International Journal of Sediment Research最新文献

This paper presents a model to characterize the distribution of non-uniform sediment in suspension above erodible sediment beds in turbulent flow under non-equilibrium conditions. The modeling process incorporates three crucial features of sediment-laden flow: mixing length, stratification, and settling velocity. The advection–diffusion equation for the $k$-th grain-size class is modified accordingly. The model's calculations encompass the determination of reference height and reference concentration, accounting for the presence of different-sized particles in the flow. The numerical solution of the model effectively captures concentration variations for distinct particle sizes in streamwise and vertical directions, as well as temporal changes. As experimental data under non-equilibrium conditions with different sediment sizes are unavailable, the study focuses on specific experiments involving various sediment beds with a mixture of different grain sizes under equilibrium conditions. The current findings reveal that the concentration magnitude decreases downstream with time for all grain sizes, eventually reaching an equilibrium state. This behavior is consistent with variations in downstream distance at a specific time. The mixing length which is concentration-dependent, first increases the suspension concentration for all grain sizes at smaller downstream distance and then the effect reverses for all grain sizes at larger downstream distance. A similar trend is observed when considering both stratification and mixing length. An error analysis evaluates the model's performance, indicating that the least error corresponds to datasets incorporating all considered effects.

Sediment control in watersheds requires information about soil erosion and sediment yield hotspot areas. Sediment connectivity is an emerging concept contributing to this field and structural sediment connectivity is a concept derived from sediment connectivity. Determining structural sediment connectivity in a watershed can yield a comprehensive image of sediment management possibilities applicable at the watershed scale. However, in most studies, the validity of extracted sediment connectivity maps has not been evaluated holistically. The current study is, therefore, designed to determine a valid structural sediment connectivity map and to use it to validate findings of sediment fingerprinting of the Idelo watershed in Zanjan province, Iran. Digital elevation model (DEM), slope, vegetation cover, and flow accumulative layers have been used in compiling the structural sediment connectivity map. Field observations were made to calculate the field connectivity index. The results showed that the mean structural sediment connectivity index of the target watershed is −6.18. Moreover, areas in the downslope section near the outlet and the narrow strips around the watershed boundaries have moderate to high structural connectivity. The results of field validation showed there is an acceptable agreement between the field connectivity index and the structural connectivity map. Also, these results confirmed previous findings of sediment fingerprinting in the study area. Based on the findings of the current study, determining the structural sediment connectivity index is an efficient method to make management and conservation decisions and control erosion and sediment in the watershed.

Settling basins are one of the structures required for removing excess sediment entering irrigation or power canals diverting water from a river. A numerical model is needed to simulate the flow and sedimentation pattern in settling basins. In the current research, a depth-averaged two-dimensional numerical model of flow and sediment is developed using the finite volume method and based on the time-splitting scheme, which also allows for simulating sediment in a non-equilibrium state. The simulation of flow and sedimentation is done by the numerical model in a decoupled method. Sensitivity analysis was applied to estimate the effects of non-equilibrium parameters and the settling velocity on the numerical results. The results revealed that Maleki and Khan's formula and Zhang and Xie's formula are suitable for estimating the suspended load adaptation coefficient and the sediment settling velocity in the numerical simulations. Investigation of the formulas for the bed adaptation length indicated that all three methods considered in the current research had almost equal accuracy in predicting the sediment concentration distribution in the settling basin. The developed model has been verified against two experimental tests, showing a good fit between observed data and the simulated results.

Severe socio-environmental pressures and land degradation are substantially impacting Ethiopia, eventually leading to low agricultural productivity, with a consequent very high rate of poverty and food insecurity. The current study investigates the future effect of four management practices on reducing sediment yield in the Fincha sub-watershed, Ethiopia, by developing a soil and water assessment tool (SWAT) model over the next three decades (2019–2050). Four best management practices (BMPs) largely applied in the region were considered here. It was found that filter strips can decrease the sediment yield by 65.64 and 58.77, soil or stone bund by 76.37 and 73.07, contour farming by 79.79 and 75.86, and terracing by 84.9% and 76.32% for the years 2019 and 2050, respectively. The impact of these BMPs on various hydrological processes also was evaluated using SWAT. It was found that BMPs are effective in reducing surface runoff and water yield and in increasing groundwater and lateral flows, while they have a reduced effect on evapotranspiration, lateral flow and water yield. The findings presented here point out that all the simulated management practices significantly lower surface runoff and consequently sediment yield across the watershed, but they are not effective enough to reduce soil erosion below a critical threshold that assures crop production. Therefore, to achieve tolerable soil loss, additional soil and land management strategies, such as biological measures and a combination of BMPs are needed and should be considered in future investigations. In summary, the current study offers evidence for managing river basins in semi-arid regions, and can help in ensuring sustainable management of natural resources.

Climate change accelerated by anthropogenic activities has led to the shrinkage and eventually disappearance of salt lakes all over the world. Gradual desiccation of Lake Urmia (LU) in northwestern Iran, as one example of desiccating lakes, has led to the exposure of the lakebed sediment with enormous dust emission potential in some parts. Sand sheets of western LU are identified as one of the major contributors to aerosols in this region. Yet, dust blown from this area is not well characterized. The aims of the current study were, therefore, to comprehensively investigate the origin of dust from sand sheets; the characteristics of dust and temporal variability of the aerosol and to test the effectiveness of the application of sodium alginate (SA) on soil crusting and stabilization. Soil samples were collected from the two prevailing soil types from sand sheets in August 2020. Dust samples were also collected during four time periods: July and August (the beginning of the dry season); October and November (the beginning of the wet season). Using SA with varying concentrations and different methods of application, the effectiveness of the induced crusts was investigated. Authigenic aragonite minerals with elongated needle shapes were found to be the major constituent of the soil and dust samples. Temporal variability of the dust characteristics and their elemental correlation to dust sources revealed that while dust source 1 (DS₁) with higher clay, salt, and silt contents contribute more to the dust composition from July to August (R² > 0.75 for DS₁ versus R² > 0.58 for DS₂), dust source 2 (DS₂) with less salinity and higher sand content becomes the major contributor to dust composition from October to November (R² > 0.91 for DS₂ versus R² > 0.75 for DS₁). Results of stabilizing both DS₁ and DS₂ showed that SA-induced crusts on DS₁ are more stable than DS₂ due to the presence of higher clay, silt, salt, organic matter, and lower aragonite minerals. SA-induced crusts by a compaction method significantly performed better than a spray of SA on either dry (DSp) or soil at its optimum water content (WSp) at all concentrations. Nevertheless, spray methods are more feasible at the field scale and in both DSp and WSp methods, SA_0.5 improved the crust thickness. Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) along with thermogravimetric analysis (TGA) confirmed the remaining SA on the soil surface three months after its application indicating the effective performance of the SA solution in sand sheets stabilization. Hence, its application at the field scale could possibly reduce aerosol release and transport to surrounding areas.

Suspended particulates and sediment are significant reservoirs of organic matter (OM) in lakes, and tracking the formation of suspended particulate organic matters (SPOMs) and sediment organic matters (SOMs) is the key to understanding the environmental behavior of OM and the carbon cycling of lake ecosystems. However, few studies have simultaneously focused on the sources of SPOM and SOM in closed inland lakes to reveal their differences and implications for water quality. The current study investigated the sources of SPOM and SOM in Daihai Lake, a typical closed inland lake in northern China, based on stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic compositions, during spring, summer, and autumn. The results showed that δ¹³C_POC and δ¹⁵N_PN (where POC and PN denote particulate organic carbon and nitrogen, respectively) of SPOM varied from −30.99‰ to −21.71‰ and 1.43‰–9.47‰, respectively. SPOM mainly originated from sewage, soil, and phytoplankton, with average contributions of 29.5%, 27.7%, and 19%, respectively, and each source of SPOM showed low spatial variation. However, the contribution of phytoplankton showed a decreasing trend from spring to summer, while the contribution of soil showed the opposite change. δ¹³C_TOC and δ¹⁵N_TN (where TOC and TN denote total organic carbon and nitrogen, respectively) of SOM varied from −26.41‰ to −23.99‰ and 3.3‰–7.66‰, respectively. Soil and sewage were the major sources of SOM, with average contributions of 43.3% and 27.8%, respectively, and each source showed small temporal and spatial variations. The differences between sources of SPOM and SOM revealed that phytoplankton-derived SPOM was easily degraded, whereas sewage- and soil-derived SPOM tended to deposit in the lake sediment. Additionally, the impact of SPOM on water quality significantly exceeded that of SOM. The source characteristics of SPOM were correlated with eutrophication and salinity indicators in the water, which have important implications for water quality. This isotopic evidence revealed that exogenous inputs were the main sources of OM in closed inland lakes, but there were some differences in the source characteristics between SPOM and SOM.

Water quality management in shallow impounded lakes is challenging due to nutrient's enrichment and algal blooms. Lake Hongze is a reservoir for the South-to-North Water Diversion Project's Eastern Route and an essential water source for Jiangsu Province, China, and its water quality closely relates to the local aquatic ecosystem and affects the water supply security of the surrounding areas. The spatial and seasonal patterns of total nitrogen, total phosphorus (TP), and chlorophyll-a (Chl-a) in the lake were investigated and the effects of floods on these patterns were assessed. Hydrological data and trophic state parameters were analyzed using 7 years of monitoring data from 16 water sampling sites throughout the lake. The statistical analysis revealed the seasonal variation characteristics affected by floods and the differences in material transport continuity between inflow and outflow boundaries. Eutrophication assessment using the trophic level index and Chl-a concentrations also indicated eutrophication was concentrated at the southeast side of the lake. Spatial interpolation of Chl-a using the ordinary kriging method clarified that existence and movement of the localized eutrophication area in Lake Hongze. The mass balance calculations of TP indicated that a substantial amount of phosphorus entered the lake during the flood season, however, most severe algal blooms occurring after the flood season. The onset of algal blooms exhibits a significant time lag in response to phosphorus input, primarily due to the influence of hydrodynamic processes within the lake during the flood season.

In conveying concentrated liquid–solid mixtures in pipelines oriented horizontally, gravitational settling promotes a concentration-rich layer of solids at the pipe invert that degrades the wall due to sliding (abrading) action against the wall. The current study investigates near-wall flow field characteristics and then obtains flow and geometry conditions using a response surface methodology (RSM) that minimizes the maximum sliding frictional power developed in the vicinity of a 90° horizontal bend for transporting a dense solid–liquid mixture. The liquid–solid flow field is mathematically modeled with a Eulerian–Eulerian approach using the realizable $k-\epsilon$ model with standard wall functions for turbulence modeling. The effect of several operating parameters such as solid concentration, mixture velocity, particle sizes, pipe diameters, and bend ratios on the near-wall flow field in the bend reveals useful insight relevant to the bend wall degradation by solid particles. A reduction of 28% in the maximum sliding frictional power is achieved with the optimized flow conditions within the operating range considered. The novel approach could be utilized in an apriori estimation of the erosion in bends for any particle-pipe wall material combination in the hydro transport of dense solids.

Total arsenic (TAs) contamination is a serious health issue that affects many parts of the world. The sources of TAs in the Himalayas and Hindu Kush Mountains are rocks containing sulfide minerals and coal. The current study investigated the concentrations of TAs in soil, vegetables, and fruits collected from the Chitral Valley in the Hindukush Mountains of Pakistan. Vegetables consisted of Solanum tuberosum (potatoes), Mentha spicata (mint), Chenopodium album (goosefoot), Coriandrum sativum (coriander), Cucumis sativus (cucumber), Amaranthus viridis (green amaranth), and Medicago sativa (alfalfa); and fruits consisted of Prunus armeniaca (apricot), Morus alba (mulberry), Juglans regia (nut), Malus domestica (apple), and Vitis vinifera (grapes). The average concentration of TAs was the highest in the Gabur soils and lowest in the Bamborait soils. In vegetables, the highest TAs concentration was found in goosefoot (11.11 ± 1.9 mg·kg⁻¹) and the lowest in cucumbers (1.38 ± 0.3 mg·kg⁻¹). In fruits, the highest TAs concentration was found in grapes (4.3 ± 0.5 mg·kg⁻¹), while no TAs concentration was detected in nuts (± indicates the one standard deviation range). The transfer factor (TF) values were high only in Bomborait soils (TF > 1). Leafy vegetables and juicy fruits (possessing high water content) were found to be more susceptible to TAs contamination. The daily intake of metals (DIA), human health risk index (HRI), and cancer risk demonstrated that the Chitral Valley is at high risk due to TAs contamination, which may pose a threat to the concerned community and ecosystem. The current findings suggest that leafy vegetables and juicy fruits in the study area should be carefully consumed.