Main Sediment Source Research Articles

Soil phosphorus composition, loss risk and contribution to the aquatic environment in a typical agricultural area

Abstract River eutrophication risk increased significantly in agricultural areas. In this paper, spatial variability of soil phosphorus (P) and loss risk in the Jialu River Basin, China, were analyzed using a geostatistical approach. The correlation between soil and river sediment P was analyzed to identify the main aquatic P source. The results showed that inorganic phosphorus (IP) was the main form of soil TP (82.13%), but the ratio of apatite phosphorus (AP) and non-apatite phosphorus (NAIP) varied between different soil types. AP was the primary form of IP in fluvo-aquic cinnamon soil, while NAIP dominated in meadow aeolian sandy soil. Calculated soil total dissolvable P (TDP, 94–622 mg/kg) exceeded the environmental threshold. High TDP (>400 mg/kg) in mixed soil and sandy soil indicated a high P loss risk. The spatial variability of soil P was moderate to weak, indicating a low heterogeneity. In sediment, IP and AP showed a significant correlation with total organic carbon (p < 0.05), indicating a P source of soil erosion. Sediment AP had a significant positive correlation with soil AP (p < 0.05), confirming soil as the main source of sediment P. Furthermore, an accumulation of sediment P along the Jialu River and its consistency with water TP was revealed.

A new methodological framework coupling computational fluid dynamics and fingerprinting for assessment of aeolian sediment transport processes

A systematic understanding of the transport processes of aeolian sand from source to sedimentary areas is important for both hazard control and fundamental mechanism research. This study proposes a methodological framework consisting of wind data standardisation, computational fluid dynamics (CFD) simulation and fingerprinting technology to clarify aeolian sediment transport processes. The methodological framework was applied to the Cuona Lake section of the Qinghai-Tibetan Railway as a case study. One main finding was that the mountain passes located on the west of the lake act as outlets that converge and accelerate the predominant wind. The Basuoqu river valley and Amdo-Cuona down-faulted valley act as a ventilation tunnel in the sedimentary area. The CFD simulation clearly showed the influence of the complex terrain on the wind flow field. Second, the area southwest of the lake was predicted to be the main sediment source; a large portion of this area has an annual wind power density exceeding 1000 W/m2. Third, the fingerprinting estimation results revealed that the predicted main source area contributed more than 80% to the target sediment, which was in good agreement with the CFD simulation result. A decision-tree is provided to guide interested users in critical choices for different situations and research objectives. This CFD- and fingerprinting- based framework has the potential to contribute significantly to aeolian research and facilitate the development of a more detailed methodology.

Modern isotopic signatures of Plata River sediments and changes in sediment supply to the western subtropical South Atlantic during the last 30 kyr

Sediments transported in rivers reflect the geology of the catchment area and its radiogenic isotopic composition. These isotopic signatures are not significantly altered by weathering, transport or deposition and hence can document variations in sediment supply. Here we present strontium (Sr), neodymium (Nd) and lead (Pb) isotope values from suspended and riverbed sediments of the Plata River drainage basin, the second largest on the South American continent, and from two marine sediment cores collected off the mouth of the Plata River in the western subtropical South Atlantic. Our modern riverine data suggest that the basin has three main sediment source areas, namely the upper Paraná River, the Uruguay River and the Andean draining rivers. Sediments from the Andean draining rivers (Salado and Bermejo Rivers) have the most radiogenic Pb (i.e. >18.5 for 206Pb/204Pb) and Sr (average of 0.726 ± 0.031; 2SD) isotopic signatures, and least radiogenic εNd values (average of −10.5 ± 3.1; 2SD). The upper Paraná and Uruguay Rivers have less radiogenic Pb (i.e. <18.5 for 206Pb/204Pb) and Sr (average of 0.715 ± 0.003; 2SD) isotopic signatures. While the upper Paraná River has average εNd values of −7.8 ± 1.1 (2SD), the Uruguay River has average εNd values of −5.9 ± 0.2 (2SD). The modern isotopic signature at the mouth of the Plata River is largely dominated by the Andean draining rivers. To reconstruct changes in sediment supply to the western subtropical South Atlantic, we used this new riverine dataset together with literature values from the Argentine continental margin to interpret the data from two marine sediment cores. The downcore records cover the last ∼30 kyr and show two short-lived excursions (i.e. Heinrich Stadial 1 and the Younger Dryas) and two long-term trends (i.e. late Pleistocene (i.e. ∼29 to 11 cal ka BP for Sr and ∼29 to 25 cal ka BP for Nd), and early and mid-Holocene). We suggest that the short-lived excursions result from increased precipitation in the headlands of the Andean draining rivers during Heinrich Stadial 1 and the Younger Dryas. The late Pleistocene long-term change showed an increase in the contribution of material from the Plata River drainage basin in relation to material from the Argentine continental margin most probably due to low sea-level. The early and mid-Holocene long-term trend showed the opposite change in sediment input and was related to decreased precipitation over most of the Plata River drainage basin.

Elucidating suspended sediment dynamics in a glacierized catchment after an exceptional erosion event: The Djankuat catchment, Caucasus Mountains, Russia

Suspended sediment yields from glacierized catchments are often among the highest in the world, and their sediment dynamics can be highly variable. This study was undertaken in the 9.1 km2 glacierized catchment of the Djankuat River located in the Russian part of the Northern Caucasus. The outlet of the study catchment is a hydrological gauging station located at an altitude of 2635 m a.m.s.l. (‘N43°12′31.71″, E42°44′05.93″). The catchment includes a temperate valley glacier (area = 2.42 km2) and three smaller hanging glaciers, several moraine deposits, rock walls, and a large and expanding proglacial area. The main goal of our study was to assess the impact of an exceptional erosion event on 1st July 2015 (with an annual exceedance probability of less than 0.1%) on suspended sediment yields and the relative contributions of various sediment sources The work combined direct suspended sediment discharge measurements at the gauging station during five ablation seasons (2015–2019) with geomorphic mapping techniques based on detailed field observations and sediment source fingerprinting. Results show that mean annual suspended sediment yields reached 1118 t km−2 year−1 which is one of the highest measured estimates for any of the glacierized mountain rivers globally. About half of the annual suspended sediment flux was exported during a limited number (1–12% of the annual events) of extreme hydrological events. The sediments mobilized by bank and riverbed erosion within the new lower reach of a tributary channel which appeared after the breakthrough of a lateral moraine became the primary sediment source. It contributed over 50% of the suspended sediment on days with extreme rainfall. Contributions to the suspended sediment load from the glacier source were event-dependent and were only dominant (c. 60–70%) in the upper reaches of the proglacial area (first 800 m). The proglacial part of the study catchment with buried ice was the main sediment source (79%) during non-rain days.

Quantitative Ascription of Sediment Discharge Changes of Two Highly Sediment-Loaded Tributaries of the Yellow River in China: The Importance of Selecting Rainfall Index and Timescale

River sediment load has been changing conspicuously worldwide. The famous sediment-laden Yellow River in China has also had a declining sediment load in the past decades. This study made a quantitative ascription of the sediment discharge changes by non-parametric Pettitt test, rainfall and sediment discharge characteristic index calculation, correlation test, double cumulative curve regression and solving differential equation in the Huangfu and the Kuye basins in the main sediment sources of the Yellow River. The results indicated that: (1) The sediment discharge decreased significantly from 1956 to 2016, while the rainfall and rainfall erosivity only had a visible but insignificant decreasing trend. (2) Rainfall erosivity is better than other rainfall characteristic indexes in relation with sediment discharge. (3) The anthropogenic factor was the main driver for the reduction of sediment discharge with a percentage of 70.2–90.5% in different periods. The contribution of rainfall changes in flood season to sediment discharge reduction surpassed that in the whole year. (4) A percentage of 88% and 93% of suspended sediment yield reduction was attributed to streamflow reduction, and 12% and 7% to changes in C-Q relationship in the Huangfu and the Kuye basins, respectively.

Understanding the influencing factors (precipitation variation, land use changes and check dams) and mechanisms controlling changes in the sediment load of a typical Loess watershed, China

The soil erosion and sediment load of the coarse sandy hilly catchment region of the Yellow River basin, which is the main source of sediment for the Yellow River, have become sources of concern for researchers as well as for the local population. Soil and water conservation measures, especially reforestation and check dam construction, have been progressively implemented in this region for several decades. During this period, the corresponding precipitation in the region is also changing dynamically. However, it is still unclear how precipitation variations, land use changes and check dams affect soil erosion and sediment yield in a typical watershed. A combination of field investigations and model simulations was employed to quantitatively identify the impacts of the above three factors on soil erosion and sediment yield in the Kuye River watershed. Significant land use changes, including the conversion of arable land and bare land into grassland, shrubland, forestland and construction land, occurred in the studied watershed from 1987 to 2016. In addition, 306 key dams were built in the watershed, with a total storage capacity of 316.64 Mm3, according to statistical data obtained in 2011. A hot spot analysis showed that the regions that were at high risk of soil erosion and sediment yield were mainly concentrated in the middle reaches of the watershed. The simulation results showed that check dams were the dominant factor affecting sediment load, reducing the total sediment load by 54% in 2006. However, from 1987 to 2016, the contributions of the three studied factors (precipitation variation, land use changes and check dams) to sediment reduction were 29%, 40% and 31%, respectively, which indicated that these factors all had significant influences on the sediment load. More attention should be paid to check dams, and corresponding measures should be taken to protect them, especially during flood periods. These results can serve as a reference for watershed management and policy implementation.

Changes in sedimentary provenance and climate off the coast of Northeast Brazil since the Last Interglacial

Neodymium (Nd) and strontium (Sr) isotopic signatures in marine sediments reflect the geology of the associated drainage basin from which those sediments are supplied. These signatures are significantly affected by relief, weathering, transport, and deposition of sedimentary contributions from the respective sources. This work makes available new data of SrNd isotope ratios and Rare Earth Element (REE) concentrations, which provides a record of the sedimentary provenance of marine sediment supplied to the continental slope off the coast of northeastern Brazil since the last 130 thousand years. Our results indicate the main source of sediments to this site was the Parnaíba sedimentary basin. Furthermore, the fluctuations in Fe/K, Al/Si ratios, and Sr values are explained by geochemical processes operating within the region, which likely reflects changes in the hydrological regime and relative sea-level, and intensity of weathering in continental rocks in glacial-interglacial timescales. We suggest that low values of 87Sr/86Sr ratios during glacial are a result of dry conditions. Also, minor fluctuations within the last glacial period may be a consequence of displacements of the Intertropical Convergence Zone (ITCZ). Such displacements cause changes in rainfall and consequently variations in chemical weathering which affect Sr isotopic fractionation. During past humid intervals, the low Nd (non-radiogenic) signal observed could be explained as a process of penetration of rainwater into the deepest non-radiogenic sediment and subsequent replacement of the isotopic signal in the environment in glacial-interglacial timescales.

Sediment source apportionment using optical property composite signatures in a rural catchment, Brazil

Identifying the key sources of fine-grained sediment is essential for protecting and improving soil and water quality. Accordingly, this contribution tested a combination of low-cost analytical procedures for assembling information on key sediment sources in an agricultural catchment in Brazil and in so doing, tested 24 components derived from a conventional printer scanner using various colourimetric models, 18 organic compounds derived from near-infrared (NIR) spectra and 13 soil constituents derived from mid-infrared (MIR) spectra. In combining the application of these low-cost tracers, the study also aimed to investigate potential scale-dependency in sediment sources. Four main sediment sources were sampled: (i) sugarcane; (ii) unpaved roads; (iii) cropland, and; (iv) channel banks and samples were collected from these at two different scales; sub-catchment (~1453 km2) and catchment-wide (~2857 km2). At both scales, channel banks were the most important sediment source followed by sugarcane. At catchment-wide scale, channel banks accounted for 75.9 ± 6.7%, 56.4 ± 16.3%, 39.1 ± 20.7% and 68.3 ± 4.9% of sampled suspended sediment using composite signatures comprising NIR, MIR or colour tracers only, or a combination of all three types of low-cost tracers, respectively. For bed sediment samples, the corresponding respective source contributions were estimated to be 43.4 ± 4.7%, 32.8 ± 7.8%, 49.2 ± 18.6% and 32.0 ± 4.6%. Our results, regardless of optical property, target sediment type, or scale, suggest that channel banks represent the primary source of the sediment problem in the study area. Targeted remedial actions therefore especially need to deliver protection for eroding channel banks.

Elucidating intra-storm variations in suspended sediment sources using a Bayesian fingerprinting approach

There is an increasing need for reliable information on the origin of fine-grained sediment transported by river systems, but critically, at temporal scales that reflect the timing and pattern of sediment mobilization and delivery in response to effective precipitation events. Temporal variability is likely to be more pronounced in steep mountainous catchments. Accordingly, the main objective of this study was to investigate the temporal variability of sediment sources during and between flood events, in a mountainous catchment in Iran, using a geochemical fingerprinting approach and Bayesian un-mixing model. Potential sediment sources were classified as either tributary sub-basin spatial end members or individual source types represented by surface soils and channel banks. A total of 34 geochemical elements, elemental ratios and weathering indices were measured as potential tracers on a total of 155 samples, including 40 target samples collected across the hydrographs of four flood events at the overall catchment outlet. Virtual mixture tests, used to compare the computed source estimates with known source mixtures, revealed better fits in the case of spatial, rather than source type apportionment. The Bayesian un-mixing model results revealed pronounced intra-storm variations in the relative contributions from both the spatial sources and source types, but with Quaternary surface soils and channel banks being dominant at different stages of the hydrographs. For all the suspended sediment samples collected throughout the three small to medium size events, the Babazid, middle upstream sub-catchment, was the major (84%–99%) sediment source while for the largest sampled event, suspended sediment samples predominantly (>98%) originated from the Kalkoshan, the most southern sub-catchment. By investigating both spatial sources and source types, temporal variations in the dominant sources were revealed. Quaternary geology and channel banks were identified as the main sediment sources. By combining instantaneous suspended sediment loads through the sampled flood events (across all floods) and using the corresponding source proportions derived from the MixSIR un-mixing model, channel banks and channel bank and surface soils generated 2911 kg and 34,171 kg of suspended sediment, respectively. Whilst the use of spatial source end members is practical in medium-size drainage basins, integration with estimates of sediment source type contributions is more informative to managers in selecting relevant sediment mitigation methods. The intra-storm results underscore the need to manage sediment loss from both surface soils and channel banks.

Syn-collisional detrital zircon source evolution in the northern Moroccan Variscides

U–Pb dating and Hf isotopic analyses of detrital zircon grains from Cambrian-Devonian strata in the Moroccan Mesetas were undertaken in order to constrain its Paleozoic paleogeographic evolution. In this work, we analyzed 12 Late Devonian-Late Carboniferous samples of syn-collisional detrital rocks from the Western and Eastern Moroccan Mesetas. All our samples present significant Ediacaran (ca. 620 Ma) and Rhyacian (ca. 2.1 Ga) detrital zircon populations, suggesting that the West African Craton remained the main source of sediments for northern Morocco at least until the Late Carboniferous. Locally, a Stenian-Tonian (ca. 1.0 Ga) detrital zircon population is also present, probably fed from intermittent and distant source areas located in NE Africa (e.g. Sahara Metacraton). The collisional evolution started with the approach of an Avalonian promontory to the northern Gondwana continental margin (latest Devonian - earliest Carboniferous), after the closure of the Rheic Ocean. This process entailed the former subduction of the Rheic oceanic lithosphere underneath the Avalonian continental terrane and the formation of a magmatic arc in the upper plate. In this scenario, the first syn-collisional sediments (Tournaisian; Tiflet and Debdou-Mekkam areas) are characterized by a Devonian detrital zircon population (ca. 370 Ma), presumably derived from the magmatic arc, and an increasing number of Mesoproterozoic dates, putatively also sourced from the continental crust of the Avalonian terrane. After the initial collision, only the Visean samples located in areas close to the exotic terrane (e.g. Ben Slimane area) displayed a minor Avalonian component. Finally, the Late Carboniferous samples from the Jerada area recorded an important Middle Carboniferous (ca. 330 Ma) detrital zircon population, probably sourced from Variscan granitoids emplaced in the Eastern Moroccan Meseta and attesting to crustal thickening and subsequent thermal maturation of the Gondwana continental crust in this area.

Paleogeographic evolution of the southern Paraná Basin during the Late Permian and its relation to the Gondwanides

The end of the Permian marks an important change in the depositional context of the southwestern Gondwanan continent. These changes are related to the last invasion of the Panthalassa Ocean, and the posterior oceanic retreat and emplacement of desertic conditions. This paper provides a detailed paleogeographic evolution of the southern portion of the Paraná Basin, supported by facies descriptions, stratigraphic analysis, and U-Pb-Hf detrital zircon analysis (LA-ICP-MS). The studied interval records a large regression that was composed of three forced-regression pulses related to important facies shifts ascribed to the outer ramp, inner ramp, and arid continental systems. Provenance zircon UPb analysis in the inner ramp and continental arid climate deposits indicates that the main sediment source was the Brasiliano basement and the Gondwanides mountain ridge, situated to the west and south. The abrupt paleogeographic change related to the evolution of a system dominated by inner ramp to arid continental facies is compatible with the tectonic reorganization of the Paraná Basin close to the Permo-Triassic limit. Here we present a paleogeographic evolution model which adds new elements to better understand the great transgressive-regressive event that occurred in southwestern Gondwana during the late Permian.

A framework for testing large-scale distributed soil erosion and sediment delivery models: Dealing with uncertainty in models and the observational data

Evaluating distributed soil erosion models is challenging because of the uncertainty in models and measurements of system responses. Here, we present an approach to evaluate soil erosion and sediment delivery models, which incorporates sediment source fingerprinting and sediment-rating curve uncertainty into model testing. We applied the Generalized Likelihood Uncertainty Estimation (GLUE) methodology to the Sediment Delivery Distributed model (SEDD) for a large catchment in Southeast Brazil. The model was not rejected, as 23.4% of model realizations were considered behavioral. Fingerprinting results and SEDD simulations showed a partial agreement regarding the identification of the main sediment sources in the catchment. However, grid-based estimates of soil erosion and sediment delivery rates were highly uncertain, which restricted the model's usefulness for quantifying sediment dynamics. Although our results are case-specific, similar levels of error might be expected in erosion models elsewhere. The representation of such errors should be standard practice.

Сток наносов и мутность воды основных притоков Ладожского озера

The vast catchment area of the Lake Ladoga is characterized by variety of underlying surface types and a complex hydrographic network. The processes of eutrophication of the southern littoral areas of the Lake Ladoga determine the relevance of assessing the removal of solid matter from the river flow to the estuaries of the tributaries of the Ladoga. Observations of sediment runoff of the main tributaries the Lake Ladoga were not carried out. In this regard, for each tributary were selected rivers-analogues the main criteria in the selection was the slope, the grain size of sediments and the catchment area (water availability). The modeling of annual solid runoff and turbidity of the Ladoga tributaries is based on an analytical formula for sediment flow by M.V. Shmakova and a stochastic model of annual solid runoff (M.V. Shmakova). According to the calculations, the annual flow of sediment entering the Ladoga water area is about 432 thousand t/year. The main sources of sediment are three major tributaries of the Lake Ladoga – the Svir, Volkhov and Vuoksa rivers, which account for 253 thousand t/year or 59 % of the total amount of sediment received in the lake. However, these watercourses have the smallest annual module solid flow, due to retention of sediment of backwater areas before hydroelectric dams on these rivers and as a consequence, a decrease in the overall sediment discharge. At the same time, the average annual solid runoff modulus for the Ladoga lake catchment area is 1.53 t/(km2·year), which corresponds well to the previous estimate of this value for the territory under consideration. The analysis of the annual module of solid runoff showed a good correspondence between the obtained values of this value and the conditions for the formation of solid runoff in the catchment, the characteristics of its soils.

Fingerprinting sediment sources of the Shouchang River in the Southeastern China

Identification of sediment sources within catchments is crucial for river and catchment management. A multivariate mixing model in conjunction with two sets of statistically verified composite fingerprints was employed to identify the main sediment source areas at five locations along the main channel of the Shouchang River, southeastern China. The fingerprint composite fingerprints derived from the principle component analysis (PCA) and discriminant function analysis (DFA) combination can better apportion the five types of potential sediment sources. This combination demonstrated that over 33.0% sediment at each location came from river bed, with the largest contribution of 42.9%. The contributions from construction lands ranged from 16.0 to 26.8%. Sediment contributions from forest lands ranged from 7.8 to 22.1%. A large portion of sediment came from paddy fields, varying from 8.7 to 31.4% at the five locations. The sediment from dry land was the smallest, with the largest contribution of 18.4%, and the least contribution of 4%. Similar findings were also identified using the composite fingerprints derived from KW-H and DFA combination. Land use, topography, precipitation, and human activities were responsible for the sediment source apportionments and their variations at the five sediment sampling sites. This study implies that the available sediment from road and bridge built as well as plant production should well be supervised, laws should be made to inhibit in-stream sand mining activity, and the connectivity between paddy fields and channels should be reduced.

Prediction of Sediment Yield in the Middle Reaches of the Yellow River Basin Under Extreme Precipitation

The Yellow River is one of the rivers with the largest amount of sediment in the world. The amount of incoming sediment has an important impact on water resources management, sediment regulation schemes, and the construction of water conservancy projects. The Loess Plateau is the main source of sediment in the Yellow River Basin. Floods caused by extreme precipitation are the primary driving forces of soil erosion in the Loess Plateau. In this study, we constructed the extreme precipitation scenarios based on historical extreme precipitation records in the main sediment-yielding area in the middle reaches of the Yellow River. The amount of sediment yield under current land surface conditions was estimated according to the relationship between extreme precipitation and sediment yield observations in the historical period. The results showed that the extreme rainfall scenario of the study area reaches to 159.9 mm, corresponding to a recurrence period of 460 years. The corresponding annual sediment yield under the current land surface condition was range from 0.821 billion tons to 1.899 billion tons, and the median annual sediment yield is 1.355 billion tons, of which more than 91.9% of sediment yields come from the Hekouzhen to Longmen sectionand the Jinghe River basin. Therefore, even though the vegetation of the Loess Plateau has been greatly improved, and a large number of terraces and check dams have been built, the flood control and key project operation of the Yellow River still need to be prepared to deal with the large amount of sediment transport.

Coupling Sediment Transport Dynamics with Sediment and Discharge Sources in a Glacial Andean Basin

Suspended and bedload transport dynamics on rivers draining glacierized basins depend on complex processes of runoff generation together with the degree of sediment connectivity and coupling at the basin scale. This paper presents a recent dataset of sediment transport in the Estero Morales, a 27 km2 glacier-fed basin in Chile where suspended sediment concentration (SSC) and bedload (BL) fluxes have been continuously monitored during two ablation seasons (2014–2015 and 2015–1016). The relationship between discharge and SSC depends on the origin of runoff, which is higher during glacier melting, although the hysteresis index reveals that sediment sources are closer to the outlet during snowmelt. As for suspended sediment transport, bedload availability and yield depend on the origin of runoff. Bedload yield and bedload transport efficiency are higher during the glacier melting period in the first ablations season due to a high coupling to the proglacial area after the snowmelt period. Instead, on the second ablation seasons the peak of bedload yield and bedload transport efficiency occur in the snowmelt period, due to a better coupling of the lower part of the basin caused by a longer permanency of snow. Differences in volumes of transported sediments between the two seasons reveal contrasting mechanisms in the coupling dynamic of the sediment cascade, due to progressive changes of type and location of the main sources of runoff and sediments in this glacierized basin. The paper highlights the importance of studying these trends, as with retreating glaciers basins are likely producing less sediments after the “peak flow”, with long-term consequences on the ecology and geomorphology of rivers downstream.

Provenance and tectonic setting of the Early Permian sedimentary succession in the southern edge of the Sydney Basin, eastern Australia

Early Permian basins formed during a major phase of crustal extension are common throughout eastern Gondwana. One of these basins, the Sydney Basin, has not been subjected to geochemical studies aimed at determining the sedimentary provenance and the tectonic setting. This study provides new geochemical data of the Lower Permian siliciclastic successions in the southern edge of the Sydney Basin. Published petrographic analysis indicates a source area containing sedimentary, felsic volcanic, plutonic, and low‐grade metamorphic rocks. Major, trace and rare earth element data suggest that the clastic rocks are geochemically mature and originated from a continental source that has been subjected to moderate to strong weathering. Further, they indicate that most source rocks were of felsic composition and that only the oldest sediments possess a more mafic signature. The provenance data presented in this study, along with published palaeocurrent data, point to the Lachlan orogen being the main source of sediments for the basin. Multi‐dimensional discrimination diagrams suggest a continental rift setting and agree with the published sequence stratigraphic framework that suggests a deepening‐upward depositional trend associated with tectonic subsidence. This study documents geochemically the provenance of the sedimentary successions within the southern edge of the Sydney Basin and the continental rift origin of the basin.

Response of interrill erosion to flow parameters of sand loess in regions with high and coarse sediment yields

In the Loess Plateau, regions with high and coarse sediment yields are the main sources of the Yellow River sediments. The responses of the interrill erosion rate of the soil in this area (Shenmu soil) to flow intensity parameters were systematically investigated through indoor artificially simulated rainfall experiments considering five slope gradients (0.1564, 0.2079, 0.2588, 0.309, and 0.3584) and five rainfall intensities (60, 80, 100, 120 and 140 mm·h−1). Thereafter, an interrill erosion model was established based on two types of soil: Shenmu soil and Ansai soil. The experimental data of Ansai soil were obtained from a study by Wu et al. (2017). The results showed that for Shenmu soil, the interrill erosion mechanism can be classified into two types. The first type was detachment-limited interrill erosion in the initial rainfall phase and transport-limited interrill erosion in the subsequent rainfall. The other type was transport-limited interrill erosion during the entire rainfall duration. Among the flow intensity parameters (i.e., mean flow velocity (R2 = 0.92), shear stress (R2 = 0.84), stream power (R2 = 0.96), and unit stream power (R2 = 0.82)), stream power was found to be satisfactory for predicting the interrill erosion rate of Shenmu soil in terms of the coefficient of determination (R2). However, the interrill erosion rate model based on the stream power for the two types of soil exhibited low prediction accuracy. Furthermore, a general flow intensity parameter was derived to predict the interrill erosion rate of overland flow. Based on this parameter, an interrill erosion rate model for the two types of soil was formulated by multiple regression analysis with an R2 value of 0.96, a relative root mean square error of 18.9%, and a model efficiency of 0.94. Overall, this general flow intensity parameter was shown to be the preferred predictor for estimating the interrill erosion rate for steep slopes in the regions with high and coarse sediment yields.

Use of geochemical fingerprints to trace sediment sources in an agricultural catchment of Argentina

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered to be significantly driving and accelerating these processes. This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF), elemental concentrations were determined and later used as soil tracers for geochemical characterization. The best set of tracers were identified using two artificial mixtures composed of known proportions of soil sources collected from different lands having contrasting soil uses. Barium, calcium, iron, phosphorus, and titanium were identified for obtaining the best suitable reconstruction of source proportions in the laboratory-prepared artificial mixtures. Then, these elements, as well as the total organic carbon, were applied for pinpointing critical hot spots of erosion within the studied catchment. Feedlots were identified to be the main source of sediments, river banks and dirt roads together are the second most important source. This investigation provides key information for optimizing soil conservation strategies and selecting land management practices and land uses which do not generate great contribution of sediment, preventing pollution of the waterways of the region.

Origin and geochemistry of surface sediments in the mud deposit area offshore the Shandong Peninsula, China

The waters offshore the Shandong Peninsula separate the North Yellow Sea from the South Yellow Sea, and receive a large amount of terrestrial material from Chinese and Korean rivers, making it an ideal area for studying land-sea interactions. However, little attention has been given to measuring sediment transportation in most previous studies. Based on an analysis in composition of major and trace elements and particle size characteristics from 62 surface sediment samples from the northeastern region off Shandong Peninsula, the type, element composition, and controlling factors of the surface sediments were investigated. In addition, the transportation of sediments from source to sink was described from measured thermohaline data. The results show two types of surface sediments: sandy silt and silt. The sediments were mainly terrestrial; and marine carbonate had little effect on sediment composition. Shown on a binary diagram of Rb/Sc to Co/Sc, the Huanghe (Yellow) and Changjiang (Yangtze) rivers are the main sources of surface sediments in the study area. The component mixing model showed that the relative contribution of sediment from the Huanghe River was up to 92%, followed by the Changjiang River (8%). The Yellow Sea Warm Current and the North Shandong Peninsula Coastal Current met at ~37.7°N in the study area, and were the main forces carrying sediment from the two main river sources. However, there was a deficit of transported material into the study area in summer. The secondary distribution of sediment from the two river sources was controlled by tidal currents and waves.