved physical statistics

Soil and water characteristic curve (SWCC) is an important soil parameter which is used to estimate various parameters to describe unsaturated soil hydrodynamic properties. Due to the large span of soil matric suction, this procedure is time-consuming and difficult to measure it in the laboratory. However it is of great significance to find a scientifically efficient and economically viable method to predict SWCC of loess soil. Based on the measurement of soil–water characteristic curves in the laboratory, this study predicted the drying curve (DC) based on the soil particle size distribution (PSD) fractal theory. It also used the domain model to predict the wetting curve (WC) based on the pore distribution, and finally obtained the complete soil–water characteristic curve of loess. These procedures improved the research status which using the drying curve to instead of the wetting curve, and this replace usually leads to a large calculation error and underestimates the safety of the slope. The method proposed in this study can quickly obtain the hysteretic soil–water characteristic curve of loess based on only the soil particle size distribution, improve the correlative calculation accuracy of unsaturated loess, and play an important role in predicting the hydraulic parameters of loess soil.

Sediment imaging and factorized Haar wavelet transformation techniques for characterizing particle size distributions of granular soils

The particle size distribution (PSD) significantly influences various mechanical behaviors of granular soils. Advances in automation and camera technology allow for a rapid, green, and accurate PSD determination. This study develops a new sediment imaging system, mainly consisting of a sediment column filled with water and a line-scan camera driven by programmable logic controller, which can automatically capture high-resolution soil segregation images. The soil particles settle through the sediment column and segregate by size, which is scanned to generate sediment images. Naturally, the coarsest particles settle at the bottom of the image, while the finest particles are located at the top. Therefore, the analysis of the sediment image enables the determination of PSD. The higher sediment column, despite of poor operationality, yields better particle segregation quality and thus the more accurate PSD result. This study proposed a factorized Haar wavelet transformation (FHWT) algorithm that can account for less perfect segregation of particles by size, enabling to shorten the height of sediment column. The proposed hardware and FHWT are evaluated by six natural sands with different colors, internal textures, and geological origins. An excellent match between image-based PSDs and sieving-based PSDs are observed. Based on FHWT, four sediment columns with different heights of 2.1 m, 1.5 m, 1.0 m, 0.5 m are tested. The results indicate that columns higher than 1.0 m yield acceptable particle segregation results. Furthermore, the proposed FHWT is also adaptable to process high-resolution images captured by advanced cameras.

Fractal characterization of soil particle size distribution under different land use patterns on the north slope of Wula Mountain in China

Fractal characterization of soil particle size distribution under different land use patterns on the north slope of Wula Mountain in China

Tillage and Cover Crop Systems Alter Soil Particle Size Distribution in Raised-Bed-and-Furrow Row-Crop Agroecosystems

Conservation alternatives that include no-tillage (NT) and cover crops (CCs) reduce soil erosion in row-crop agroecosystems. However, little information is available about how these alternatives affect soil textural properties responsible for soil fertility. This study evaluated the soil particle size distribution and volumetric water content after three years of consistent management in a raised bed system. There were four treatment systems in a dryland maize/soybean rotation on a silt loam soil (Oxyaquic Fraglossudalfs) that included: NT + CCs, conventional tillage (CT) + CCs, CT + winter weeds, and CT + bare soil in winter in northwest Mississippi. The NT + CC system retained 62% more coarse sand in the furrow than the other systems (2.1% compared to 1.3%; p = 0.02). Regardless of the location, the NT + CC system (2.5%) retained 39% more fine sand than the CT + CC system (1.8%; p = 0.01), suggesting that coarse and fine sands were being trapped in furrows combining NT + CC systems, minimizing their off-site transport. In furrows, CCs increased soil volumetric water content by 47% compared to other winter covers. In beds, NT + CCs increased bed water contents by 20% compared to CT + CCs (17.1 to 14.3%; p &lt; 0.01). Implementing conservation alternatives may promote the retention of sand fractions in silty loam soils that are important in supporting soil fertility and crop sustainability.

Importance of geotechnical soil properties for precision Forest activities in a karst area

Some soil behaviors change significantly as water content varies over time. The particle size distribution of soils has a direct impact on mechanical properties such as soil water content, resistance to dispersion, swelling-shrinkage, fluidity, plasticity, and stickiness. This study was conducted to investigate the usability of Atterberg limits, consistency index and coefficient of linear extensibility (COLE) in the temporal planning of ecosystem restoration activities such as silvicultural interventions, tillage, afforestation, and the construction of forest roads, etc. Surface soil samples were collected from the sections numbered 263, 264, 266, 268, 317, 318, 319, 323, 324,325 and 366 of the degraded forest of the Andırın forestry operations department. The COLE, liquid limit (LL), plastic limit (PL), plasticity index and consistency index values of soil samples were determined. The LL values ranged from 17.5 to 62.4%, the PL values from 8.2 to 46.8% and the PI values from 6.4 to 15.5. The highest COLE value (0.13) was recorded in the section 318, while the lowest COLE value (0.03) was in section 325.The LL and PL values have a positive linear relationship with clay and organic matter content. All sections have karstic characteristics, but the mechanical characteristics of the soils differ significantly between the sections. Silvicultural interventions carried out especially in section 318, which had the lowest consistency index (Ic = 0.70), and sections 263, 264, 317 and 319, where the consistency index is >2,should take mechanical properties into account, and the planting time intervals should be determined, accordingly for sustainable forestry.

Adhesion theory and model for air humidity impact on dust emission

It has been suggested that air humidity influences dust emission under very dry conditions and adhesion might be the responsible process which changes the binding between soil particles. The process of adhesion is so far poorly understood and difficult to quantify. Here, a critical examination of the relevant studies is provided, and an adhesion model is proposed. Both isothermal-kinematic and diffusion processes can limit the soil liquid–water and water–vapor exchange in soil, but for the particle size range concerned in aeolian studies, diffusion appears to be the limiting process. The model shows that soil moisture in the topsoil layers is positively correlated with air humidity, but with delays of several hours. The model performance is influenced by several parameters but is particularly sensitive to the equilibrium soil water–vapor content. This implies that soil microscopic properties can strongly influence adhesion. A new formulation of soil water retention function covering the entire soil moisture range is also proposed, which links soil water retention function and pore size distribution. Using a relationship between soil particle-size and pore-size distributions, an adhesion-affected grain size can be estimated, which defines the upper size limit of soil particles influenced by soil moisture. This study explains how air humidity influences soil moisture through adhesion and dust emission and why low air humidity promotes the emission of finer dust particles.

WET SEPARATION OF PALM KERNEL AND SHELL MIXTURE USING LATERITE AND ANTHILL SLURRY.

Palm kernel, one of the end products of oil palm fruits processing is recovered by cracking of the palm nuts which is first dried to aid efficient kernel recovery. The possibility of separating oil palm kernel and shell mixture using media other than kaolin in wet separation was investigated in this study. The separation efficiency of laterite was compared with that of anthill. The effect of media type, pH, specific gravity, slurry viscosity on the efficiency of separation were investigated. The media/water percentages of 0, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80% w/v were prepared in bowls for each media at a time and used to separate the cracked nut (palm kernel and shell mixture). The soil particle size distribution showed that laterite contains 40.3% clay while anthill contains 20.3%. The laterite and anthill slurry shows that the specific gravity and the viscosity increases with increase in media percentage while the pH decreases. Optimum kernel recovery percentages (%Kr) of 99.3 and 99.6% was observed at 30 and 35% ratio respectively for laterite and %Kr of 98.9 and 98.4% at 45 and 50% ratio for the anthill slurry. Among the media used, laterite was found to be comparable to clay at a medium-to-water percentages of 30 and 35% giving optimum efficiency. Thus, it is recommended laterite can be used for wet separation when compared to anthill.

A new algorithmic approach for predicting the particle size distribution of dispersed soil suspensions using an automated optical settling column

Analyzing a large number of samples for their dispersive properties and particle size distribution (PSD) is often cumbersome and time-consuming, particularly when using traditional hydrometer or pipette-based methods. In this study, we analyzed the efficacy and rapidity of an automated, optical settling column (OSC) to measure the PSD of soils. The OSC provided backscattering and transmission intensity profiles at preprogrammed time intervals that illustrated sedimentation/flocculation processes of suspended particles, making the approach desirable for soil dispersion studies. Settling experiments were performed using 177 soil samples collected from 59 sampling locations across the United States. All soil samples were pretreated with sodium hexametaphosphate (HMP) to achieve maximum dispersion and analyzed with the OSC. The effects of settling run time and sampling frequency were also investigated. The results were compared with separate soil PSD data obtained using the common particle sizing analysis, the pipette method. Using feature engineering and dimensionality reduction, we created different novel methods of modeling the PSD data. Resampling was employed to compare accuracy of these novel methods by generating 300 instances of model performance for each method. We further estimated model generalization using two techniques: (i) a holdout (HO) estimation approach to suggest the “best-case” performance and (ii) an averaged model performance to provide a more conservative performance estimate. The best method studied here provided PSD values that deviated from those gathered through the pipette method by between 2.8% − 3.3% for clay, 5.7% − 9.4% for silt, and 6.5% − 9.6% for sand.

Variation in the physical properties of soil in relation to natural and anthropogenic factors in the hilly loess region of China

Soil particle size distribution (PSD), bulk density (BD), saturated hydraulic conductivity (Ks), soil water content (SWC) and generalized soil structure index (GSSI) are key physical properties for vegetation growth and are easily affected by natural and anthropogenic factors. However, how these soil physical properties respond to land use, slope aspect, slope position, and their interactions are less clearly understood. Here, an experiment with three land uses (cropland, grassland, and black locust [Robinia pseudoacacia L.] forests after 4, 9, 15, and 19 years of restoration), two slope aspects (south and north slope) and two slope positions (up and down slope) were conducted in the hilly loess region of China. The results showed the following: (1) The variation in different physical properties were driven by different factors of land use, slope aspect, slope position and their interactions. (2) The 9, 15 and 19 year old locust forests significantly decreased the BD by 6.75 %–19.32 % and increased the Ks by 69.96 %–195.97 % compared with grassland, while the cropland had higher SWC and GSSI values than the grassland and locust forests. (3) Soil physical properties were higher on the north slope than on the south slope and were larger on the down slope than on the up slope. (4) The BD, Ks, SWC, and GSSI of locust forests displayed different changes with the restoration year. (5) The key factor affecting forest growth and soil quality improvement varied with forest ages. Overall, 19 year old locust was the most effective at improving the BD and Ks. Furthermore, slope aspect, slope position and restoration time should be considered when evaluating the response of physical properties to land uses.

Point Pedotransfer Functions (PPTF) for Estimating Soil Water Retention Curve by Multiple Linear Regression Methods

The aim of this study was to derive and find the best Point Pedotransfer Functions (PPTF) for estimating SWRC for Iraqi soils using the multiple regression methods. Soil samples were collected from 30 different sites of Iraqi soil at two depths: 0-0.3 m and 0.3-0.6 m, in order to obtain the required database for the derivation of PTF, which includes the soil particle size distribution, carbonate minerals, bulk density, particles density, organic matter, saturated hydraulic conductivity, capillary height and the boundaries of available water. Measured characteristics were considered as explanatory variables (EV). Volumetric water content was measured at suctions 0, -5, -10, -33, -500, -100, -500, -1000, and -1500 kPa and considered as response variables (RV). PPTF was derived using SAS statistical software based on multiple linear regression. Three methods for fitting the PPTF to EV were Maximum R2 Improvement (MR), Backward Elimination (BW) and Forward selection (FW). The prediction accuracy was evaluated through Mean Bias Error (MBE), Mean Absolute Error (MAE), root mean squared error (RMSE) and Coefficient Of Determination (R2). The results showed that all EVs were included in the PPFT derivation by MR method, while in the BW and FW methods the significant level of entery (SLENTRY) of EV was 0.1. It was also found that variables w1, capillary height, available water, bulk density, and porosity were included in the derivation of most of the models using the BW and FW method. Besides no statistically significant differences were found among the values of MBE, MAE, RMSE, and R2 of the PPTF although the number of selected EV are different.

Fractal Characteristics of the Particle Size Distribution of Soil along an Urban–Suburban–Rural–Desert Gradient

In order to investigate the difference in particle size distribution of soil along an urban–suburban–rural–desert (USRD) gradient in an arid zone, surface soil (0–20 cm) samples were gathered at the urban, suburban, rural, and desert gradients in Urumqi, a northwestern Chinese city. Laser diffraction technology was adopted for determining the particle size distribution of the soil. Comparisons were made regarding the particle size distribution traits and soil properties in different gradient zones based on parameters such as the mean particle size (MG), fractal dimension (Dv), sorting coefficient (ơG), kurtosis (KG), and skewness (SKG). Results indicate that (1) particle size distribution in the urban, suburban, and rural soils was mainly sand particle sizes, whereas the desert soil was mainly composed of silt particle sizes. The average Dv value ranking for soil in each gradient is desert &gt; suburban &gt; urban &gt; rural. (2) The width and peak of the soil particle size frequency curve ranged within 0–500 μm, and the width and peak of the soil particle size frequency curve of each gradient were different. (3) The MG of rural soil was the highest, whereas the MG of desert soil was the lowest. The ơG values of the surface soil of each gradient were all greater than 4.0, and the sorting performance was extremely poor. The SKG of the desert and urban soil particle size showed extremely positive and negative skewness, respectively, while the SKG of the rural and suburban soil particle size showed extremely negative skewness. The KG values of the particle sizes of the rural and suburban soils exhibited narrow and medium peaks, whereas those of the urban and desert soils exhibited very broad and flat peaks. (4) The Dv of the soil in each gradient was strongly influenced by the soil particle size distribution, with the clay content of the soil playing a dominant role. Finally, the fractal dimension was identified as an indicator of the characteristics of the fine particle matter content in the soil structure. The novel contribution of this work is to clarify the fractal differences in the particle size distribution of soil along an urbanization gradient. The present research findings can offer fundamental information relating to the characteristics of soil particle size distribution along an urbanization gradient zone.

Characterizing hydrological-sensitive areas of the Kinyerezi river sub-catchments in Dar es Salaam, Tanzania using the topographic index approach

Abstract Several areas experience frequent floods due to anthropogenic activities. Among them, is the Dar es Salaam city, which experiences frequent floods along the Msimbazi River, whose flows originate from different tributaries including the Kinyerezi River. This study aims to evaluate the hydrological-sensitive areas of the Kinyerezi River sub-catchments using topographic index values (λ*) that enable the identification of areas with a higher probability of generating surface runoff. A digital elevation model was utilized to delineate the Kinyerezi River sub-catchment characteristics using ArcGIS 10.4. Soil infiltration rates (Ks) on selected open places were determined using a Guelph permeameter. Soil particle size distributions were analyzed and the λ* values were evaluated. The results showed the particle size distribution contains sand and silt-clay ranging from 46 to 84% and 16 to 53%, respectively. The Ks ranged from 0.6 to 7.8 mm/h while the sub-catchment KS3 scored the highest λ* value of about 10.7. Hence, there is a higher probability for generating surface runoff. Sub-catchment KS16 scored the smallest λ* value of 5.7, perceived to generate less surface runoff. Low-impact development practices capable of capturing runoff and enabling infiltration, evaporation, and detention should be employed in sub-catchments with higher λ* values.