Identification Of Sediment Sources Research Articles

Remotely mapping gullying and incision in Maryland Piedmont headwater streams using repeat airborne lidar

Headwater streams can contribute significant amounts of fine sediment to downstream waterways, especially when severely eroded and incised. Potential upstream sediment source identification is crucial for effective management of water quality, aquatic habitat, and sediment loads in a watershed. This study explored topographic openness (TO) derived from 1-m lidar for its ability to predict incision in headwater streams and to remotely detect changes in incision over time. Field surveys were conducted in one forested and two recently urbanized headwater watersheds in the Maryland Piedmont physiographic province, USA to characterize the level of stream channel incision (none, moderate, or severe) in the main stem of each watershed. Predictions of the severity of stream channel incision derived from TO were compared against the field surveys. Channel incision was detected with an overall accuracy of 67 %, with best performance in reaches with either severe or no incision (79–86 % accuracy). The method was also applied to repeat lidar collected over the same area to model the extent of channel incision in 2002 before urban development began and in 2008 and 2013 during active construction in the urban watersheds. Results showed increasing incision over time in all three watersheds, with similar patterns in the forested and urban watersheds. This new method of remotely measuring channel incision can be used to identify potential sediment sources across a watershed, enhance water and habitat quality predictions, and detect changes over time where multiple years of overlapping lidar are available.

Variations in weathering conditions related to sea level changes during the Albian-Santonian interval in the Western Australian margin as evidenced by clay minerals and Nd/Sr isotopes

The Albian-Santonian interval (∼113–83 Ma) is a key interval for Cretaceous climatic and environmental changes. This interval is associated to a rise in sea level until the Late Cenomanian (∼ 94 Ma) and to a progressive increase in oceanic temperatures, leading to consider the Late Cenomanian-Santonian interval (∼ 94–83 Ma) as the warmest period of the last 200 Myr. While the Albian-Santonian interval has been well studied in the Northern Hemisphere, the climatic and environmental variations and their consequences on weathering conditions are less documented of the Southern Hemisphere, especially in mid and high latitudes. To better understanding the evolution of weathering conditions, associated to continental climate and sea level changes during this key period, an integrated study, based on a coupled mineralogical and geochemical approach, was carried out on the clay-sized (< 2 μm) fraction from sediments of International Ocean Discovery Program Site U1513 (Mentelle Basin, South-western Australia) and Oceanic Drilling Program Site 763 (Carnarvon Basin, North-western Australia). To determinate variations in weathering conditions, the mineral assemblages of the clay fraction was determined by X-ray diffraction and observed for selected samples by electron microscopy. To identify sources of clay minerals, the concentrations of major and selected trace elements, including rare earth elements, together with strontium and neodymium isotopic measurements were performed on the clay-sized fraction. The X-ray diffraction analyses reveal that clay fraction is dominated by R0-type illite/smectite mixed-layers (smectites), followed by variable proportions of illites, kaolinites for both sites and only on Site 763 of palygorskites. These clay minerals are associated with opal and clinoptilolites. Electron microscopy observations have highlighted the dominance of detrital fleecy smectites but also the occurrence of recrystallized lathed smectites and volcanogenic folded smectites for Site U1513, and authigenesis of clay minerals, associated to palygorskites especially on Turonian to Santonian deposits for Site 763. This authigenesis, confirmed by negative cerium anomaly, is also carried by other minerals in the clay-sized fraction (e.g., clinoptilolites, barite). These different authigenic minerals record a seawater-derived isotopic signature. Therefore, isotopic compositions of the clay-sized fraction reflect a mix between a continental contribution, carried by detrital clay minerals and marine one, supported by authigenic minerals, which complicates the identification of sediment sources. However, despite this, our study demonstrates the major influence of sea level variations on mineralogical variations from Albian to Cenomanian in Western margin of Australia. The decrease in kaolinite proportions at Site U1513 from the Albian to the end of the Cenomanian, is probably related to the increase of sea level, which cause a decrease in detrital inputs in the Mentelle Basin associated with a decrease of weathering and drainage conditions. The progressive sea level rise has also enhanced the effect of the differential settling process of clay minerals by the deposition of coarse clays (e.g., kaolinites and illites) on the continental shelf. Kaolinite-bearing clay deposits, derived from the weathering of the Western Australian Craton during the Albian-Cenomanian times, have been progressively substituted from the Turonian by a carbonate sedimentation, for which the terrigenous component consists only of rare detrital and volcanogenic smectites. In Site 763, the occurrence in kaolinite content during the Coniacian would indicate a decrease of differential settling process related to the weathering of the north part of the Western Australia Craton.

Spatiotemporal ecological risk evaluation and source identification of heavy metals and nutrients in the water and lake surface sediment in a protected catchment area of a volcanic lake.

Indonesia has numerous lakes; however, research on the spatiotemporal sediment quality and source identification in lakes remains limited. The overaccumulation of heavy metals and nutrients in lakes severely threatens aquatic ecosystems. This study aims to identify potential sources of metallic deposits (Cu, Pb, Cr, Fe, Al, and Cd) and nutrients (TN and TP) in lake-surface sediment, utilizing enrichment factors (EF), geoaccumulation indices (Igeo), potential ecological risk indices (Er), and risk indices (RI). Multivariate statistical analyses, including principal component analysis (PCA) and Pearson's correlation analysis, were conducted to pinpoint pollution sources linked to land use. Eight sampling sites for surface sediment and water were examined in both wet and dry seasons at Menjer Lake, chosen for its diverse applications in tourism, hydropower, floating net cages, and extensive agriculture in its catchment. Correlation and PCA results indicated that Pb, Fe, and Al mainly originate from tourism, while Al, Fe, TN, and TP are associated with agriculture. The highest average loading from land use was observed in agriculture (> 0.8), floating net cages (> 0.76), and tourism (> 0.68). Furthermore, the highest loading from nutrients and all metals were TP (> 0.71) and all metals (> 0.35), respectively. Ecological risk assessment revealed low to moderately polluted EFs and Igeo in the dry season. However, Menjer Lake's Er and RI for heavy metals were generally classified as unpolluted.

Modeling of Suspended Particulate Matter Concentration in an Extremely Turbid River Based on Multispectral Remote Sensing from an Unmanned Aerial Vehicle (UAV)

Following consecutive years of governance efforts, there has been a substantial reduction in sediment transport in the Yellow River, resulting in significant changes in its water–sediment dynamics. This necessitates precise monitoring of sediment-bearing tributary inflows, a crucial requirement for effective governance strategies on the Loess Plateau’s current developmental stage. While satellite remote sensing technology has been widely used to estimate suspended particulate matter concentration (CSPM) in open water bodies like oceans and lakes, its application in narrow rivers presents challenges related to hybrid pixel and proximity effects. As a result, the effectiveness and competence of satellite remote sensing in monitoring CSPM in such confined river environments are reduced. This study attempted to use unmanned aerial vehicle (UAV) remote sensing with multispectral technology to invert CSPM in the Wuding River, a sediment-bearing Yellow River tributary. A novel CSPM concentration inversion model was introduced for highly turbid river settings. The results showed that the accuracy of the new band ratio model in this study is significantly improved compared with the existing models. The validation dataset had a coefficient of determination (R2) of 0.83, a root mean square error (RMSE) of 3.73 g/L, and a mean absolute percentage error (MAPE) of 44.95% (MAPE is 40.68% at 1–20 g/L, and 12.37% at &gt;20 g/L). On this basis, the UAV also monitored the impacts of heavy rainfall on the CSPM, resulting in a rapid rise and fall in CSPM over a period of ten hours. This study demonstrated the potential of UAV remote sensing for CSPM monitoring in extremely turbid narrow rivers (tens to tens of meters), especially before and after rainfall sediment production events, which can provide technical support for accurate sediment management and source identification in the main tributaries of the Yellow River and help realize the goal of high-quality development of the Yellow River Basin.

Sediment source and sink identification using Sentinel-2 and a small network of turbidimeters on the Vjosa River

Abstract. Measurement of suspended sediment concentration (SSC) at a basin outlet yields a basin-integrated picture of sediment fluxes; however, it does not give a full spatial perspective on possible sediment pathways within the catchment. Spatially resolved estimates of SSC along river networks are needed to identify sediment sources and sinks, to track erosion gradients, and quantify anthropogenic effects on catchment-scale sediment production, e.g., by dam construction or erosion control. Here we explore the use of high-resolution Sentinel-2 satellite images for this purpose in narrow and morphologically complex mountain rivers, combined with ground station turbidity sensing for calibration and supported by a Lagrangian kayak-derived river profile measurement. The study is carried out on the Vjosa River in Albania, which is one of the last intact large river systems in Europe. We developed a workflow to estimate river turbidity profiles from Sentinel-2 images including atmospheric, cloud cover, and deepwater corrections for the period May 2019 to July 2021 (106 images). In situ turbidity measurements from four turbidity sensors located along the Vjosa River provided ground truthing. A multivariate linear regression model between turbidity and reflectance was fitted to this data. The extracted longitudinal river turbidity profiles were qualitatively validated with two descents of the river with a turbidity sensor attached to a kayak. The satellite-derived river profiles revealed variability in turbidity along the main stem with a strong seasonal signal, with the highest mean turbidity in winter along the entire length of the river. Most importantly, sediment sources and sinks could be identified and quantified from the river turbidity profiles, both for tributaries and within the reaches of the Vjosa. The river basin and network acted as a sediment source most of the time and significant sediment sinks were rare. Sediment sources were mostly tributaries following basin-wide rainfall, but within-reach sources in river beds and banks were also possible. Finally, we used the data to estimate the mean annual fine sediment yield at Dorez at ∼2.5±0.6 Mt yr−1, in line with previous studies, which reveals the importance of the Vjosa River as an important sediment source of the Adriatic Sea. This work presents a proof of concept that open-access high-resolution satellite data have potential for suspended sediment quantification not only in large waterbodies but also in smaller rivers. The potential applications are many, including identifying erosion hotspots, sediment activation processes, local point sources, glacial sediment inputs, and sediment fluxes in river deltas, with a necessary future research focus on improving accuracy and reducing uncertainty in such analyses.

Refining fine sediment source identification through integration of spatial modelling, concentration monitoring and source tracing: A case study in the Great Barrier Reef catchments

Excess fine sediment delivery is a major contributor to the declining health of the Great Barrier Reef and identifying the dominant source areas of fine sediment has been critical to prioritising erosion remediation programs. The Bowen River catchment within the Burdekin Basin has been recognised as a major contributor and hence received considerable research investment over the last two decades. This study adopts a novel approach to integrate three independently derived sediment budgets produced from a catchment scale sediment budget model (Dynamic SedNet), targeted tributary water quality monitoring and geochemical sediment source tracing to refine and map the sediment source zones within the Bowen catchment. A four year study of water quality monitoring combined with modelled discharge estimates and geochemical source tracing both identified that the Little Bowen River and Rosella Creek were the largest sources of sediment in the Bowen River catchment. Both data sets contradicted initial synoptic sediment budget model predictions due to inadequate representation of hillslope and gully erosion. Recent improvements in model inputs have resulted in predictions that are consistent with the field data and are of finer resolution within the identified source areas. Priorities for further investigation of erosion processes are also revealed. Examining the benefits and limitations of each method indicates that these are complimentary methods which can effectively be used as multiple lines of evidence. An integrated dataset such as this provides a higher level of certainty in the prediction of fine sediment sources than a single line of evidence dataset or model. The use of high quality, integrated datasets to inform catchment management prioritisation will provide greater confidence for decision makers when investing in catchment management.

Using geochemical elements to discriminate sediment sources in a typical karst watershed

Knowledge of temporal variations in sediment sources is necessary to identify the principal sources of sediment for effective implementation of soil conservation measures and to improve the calibration and validation of process-based soil erosion models. Quantitative information on sediment provenance is often limited in karst regions because of their complex surfaces and underground three-dimensional erosion systems. Peak-cluster depressions are typical landforms in karst areas and can well intercept most sediment from hillsides such as dams or reservoirs. Thus, peak-cluster depressions are suitable areas for sediment source identification. The objective of this study was to quantify the contribution of sediment sources in a typical karst watershed and to identify temporal variations in sediment sources in the watershed in the past 60 years. We collected 194 soil samples from three sediment profiles in a karst depression and 58 source samples from cropland, fissure soil, and forestland. We used a composite fingerprinting method based on 45 geochemical properties and an IsoSource multivariate mixed model in a typical karst watershed. The results indicate that cropland was the principal sediment source (89.2 %) in the last 60 years, followed by fissure soil (9.6 %) and forestland (1.2 %). Importantly, compared with the period from 1949 to 1999, the contribution of sediment from fissure soil reached a maximum value of approximately 20 % from 1999 to 2015. This result implies that the “Grain for Green” program, which was implemented in 1999, clearly reduced the amount of soil erosion from cropland. Therefore, the program may greatly affect sediment deposition in karst depressions. Using metal ratios as fingerprint factors, the IsoSource mixed model can be effectively used to study the source of sediments in karst watersheds quantitatively. This study can aid the existing understanding of soil erosion processes and contributes to the sustainable development of agro-ecology in karst watersheds.

Extreme Flood Sediment Production and Export Controlled by Reach‐Scale Morphology

AbstractRapid earth surface evolution is discrete in nature, with short‐duration extreme events having a widespread impact on landscapes despite occurring relatively infrequently. Here, we exploit a unique opportunity to identify the broad, process‐based, controls on sediment production and export during extreme rainfall‐runoff events through a multi‐catchment analysis. A 3 hr extreme rainfall event generated significantly different impacts across three catchments, ranging from (a) sediment export exceeding two orders of magnitude more than the typical long term average to (b) a minimal impact, with this variability primarily controlled by catchment steepness and the presence of reach‐scale morphological transitions caused by postglacial landscape adjustment. In any catchment worldwide where populations are at risk, we highlight the importance of combining topographic analysis with detailed mapping of channel bed material (e.g., presence of transitions between process domains) and identification of sediment sources within morphological transition zones for accurately predicting the impact of extreme events.

Extraction of effective sedimentary signals from rivers in Bangladesh and their application in the Bay of Bengal

River sediments compositions in Bangladesh were measured to extract effective signals of chemical weathering, sedimentary processes and provenances and applied to sedimentary record in the Bay of Bengal (BoB). Weathering indexes including the chemical index of alteration (CIA), weathering index of Parker (WIP), αAlE and related diagrams indicated overall weak to intermediate chemical weathering intensity in modern Ganges-Brahmaputra-Meghna (G-B-M) catchment. Sedimentary processes controlled sediment mineralogical and chemical composition to a certain extent, as reflected in the distinctions between suspended loads and bedloads. The suspended loads were richer in phyllosilicates than the bedloads in the Brahmaputra and the Meghna River sediments, and the Meghna River bedload exhibited sedimentary recycling and quartz dilution features. The Ganges River sediments showed multiple recycling and source mixing features. Extracted provenance proxies indicated that the Brahmaputra River sediments got relatively more effects from Himalayan mafic to intermediate rocks, while the Ganges River sediments indicate a mixture from the Himalaya and Indian Peninsula. more effects from ultramafic rocks were revealed for the Meghna River sediments. By comparing the extracted provenance proxies of different rivers and applying them to the identification of sediment sources in the Bay of Bengal (BoB), the Brahmaputra River is suggested to have been the primary supplier of sediments to the central-northern BoB since the last glacial period as a result of the highest erosion rate in the eastern syntaxis, which provides a new understanding of the sediment “source-sink” process in the BoB and indicates that effective extraction of fluvial information is crucial for marine sedimentology studies.

Accuracy verification of optical fingerprinting methods in sediment tracing study

AbstractSediment fingerprints have been widely used in source identification studies. Optical features have become a powerful substitute for traditional fingerprints in recent years due to their fast measurement and low analysis costs. However, the accuracy of optical fingerprinting methods has received little attention. Here, artificial mixing and indoor scouring experiments were carried out to compare and assess the accuracy of optical fingerprinting results using three spectroscopic ranges [visible (VIS), near‐infrared (NIR), and mid‐infrared (MIR) spectroscopy] in multivariate models and using 19 colour parameters [such as red (R), green (G) and blue (B) in an RGB system; virtual component X (X), brightness (Y) and virtual component Z (Z) in a CIE XYZ system and so on] coupled with the conventional method. Furthermore, we examined how sediment sorting (particle sorting and organic matter enrichment) affects the accuracy of source apportionments. The results showed that VIS, NIR and MIR spectroscopic tracers presented high accuracy in scouring and artificial mixtures, with mean absolute error (MAE) values of 4.98% and 5.91%. In contrast, the colour parameters had weak performances in two experiments (MAE = 16.83% and 15.05%). Additionally, similar fingerprinting results of the scouring mixtures (MAE = 7.95%) and artificial mixtures (MAE = 8.20%) indicated that slight particle sorting and organic matter enrichment have little effect on the accuracy of optical fingerprinting results. Our study shows that sediment fingerprinting based on optical features, especially three spectroscopic ranges, has good applicability in sediment source identification.

Assembly process and source tracking of microbial communities in sediments of Dongting Lake

Sediment source tracing can accurately provide a theoretical basis for controlling soil erosion effectively, by identifying the most serious types of land use. Traditional sediment tracing methods are based on physical, chemical, biological, and composite fingerprinting, which have not included microbes. As high-throughput sequencing becomes more prevalent, microorganisms can provide more information than what we think. Thus, whether the microorganism can also be used as a special fingerprint factor for sediment source identification during soil erosion, we have tested it by using microbial source tracking tool FEAST to quantify the microbe contribution from five types of eroded land (including dryland, urban, paddy field, forest and grassland) to the depositional areas (Niubitan) in the Yuanjiang basin. The source microbial community in the erosive area was heterogeneous, and assembly process analysis further demonstrated that the source tracking results could reach higher accuracy. The results of FEAST showed that dryland (35.50%), urban (17.21%), paddy field (8.14%), and forest (1.07%) were the major contributors to Niubitan. Our results follow the general soil erosion rules and prove its validity. Taken together, a new perspective is provided by these results for tracing sediment sources in erosion-sedimentary systems.

Sediment source determination for a series of connected check dams in an agricultural catchment in the Chinese Mollisol region

The composite fingerprinting approach is valuable in sediment source identification at different temporal and spatial scales. However, few studies have estimated watershed sediment source connections and transport impacted by multiple check dams. This is due to the complexity of particle sorting under flood discharge practices. Here, we attempt to identify sediment sources with three connected check dams in an agricultural Mollisol catchment in Northeast China based on optimal fingerprints screened from different size fractions (i.e., <10, <63, and <1000 μm). The results showed consistent sediment contributions based on fine particle size ranges (i.e., <10 and <63 μm) but an inconsistent contribution based on a coarse particle size range (i.e., <1000 μm), regardless of the particle size or the organic corrections applied. Sediment deposited in check dams No. 1 and No. 2 was mainly from hillslopes (cropland) (>66.7 %), while sediment in check dam No. 3 was from its adjacent upstream check dam (i.e., No. 2; >60.5 %) based on optimal fingerprints screened from <10 and <63 μm particle size ranges. However, when fingerprints were screened from a coarse particle size (<1000 μm), sediment in all three check dams was mainly from gully slopes (>79.0 %), regardless of the specific surface area (SSA) of particles or the soil organic carbon (SOC) correction factors used in the model except for SOC correction for check dam No. 2. Conversely, sediment was mainly derived from hillslopes when fingerprint values were corrected using SSA and SOC, except that no optimal fingerprints were selected. This indicated the feasibility of sediment source discrimination based on the composite fingerprinting approach for sediment source identification in catchments with a series of connected check dams under the condition that particle fractions impacted by check dams are relatively weak. However, optimal fingerprints screened from a relatively wide range of coarse particles caused divergent results regardless of the particle size or the organic correction factors used in model estimation or in fingerprint values. Further studies are necessary to explore the reliability of the composite fingerprinting approach for sediment source tracing under a series of connected check dams, where coarse sediment is selectively deposited and fine sediment is massively discharged under flood discharge practices.

Dry-season sources of riverine sediment from the tropical mixed urban-agricultural watershed of the Mun River Basin in northeastern Thailand

Northeastern (NE) Thailand is well recognized as the land for rice cropping and consequently, it is potentially contaminated with chemicals from soil fertilization, pest/weed control, and urban discharges. The Mun River basin in NE Thailand principally is comprised of rice paddies and sedimentation in the river has been pronounced, but the studies on sediment source identification are limited. The current study aims to identify sediment sources in the Mun River basin and discuss possible impacts on ecosystems attributed to exposure to polluted sediment. The assessment relies upon physicochemical properties and heavy metal contents (iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), nickel (Ni), and Zinc (Zn)) in the fine-grained sediment (<63 μm) taken from the Mun River basin and the Chi River in the dry season of 2020–2021. The findings revealed that the heavy metals in the sediment had not accumulated to levels of concern. Most sediment was from natural sources, including Fe- and Mn-rich sediment, Cr-dominant sediment, and Ni- and Cu-rich sediment. Fe- and Zn-rich sediment was, however, found in the urban watershed of Lam Ta Klong, and it could originate from mixed urban sources. Fe-rich sediment was predominant in the Mun River basin, which and could be a significant sink and source of toxic elements from agricultural and urban discharges. It is suggested that the toxic compounds in the sediment should be consistently monitored, whereas ecological and health risk assessment should be focused on the mobile forms.

GEOCHEMISTRY AND ROCK MAGNETIC ANALYSIS ON SURFACE SEDIMENT IN LAMPENISU RIVER: A QUEST FOR MG SOURCE TO LAKE TOWUTI, INDONESIA

Sediment from Lake Towuti has been extensively studied to reconstruct past climate and environmental changes. One of the remaining questions is the source of magnesium (Mg) and calcium (Ca) in the northern part of Lake Towuti. In this study, the source of high Mg and Ca content is examined by analysing surface sediment from the Lampenisu River (LR) and Mahalona River (MR) that merge before entering Lake Towuti. Twelve surface sediments from MR, LR, and the confluence of the two rivers (LMR) were subjected to geochemical (XRF), mineralogical (XRD), and rock magnetic (susceptibility and hysteresis parameter) analyses. The result shows that the Mg and Ca content in LR samples are higher than in MR samples. LR samples have a higher susceptibility and a lower frequency dependent susceptibility than MR samples. XRD analyses on extracted magnetic grains show the presence of minerals with a sodalite crystal structure, possibly valleyite in LR but not in MR samples. If valleyite indeed occurs in LR samples, it may contribute to their relatively high Ca content. At the same time, the high content of Mg in LR samples is likely due to the serpentinized peridotite rocks. LR is thereby considered to be the source of high Mg and Ca content in the northern portion of Lake Towuti. This study shows the importance of sediment-source identification in big lakes such as Lake Towuti, where the influx could come from several rivers around the lake.

Tracer elements revealed the soil organic carbon sources in a dam-controlled watershed

The dynamics of the soil organic carbon (SOC) pool and the mechanisms that underpin those dynamics are at the frontier of terrestrial carbon (C) cycling research. Soil erosion seriously affects the migration and redistribution of SOC, driving a critical part of the C cycle. In this study, soil samples were collected from a 14.69 m sediment profile formed between 1960 and 2017, which was located in a small agricultural catchment on the Loess Plateau in northwest China. Nuclear tracer elements (137Cs, 210Pb) and stable C isotopes (δ13C) from organic matter were used to quantitatively identify the SOC sources in different siltation stages. The method used assumes that the contribution of a source is proportional to the elemental concentration in that source. SOC in soil samples from different erosion source areas (farmland, forest land, grassland, shrub land and ditch wall) were compared against the deposit in the check dam. The concentration of SOC in the sediments of the check dam was between 1.21 g kg−1 and 4.03 g kg−1. Nearly half of the SOC in the check dam sediments was traced back to the ditch wall. Farmland contributed 24.8 %, while shrub land contributed the least SOC at 0.4 %. SOC erosion attributed to farmland decreased gradually, while the relative contribution from the ditch wall increased. Within the agricultural catchment area, there was a net migration of SOC from the various land cover types (the source) to the sedimentary area behind the dam (the sink). These results indicate that a dynamic balance exists between redistribution and heterotopic storage of SOC during sedimentation. This study provides an opinion for sediment source identification and the soil C cycle in watersheds on the Loess Plateau.

Magnetic properties of the surface sediments from the Huguangyan Maar Lake in tropical Southern China and the sediment source identification

ABSTRACTDeciphering the source(s) of sediment deposited in Hugunagyan Lake in South China using magnetic properties will advance our understanding of the evolution of East Asian monsoon systems. However, the source of magnetic minerals in the surface sediments of this lake is unknown, still needing further exploration. Due to simple hydrological systems, the Hugunagyan Lake provides a unique record for investigating the magnetic property of sediments and surface processes. In this study, based on the magnetic properties of 43 surface sediment, 12 surface soil, and 7 volcanic rock samples from the catchment, we demonstrate that the magnetic minerals in sediments were dominated by fine super paramagnetic magnetic particles, with coexistence of pseudo‐single‐domain states minerals. There are no signatures showing the presence of biogenic and authigenic magnetite. The magnetic properties of surface sediments display significant differences between the potential sources of aeolian dust from the loess in North China and modern surface soils in Central Asia, suggesting that the magnetic minerals mainly originate from the weathered materials in the catchment, and there are no further signals of winter monsoon‐driven aeolian dust input.

Temporal and Spatial Distribution of Surface Sediment and Its Implications in the Yangtze Subaqueous Delta

Characteristics of sediments vary significantly temporally and spatially in the Yangtze subaqueous delta and adjacent East China Sea shelf due to complicated dynamic conditions. Magnetic properties of sediments are sensitive to hydrodynamics and provenance, and therefore can indicate sediment transportation and deposition. High-resolution surface sediments collected in different seasons and years from the Yangtze subaqueous delta and neighboring East China Sea shelf were subjected to environmental magnetic analyses. In combination with granulometric analysis, this paper discusses temporal and spatial variations of magnetic properties and their implications for indicating sediment transportation, sediment source identification, and hydrodynamic response. The results show that magnetic parameters SIRM and XARM/SIRM suggest sediment transportation path from the Yangtze River into the East China Sea, with majority migrating to the south and southeast and then deposited to the west of 123°E, while a little fine sediment delivered to the northeast in summer. Cluster analysis demonstrates three sedimentation districts according to magnetic properties and particle size in the study area, which represent modern Yangtze sediment, late Pleistocene relict sand, and their mixture, respectively. Temporal-spatial changes in particle size of sediments suggests erosion outside the North Branch in the past few years, while opposite trend of changes on particle size of surface sediment in the adjacent area might reflect different degrees of erosion.

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.

Magnetic investigation of surface sediments of the northwestern South China Sea: Implication for sediment provenance and transportation

Abstract Environmental magnetism has been widely used as a rapid, cost-effective, and non-destructive method in various fields including sediment source identification. Systemic magnetic measurements were performed for surface sediments collected from sixty-eight stations within the eastern Beibu Gulf to the south of the Hainan Island. The results indicate that a mixture of single domain (SD) and multi-domain (MD) or persuade single domain (PSD) magnetite and a small part of hematite controlled the magnetic properties of the studied sediments. From north to south, concentration of magnetic minerals slightly decreased and then increased. The study area is partitioned to three sedimentary zones from west to east. Terrigenous input materials from the Qinzhou bay, the Red river, and rivers in the Hainan Island are transported from zone I, II, to III. Terrigenous input dominated sediments of the northern and eastern BBG. Both north–south terrestrial materials and south-north marine sediments carried by offshore tidal current are mixed at further outward to the south of the Hainan Island. The present study proves the effectiveness of the magnetic method for examining provenance and transportation of sediments. We believe that sediments in the eastern Beibu Gulf to the south of the Hainan Island were transported from Qinzhou bay, Red river, and rivers in the Hainan Island.

Identification of sediment sources and exploration of scale effects in the black soil region of Northeast China

Sediment provenance plays an important role in describing soil erosion characteristics and assessing the benefits of soil and water conservation measures. To further understand the transfer of sediment, a Bayesian mixing model-based fingerprint tracing technique was used in this study to quantify the relative contributions of sediment sources to the bottom of the gullies. Two catchments, the Hebei catchment with an area of 27.6 km2 and its sub-catchment with an area of 3.5 km2, located in the black soil region of Northeast China, were selected to identify sediments from cultivated topsoil, uncultivated topsoil, and gully soil. Seventy soil samples were collected from each catchment to characterize the sediment sources. Five sediment samples deposited in gully bottoms were collected from each catchment. Although a composite sampling method was applied, the spatial variability in the fingerprints between the Hebei catchment and its sub-catchment showed significant (p < 0.01) differences. The different optimum composite fingerprints obtained for the two catchments were: Ba, Ga, Br, Ce, and P for the Hebei catchment and Ba, Ga, Br, and As for its sub-catchment. In both catchments, over 95% of the sediment deposited in the gully bottoms was from cultivated topsoil and gully soil. However, the relative sediment contribution of cultivated topsoil and gully soil were significantly (p < 0.01) different between the two catchments. Notably, 42.0% and 47.8% of sediments were from cultivated topsoil while 55.3% and 49.6% of sediments were from gully soil (mean absolute fit > 0.95) in the Hebei catchment and its sub-catchment, respectively. Most of the sediment from the gully (>60%) was deposited in the upper segment of the gully bottom while the sediment from cultivated topsoil gradually increased in the lower segment.