International Journal of Sediment Research最新文献

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.

The release of internal phosphorus (P) is a key and complex process relative to a lake’s nutrient levels. The P response to nitrogen input should be clarified to obtain better detail, especially with respect to the mediation role of iron (Fe) connecting nitrogen and P. A simulation study was done in batch vials containing sediment and overlying water collected from Lake Moshui—a shallow lake. Because of nitrate (${\text{NO}}_3^{-}$) input, the abundances of Firmicutes and Proteobacteria at the phylum level increased, as did the abundances of Crenothrix, Sideroxydans, and Flavobacterium at the genus level. Moreover, nitrate input enhanced the proliferation of nitrate-reducing Fe(II) oxidization bacteria and the activity of denitrifying enzyme in sediment, but decreased the concentrations of total phosphorus (TP), soluble reactive P, and enzymatically hydrolyzable P in the water phase. The suppressive effect of nitrate on P release was mainly attributed to the increase in Fe(III) (hydr)oxides generated by Fe(II) oxidation. With sequential extraction, two types of dominant iron fractions—easily reducible oxides and reducible oxides (Fe_ox1 and Fe_ox2, respectively)—seemed to contribute to the fixation of P largely in the sediment. In addition, more P is converted to Fe_ox2, which is induced by the transformation of Fe_ox1 to Fe_ox2. Driven by nitrate, a higher content of P bound to Fe_ox1 and Fe_ox2 was observed after a 7-day incubation, indicating the potential function of the Fe(II) oxidation process. The current study revealed that the P transformation is influenced by nitrate input from the angle of iron as the connecting bridge to better understand the geochemical cycle of P in the anoxic environment of lakes.

A model of the channel and catchment components of sediment runoff has been developed. The model makes it possible to estimate the intensity of redistribution of river and bottom sediment in the riverbed, the size distribution of deposited or migrating particles, the mass of particles in the riverbed and catchment components of sediment load, as well as the contribution of the catchment component. The model is based on the assessment of the transport potential of the watercourse and the dynamics of the curves of the granulometric composition of bottom sediment, and products of soil and channel erosion. This approach is focused on the steady flow movement without additional sources of tributary sediment, intensive abrasion of river banks, and products of anthropogenic load. Calculations based on the model applied to the Narva River showed that the contribution of the catchment component to the sediment flow of this watercourse after intense rain is approximately 98%. The obtained results are well confirmed by the weak dynamics of channel deformations in the studied part of the watercourse.

The current study deals with experiments on hydro-suction removal of cohesionless bed material from reservoirs. The primary focus lies in scrutinizing the scour profile and the volume of bed material removed through hydro-suction. A comprehensive record of 252 datasets was collected from experiments done on various combinations of governing parameters. The resultant equilibrium scour profile exhibited a symmetrical configuration resembling a semi-ellipsoidal shape. Notably, for the densimetric Forude number equal to or less than 5.8, a small central hump within the scour hole was seen. The investigation found that the optimal sediment removal efficiency was obtained when the C/D ratio was zero (where C is the suction inlet height and D is the suction pipe diameter) and with the highest densimetric Froude number. The sediment to water volume removal was highest in the initial few seconds, and reduced swiftly, followed by a subsequent smaller peak and gradually decreased to zero at equilibrium. Empirical equations for computing maximum scour depth, scour radius, and scour profile at equilibrium also were developed, which predict values within a commendable ±10% error range.

Identifying organic carbon (OC) sources in lake sediment is essential for elucidating biogeochemical cycling processes and effectively supporting watershed management. However, the complexity of sources as well as environments in the land–river–lake continuum makes it challenging to accurately identify OC sources. Accordingly, the current study utilized a systematic approach to identify and validate OC sources in a typical land–river–lake continuum. Two tracer groups (group 1: δ¹³C and δ¹⁵N; group 2: fluorescence index and biotic index, respectively (where C is carbon and N is nitrogen)) and one model (MixSIAR) were eventually selected from five tracer groups and two models to identify the OC sources in a land–river–lake continuum according to a consistency evaluation and virtual mixing test. The results showed that the distribution of OC sources in lake sediment was spatially heterogeneous. Closer to the lake center (from sampling site S1 to S3), the autochthonous contributions increased while the allochthonous contributions decreased. Downstream of the inlet river (site S1) was dominated by allochthonous contributions (78.6%), especially cropland (28.7% ± 0.5%, where ± indicates a standard deviation range) and urban land (30.5% ± 2.5%). From site S1 to S2, the allochthonous contribution decreased 11.4%. Autochthonous OC gradually became the major source closer to the lake center (site S3: phragmites: 48% ± 4.5%). This distribution of OC sources in the land–river–lake system was attributed to the mixing effect of the autochthonous sources, selective transport of sediment, and human activities. The current findings may aid in validating the ability of different tracers and models to identify OC sources in complex ecosystems and also provide a theoretical basis for watershed management.

A river's planform pattern changes due to erosion of banks and the bed near the outer bend. The primary cause of these planform changes is the formation of helical flow patterns in response to centrifugal forces. Uncontrolled bed scouring can have a negative impact on the river's geometry, aquatic habitat, and floodplains. To alleviate this scouring, various structures, such as spur dikes, can be placed at any accessible location along the bend. The current research was accomplished by installing two meandering models with different sinuosities of 1.3 and 1.5, in a flume. For both sinuosities, the maximum bed scour was observed at an approximate angle of 45° relative to the bend apex. Thus, the main objective was to control this maximum scour by installing spur dikes with varying porosities, ranging from 0% to 75%, at five locations along the outer bend. The spur dikes were found to divert the helical flow regime away from the outer bend and protect the riverbed from severe scouring. However, the results show that the effectiveness of spur dikes decreases as sinuosity increases. Furthermore, for both meandering models, a 50% permeable spur dike installed at the +30° location yielded the best performance. Finally, a regression-based predictive equation is proposed to determine the proportion of scouring around a spur dike in a meandering channel.

Spur dikes are structures built along riverbanks that serve two purposes: stabilizing the banks and minimizing erosion risk by controlling water flow in the river channel. The current study used L-shaped spur dikes in an alluvial channel to analyze the bed morphology and flow pattern in the spur dikes zone with the influence of no-seepage and two distinct seepage velocities, V_S1 = 0.075 mm/s and V_S2 = 0.15 mm/s near the channel bed z/h < 0.2. The experimental study was also done to examine and compare the transformation in the local scour depth for the seepage condition. According to the study results, downward seepage movement causes significant modification in the channel's bed elevation and the development of scour depth. Observations indicate that the maximum local scour occurs at the first spur dike's leading edge. Seepage velocity V_S1 results in a 16.1% increase in the maximum scour depth compared to the no-seepage scenario. In comparison, seepage velocity V_S2 causes an increase of 25.2% in the maximum scour depth. Due to downward seepage, the flow distribution is shifted down near the channel's boundary. With an increase in the seepage rate, the magnitude of velocity, Reynold shear stress, turbulent kinetic energy, and bed shear stress also rise close to the channel's boundary. The current study also examined bursting events near the channel's bed under seepage and no-seepage conditions. These events included outward interaction, inward interaction, ejection, and sweep. Quadrant analysis of velocimeter data revealed that ejection and sweep were the dominant events contributing to the production of Reynolds shear stress in seepage and no-seepage flows. Meanwhile, outward interactions and inward interactions made minor contributions compared to ejection and sweep events to the Reynolds shear stress.