Understanding historical sediment sources and their drivers is essential for effective watershed management. This study provides a novel, century-scale assessment of sediment source dynamics by integrating geochemical and compound-specific stable isotope (CSSI) fingerprinting in the Zarivar Lake watershed, Iran. We measured tracers in potential sources, riverine sediments, and a lake sediment core. Consensus Ranking (CR) and Consistent Tracer Selection (CTS) were used to optimize the tracer combinations for robust source apportionment. This integrated approach identified channel banks (0.39 +/- 0.09), uncultivated subsoil (0.29 +/- 0.10), and irrigated farming (0.16 +/- 0.07) as the dominant sediment sources from 1950s to 2018. Four distinct episodes of sedimentation fluctuations were identified: (i) an early-1930s peak linked to channel modifications; (ii) an early1940s peak associated with extreme rainfall and mass movements; (iii) mid-1970s to 1980s peaks driven by deforestation and climatic extremes; and (iv) a sharp post-2008 decline following check dam construction, demonstrating the efficacy of sediment flux reduction. The findings reveal that changes in sediment loads were primarily governed by anthropogenic activities, while precipitation often acted as the primary amplifier of these impacts. This research underscores the power of a hierarchical geochemical-CSSI approach to provide a sourcespecific, century-scale perspective that is critical for designing effective conservation strategies in anthropogenically modified watersheds facing climate change.

Beryllium-7 has been widely applied as sediment tracer in river basins, however, factors influencing its geochemistry in this context have rarely been addressed. We investigated sediment-water interactions controlling the distribution of 7Be in channel sediments for improved storage time and particulate contaminant dynamic assessments in a catchment affected by legacy and contemporary mining pollution. The investigation was undertaken in the River Fal, UK, to assess sediment storage times and particulate contaminant dynamics. Samples were collected and analysed for 7Be, 137Cs, 210Pb and 238U by gamma spectrometry, aqua regia extractable P, As, Fe, Cu, Pb, Sn and Zn by inductively coupled plasma (ICP) spectrometry and Total Organic Carbon (TOC) by CHN analyser. Particle size distribution (PSD) and the 1 mol L− 1 HNO3 extractable Fe and Mn fractions were analysed by laser diffraction and ICP, respectively, to assess relationships with the radionuclide activities. Dissolved and the 1 mol L− 1 HCl extractable 9Be was quantified to determine its distribution coefficients (Kd). Beryllium-7 was significantly correlated with the specific surface area (SSA), TOC and the Fe and Mn extractable fractions. A strong inverse correlation between the 9Be Kd and suspended sediment concentration (SSC) demonstrated the particle concentration effect. Suspended sediments (SS) showed higher SSA than the channel bar sediments (CBS). Storage times and the proportion of recently deposited sediments (

In East Africa, soil is being washed away from the land into rivers faster than ever. This is because of changes in how people interact with their land, soil, and plants. First, forests were cut down to make farms. Later, growing numbers of animals overgrazed grasslands. Without trees and grasses to protect the soil, heavy rain quickly began washing it away. Steep, deep cuts in the land, called gullies, then form and keep growing faster and faster, carrying away soil, water, nutrients, and even seeds. This makes it hard for plants to grow back. In response, people are starting to take action. They are using traditional tools to slow down water, regrow plants, and fix damaged land. However, they need help from governments and scientists to apply these solutions to bigger gullies and across larger regions. Protecting healthy soils is important so that people in East African can keep producing enough food in the future.

Despite increasing recognition of the importance of polar fjords as an emerging carbon sink, relatively few estimates of organic carbon stocks, deposition and accumulation potential exist for the West Antarctic Peninsula (WAP). We assessed the long-term accumulation of organic carbon in three deglaciating Antarctic fjords by combining total organic carbon (TOC) and 210Pb measurements. These data enabled calculations of carbon flux and sequestration (carbon remaining after 100 years), while the susceptibility of the carbon pool to further degradation was assessed by thermogravimetric analysis (TGA). Organic carbon surface deposition rates were highly variable (11.99 ± 8.27 g C m-2 yr-1), while organic carbon burial rates were more consistent (3.55 ± 1.75 g C m-2 yr-1). Burial efficiencies ranged from 30.59% to 54.44% (mean 39.84%). These results are comparable with previous predictions of carbon sequestration in WAP fjords, highlighting the role of fjords as global hotspots of long-term accumulation, and support the hypothesis that deglaciating polar fjords act as a significant negative (mitigating) feedback on global climate change.

Accelerated soil erosion is a major cause of land degradation in East Africa's agricultural and pastoral landscapes with severe consequences for food, water and livelihood security. In this study, we aimed to provide a tool to support the sustainable management of land and water resources in a region significantly impacted by land degradation. We employed source apportionment methods to quantify the relative contribution of sediment sources within the Nyando and Sondu-Miriu River basins and their subcatchments in the Winam Gulf, Kenya. A total of 237 riverbed sediment samples and 76 composite surface soil samples were collected from the Nyando and Sondu-Miriu River basins. The total elemental concentrations of these samples, determined using ICP-MS/ MS, were utilised as geochemical tracer properties. Conservativeness index, consensus ranking and consistent tracer selection methods were then used to identify the optimum unmixing tracers before applying the frequentist unmixing model FingerPro to determine sediment provenance. Sediment source analysis revealed that the Ainamutua and Nyando-Kipchorian subcatchments, areas predominantly affected by land degradation activities such as poor crop management practices and deforestation on steep slopes, contributed 39 f 4 % and 44 f 4 %, respectively. In contrast, the Awach Kano and Nyaidho subcatchment, with a higher proportion of treecover and lower soil erosion rates, only contributed 17 f 7 %. In the Sondu-Miriu, the Yurith and Kipsonoi subcatchments contributed 68 f 5 % and 20 f 6 %, respectively, due to the predominance of forest encroachment and ridges in the Yurith subcatchment. Additional fingerprinting analysis within each of the Nyando and Sondu-Miriu basins reveals the significance of land use, landform and soil types on source contributions. Quantifying sediment source contributions within large river basins provides essential information for environmental managers and policymakers developing integrated catchment management plans. The results from this study can be used to implement sustainable land use policy focused on soil restoration in the Lake Victoria drainage basin.

Under climatic warming and increased melting, glaciers and ice caps are becoming secondary sources of contaminants deposited decades ago. Cryoconite, an organic-rich material found on the surface of many glaciers, is particularly efficient at accumulating airborne contaminants due to biogeochemical exchanges with the organic matter within cryoconite. Atmospherically derived radioactive isotopes, commonly referred to as fallout radionuclides, have now been found to accumulate in cryoconite globally. However, data from the polar regions, especially ice sheets and ice caps, is scarce. This study helps to address this regional gap in understanding fallout radionuclide accumulation in glacial settings. We present the first radioactivity dataset from cryoconite on a Greenlandic ice cap and assess the role of cryoconite in the distribution of radioactive species in the High Arctic. Forty-six cryoconite samples were collected from the Flade Isblink ice cap (NE Greenland) in August 2022. These samples were analysed via alpha and gamma spectrometry for atmospheric radionuclides, including 137Cs, 241Am, 210Pbexc., 207Bi, 7Be, and several plutonium isotopes. The results of this study confirm cryoconite's exceptional ability to accumulate fallout radionuclides, even in remote and relatively pristine regions such as Northern Greenland. The activities of radionuclides in cryoconite from Flade Isblink are among the highest reported across the High Arctic and the highest ever reported from Greenland. Flade Isblink's radioactivity source is compatible with the stratospheric reservoir established during atmospheric nuclear tests and with weapon-grade fissile fuel, likely originating from Novaya Zemlya. Our findings emphasise the necessity for continued research efforts on the release of legacy contaminants from glaciers, particularly given accelerated global warming and consequent glacier retreat.

Human displacements, especially those driven by violent conflicts forcing sudden population migrations, wield profound and enduring impacts on landscapes, instigating substantial disruptions to the natural environment. Beyond immediate destruction, these consequences pose challenges to ecosystem health, food security, and biodiversity conservation, particularly exacerbated in the absence of effective governance. Traditional land management practices, agriculture, and conservation efforts are disrupted, constraining the implementation of long or medium-term conservation practices in agriculture. These disruptions may contribute to increased erosion and sediment transport, depleting soil nutrients and resulting in natural disasters such as flash floods, landslides, and water quality degradation. This phenomenon is particularly pronounced in regions experiencing high rainfall intensity, coupled with inadequate land use and agricultural management practices. Understanding the primary factors behind the last decades escalation in land degradation and subsequent sediment export is crucial to prevent further ecosystem degradation and heightened instability in conflict-affected areas. To address this, we have developed an integrated approach involving core sampling, sediment fingerprinting techniques, high-resolution sediment sampling, and automated remote sensing routines to pinpoint hotspot areas and track conservation efforts. Using the Lake Kivu region as a case study, situated on the border between Rwanda and the Democratic Republic of the Congo, an area marked by prolonged violent conflict since the early 1990s, we evaluate the applicability of this combined approach. The preliminary results from the multiple techniques independently suggest an increasing trend in exported sediment over the last decade. This trend is particularly pronounced in areas characterized by high instability and economic challenges. In contrast, relatively more stable regions exhibit a stabilization in sedimentation rates. This stability is attributed primarily to the implementation of conservation practices and the presence of robust transport infrastructures, both playing crucial roles in landscape conservation. Results underscore the method's effectiveness in elucidating lasting effects on landscapes impacted by 'polycrisis', necessitating consolidated and comprehensive responses over mere technical solutions. The research objective is to target specific areas within conflict-affected regions, with a focus on mitigating environmental degradation and associated challenges.

Saltmarshes play a key role in the coastal carbon cycle through the capture and storage of organic carbon. Assessments of both organic carbon (OC) stocks and rates of OC accumulation are vital for quantifying saltmarsh contributions to climate-change mitigation and for guiding efforts to protect and restore coastal ecosystems. Current assessments of the magnitude of the store and rate of OC accumulating in UK saltmarshes are based on a small and spatially limited dataset. To address this knowledge gap, we collected sediment cores to quantify the OC stored in the soil and biomass of 26 saltmarshes and estimate OC accumulation rates for 22 saltmarshes distributed around the UK.Across the saltmarshes, the estimated average store is 11.55 ± 1.56 kg C m-2 with values ranging between 2.24 kg C m-2 and 40.51 kg C m-2. These saltmarshes accumulate OC at a rate of 110.88 ± 43.12 g C m-2 yr-1 with values ranging from 27.57 g C m-2 yr-1 to 343.68 g C m-2 yr-1. These highly variable OC stocks and accumulation rates are dependent on interlinked factors, including local geomorphology, organic carbon source, sediment type (mud vs sand), sediment supply, and relative sea-level history.By upscaling these estimates to all UK saltmarshes, it is calculated that these systems currently store 5.20 ± 0.65 Mt of OC and accumulate 46563 ± 4353 tonnes of OC annually. The low OC accumulation rates indicate that UK saltmarshes have relatively low additional Greenhouse Gas (GHG) abatement potential, but that they contain significant stores of OC within the ecosystem. This highlights the crucial need for the protection and restoration of existing OC stores within UK saltmarshes, providing climate benefits several times more significant than the annual accumulation of OC in these ecosystems.

Effective land–lake management for resilience requires an integration of knowledge mobilization, capacity building, and collaborative partnerships that bridge science, policy, and community practice. This study aims to enhance understanding of land–lake socio-ecological linkages and to strengthen how geochemical evidence and participatory knowledge are translated into action among diverse actors. The paper draws on outcomes from a series of multi-stakeholder workshops implemented under the Royal Society International Collaboration Grant, “Dynamics of Environmental Geochemistry and Health in a Lake-Wide Basin,” held at the Kenya Marine and Fisheries Research Institute (KMFRI) in Kisumu, Kenya, between 2023 and 2024. The workshops brought together government agencies, researchers, extension officers, private sector representatives, and community groups from across the Lake Victoria Basin. Collectively, participants identified critical knowledge and capacity gaps limiting the application of geochemical data to inform management and policy. Through participatory discussions, the workshops emphasized the need to integrate sediment fingerprinting, nutrient mapping, and catchment monitoring into county-level planning. Key themes included hotspot identification, restoration, and evidence-based decision-making to reduce land-to-lake sediment transfers that degrade both terrestrial and aquatic productivity. Participants co-developed pathways for climate-smart and regenerative agri-industries, policy briefs, and communication tools tailored for multiple audiences, including low-literacy and disability-inclusive formats. The process also led to the proposal of a multi-agency coordination committee to oversee ongoing collaboration, data sharing, and monitoring of land–lake activities within the Winam Gulf basin. Anchored in social–ecological resilience and adaptive knowledge mobilization frameworks, the study demonstrates that sustained interaction between scientific diagnostics and community engagement can foster adaptive learning and institutional linkages essential for resilience. The findings underscore the importance of early stakeholder inclusion, transparent data exchange, and participatory governance as foundations for sustainable land–lake management and long-term ecosystem health in the Lake Victoria Basin.

The depletion of fertile topsoil presents a critical challenge in tropical mountain agroecosystems. Impacts are intensified during heavy storm events that strip unprotected topsoils and pose risks to downstream water ecosystems. To better understand such dynamics, we investigated an agricultural mountainous catchment located on the Democratic Republic of the Congo shore of Lake Kivu. This area is characterised by weak governance systems exacerbated by protracted violent conflicts, which have prevented the application of remediation practices to address extensive land use changes, including deforestation and monoculture proliferation, notably banana plantations. Additionally, the spread of Banana Xanthomonas wilt (BXW) has further augmented land use impacts. Herein the complete diseased mat uprooting (CDMU) method employed to combat the disease has resulted in significant erosion and sediment export rates. Following the recovery of banana plantations from CDMU, sediment export rates continued to increase without a clear responsible party but more as a legacy of past and present land degradation activities and embedded soil erosion and connectivity process pathways. To analyse the impact of high-intensity storm events coupled with the aftermath of conflict instability and the effects of BXW on erosion dynamics, the sediment fingerprinting technique was implemented. We collected 60 sediment source samples across a 42 km2 catchment, predominantly cultivated since the mid-20th century. Samples spanned four main land uses/land covers: seasonal crops, banana plantations, bare or degraded soil, and channel banks. Additionally, mixture/target samples were collected at the summit of six fluvial terraces located at different altitudes along the vertical profile of the river after a high-intensity storm event. These terraces serve as natural indicators of sediment accumulation under different flow intensities, with higher terraces representing sediment deposition during higher discharge. Furthermore, sediment samples were collected via a gravity core in delta deposits at the river's inflow into the lake, allowing us to identify the main sources contributing to fine sediment export to the lake. This methodology enabled us to assess how sediment provenance has changed in response to varying discharge levels while elucidating the primary sources responsible for fine sediment inputs to the lake and the subsequent water quality decrease. Our analysis indicates increased contributions occurred from channel banks and degraded areas as discharge increased. Despite steep channel banks and degraded soils being primary sediment sources on the terraces, agricultural and banana sources predominantly contributed to the fine sediments exported to the lake. These findings underscore the hazards of high-intensity storm events in these fragile ecosystems and highlight the role of current banana plantation and cropland management in degrading land and water quality. Understanding the primary factors driving land degradation and sediment export is crucial for preventing further ecosystem degradation and mitigating heightened instability in conflict-affected areas. This research suggests that remediation practices should be incentivised to create buffer structures in upslope agricultural areas and protect the fertile sediments from banana plantations from being exported to the lake if socio-cultural and economic hurdles to implementation can be overcome.

The ability of saltmarshes to accrete sediments and keep pace with sea-level rise is key to their multifaceted role as nature-based solutions to current environmental challenges, including their capacity to accumulate and store ‘blue’ carbon. While saltmarshes can gain elevation through in-situ organic production and trapping of organic and minerogenic sediments, thresholds exist above which rates of sea-level rise outstrip saltmarshes’ vertical accretion capability. Current and future anthropogenically enhanced rates of sea-level rise may therefore pose a significant threat to saltmarsh resilience. A negative accretionary balance (i.e. sea-level rates exceeding sediment accumulation) may result in transgression and potentially erosion, impacting on a range of ecosystem services and threatening stored carbon. Consequently, understanding the relationship between sea-level rise and saltmarsh accretion is critical for projecting future changes to saltmarsh ecosystems. Here, we use age-depth models based on Bayesian analysis of 210Pb, 137Cs and 241Am activities to quantify sediment accumulation rates for 34 cores from 21 saltmarshes distributed around the coastline of England, Scotland, and Wales. These sites were selected to encompass the range of different marsh types found in Great Britain, including large open-coast systems, back barrier, estuarine-fringing, and loch-head marshes. Site average sedimentation rates vary between 0.12 and 1.28 cm yr-1, with a mean of 0.41 ± 0.16 cm yr-1. We compare sedimentation rates at 1 cm depth increments with corresponding site- and time-specific rates of sea-level rise, modelled using estimates of barystatic, sterodynamic and inverse barometric contributions that we benchmark against long tide-gauge records. This comparison enables us to determine the accretionary balance and its development since the start of the 20th century at each core location. We discuss these results in the context of spatially explicit projections of accelerated future sea-level rise around the coast of Great Britain.

Excess fine sediment supply and its associated contaminants can have detrimental effects on water quality and river ecology with sediment deposition on, and subsequent infiltration in, streambeds impacting riverine habitats. Fallout radionuclides (FRNs) are used as tracers in aquatic systems, and the 7Be/210Pbex ratio is a useful indicator for sediment residence/storage time. Suspended and submerged mid-channel bar sediments were collected during five surveys within a 5 km reach of a typical temperate lowland agricultural river system. Solids were analysed by gamma (7Be and 210Pbex) and inductively coupled plasma (ICP, trace metals and phosphorus) spectrometry, and analysed for total nitrogen and organic carbon, to assess sediment dynamics and associated contaminant and nutrient storage. Significant spatial and temporal variation in 7Be/210Pbex activity ratios was observed, indicating changes in sediment sources closely related to contaminant inputs from legacy mining and agriculture. Storage times and the proportion of recently deposited sediment (RDS) varied between sampling sites and seasons in response to local channel characteristics and floods, which also influenced particulate contaminant distributions. This study demonstrates that FRN technology offers improved understanding of fine sediment and contaminant storage and turnover in river channel systems, which is vital to aid sediment management, river restoration and to tackle the global challenge of siltation and associated pollution in riverine habitats.

The aims of this research were to assess the sources of variability of particulate FRNs (7Be, 210Pbex and 137Cs) in river channels, the influence of sediment properties such as particle size distribution (PSD) and organic matter (OM) on FRN distributions, and to discuss the implications for sediment tracing in rivers. Suspended and channel bed sediment samples were collected in the River Avon (Devon, UK) during five strategic surveys involving a wide variation of river flows, including flood conditions. Particulate matter was analysed for 7Be, 210Pbex and 137Cs by gamma spectrometry, PSD by laser diffraction, and organic constituents, total organic carbon (TOC) and total nitrogen (TN) by elemental analysis. FRNs activity concentrations vary significantly both spatially, characterised by changes in activity concentrations within and between locations, and temporally, with changes during the storm hydrograph and between seasons. Variability was attributed to changes in sediment sources and, on some occasions, to significant correlation of activity concentrations with sediment properties. The results also highlighted the influence of changes in channel characteristics and the magnitude and frequency of floods on FRN distributions. In the context of sediment tracing, attention should be given to seasonal changes in riverine conditions that have the potential to affect 7Be and 137Cs conservativeness. Application of FRNs in sediment fingerprinting studies should be accompanied by appropriate temporal characterisation of potential sediment sources. Finally, potential contribution of 7Be-depleted sediment from channel resuspension to the suspended load should also be considered.

Saltmarshes are a crucial component of the coastal carbon (C) system and provide a natural climate regulation service through the accumulation and long-term storage of organic carbon (OC) in their soils. These coastal ecosystems are under growing pressure from a changing climate and increasing anthropogenic disturbance. To manage and protect these ecosystems for C and to allow their inclusion in emissions and natural-capital accounting, as well as carbon markets, accurate and reliable estimates of OC accumulation are required. However, globally, such data are rare or of varying quality. Here, we quantify sedimentation rates and OC densities for 21 saltmarshes in Great Britain (GB). We estimate that, on average, saltmarshes accumulate OC at a rate of 110.88 +/- 43.12 g C m- 2 yr- 1. This is considerably less than widely applied global saltmarsh averages. It is therefore highly likely that the contribution of northern European saltmarshes to global saltmarsh OC accumulation has been significantly overestimated. Taking account of the climatic, geomorphological, oceanographic, and ecological characteristics of all GB saltmarshes and the areal extent of different saltmarsh zones, we estimate that the 451.65 km 2 of GB saltmarsh accumulates 46,563 +/- 4353 t of OC annually. These low OC accumulation rates underline the importance of the 5.20 +/- 0.65 million tonnes of OC already stored in these vulnerable coastal ecosystems. Going forward the protection and preservation of the existing stores of OC in GB saltmarshes must be a priority for the UK as this will provide climate benefits through avoided emissions several times more significant than the annual accumulation of OC in these ecosystems.

To estimate a watershed’s response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m−2 year−1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m−2 year−1 respectively. During this period, the watershed underwent extensive deforestation (12

Land degradation resulting from soil erosion is a global concern, with the greatest risk in developing countries where food and land resources can be limited. The use of fallout radionuclides (FRNs) is a proven method for determining short and medium-term rates of soil erosion, to help improve our understanding of soil erosion processes. There has been limited use of these methods in tropical Africa due to the analytical challenges associated with 137Cs, where inventories are an order of magnitude lower than in the Europe. This research aimed to demonstrate the usability of 239+240Pu as a soil erosion tracer in western Kenya compared to conventional isotopes 210Pbex and 137Cs through the determination of FRN depth profiles at reference sites. Across six reference sites 239+240Pu showed the greatest potential, with the lowest coefficient of variation and the greatest peak-to-detection limit ratio of 640 compared to 5 and 1 for 210Pbex and 137Cs respectively. Additionally, 239+240Pu was the only radionuclide to meet the 'allowable error' threshold, demonstrating applicability to large scale studies in Western Kenya where the selection of suitable reference sites presents a significant challenge. The depth profile of 239+240Pu followed a polynomial function, with the maximum areal activities found between depths 3 and 12 cm, where thereafter areal activities decreased exponentially. As a result, 239+240Pu is presented as a robust tracer to evaluate soil erosion patterns and amounts in western Kenya, providing a powerful tool to inform and validate mitigation strategies with improved understanding of land degradation.

Siltation and the loss of hydropower reservoir capacity is a global challenge with a predicted 26 % loss of storage at the global scale by 2050. Like in many other Latin American contexts, soil erosion constitutes one of the most significant water pollution problems in Chile with serious siltation consequences downstream. Identifying the sources and drivers affecting hydropower siltation and water pollution is a critical need to inform adaptation and mitigation strategies especially in the context of changing climate regimes e.g. rainfall patterns. We investigated, at basin scale, the main sources of sediments delivered to one of the largest hydropower reservoirs in South America using a spatio-temporal geochemical fingerprinting approach. Mining activities contributed equivalent to 9 % of total recent sediment deposited in the hydropower lake with notable concentrations of sediment-associated pollutants e.g. Cu and Mo in bed sediment between the mine tributary and the reservoir sediment column. Agricultural sources represented ca. 60 % of sediment input wherein livestock production and agriculture promoted the input of phosphorus to the lake. Evaluation of the lake sediment column against the tributary network showed that the tributary associated with both dominant anthropogenic activities (mining and agriculture) contributed substantially more sediment, but sources varied through time: mining activities have reduced in proportional contribution since dam construction and proportional inputs from agriculture have increased in recent years, mainly promoted by recent conversion of steep lands from native vegetation to agriculture. Siltation of major hydropower basins presents a global challenge exemplified by the Rapel basin. The specific challenges faced here highlight the urgent need for co-design of evidence-led, context-specific solutions that address the interplay of drivers both within and without the basin and its communities, enhancing the social acceptability of sediment management strategies to support the sustainability of clean, hydropower energy production.

Climate change poses an immediate threat to tropical soils with changes in rainfall patterns resulting in accelerated land degradation processes. To ensure the future sustainability of arable land, it is essential to improve our understanding of the factors that influence soil erosion processes. This work aimed to evaluate patterns of soil erosion using the activity of plutonium isotopes (Pu) at sites with different land use and clearance scale in the Winam Gulf catchment of Lake Victoria in Kenya. Erosion rates were modelled at potential erosive sites using the MODERN model to understand small-scale erosion processes and the effect of different management practices. The lowest soil redistribution rates for arable land were 0.10 Mg ha−1 yr−1 showing overall deposition, resulting from community-led bottom-up mitigation practices. In contrast erosion rates of 8.93 Mg ha−1 yr−1 were found in areas where steep terraces have been formed. This demonstrates the significance of community-led participation in effectively managing land degradation processes. Another key factor identified in the acceleration of soil erosion rates was the clearance of land with an increased rate of erosion over three years reported (0.45 to 0.82 Mg ha−1 yr−1) underlining the importance vegetation cover plays in limiting soil erosion processes. This novel application of fallout plutonium as a tracer, highlights its potential to inform the understanding of how soil erosion processes respond to land management, which will better support implementation of effective mitigation strategies. Modelling of soil erosion and deposition patterns using the MODERN model to calculate the depth of soil loss/gain.

Under climatic warming, glaciers are becoming a secondary source of atmospheric contaminants originally released into the environment decades ago. This phenomenon has been well-documented for glaciers near emission sources. However, less is known about polar ice sheets and ice caps. Radionuclides are one of the contaminants that can be remobilised through ice melting and accumulate in cryoconite material on the surface of glaciers. To understand the cycling of radionuclides in polar glacial contexts, we evaluate the radioactivity of cryoconite samples from Flade Isblink, a High Arctic ice cap in northeast Greenland. The measured radioactivity is among the highest reported across the High Arctic and the highest from Greenland. The high variability observed among the samples is explained by considering the different macroscopic features of single cryoconite deposits. The radioactivity source is compatible with the stratospheric reservoir established during atmospheric nuclear tests and with weapons-grade fissile fuel, likely originating from Novaya Zemlya proving grounds. This study shows that the ability of cryoconite to accumulate radioactivity in remote areas is undisputed, highlighting the need for a deeper understanding of the remobilisation of radioactive species in polar glacial contexts.

AbstractThis chapter provides an overview of nuclear tools used in sediment source apportionment studies, summarising essential information about the use of fallout radionuclides, elemental geochemistry, and compound-specific stable isotopes. Exemplar studies are described to show how the method can inform decision making at farm and basin scales to control diffuse water pollution by agriculture.