Sediment Source Fingerprinting Research Articles

Enhancing sub-catchment sediment source fingerprinting using chemometric models for DRIFTS in different particle size subfractions

Understanding the origins of sediment within stream networks is critical to developing effective strategies to mitigate sediment delivery and soil erosion in larger drainage basins. Sediment fingerprinting is a widely accepted approach to identifying sediment sources; however, it typically relies on labor-intensive and costly chemical analyses. Recent studies have recognized diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as a non-destructive, cost-effective, and efficient alternative for estimating sediment contributions from multiple sources. This study aimed to assess (i) the effects of different particle size fractions on DRIFTS and conservatism tests, (ii) the effects of spectral pre-processing on discriminating sub-catchment spatial sediment sources, (iii) the efficiency of partial least squares regression (PLSR) and support vector machine regression (SVMR) chemometric models across different spectral resolutions and particle size fractions, and (iv) the quantification of sub-catchment spatial sediment source contributions using chemometric models across different particle size fractions. DRIFTS analysis was performed on three particle size fractions (<38 μm, 38–63 μm, and 63–125 μm) using 54 sediment samples from three different sub-catchments and 26 target sediment samples from the Andajrood catchment in Iran. Results showed significant effects of particle size fractions on DRIFTS for both sub-catchment sediment sources and target sediment samples. Conservatism tests indicated that DRIFTS behave conservative for the majority of target sediment samples. Spectral pre-processing techniques including SNV + SGD1 and SGD1 effectively discriminated sources across all particle size fractions and spectral resolutions. However, the optimal combination of pre-processing, spectral resolution, and regression models varied between sub-fractions. Validated model estimates revealed that sub-catchment 1 consistently contributed the most sediment across all particle size fractions, followed by sub-catchments 3 and 2. These results highlight the effectiveness of DRIFTS as a rapid, cost-effective, and precise method for discriminating and apportioning sediment sources within spatial sub-catchments.

Using stable carbon isotopes of lignin-derived methoxy to improve historical apportionments of particulate organic matter and sediment sources incorporating multiple Suess corrections

PurposeSoil erosion models are essential to improving sediment management strategies. Sediment source fingerprinting is used to help validate erosion models. Fingerprinting sediment sources with organic isotopic tracers faces challenges from aquatic sources and co-linearity. To address these complexities, integrating another land-use-specific tracer is essential. Suess corrections incorporating multiple mean-residence-times are necessary to accurately model historical sediment apportionments. In previous studies, compound specific isotopic tracers indicated forest as the dominant source. We hypothesize that there is an overestimation of forest contribution, attributed to the misclassification of particulate organic matter as forest.MethodsIn this study, we utilize stable carbon isotope (δ13C) values of fatty acids and the average chain length in combination with the δ13C values of lignin-derived methoxy groups as an additional tracer. We apply different Suess corrections to explore the effect of the changing atmospheric δ13CO2 values on sediment apportionment. The performance of the unmixing model is evaluated with 300 mathematical mixtures. To determine shifts in sediment sources throughout the last 130 years, particulate organic matter contributions are determined and removed to apportion sediment soil sources. We investigate the potential misclassification of forest contributions by merging particulate organic matter and forest sources to simulate tracers which are unable to discriminate.ResultsThe inclusion of δ13C values of lignin methoxy groups and the alkane average chain length as additional tracers successfully removed tracer co-linearity. Additionally, we used an updated concentration dependent point in polygon test to identify sediment with increased potential for incorrect source apportionments. Changes in the dominant sediment sources over time (Forest: pre-1990, Pasture: 1910–1940, Arable: post 1940) highlight the effect of policy-induced land-use changes. Additionally, the inability to discriminate particulate organic matter and forest sources was revealed to cause a 37% overestimation of forest contributions from 1944 to 1990.ConclusionUsing δ13C values of lignin methoxy groups as an additional tracer, we identified critical points in the 130-year sediment history of Lake Baldegg. Furthermore, we highlight the importance of incorporating multiple Suess effects. Through mathematical mixtures, we assessed the confidence that should accompany apportionment estimates. While merging forest and particulate organic matter sources did not result in forest as the dominant source over the last 130 years, separating these sources resulted in more accurate apportionment. These insights offer valuable information to enhance the accuracy of sediment fingerprinting, which can then be used to assist soil erosion models employed for sediment mitigation policies.

Source fingerprinting sediment loss from sub-catchments and topographic zones using geochemical tracers and weathering indices

Application of sediment source fingerprinting techniques to generate reliable information on sediment sources is growing, because of the global environmental importance of elevated fine-grained sediment mobilisation and delivery to rivers. Despite the application of fingerprinting at different spatial scales (e.g., land use types, geological units, and tributary sub-catchments), it has rarely been used to investigate the sediment contribution of topographic zones. The application of sediment sourcing techniques to topographic zones can be helpful in better understanding the spatial distribution of sediment sources within a catchment and the contribution of different topographic features to sediment production and transport. Against this background, this study assessed both topographic zone and tributary sub-catchment spatial sediment sources in the Kan River catchment, Iran. For this purpose, targeted sampling was performed for each classification of spatial sediment sources, and different tracers (geochemical, elemental ratios, and weathering indices) were measured for 80 surface soil samples collected in topographic zones, 20 bed sediment samples collected in sub-catchments, and 11 suspended sediment samples retrieved at the outlet of the main catchment. Three new statistical approaches were applied to identify composite signatures for spatial sediment source discrimination. These approaches combined the Kruskal-Wallis H-test with Particle Swarm Optimization (KW-PSO), Multi-Layer Perceptron (KW-MLP), and Radial Basis Function (KW-RBF) algorithms. A Bayesian un-mixing model was used to apportion the spatial sediment sources. The three composite signatures identified for elucidating the contributions from either classification of spatial sources generated consistent results. The results clarified that the median contribution from topographic zone 1 equated to it being the major spatial sediment source on the basis of topographic zones, with the contributions estimated at 57%, 49%, and 52% (5%-95% uncertainty range) based on the KW-PSO, KW-MLP and KW-RBF signatures, respectively. In terms of the tributary sub-catchments, the Sangan sub-catchment was identified as the dominant spatial sediment source, with corresponding estimated median contributions of 84%, 83%, and 97%, respectively. A combination of weathering indices and elemental fingerprint properties generated statistically robust composite signatures, providing further evidence that the former can augment more conventional tracers. The predicted source proportions can be explained by topographic characteristics from the digital elevation model of the different spatial topographic zones. Therefore, we conclude that topographic features can be an effective predictor of sediment sources.

Comparison of sediment biomarker signatures generated using time-integrated and discrete suspended sediment samples

Sediment source fingerprinting using biomarker properties has led to new insights in our understanding of land use contributions to time-integrated suspended sediment samples at catchment scale. A time-integrated mass-flux sampler (TIMS; also known as the ‘Phillips’ sampler), a cost-effective approach for suspended sediment collection in situ. Such samplers are widely being used to collect sediment samples for source fingerprinting purposes, including studies using biomarkers as opposed to more conventional tracer properties. Here, we assessed the performance of TIMS for collecting representative sediment samples for biomarkers during high discharge events in a small lowland grassland-dominated catchment. Concentrations of long odd-chain n-alkanes (> C23) and both saturated free and bound fatty acids (C14-C32), as well as compound-specific 13C were compared between sediment collected by both TIMS and autosamplers (ISCO). The results showed that concentrations of alkanes, free fatty acids, and bound fatty acids are consistently comparable between TIMS and ISCO suspended sediment samples. Similarly, compound-specific 13C signals were not found to be significantly different in the suspended sediment samples collected using the different samplers. However, different magnitudes of resemblance in biomarker concentrations and compositions between the samples collected using the two sediment collection methods were confirmed by overlapping index and symmetric coordinates-based correlation analysis. Here, the difference is attributed to the contrasting temporal basis of TIMS (time-integrated) vs. ISCO (discrete) samples, as well as potential differences in the particle sizes collected by these different sediment sampling methods. Nevertheless, our findings suggest that TIMS can be used to generate representative biomarker data for suspended sediment samples collected during high discharge events.

‘Paleofloodscapes’: Application of sediment source fingerprinting to track flood regime change over space and time at the Peace-Athabasca Delta, Canada

Deltas are hydrologically dynamic landscapes where river floodwaters create a mosaic of productive ecosystems that provide important services. The flood regime, however, is vulnerable to upstream anthropogenic activities, climate change and geomorphic processes. Deciphering the roles of multiple potential stressors on flood regime change is critical for developing appropriate adaptive and mitigative strategies but requires knowledge of hydrological variability at broader scales of space and time than is typically available from instrumental and observational records. At the globally recognized Peace-Athabasca Delta (Canada), the timing, magnitude and causes of reduced flooding and drawdown of perched basin water levels remain an intense focus of investigation. Here we employ novel ‘paleofloodscapes’, generated from geospatial interpolation of Bayesian mixing model fingerprinting of sediment elemental concentrations, to quantify variation in the delta's flood regime during the past ~140 years. Results reveal that flooding of the delta began to decline several decades before hydroelectric regulation of Peace River flow, not coincident with it, and the influence of floodwaters from the unregulated Athabasca River has declined more than the regulated Peace River. A key discovery is that widespread flooding of perched basins occurs when ice-jam events on the river(s) coincide with a relatively high water-plane in the delta's open-drainage network. Without knowledge of open-drainage water levels, inferred change to the flood regime of perched basins may be inaccurate when derived solely from analyses of Peace River hydrometric data and climatic records. The paleofloodscapes illustrate that rising sediment delivery caused by a natural river avulsion in 1982 may undermine the intended purpose of a proposed weir installation. The most recent paleofloodscape, developed from lake surface sediment sampling shortly after widespread flooding, demonstrates the value of the approach as a landscape hydrological monitoring tool, and is readily transferrable to other floodplains to track flood regime change.

Soil erosion, sediment sources, connectivity and suspended sediment yields in UK temperate agricultural catchments: Discrepancies and reconciliation of field-based measurements

Robust understanding of the fine-grained sediment cascades of temperate agricultural catchments is essential for supporting targeted management for addressing the widely reported sediment problem. Within the UK, many independent field-based measurements of soil erosion, sediment sources and catchment suspended sediment yields have been published. However, attempts to review and assess the compatibility of these measurements are limited. The data available suggest that landscape scale net soil erosion rates (∼38 t km−2 yr−1 for arable and ∼26 t km−2 yr−1 grassland) are comparable to the typical suspended sediment yield of a UK catchment (∼44 t km2 yr−1). This finding cannot, however, be reconciled easily with current prevailing knowledge that agricultural topsoils dominate sediment contributions to watercourses, and that catchment sediment delivery ratios are typically low. Channel bank erosion rates can be high at landscape scale (27 km−2 yr−1) and account for these discrepancies but would need to be the dominant sediment source in most catchments, which does not agree with a review of sediment sources for the UK made in the recent past. A simple and robust colour-based sediment source tracing method using hydrogen peroxide sample treatment is therefore used in fifteen catchments to investigate their key sediment sources. Only in two of the catchments are eroding arable fields likely to be important sediment sources, supporting the alternative hypothesis that bank erosion is likely to be the dominant source of sediment in many UK catchments. It is concluded that the existing lines of evidence on the individual components of the fine sediment cascade in temperate agricultural catchments in the UK are difficult to reconcile and run the risk of best management interventions being targeted inappropriately. Recommendations for future research to address paucities in measured erosion rates, sediment delivery ratios and suspended sediment yields, validate sediment source fingerprinting results, consider the sources of sediment-associated organic matter, and re-visit soil erosion and sediment cascade model parameterisation are therefore made.

Comparison of Sampling Designs for Soil Sediment Source Fingerprinting

ABSTRACT Sediment fingerprinting is increasingly being used to provide information that can help guide management decisions at the watershed scale. The objectives of this study were to investigate the implications of different sediment fingerprinting sampling designs on characterizing sediment dynamics in the Beheshtabad Watershed in Chaharmahal va Bakhtiari Province, western Iran. First, nitrogen, organic carbon, phosphorus, potassium, calcium, sodium, zinc, manganese, iron, and lime fingerprints were used to discriminate among four potential sediment sources including agricultural topsoil, rangeland, as well as rainfed and urban lands. Then, the suspended sediment was collected from drainage areas at five sites. Nested and local-location fingerprinting sampling designs were employed to evaluate the influence of geomorphic connectivity and land use on apportionment results by using the same source and sediment data set. By averaging all locations using the nested method, agricultural land with an average of 69% had the highest contribution to sedimentation followed by rainfed land with an average of 19.9%, rangeland with an average of 6.8%, and urban lands with an average of 5.99%. Compared to the mean of the total method samples, the local method showed greater soil loss from agricultural lands and lower soil loss from rangeland and rainfed lands. Generally, surface soil in sediments came from agricultural land use. According to the results, total nitrogen, phosphorus, organic carbon, and calcium were the optimum tracers that correctly distinguished source samples. Overall, each of the two fingerprinting sampling designs provided the same information. Thus, the fingerprinting method can determine the sources of sediments. Given the importance of the fingerprinting method, future studies can focus on determining the appropriate combination of tracers and the effect of sediment sampling time.

The spatio-temporal dynamics of suspended sediment sources based on a novel indexing approach combining Bayesian geochemical fingerprinting with physically-based modelling

Applications of sediment source fingerprinting continue to increase globally as the need for information to support improved management of the sediment problem persists. In our novel research, a Bayesian fingerprinting approach using MixSIAR was used with geochemical signatures, both without and with informative priors based on particle size and slope. The source estimates were compared with a newly proposed Source Sensitivity Index (SSI) and outputs from the INVEST-SDR model. MixSIAR results with informative priors indicated that agricultural and barren lands are the principal sediment sources (contributing ∼5–85% and ∼5–80% respectively during two sampling periods i.e. 2018-2019 and 2021–2022) with forests being less important. The SSI spatial maps (using % clay and slope as informative priors) showed >78% agreement with the spatial map derived using the INVEST-SDR model in terms of sub-catchment prioritization for spatial sediment source contributions. This study demonstrates the benefits of combining geochemical sediment source fingerprinting with SSI indices in larger catchments where the spatial prioritization of soil and water conservation is both challenging but warranted.

Sediment source fingerprinting and the temporal variability of source contributions

Sediment source fingerprinting has been progressively developed and refined over the past 40 years or more and now represents a widely used and valuable technique, with important practical applications. However, relatively little attention has been given to the target samples and the extent to which they are able to provide meaningful information on short- or longer-term relative source contributions for a given study catchment. A key issue here is the inherent short- and longer-term temporal variability of source contributions and the extent to which such variability is taken into account by the target samples. The objective of this study was to investigate the temporal variation of source contributions from the Qiaozi West catchment, a small (1.09 km2) gully catchment located within the Loess Plateau of China. The target samples represented a suite of 214 spot suspended sediment samples collected during eight representative wet season rainfall events occurring over two years. A suite of geochemical properties was used as fingerprints and standard source apportionment calculations indicated that the gully walls contributed the most sediment (load-weighted mean 54.5%) and, together with cropland (load-weighted mean 37.3%), and gully slopes (load-weighed mean 6.6%) were the main sediment sources. The 214 individual target samples indicated that the contribution of cropland sources varied between 8.3% and 60.4%, gully walls between 22.9% and 85.8% and gully slopes between 1.1% and 30.7%, representing ranges of 52.1%, 62.9% and 29.6% respectively. In order to explore whether the temporal variability of source contributions demonstrated by the study catchment should be seen as typical, equivalent information was abstracted from 14 published studies for other catchments of varying size and located in different environments worldwide. This information demonstrated similar temporal variability of the relative contributions of the major sources, which were typically characterized by ranges of the order of 30–70%. The temporal variability associated with the estimates of relative source contributions provided by target samples has important implications for the uncertainty associated with such estimates derived using source fingerprinting techniques based on a limited number of target samples. Further attention needs to be directed to the design of sampling programmes used to collect such samples and to taking account of such uncertainty in source apportionment calculations.

Late Pleistocene dynamics of dust emissions related to westerlies revealed by quantifying loess provenance changes in North Tian Shan, Central Asia

Wind-blown loess, as the geological record of dust, is a promising archive to explore paleoclimate change and paleo-dust cycle from source to sink over the westerly-dominated Central Asia (CA). However, it is still not fully established how loess deposition in CA physically connects to the westerlies. In this study, based on trace element analyses of the Nilka (NLK) loess section from eastern Ili Basin, we used sediment source fingerprinting (SSF) and random forest (RF) to quantitatively restore loess provenance changes in North Tian Shan, CA, covering the past 71 ka. The results reveal that alluvium and proluvial on the piedmont slopes/plains over the region served as the primary sources for the NLK loess (averaging ∼ 72 %), with less contributions of deserts (∼28 %). The temporal variations of the major source contributions, combined with density plots of the RF results, suggest that the enhanced westerly-linked moisture transport controlled by both obliquity and precession forcings has largely suppressed the loess accumulation despite the possibility that the strengthened westerlies led to the increased supply of the distant sources. This indicates an intimate linkage between the SSF results, the local paleoenvironment and the large-scale paleoclimatic systems. In addition, the relatively smaller contributing proportions of the Kazakh deserts confirm that the CA loess is not mainly derived from the deserts. In conclusion, quantifying loess provenance changes here represents one potential approach for resolving the relationships between dust cycles and climate forcings, which is relevant for paleoclimate reconstruction based on the comparatively patchy (non-plateau) piedmont loess in CA.

Land-use-based freshwater sediment source fingerprinting using hydrogen isotope compositions of long-chain fatty acids

Rapidly changing land use patterns and frequent extreme weather events have resulted in an increased sediment flux to freshwater systems globally, highlighting the need for land-use-based sediment source fingerprinting. Application of variability in hydrogen isotope compositions (δ2H values) of vegetation-specific biomarkers from soils and sediments is relatively underexplored for land-use-based freshwater suspended sediment (SS) source fingerprinting, but has the potential to complement the information from routinely applied carbon isotope analysis and provide new insights. We analysed δ2H values of long-chain fatty acids (LCFAs) as vegetation-specific biomarkers in source soils and SS collected from the mixed land use Tarland catchment (74 km2) in NE Scotland, to identify stream SS sources and quantify their contributions to SS. Plant growth form was the primary control on source soils LCFAs (n-C26:0, n-C28:0, n-C30:0) δ2H variability, while the isotopic composition of source water had no significant control. Forest and heather moorland soils covered with dicotyledonous and gymnosperm species were differentiated from arable land and grasslands soils covered with monocotyledonous species. SS samples collected for fourteen months from the Tarland catchment with a nested sampling approach showed monocot-based land use (cereal crops, grassland) to be the major source of SS with 71 ± 11% contribution on catchment-wide scale averaged throughout the sampling period. Storm events after a dry summer period and sustained high flow conditions in the streams during autumn and early winter suggested enhanced connectivity of more distant forest and heather moorland land uses covering relatively steep topography. This was shown by an increased contribution (44 ± 8%) on catchment-wide scale from dicot and gymnosperm-based land uses during the corresponding period. Our study demonstrated successful application of vegetation-specificity in δ2H values of LCFAs for land-use-based freshwater SS source fingerprinting in a mesoscale catchment where δ2H values of LCFAs were primarily controlled by plant growth forms.

Using Source Fingerprinting Techniques to Investigate Sediment Sources during Snowmelt and Rainfall Erosion Events in a Small Catchment in the Black Soil Region of Northeast China

Concern for the offsite impact of eroded sediment and the need to develop effective catchment sediment management strategies has directed attention to the need for an improved understanding of the primary sediment sources within catchments and the potential of sediment source fingerprinting techniques to provide such information. The study reported here was undertaken in the black soil region of Northeast China, where soil erosion is seen as a serious threat to the sustainable use of soil resources and offsite impacts of eroded soil are also concerned. The study applies source fingerprinting techniques to the evaluation of sediment sources in a small (3.46 km2) agricultural catchment. Sediment sources from five snowmelt and five rainfall events of varying magnitude were contrasted. Three key potential sediment sources were identified within the study catchment: gullies, cultivated topsoil and uncultivated topsoil. Geochemical properties of the source materials (Ti, Ga, Br and Ba) were used as composite fingerprints capable of discriminating between the three potential sources. A mixing model, optimized using a genetic algorithm and coupled with a Monte Carlo procedure to quantify the uncertainty associated with the resulting estimates, was used for source apportionment. The results indicated mean source contributions for the set of 10 events for cultivated topsoil, uncultivated topsoil and the gullies of ~30%, ~10% and ~60%, respectively. In general, snowmelt and rainfall events were characterized by increased contributions from gully sources and cultivated topsoil, respectively. The study is seen as demonstrating the potential for using source tracing techniques to investigate sediment sources in environments where strong seasonal contrasts between snowmelt and rainfall events exist.

Fingerprinting Sediment Origin of the Silting Process of Urban Reservoirs

The silting process of urban reservoirs has been occurring in many regions across the world. However, identifying the main sources of sediment and controlling the silting process in urban reservoirs are still unsolved problems in many regions, mainly in developing countries such as Brazil. In this study, we identify which land use most influences the siltation of reservoirs, and how the different tributary streams contribute to this process in two urban reservoirs located in Campo Grande, Midwestern Brazil. Thus, we applied a sediment source fingerprinting (SSF) approach, associated with land use analysis, and the bathymetric data of reservoirs connected to the stream and drainage network, obtained between the years 2008 and 2018. The reduction in the volume and area of the reservoir during the study period were 45% and 39%, respectively. We found a proportional relationship between the reduction in the reservoir volume and the increase in the impermeable areas of the studied basin. We also noted that the sediments deposited in the reservoir originate from bare soil, banks, and bed in the proportions of 46.9%, 37.1%, and 17.2%, respectively. Our findings show that the use of bathymetric surveys and data on land use and land cover, associated with the source tracing technique, are useful alternatives to identifying sediment mobility in urban basins, especially in those where the drainage network is connected to water courses. We conclude that the factors that most contribute to the silting up of reservoirs are the erosion of banks and beds, sediment remobilization and the connectivity of the drainage network with water courses.

Sediment Source Fingerprinting and Its Control Strategies of the Lakes in Jiuzhaigou World Natural Heritage Site

Reliable quantitative information regarding sediment sources is essential for target mitigation, particularly in settings with a large number of loose provenances caused by earth disasters. The lakes in the Jiuzhaigou World Natural Heritage Site (WNHS) are facing serious environmental problems of silting and swamping, which threaten the sustainability of the area, especially after the earthquake on 8 August 2017 (the “8.8 earthquake”). Therefore, a field investigation was conducted after the “8.8 earthquake” (June 2020), and the Arrow Bamboo and Rhino Lakes, which were affected by the earthquakes to different degrees, were selected as the research objects. Based on the data of 27 environmental indicators from 31 surface sediment and soil samples in and around the lakes, the spatial distribution characteristics of the lake sediment sources were quantified using composite fingerprint recognition technology. Furthermore, a high protection standard of a WHNS and a process treatment scheme for reducing the siltation of the Jiuzhaigou lakes were proposed. The results showed that the contribution ratio of loose matter sources entering the lake on the road-side of the Arrow Bamboo and Rhino Lakes (16.5% and 21.8%, respectively) was lower than that on the forest-side (83.5% and 78.2%, respectively), indicating that physical barriers such as roads can effectively reduce the sediment input, while the lake forest side contributes a large number of loose matter sources, which has not attracted attention in the past and requires protection. High protection standards for the Jiuzhaigou WHNS are suggested. Accordingly, the entire control scheme of Jiuzhaigou lake sediment reduction including “monitoring–control–interception–buffer–cleaning” is provided. Source erosion monitoring is the first step in blocking the sediment source. Vegetation restoration and surface coverage should be conducted in areas where water and soil losses have occurred. Necessary engineering measures should be implemented to intercept loose material sources at points where geological disasters occur frequently. A buffer zone should be established between the lake and the mountain to intercept the sediment. Sediment caused by geological disasters with low interference must also be cleaned from the lake. The level of nutrients in the lake must be controlled by the regular cleaning of plant debris from the lake and lakeside.

Using check dam deposits to reconstruct changes in the sediment response of a small catchment on the Loess Plateau in China, during the period 1960–1990

AbstractInformation on both the magnitude and relative contributions of inter‐gully and gully areas to the sediment yield from small catchments in the Loess Plateau of China represents an important requirement for understanding catchment sediment dynamics, assessing the sensitivity of catchment sediment budgets to environmental change and developing effective soil and water conservation strategies. Contemporary catchment monitoring programmes can provide such information, but there is also a need to consider past behaviour. Where long‐term records are lacking, attention has been directed to the potential for using the sediment deposits behind check dams to reconstruct the sediment response of the upstream catchment. This contribution reports a study of the 0.181 km2 Nianyangou catchment located in the hilly region of the Chinese Loess Plateau, in Shaanxi Province, China, which has extended a previous study aimed at using individual flood couplets preserved in the check dam deposits to reconstruct the record of annual sediment yield, to include the use of sediment source fingerprinting techniques to document changes in the annual sediment contribution from inter‐gully and gully areas for the period 1960–1990. The sediment response of the catchment provided evidence of two change points in 1964 (Period 1–Period 2) and 1983 (Period 2–Period 3), which reflect the introduction of soil and water conservation measures in the mid 1960s through to the 1970s and a change in the land tenure system in 1983. The annual sediment yields from inter‐gully and gully areas follow the trend P1 &gt; P3 &gt; P2, whereas the equivalent information on the relative contribution of inter‐gully and gully areas follow different trends P3 &gt; P1 &gt; P2 and P2 &gt; P1 &gt; P3, respectively.

Novel sediment source fingerprinting quantifying erosion-induced total nitrogen and total phosphorus outputs from an intensive agricultural catchment, North China

Intensive farming is a primary cause of increased sediment and associated nitrogen (N) and phosphorus (P) loads in surface water systems. Determining their contributing sources, pathways and loads present major challenges in the high-intensity agricultural catchments. Herein, we quantify the sediment sources and magnitude of sediment total N and total P from different sources using a novel application of compound-specific stable isotope (CSSI) and fallout radionuclides (FRNs) of 137Cs and 210Pbex in an intensive agricultural catchment in North China. Sediment sources from surface and sub-surface soils were estimated from FRNs fingerprint and accounted for 62 ± 7% and 38 ± 7% respectively, while surface soil from land uses that originated from hillslope were identified by CSSI fingerprint. Using a novel application of FRNs and CSSI sediment fingerprinting techniques, the dominant sediment source was derived from maize farmland (44 ± 0.1%), followed by channel bank (38 ± 7%). The sedimentation rate (13.55 ± 0.30 t ha−1 yr−1) was quantified by the 137Cs cores (0–60 cm) at the outlet of this catchment. The total N and total P in sediment were both mostly derived from maize farmland and least from channel banks. The channel banks are significant sediment sources but contribute little to the input of sediment N and P for eutrophication. It implies that chemically-applied farmlands are the main hotspots for catchment erosion control and pollution prevention. The novel application of FRNs and CSSI techniques cost-effectively quantified sediment N and P loads from different sources with a single visit to the catchment, enabling rapid assessment for optimizing soil conservation strategies and land management practices. Keywords: Sediment sources, Land use, N and P loads, Compound-specific stable isotope, Fallout radionuclides.

Sediment source apportionment using geochemical composite signatures in a large and polluted river system with a semiarid-coastal interface, Brazil

The Ipojuca River is the third most polluted fluvial system in Brazil. Sediment-associated metal fluxes threaten the environmental health in the estuary of this system. However, the sources supplying these particle-bound contaminants have not been determined yet. Sediment source fingerprinting provides a powerful technique to obtain such information. Accordingly, the aim of this study was to quantify the source contributions to suspended and bed sediments in this polluted river system with a semiarid-coastal interface using geochemical tracers. A total of 20 geochemical tracers measured on 207 source samples were used as potential fingerprint properties to discriminate and quantify the contributions of potential sources classified according to three distinct typologies (distribution of land uses, soil classes, and the environmental contrasts between the upper and lower catchment). All analyzed elements passed the range test for conservative behaviour. Using the MixSIAR model, the lower catchment, Oxisols, and sugarcane croplands were identified as the dominant sediment sources. These new data provide a basis to target the management of excessive sediment loads and sediment-associated contaminants moving towards estuarine and coastal environments. The multiple sources framework discussed herein can also help to improve the appeal of sediment source fingerprinting among environmental policymakers given the capacity for informing targeted management.

Using particle size distributions to fingerprint suspended sediment sources—Evaluation at laboratory and catchment scales

AbstractApplications of sediment source fingerprinting studies are growing globally despite the high costs and workloads associated with the analyses of conventional fingerprint properties on target sediment samples collected using traditional methods. To this end, there is a need to test new fingerprint properties that can overcome these challenges. Sediment particle size could potentially contribute here since it is relatively easy to measure but, until now, has rarely been deployed as a fingerprint itself. Instead, particle size has been used to ensure that source and target sediment samples are more directly comparable on the basis of the fingerprints used. Accordingly, this work examined whether particle size distributions (PSDs) could be used as a reliable fingerprint for apportioning sediment sources, in combination with a grain size un‐mixing model. Application of PSDs as a fingerprint was tested at two scales: (i) in a laboratory setting where soil samples with known PSDs were used to generate artificial mixtures to evaluate un‐mixing model results, and (ii) a catchment setting comparing PSDs in a confluence‐based approach to test if downstream target sediment PSDs could be un‐mixed into the contributions of sediment coming from an upstream and a tributary sampling site. Laboratory results showed that the known proportions of the two, three and four soil samples in the artificial mixtures were predicted accurately using the AnalySize grain size un‐mixing model, giving average absolute errors of 9%, 8% and 6%, respectively. Catchment results showed variable performances when comparing un‐mixing results with sediment budget estimations, with the best results obtained at higher discharge values during storm runoff events. Overall, our results suggest the potential of using PSDs for estimating contributions of sediment sources delivering SS with distinct PSDs when sources are located at short distance to the downstream sampling site.

Quantification of the aeolian sand source in the Ulan Buh Desert using the sediment source fingerprinting (SSF) method within MixSIAR modelling framework

Identifying and quantifying source contributions of aeolian sands in desert where extensive dunes and paleo-lakes coexist is crucial to elucidate the formation mechanism of aeolian and lacustrine landforms in the earth system. In this study, we identified the aeolian sediment sources in the Ulan Buh Desert (UBD) using geomorphological and sedimentological methods, and further quantified the source contributions via the sediment source fingerprinting (SSF) method within MixSIAR modelling framework. Our results revealed that the mean contribution from each source to the UBD sediments were assessed to be 32.2 % for detrital deposits weathered and eroded from the Helan Mountains (HLM), Bayan Urals Mountains (BUM), and Langshan Mountains (LM), 26.2 % for aeolian and Gobi deposits from the adjacent Yamalik Desert (YMD) and Bayin Wendur Desert (BWD), 26.1 % for aeolian and Gobi sediments from the upwind Badain Jaran Desert (BJD), and 15.5 % for the paleo-lacustrine sediments in the UBD. The bulk fraction sands in the UBD are mainly contributed by detrital deposits from its surrounding mountains, whereas the fine sands are supplied by the upwind deserts of the UBD. As shown by the dunes migration rate (averaged 9.1 m/yr) and direction (averaged 118.3°) in the YMD, sands from upwind desert can be easily transported to the adjacent downwind desert, i.e., the UBD. Therefore, much attention should be paid to their role in sediment source contribution rather than ignore them for their limited area. Similarly, although the sediment source contribution from paleo-lacustrine deposits within the desert is relatively small, they served as a direct source for the UBD. The GOF evaluation demonstrated that the MixSIAR Bayesian model is an effective approach to aid aeolian sediment fingerprinting. In addition, we found that the aeolian sediments in the UBD is the combined results of wind and fluvial systems.

Improving the performance of an unmixing model in sediment source apportionment using synthetic sediment mixtures and an adaptive boosting algorithm

Tracing technology is increasingly being used in fluvial and aeolian sediment provenance assessments. Using synthetic sample mixtures in validations of unmixing model performance is becoming a standard step in sediment source fingerprinting. With tracer variability fully considered in the sources and target sediment, this study explored a semiempirical modelling strategy based on virtual sediment mixtures and the adaptive boosting (AdaBoost) algorithm. The obtained integrated unmixing model contained multiple composite fingerprints, and the weight coefficient was obtained from the iterative process. The performance of the integrated unmixing model was compared with that of unmixing models applying single or equal-weighted multiple composite fingerprints. All generated virtual sediment mixtures (280) were split into a training dataset (240) and a test dataset (40) to validate the generalization ability of the models. The results showed that the integrated unmixing model achieved better performance than the unmixing models with a single composite fingerprint (basic models). The integrated unmixing model yielded an average mean absolute error (A-MAE) of 5.51% for training data and 5.72% for test data, and it achieved better accuracy than the best basic model (6.23% on the training and 6.75% on the test dataset, composite fingerprint C-1) or equal-weighted model (6.32% on the training and 6.41% on the test dataset, average of 42 basic models). The robustness of the model accuracy was also improved with the AdaBoost algorithm. The modelling approach proposed in this study has the potential to maximize the use of all tracer information and further improve the reliability of sediment fingerprinting.