Average Sediment Research Articles

Coupling of sediment transport phenomena with turbulent surface flows: mathematical modeling, finite volume approximation and test simulations

Several sediment transport models coupled with shallow water equations have been developed in the literature over the past few decades. The water flow in the presence of abrupt bottom slopes distorts and cause turbulence. This phenomenon is well-known in the sediment transport theory. Sediment transport models based on shallow water equations do not include turbulence effects or the phase-lag between water velocity and bottom velocity. In this study, we consider a one-dimensional free surface turbulent water flow with sediment and morphodynamic. We propose a new one-dimensional acceleration-dissipation mathematical sediment transport model that considers the distortion of horizontal profile velocity in transport. The model is an improved version of existing averaged sediment transport models. In the new model, there is a distinction between fluid velocity and bottom velocity through a new bedload equation. The mathematical model is a system of nonlinear hyperbolic partial differential equations that are approximated by a stable and robust finite volume scheme presented in the path-conservative framework. Numerical tests are performed to demonstrate the efficiency of the developed theory.

Predicting sediment yield and locating hotspot areas in the Hamesa watershed of Ethiopia for effective watershed management

Abstract Locating hotspots and assessing sediment accumulation are crucial aspects of water body management. The primary aim of this study was to examine sediment yield in the Hamesa watershed utilizing the Soil and Water Assessment Tool (SWAT) model and to propose best management practices. The basin was divided into 15 sub-basins, with 103 hydrological response units at the outlet of the Hamesa watershed. Simulation was conducted using meteorological and spatial data. Monthly streamflow and sediment data were calibrated for the period from 2000 to 2010 and validated for the period from 2011 to 2015 using the SWAT Uncertainty Calibration Program Sequential Uncertainty Fit (SUFI-2). Model performance was assessed using metrics including the coefficient of determination (R2), Nash–Sutcliffe model efficiency, observation standard deviation ratio, and percentage bias, which demonstrated very good results in both calibration and validation periods. The average annual sediment production in the Hamesa watershed was estimated at 9,800 t/year. Nine out of 15 affected sub-basins were categorized as producing moderate to very high sediment content (4.54–12.82 t/ha/year) and were chosen for sediment reduction scenarios. This study will play a significant role in managing impacted watersheds affected by soil erosion.

Hydro-sediment responses to management options under current and future climate change scenarios in Maybar watershed, South Wollo Zone, Ethiopia

Climate change coupled with inappropriate land use management is a serious environmental challenge in the highland part of Ethiopia. The aim of this study was to investigate hydro-sediment responses to management options under current and future climate change scenarios in Maybar watershed, Northern Ethiopia. We employed soil and water assessment tool (ArcSWAT 2012.10_7.24) for hydrologic modeling and CORDEX-climate data under RCP 4.5 and RCP 8.5 emission scenarios for climate projections. Soil map was prepared by digitizing soil characterization map of the watershed generated by Weigel in 1986. DEM data with 2 m spatial resolution was obtained from water and land resource center and land use classification was done through digitization of google earth images. Better agreement between calibrated SWAT simulation and observed variables was achieved. Delta change bias correction method was employed to improve the climate simulation in reproducing the observed climate variables. We found a considerable increase in annual precipitation by 18.71 % and 22.33 % for RCP 4.5 and RCP 8.5, respectively compared with the current climate conditions. Climate change induced hydro-sediment results were observed to be consistent with predicted precipitation. Under the current climatic conditions, average sediment yield at the sub-basin scale varies from negligible (under terrace complementation) to approximately more than 50 t ha−1 yr−1 with a basin average of 32 t ha−1 yr−1 (under no-terrace conditions). The implementation of management alternatives gets the dry season's hydrological behavior of the catchment improved and climate change induced sediment yield reduction. Generally, the information could possibly support decision makers and planners to implement best-fitted management options and thereby reduce current and expected aggressive sediment loss situations.

Responses of runoff and sediment yield to slope length and gravel content of Lou soil engineering accumulation slope in Guanzhong region, Northwest China.

With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.

The effects of local variations in conditions on carbon storage and release in the continental mantle.

Recent advances indicate that the amount of carbon released by gradual degassing from the mantle needs to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the past. Variations in rock types and oxidation state may be very local and exert strong influences on carbon storage and release mechanisms. Deep subduction may be prevented by diapirism in thick sedimentary packages, whereas carbonates in thinner sequences may be subducted. Carbonates stored in the mantle transition zone will melt when they heat up, recognized by coupled stable isotope systems (e.g. Mg, Zn, Ca). There is no single 'mantle oxygen fugacity', particularly in the thermal boundary layer (TBL) and lowermost lithosphere, where very local mixtures of rock types coexist. Carbonate-rich melts from either subduction or melting of the uppermost asthenosphere trap carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply derived, reduced melts may form further diamond reservoirs, recognized as polycrystalline diamonds associated with websteritic silicate minerals. Carbon is released by either edge-driven convection, which tears sections of the TBL and lower lithosphere down so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms operate at steps in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and turning up unexpected results that are not seen in studies of single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate for small-scale processes; an increased focus on local variations will help to refine carbon budget models.

The Influence of Current Magnitudes and Profiles on the Sedimentation of Magnetorheological Fluids: An Experimental Work

Magnetorheological fluids (MRFs) are widely used for various kinds of controllable devices since their properties can be controlled by an external magnetic field. Despite many benefits of MRFs, such as fast response time, the sedimentation arisen due to the density mismatch of the compositions between iron particles and carrier oil is still one of bottlenecks to be resolved. Many studies on the sedimentation problem of MR fluids have been carried out considering appropriate additives, nanoparticles, and several carrier oils with different densities. However, a study on the effect of current magnitudes and profiles on the sedimentation is considerably rare. Therefore, this study experimentally investigates sedimentation behaviors due to different current magnitudes and different magnitude profiles such as square and sine waves in different diameters. The evaluation was performed by visual observation to obtain the sedimentation rate. It was found that the average sedimentation rate of the square type of current is slower compared to the sinusoidal type. It has also been identified that the higher intensity of the applied current results in a stronger electromagnetic field, which could slow down the sedimentation. The results achieved in this work can be effectively used to reduce particle sedimentation in the controller design of various application systems utilizing MRFs in which the controller generates a different magnitude and different profile of the external magnetic field.

Sediment production process and hydraulic characteristics of ephemeral gully erosion in granite hilly area

Ephemeral gully (EG) erosion represents the early stage of large-scale gully (locally named as “Benggang”) development on Ultisols in the granite hilly area. However, the EG erosion process and the mechanism underlying sediment production have not been fully elucidated. In this study, a series of field scouring experiments were conducted under different flow discharge levels (10, 15, 20, 25, and 30 L·min−1), and the primary EGs in three typical soil layers with different weathering degrees (red soil layer (RL), transition layer (TL), and sandy layer (SL)) was dynamically monitored. The results indicated that the ratio of width to depth of the EGs rapidly decreased as the flow discharge increased. At 30 L·min−1, the average sediment yield and transport rate (Sr) of the SL were 4.85 and 5.39 times, greater than those of the RL, respectively. The sediment particles were concentrated within the 1–2 mm particle size range, accounting for over 35 %. In addition, the mean weight diameter of the sediment particles in the RL was the largest. The sediment distribution characteristics did not respond to flow changes but were affected by EG morphological changes. With increasing flow discharge, the flow shear stress and stream power increased. Further analysis revealed that the coupling effect of flow hydraulic characteristics and EG morphological evolution drove the EG erosion sediment production process, and the Sr of the SL was highly sensitive to flow discharge changes. The soil disintegration rate was an internal factor that directly affected soil loss in the EGs, with a path coefficient of 0.71. The bulk density, organic matter content, and sand content were all indirect influencing factors. The RL exhibited greater anti-erodibility than the other layers and could serve as an effective protective layerfor granite hilly areas. These findings provide a theoretical basis for improving soil loss management systems.

Modeling the sediment yield and estimating the best management practices in the Seybouse basin, Northeastern Algeria.

Identifying vulnerable areas to erosion within the watershed and implementing best management practices (BMPs) are crucial steps in mitigating watershed degradation by minimizing sediment yields. The present study evaluates and identifies the BMPs in the Seybouse basin, northeastern Algeria, using the Soil and Water Assessment Tool (SWAT) model. After successful calibration and validation, the model demonstrated a satisfactory ability to simulate monthly discharge and sediment. Then, the calibrated model was employed to evaluate the efficacy of diverse management practices in sediment control. In the SWAT, three soil and conservation practices, as well as vegetated filter strips (VFSs), grade stabilization structures (GSSs), and terracing were evaluated. The average annual sediment yield in the Seybouse watershed is determined to be 14.43 t/ha year, constituting 71% of the total soil loss. VFS demonstrated a sediment reduction of 37.30%, GSS 20.40%, and terracing 42.30%. Among these strategies, terracing results in the greatest reduction, followed by VFS. The results of this study area can be useful for informed decision-making regarding optimal watershed management strategies.

Sounding out maerl sediment thickness: an integrated data approach

Maerl beds are listed as a priority marine feature in Scotland. They are noted for creating suitable benthic habitat for diverse communities of fauna and flora and in supporting a wide array of ecosystem services. Within the context of climate change, they are also recognised as a potential blue carbon habitat through sequestration of carbon in living biomass and underlying sediment. There are, however, significant data gaps on the potential of maerl carbon sequestration which impede inclusion in blue carbon policy frameworks. Key data gaps include sediment thickness, from which carbon content is extrapolated. There are additional logistical and financial barriers associated with quantification methods that aim to address these data gaps. This study investigates the use of sub-bottom profiling (SBP) to lessen financial and logistical constraints of maerl bed sediment thickness estimation and regional blue carbon quantification. SBP data were cross validated with cores, other SBP data on blue carbon sediments, and analysed with expert input. Combining SBP data with estimates of habitat health (as % cover) from drop-down video (DDV) data, and regional abiotic data, this study also elucidates links between abiotic and biotic factors in determining maerl habitat health and maerl sediment thickness through pathway analysis in structural equation modelling (SEM). SBP data were proved to be sufficiently robust for identification of maerl sediments when corroborated with core data. SBP and DDV data of maerl bed habitats in Orkney exhibited some positive correlations of sediment thickness with maerl % cover. The average maerl bed sediment thickness was 1.08 m across all ranges of habitat health. SEM analysis revealed maerl bed habitat health was strongly determined by abiotic factors. Maerl habitat health had a separate positive effect on maerl bed sediment thickness.

The Cyclostratigraphy of the Eastern Paratethys Konkian: Zelensky Section (Taman Peninsula)

The Eastern Paratethys Konkian sedimentary successions of the Zelensky section (Taman peninsula, Russia) were investigated by cyclostratigraphy methods based on magnetic susceptibility measurements. Cyclostratigraphy is a new scientific direction in stratigraphy and sedimentology, the purpose of which is to identify astronomical cyclicity for the reconstruction geochronology using high-precision technologies. Time series analysis (Lomb-Scargle and REDFIT periodograms, wavelet) revealed statistically significant signals corresponding most likely to long-term insolation periodicities in studied sediments. In the deep-water Konkian sediments of the Zelensky section, the signal at 3.3 m corresponds to the 100-kyr eccentricity cycle. The astronomically tuned these sediments result in an average sedimentation rate of about 3.3 cm/kyr with the duration of accumulation of the Sartaganian and Veselyankian beds about 200 kyr. The obtained cyclostratigraphic results generally do not contradict the new data about the possible duration of the Konkian (Kartvelian, Sartaganian and Veselyankian beds) of about 750 kyr [Palcu et al., 2017].

Analysis of characteristic index and prediction of river bottom tearing scour in the Yellow River

Abstract River bottom tearing scour (RBTS) has a strong effect on the scouring and moulding of channel in the Yellow River. Due to the special forming conditions, complex influencing factors, and limited observed data, it is difficult to predict whether RBTS will occur accurately. By collecting and disposing of the hydrodynamic, sediment, and initial boundary data of 246 flood events related to RBTS in three typical reaches of the Yellow River basin, the correlation between different characteristic influencing factors and the occurrence and absence of RBTS were analysed, and prediction models based on machine learning algorithms were constructed. The results showed that under the existing data conditions, the maximum sediment concentration Sm, average sediment concentration Sp, flood growth rate ν, and shape coefficient δ were the four key indices to more easily distinguish whether RBTS will occur. The support vector machine algorithm model had the best performance results and exhibited higher accuracy and precision in predicting its occurrence compared with other models under given water and sediment conditions. The method proposed in this study provides a new method for accurately predicting RBTS in the Yellow River.

Changes in the Hydrological Characteristics of the Attabad Landslide-Dammed Lake on the Karakoram Highway

Understanding the evolving hydrological characteristics of landslide-induced barrier lakes is crucial for flood control, forecasting, early warning, and safety measures in reservoir areas. This study examines the changes in the hydrological characteristics of the Attabad landslide-dammed lake over the past decade after the occurrence of the landslide, focusing on lake area dynamics and sediment concentration. High-resolution satellite images from QuickBird, Pleiades, and WorldView2 over seven periods were analyzed. The findings indicate that the lake area has gradually decreased, with the center of mass shifting towards the lake dam, indicating a trend towards stability. The suspended sediment in the barrier lake is distributed in a strip running from north to south, then northeast to southwest, with the sediment concentration decreasing from the lake entrance to the dam and from the lake bank to the center. Over time, the average sediment concentration has decreased from 2010 to 2020, with higher concentrations in summer than in winter. Notably, during the 2017–2020 period, the lower-middle parts of the lake experienced a higher sediment concentration, while the dam area witnessed lower concentrations, thereby reducing the sediment impact on the dam. Furthermore, the sediment content in the middle of the dammed lake is relatively high, which may lead to the formation of a new dammed dam in the middle and the division of the original dammed lake into two smaller lakes, which will affect the stability of the dammed lake.

Impact of land-use change on salt marsh accretion

Salt marsh vertical accretion that keeps pace with relative sea-level rise (RSLR) promotes habitat resilience and a continuously growing carbon stock. Vertical accretion, however, hinges on various salt marsh biogeomorphic feedback loops that respond to changing sediment supply, storms events, accelerating RSLR, elevation, and vegetation density. During the latter half of the 20th century, a large proportion of watersheds on the lower coastal plain of North America experienced land cover change. Many salt marshes show slow rates of vertical accretion over that period suggesting degradation and destabilization attributed to reduced upstream sediment loads and changing proportions of mineral sediment to organic matter. Here, we investigated a potential dichotomy observed at many sites in coastal North America between previously published accretion rates of the subtidal bay bottoms and adjacent salt marshes that were exceeding and lagging behind RSLR since 1950 CE, respectively. In 12 small coastal watersheds that formed within tributary and coastal prism incised valleys, we coupled 210Pb-derived accumulation rates of fringing salt marshes and previously published data from adjacent tidal creek bay bottoms with geospatial analysis of watershed land cover change since 1959, inundation duration, and vegetation density. Accumulation rates were higher at marsh sites within tributary incised valleys with lower relief watersheds, smaller tidal ranges, shorter inundation times, higher vegetation densities, and where land cover changes were dominated by increased cleared forest area. Additionally, mass accumulation rates (MAR) accelerated at 8 of the 12 marsh sites after a Major Land Cover Change (MLCC). Despite this acceleration in MAR, only 2 marsh sites recorded average sediment accumulation rates (SAR) greater than RSLR after a MLCC, which suggests that most of the marsh sites are drowning or being converted to subtidal habitat. This may be misleading, however, because modern marsh platform elevations at all but one marsh site were above local mean sea level, so the marshes could be accommodation limited. This work supports the disconnect found in previous research suggesting that estuaries are accumulating sediment at sustainable rates while their fringing salt marshes are not, which illuminates the complexities associated with sedimentation regimes in small local watersheds and their fringing salt marshes.

Event-scale suspended sediment fluxes in a dryland environment valley-bottom wetland: Implications for downstream sediment and phosphorous fluxes

Suspended fine sediment in rivers and small streams contributes to fluvial pollution loads because of its association with anthropogenically introduced heavy metals, pesticides / herbicides, and nutrients, including phosphorous (P). By acting as sinks for suspended sediment, wetlands located along drainage lines have considerable potential in reducing downstream sediment and nutrient fluxes. The aim of this research was to document downstream sediment fluxes within a single valley-bottom wetland to establish the effectiveness of this common wetland type in retaining P attached to sediment. The study was accomplished by conducting a topographic survey (dGPS and 0.5 m Lidar-derived DEM) with surface and sub-surface sediment sampling to establish long-term (decades to centuries) processes of erosion and deposition within the wetland, as well as consider storage of P. This was paired with event-based suspended sediment sampling at eight positions within the wetland over a wet season, as well as time-averaged suspended sediment sampling at a seasonal-scale at the wetland inlet and outlet. Sediment samples were characterised in terms of organic content, total phosphorous and particle size, which were determined using loss-on-ignition, ICP-AES following aqua regia extraction, and a combination of dry sieving and settling, respectively.Over the wet season, average suspended sediment concentrations increased to a maximum value of 0.26 g.L−1 and then declined, potentially because of the exhaustion of locally available sediment. The total P concentration of incoming sediment was 2174 mg/kg compared to 800 mg/kg at the wetland outlet. However, when considering the seasonal flux for the single year sampled, it was found that the wetland was a net downstream contributor of sediment (11 g of sample were retained at the inlet, relative to 19 g at the outlet). Despite this, the wetland retained ∼37 % of the total P supplied to it from upstream sources, with the remainder passing through the wetland as a result of sediment reworking in reforming channels. Thus, while wetlands may be effective at retaining some sediment and nutrients, they are not an alternative to more formal water treatment works.

Integrated modelling of flow-sediment transport and power generation in the Three Gorges Reservoir

Reservoirs play a crucial role in regulating runoff and generating energy. However, they also lead to significant sedimentation in the reservoir area. In this study, we propose an integrated model that combines a 1-D hydro- and sediment dynamic module with a power generation module. The model considers both suspended and bed load transports. This model is applied to the Three Gorges Reservoir (TGR) and evaluate its performance against corresponding measurements. The results demonstrate that:① the proposed model accurately reproduces the processes of flow and sediment transport, bed deformation, and power generation during the hydrological years of 2019 and 2020. The relative errors for average discharge and bed deformation volume are <6 % and 10 %, respectively. Moreover, the calculated total power (982 × 108–1115 × 108 kW·h) closely agree with the measured values (969 × 108–1118 × 108 kW·h); ② the inflows of small tributaries have a noticeable impact on the calculated water discharge in the TGR. This impact will lead to a 16 % increase in average discharge and alter the magnitudes and occurrence times of flood peaks; ③ the flocculation of fine sediment particles significantly affects sediment transport, particularly in the sub-reach close to the dam. This flocculation will result in a 37 %–57 % reduction in average suspended sediment discharge and a 63 %–93 % reduction in peak sediment discharge. This research provides a comprehensive tool for simulating flow and sediment transport as well as power generation, which can support the optimal regulation of the TGR.

The possible anti-inflammatory effect of extra virgin olive oil with colchicine in treatment of resistant cases of familial Mediterranean fever in a cohort of pediatric Egyptian patients

BackgroundPeople of Mediterranean descent are primarily affected by the autoinflammatory genetic condition known as familial Mediterranean fever (FMF). The disease is resistant to colchicine therapy in 10–20% of patients. Numerous recent animal studies showed promising results of extra virgin olive oil (EVOO) to control inflammation. The objective of this study was to assess the effectiveness of combining EVOO with colchicine in the treatment of colchicine-resistant familial Mediterranean fever (CRFMF) patients.ResultsBoth the frequency of episodes and inflammatory indicators significantly decreased after a three-month course of daily EVOO treatment with colchicine. The average erythrocyte sedimentation rate (ESR) of patients was 78.6 mm/h before the EVOO administration, and it dropped to 27.8 mm/h, after that. Additionally, after taking EVOO, the mean serum amyloid A (SAA) decreased from 123.82 mg/dl to 59.78 mg/L. Also, the average C-reactive protein (CRP) decreased from 34.22 to 7.84 mg/dl following its administration; the mean nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) level decreased from 134.92 to 64.23 pg/ml. The mean caspase-1 level decreased from 7.8 to 4.98 ng/ml; and the mean levels of cytokines, interleukin 6 (IL-6), interleukin 1 beta (IL-1 β), and tumor necrosis factor-alpha (TNF-α) decreased from 9.8, 18.14, and 52.7 pg/ml, respectively, to 5.95, 12.51, and 29.39 pg/ml. Finally following the administration of EVOO, there was a notable overall improvement in the quality of life of (CRFMF) patients.ConclusionEVOO demonstrated a significant positive impact when paired with the tolerated dosage of colchicine in the management of CRFMF. Improvements were observed in both clinical and laboratory settings, including a reduction in the attack frequency and serum levels of inflammatory markers, such as NLRP3, caspase-1, ESR, CRP, IL-1β, IL-6, and TNF-α without any negative side effects.

Forecasting empirical formula for suspended sediment load prediction at upstream of Al-Kufa barrage, Kufa City, Iraq

Abstract The objective of this study was to predict the suspended sediment load at upstream of the Al Kufa barrage. Ten cross-sections in the upstream region have been identified to collect field measurements. As part of the inquiry, the fluid and hydraulic parameters were measured in the field and sediment samples were collected in sections to develop an empirical formula. These variables included the gravitational constant (g), hydraulic radius (R h), mean velocity (V), median particle size (d 50), river top breadth (B), kinematic viscosity (v), and (ρ) water density. The formula was created using both statistical analysis and dimensional analysis techniques. The results showed that the newly developed formula agreed well between the calculated and observed suspended sediment discharges based on the determination coefficient R 2 of 0.979. There was a very high acceptance between the average sediment discharge from the new formula, equal to 7.365 kg/s, and the average sediment discharge from field measurements (7.142 kg/s).

Experimental Study on Runoff and Sediment Production of the Fully Weathered Granite Backfill Slope under Heavy Rain in Longling, Yunnan Province

Heavy or intermittent rainfall can cause slopes to become unstable and erode, resulting in significant damage, loss of life, and destruction of property. Targeted management solutions are based on an analysis of slopes’ flow generation and sediment production patterns during periods of rainfall. This study used a fully granite backfill slope as its research subject and examined the features of slope erosion during intermittent rainfall. We examined the processes of slope flow generation and soil erosion during intermittent rain through indoor artificially simulated rainfall experiments. Three intermittent rainfall events with a 220 mm/h intensity were designed during the experiment. Each rainfall event lasted for 60 min, with an interval of 60 min between the events. By analyzing multiple rainfall events, this study reveals the patterns of runoff and sediment yield on different slopes in response to variations in rainfall intensity and slope gradient. The runoff volume on other slope surfaces exhibits a similar pattern in reaction to changes in rainfall events. As the frequency of rainfall events increases, the surface runoff tends to be higher. Additionally, with variations in slope steepness, the runoff volume generally follows an increasing trend. Notably, the slope with a 20° incline shows the smallest runoff volume. The sediment yield on different slope surfaces gradually increases as the slope increases. In particular, on a 20° slope, the sediment yield experiences a substantial increase, indicating that the impact of the slope on the sediment yield becomes more pronounced. In different rainfall events, the morphology of the slope changes due to the influence of gravity and hydraulics, resulting in oscillations in both the average runoff rate and sediment yield. Furthermore, as the slope steepens, the amplitude of these oscillations increases. The process of slope erosion involves three stages: raindrop splash erosion, runoff erosion, and collapse damage. The sequence of slope damage locations is as follows: footslope, mid-slope, and hilltop. For the backfilled slope of completely weathered granite, the artificial slope can be controlled to around 20°. Erosion on the slope mainly occurs after the formation of gullies, and slope management should focus on preventing gully formation before it happens.

The effect of grain size on the distribution and fractionation of the major chemical trace and rare earth elements in shale, silt and sand rocks of the Muqdadia formation in north of Iraq

(17) samples were collected from Muqdadia formation from various areas in Erbil governorate and Aqra district north of Iraq, which were represented by the sections (A, B, D, R, W). (10) samples were used in analyzing the element using Plasma–Mass Spectrometry (ICP–MS) Analysis and the Inductive Couple Plasma–Mass Spectrometry (ICP–MS) Analysis for four granule sizes after these granules were separated from each sample. The elements included were Al, Fe, Mg, Ca, Na, K, Ti, P, Rb, Cs, Sr, Ba, Au, Mo, Pb, Cu, Zn, As, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Cr, Ni, Co, Mn, Sc, V, Zr, Hf, Ta, Nb, Th, U, Ga, La, Dy, Ho, Er, Tm, Yb, Lu, Y.The geochemical study revealed that there is no significant variation in the content of the main, trace and rare earth elements in the four sizes of shale, silt, fine sand and coarse sand. Also, it was found that the sizes of silt and fine sand contain the highest portion of the trace elements and the rare earth element.It was also, noticed that the patterns of the rare earth elements in the granule sizes are similar in general with some differences, as these differences were reflected in some changes in the portions of these elements.In general, it was observed that the total content of the rare earth elements in the various sizes is relatively small and this might be due to two main factors; the high decrease by calcite (calcium carbonate) and the free silica (quartz) and the other reason is that the mineral that contain REEs are mostly derived from rock sources (mafic or ultra-mafic), which contain these elements with low concentrations.Patterns of REE in the study samples and the four sizes are similar to the pattern of (PAAS) with slight differences like the presence of LREE and on a lower level in HREE and also the presence of negative anomaly Ce*/Ce in the size of shale, silt, fine sand and coarse sand.Although there are variations in the values of anomaly Eu* /Eu, the values are not far from the acceptable PAAS values and they are, generally, higher than PAAS due to the presence of the mafic and ultra-mafic component in the sediments of the current study. In all the sizes, except the shale size, it was found that ∑ REE varies and increases with the increase of the contents of Al2O3 and Fe2O3.As for the shale size, it was found that the relationship between REE∑, Mn and P2O5 is negative and this is because the shale were sedimented in river environments that don’t permit them to absorb sufficient amounts of REE as is the case with the shale that are sedimented in sea environments where there is a direct contact with the seawater that although contains slight concentrations of REE but they are effective when they are adsorbed on shale particularly when the average sedimentation of the shale is low. But in the current study, the shale is river sediments and the river contains insignificant concentrations of REE and the sediment in the river is faster compared to the sea environment and this case doesn’t permit the shale to adsorb large portions of REE.

Quantitative risk analysis of sediment heavy metals using the positive matrix factorization-based ecological risk index method: a case of the Kuye River, China.

Identifying the sources of heavy metals (HMs) in river sediments is crucial to effectively mitigate sediment HM pollution and control its associated ecological risks in coal-mining areas. In this study, ecological risks resulting from different pollution sources were evaluated using an integrated method combining the positive matrix factorization (PMF) and the potential ecological risk index (RI) model. A total of 59 sediment samples were collected from the Kuye River and analyzed for eight HMs (Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg). The obtained results showed that the sediment HM contents were higher than the corresponding soil background values in Shaanxi Province. The average sediment Hg content was 3.42 times higher than the corresponding background value. The PMF results indicated that HMs in the sediments were mainly derived from industrial, traffic, agricultural, and coal-mining sources. The RI values ranged from 26.15 to 483.70. Hg was the major contributor (75%) to the ecological risk in the vicinity of the Yanjiata Industrial Park. According to the PMF-based RI model, coal-mining activities exhibited the strongest impact on the river ecosystem (48.79%), followed, respectively, by traffic (34.41%), industrial (12.70%), and agricultural (4.10%) activities. These results indicated that the major anthropogenic sources contributing to the HM contents in the sediments are not necessarily those posing the greatest ecological risks. The proposed integrated approach in this study was useful in evaluating the ecological risks associated with different anthropogenic sources in the Kuye River, providing valuable suggestions for reducing sediment HM pollution and effectively protecting river ecosystems.