Radionuclide Tracing in Global Soil Erosion Studies: A Bibliometric and Systematic Review

Abstract

Radionuclide tracer technology, as a state-of-the-art tool for quantifying and monitoring soil erosion processes, has attracted much attention in global sustainable land management research in recent years. However, existing studies are fragmented in methodological applications, lack systematic knowledge integration and interdisciplinary perspectives, and lack global research trends and dynamic evolution of key themes. This study integrates Bibliometrix, VOSviewer, and CiteSpace to conduct bibliometric and knowledge mapping analysis of 1692 documents (2000–2023) in the Web of Science Core Collection, focusing on the overall developmental trends, thematic evolution, and progress of convergence and innovation. The main findings of the study are as follows: (1) China, the United States, and the United Kingdom are in a “three-legged race” at the national level, with China focusing on technological application innovation, the United States on theoretical breakthroughs, and the United Kingdom contributing significantly to methodological research; (2) “soil erosion” and “¹³⁷Cs” continue to be the core themes, while “climate change” and “human impact” on soil erosion and its reflection in radionuclide tracing became the focus of attention; and (3) multi-scale radionuclide tracing (watershed, slope), multi-method synergy (radionuclide tracing combined with RS, GIS, AI), and the integration of advanced measurement and control technologies (PGS, ARS) have become cutting-edge trends in soil erosion monitoring and control. This study provides three prospective research directions—the construction of a global soil erosion database, the policy transformation mechanism of the SDG interface, and the iterative optimization of multi-radionuclide tracer technology, which will provide scientific guidance for the realization of the sustainable management of soil erosion and the goal of zero growth of land degradation globally.

1. Introduction

With the advancement of the global Sustainable Development Goals (SDGs), soil erosion has been recognized as one of the core challenges to global environmental sustainability, directly affecting the quality of soil resources and ecosystem functions [1,2,3]. Radioactive nuclide tracer technology quantitatively measures soil erosion and deposition by utilizing the spatial distribution and depth profiles of radioactive nuclides (¹³⁷Cs, ²¹⁰Pb, and ⁷Be) produced by atmospheric deposition in the soil. Following atmospheric deposition, these nuclides rapidly and strongly adsorb onto fine soil particles and migrate with them. By comparing the measured radioactive nuclide inventory (or activity depth profile) at a given location with a locally established reference inventory, deficits indicate net erosion, while surpluses indicate net deposition; mass balance equations then convert these signals into soil loss or gain per unit area. Due to its unique advantage in precisely tracking deposition and erosion processes across multiple scales from plots to watersheds, it has become an important tool for monitoring soil dynamics and revealing erosion mechanisms [4,5]. Reflecting this methodological promise and policy relevance, research activity in the field has risen sharply and is increasingly positioned within sustainable land management and ecological restoration agendas [6,7,8].

At the same time, the application of radionuclide tracers in complex and interdisciplinary research systems is subject to non-trivial boundary conditions that deserve explicit acknowledgment. (1) Time integration windows are intrinsic to fallout radionuclides—⁷Be (event–season), ¹³⁷Cs (multi-decadal), ²¹⁰Pb (centennial)—so misalignment with management or model horizons can bias inference [9,10]. (2) Spatial heterogeneity and baseline uncertainty (reference inventories, canopy interception, texture, microtopography) challenge normalization and cross-site comparability [11]. (3) Post-depositional mobility and particle-size selectivity (storage/remobilization, size-dependent transport, bioturbation) can decouple inventories from single-episode fluxes, demanding multi-tracer use or independent validation [12,13]. (4) Scale transfer from plot/hillslope to catchment or regional assessments requires explicit upscaling assumptions and uncertainty propagation, particularly when coupling to process models (e.g., RUSLE/SWAT) [14,15]. (5) Practical constraints—sampling density, lab throughput/QA–QC, and cost in remote or hazardous terrain—limit replication and highlight the value of integrative designs and transparent uncertainty analysis [16].

Against this backdrop, a rigorous, multi-method bibliometric synthesis is both necessary and urgent. The literature now spans geomorphology, hydrology, geochemistry, remote sensing, and data science, such that qualitative, experience-based reviews alone cannot reliably recover field structure or frontier dynamics. Bibliometrics provides transparent, reproducible procedures grounded in objective indicators (e.g., output, citations) and network analytics (e.g., PageRank, betweenness centrality) to identify influential actors, bridge nodes, and evolving themes across co-authorship, co-citation, and keyword networks [17,18]. By systematically mapping structural relationships and temporal trajectories, our approach moves beyond narrative assessment, enabling quantifiable comparisons of journals, institutions, and collaboration patterns; revealing the evolution of research hotspots; and linking methodological developments to practice-relevant agendas, including SDG-aligned monitoring and restoration priorities [19,20]. The combined use of descriptive performance metrics and scientific mapping is indispensable for synthesizing a rapidly expanding, interdisciplinary evidence base and for informing where radionuclide tracer research can most effectively advance science and policy.

Based on the 1692 relevant papers in the Web of Science database from 1 January 2000 to 31 December 2023, this study conducted a systematic investigation and a big data-driven in-depth analysis of the current status and development trend of the application of radionuclide tracer technology in soil erosion research by using three major tools, namely Bibliometrix, VOSviewer, and CiteSpace. Our study focuses on the following three core questions:

Q1: What are the current general dynamics of the field? Based on the results in Section 3, we map out the academic landscape of the field in terms of the literature output, core journal distribution, highly cited papers, institutional and regional collaboration networks, and author collaboration patterns. Q2: What are the evolutionary trends of key research themes over the past two decades? By analyzing keyword co-occurrence networks and their clustering results from Section 3, alongside the discussion in Section 4, we reveal historical changes and shifts in research hotspots. Q3: How can the innovative assessment of soil erosion processes using radionuclide tracer technology in complex terrain and extreme climates be integrated to support the sustainable management of soil resources? This question is divided into four thematic subsections in Section 4, which explore technical challenges and optimization strategies in different scenarios. Meanwhile, the section highlights the significance of this review compared with the previous literature reviews in Section 4.5, emphasizing research shortcomings and contributions. Section 5 summarizes the conclusions and offers future perspectives.

Through a multi-faceted and integrated bibliometric analysis, this study not only presents the developmental lineage of radionuclide tracer technology in the field of soil erosion but also provides quantitative decision-making references for the practical innovations of this technology in soil health assessment, management strategy development, and sustainable soil and water conservation engineering. We expect that the results of this research will reveal new opportunities for cross-disciplinary collaboration and facilitate new ideas and continuous innovations related to ecosystem conservation, thus enhancing the resilience of sustainable soil development.

2. Materials and Methods

2.1. Data Sources

This study was conducted on 16 August 2024, using the Web of Science Core Collection database. The representative search query was TS = ((“Soil Erosion” OR “Erosion of Soil” OR “Soil Degradation” OR) AND (“Nuclear Tracing” OR “Nuclear Tracers”). To ensure the comprehensiveness of the search, the keyword list included professional terms and common variants from the relevant field. The complete search query is detailed in Supplementary File S1. To maximize comprehensiveness, the search phase did not restrict document types (journal articles, reviews, conference papers, etc., were all retained). The initial search yielded 1693 records. After deduplication using CiteSpace and manual verification, the final dataset consisted of 1692 unique records (n = 1692).

The analysis covers the time window from 1 January 2000 to 31 December 2023, based on the following considerations: research methods have been standardized during this period, the literature is comprehensively included in the Web of Science database, and the citation network is complete, ensuring the scientific rigor and reliability of the results. However, early studies (from the 1960s–1970s, the initial phase of radionuclide application, and the 1980s–1990s, the exploratory phase for alternative radionuclides such as ²¹⁰Pb) were often in non-digital formats or published in regional journals, resulting in incomplete coverage in the database and potential bias if included in the analysis.

2.2. Data Visualization Analysis

We adopt a three-in-one toolkit architecture: Bibliometrix (R package; Aria & Cuccurullo, 2017; v4.4.1/v4.2.3) provides an open-source structured analysis framework, with its unique contribution lying in performing descriptive statistics, network metric calculations (such as PageRank), and multi-index influence assessments (H/G/M indices), supporting cross-disciplinary performance analysis [21]; VOSviewer (van Eck & Waltman, 2010; v1.6.20) specializes in high-resolution scientific mapping, with a minimum co-occurrence frequency threshold of 5 for keywords to ensure network readability and representativeness [22]; CiteSpace (Chen, 2006; v6.3.R1) focuses on diagnosing the dynamic evolution of keywords, employing log-likelihood ratio (LLR) clustering annotation and temporal analysis [23]. It uses the LLR method for clustering annotation, which more accurately identifies clustering features than traditional word frequency analysis [24] while using the Silhouette value (range −1 to 1, with values closer to 1 indicating better performance) to assess clustering quality. This combination covers the entire chain from static structural analysis (Bibliometrix/VOSviewer) to dynamic trend detection (CiteSpace), avoiding the limitations of a single tool and significantly enhancing the robustness, transparency, and multidimensional interpretability of the analysis. The overall research methodology process is detailed in the framework diagram in Figure 1.

A comprehensive analytical framework based on multidimensional indicators and a diverse toolkit was simultaneously constructed. In terms of indicator selection, we employed three complementary sets of indicators, including (1) network-based indicators such as PageRank and betweenness centrality, used to capture the structural importance and bridging role of key nodes in co-authorship and co-citation networks. Node sizes are visualized to correspond to PageRank values, and the thickness of connecting lines reflects the intensity of collaborative relationships [25,26]; (2) international cooperation metrics, including the ratio of single-country publications (SCP) to multi-country publications (MCP) [27]; (3) author-level evaluation metrics, combining the H-index (balancing output and citations), G-index (emphasizing highly cited literature), and M-index to conduct a multidimensional assessment of academic influence within a unified time window (from the first publication year of each object to the end of 2023), effectively overcoming the limitations of single metrics [28]. Altogether, this methodology demonstrates an overall improvement in the depth and accuracy of bibliometric research.

3. Results

3.1. Publication Trend Analysis

The evolution of radionuclide tracer applications in soil erosion research from 2000 to 2023 was delineated into three distinct phases based on publication output and citation trends (Figure 2a). During 2000–2007, the annual publications rose from 26 to 56 (≈11.6% annual growth), and citations climbed from 5 to 593. In the 2008–2015 phase, publications remained between 51 and 95 per year, while citations increased from 849 to 2321 (≈15.5% annual growth). From 2016 to 2023, research activity intensified, with average annual publications increasing from 85 to 112 (≈4.0% annual growth) and citations peaking at 4763 in 2023. This surge can be attributed to major national initiatives such as the 2016 China Soil Pollution Prevention and Control Action Plan, as well as increased funding support.

Within the research field, the average number of citations per paper is 28.47, with an average publication time of approximately 10.2 years and a cumulative total of 51,371 citations, indicating significant academic influence and research depth. As shown in Figure 2b, academic articles dominate the field, accounting for approximately 93.9% (1589 papers) of the total, while review articles account for 3.5% (59 papers) and other types of the literature constitute an extremely low proportion. This distribution structure reflects the field’s focus on original empirical research while also emphasizing academic exchange and review-based summaries.

Figure 2c shows that the research landscape aggregated by discipline has continued to expand across three phases. The cumulative number of publications increased from 564 in 2000–2007 to 866 in 2008–2015 and further to 1246 in 2016–2023, corresponding to compound annual growth rates of approximately 5.5% and 5.8% for the two phases, respectively. In terms of structure, agriculture and geology have consistently maintained high output levels; meanwhile, the focus on environmental sciences and ecology and water resources has significantly increased: environmental sciences and ecology accounted for approximately 19.2%, 20.6%, and 20.0% of the total during the 2000–2007, 2008–2015, 2016–2023, with shares of approximately 19.2%, 20.6%, and 20.8%, respectively, maintaining an overall average of approximately 20%. The share of water resources research increased from 8.7% in the 2008–2015 phase to 10.9% in the 2016–2023 phase (+2.2 percentage points). This aligns closely with the accelerating convergence of policy and research focus on ecosystem resilience and soil and water management in recent years and also aligns with the evidence requirements for soil/water degradation monitoring and governance outlined in the United Nations’ 2030 Agenda for Sustainable Development, specifically SDG 15 (Life on Land) and SDG 6 (Clean Water and Sanitation).

3.2. Core Journal Distribution Analysis

Bradford’s law was applied to identify a core set of journals in radionuclide tracer applications to soil erosion research, thereby providing a theoretical underpinning for disciplinary focus [29]. As illustrated in Figure 3a, the field’s journals were classified into a core zone (Zone 1) and a peripheral zone (Zone 2). The core zone comprises eight interdisciplinary journals that account for the majority of publications, namely the Journal of Environmental Radioactivity, Catena, Earth Surface Processes and Landforms, Geomorphology, Soil & Tillage Research, Science of the Total Environment, Geoderma, and the Journal of Soils and Sediments.

Within Zone 1, the Journal of Environmental Radioactivity and Catena stand out by publishing 117 and 109 articles, respectively—226 in total—representing roughly 40% of the core zone’s output (Figure 3b), underscoring their dominant roles. Academic influence metrics further highlight the prestige of these journals: their 2022–2023 journal impact factors (IFs) of 6.1 for Soil & Tillage Research, 5.6 for Geoderma, and 5.4 for Catena (Figure 3c), along with high H-index and CiteScore metrics, confirm their sustained impact.

Over the past two decades, most core journals have shown continuous growth in annual publications—from single digits in 2000 to over 100 by 2023—mirroring the rapid advancement and increased scholarly attention in this domain. These trends align with the predictions of Bradford’s law and reinforce the central status of these key journals.

3.3. Highly Cited Paper Analysis

Specifically, four seminal papers were chosen from the ten most globally cited works to highlight the methodological significance of radionuclide tracer techniques in soil erosion research (Table 1). A comprehensive review highlighted the advantages and limitations of ¹³⁷Cs, excess ²¹⁰Pb, and ⁷Be for quantifying soil erosion and deposition rates, laying the methodological groundwork for multi-timescale erosion rate estimation; it has accrued 328 global citations and 208 local citations (LCS/GCS ratio 63.41%) [9]. The most-cited article in Land Degradation & Development systematically presented the multifaceted impacts of soil erosion on agricultural productivity, water quality, biodiversity and carbon fluxes—thereby establishing core concepts for sustainable land management—and has amassed 812 global citations (33.83 per year) despite a 4.73% local citation share [30]. A Science publication provided novel insights into sediment transport through studies of natural river evolution, advancing radionuclide tracer applications in fluvial and depositional contexts; it has attracted 628 citations (36.94 per year), with a 1.59% local citation share [31].

Table 1 presents five highly cited review articles and five highly cited research papers that, collectively, reflect a multidisciplinary framework—spanning soil science, geomorphology, hydrology, and biogeochemistry—and cover study scales from single-storm [33,34events to century-scale timelines, underscoring the broad applicability of radionuclide tracer methods [32], Moreover, environmental drivers such as wildfire and karst terrain have been shown to modulate erosion processes [33,34], The literature also highlights the integration potential of radionuclide tracer techniques with machine learning approaches [35,36] and demonstrates applications in sediment source apportionment, transport pathways, and depositional dynamics [37].

Table 1. Top ten most-cited papers: bibliometric characteristics.

Title	TC	LCS	GCS	LCS/GCS	References	Journals
Soil degradation by erosion (Original Research)	33.83	35	812	4.73	[30]	Land Degradation &Development
Natural streams and the legacy of water-powered mills (Original Research)	36.94	10	628	1.59	[31]	Science
Comparative advantages and limitations of the fallout radionuclides 137Cs, 210Pbex and 7 Be for assessing soil erosion and sedimentation (Review)	19.29	208	328	63.41	[9]	Journal of Environmental Radioactivity
Biogeochemical processes and geotechnical applications: progress, opportunities and challenges (Review)	49.17	0	590	0	[38]	Géotechnique
Post-wildfire soil erosion in the Mediterranean: Review and future research directions (Review)	37.86	4	530	0.75	[34]	Earth-Science Reviews
(Dis)Connectivity in catchment sediment cascades: a fresh look at the sediment delivery problem (Review)	39.17	19	470	4.04	[32]	Earth Surface Processes and Landfroms
Karst hydrology: recent developments and open questions (Review)	20.35	1	468	0.21	[33]	Engineering Geology
Landscape form and millennial erosion rates in the San Gabriel Mountains, CA (Original Research)	25.8	6	387	1.55	[35]	Earth and Planetary Science Letters
The late-Holocene Gargano subaqueous delta, Adriatic shelf: Sediment pathways and supply fluctuations (Original Research)	13.77	6	194	3.09	[37]	Marine Geology
Marsh vertical accretion via vegetative growth (Original Research)	15.89	3	302	0.99	[36]	Estuarine, Coastal and Shelf Science

Note: TC Per Year = citations per year (2000–2023), LCS = local citation score (2000–2023), GCS = global citation score (2000–2023), LCS/GCS = proportion of domain-specific impact.

Table 1. Top ten most-cited papers: bibliometric characteristics.

Title	TC	LCS	GCS	LCS/GCS	References	Journals
Soil degradation by erosion (Original Research)	33.83	35	812	4.73	[30]	Land Degradation &Development
Natural streams and the legacy of water-powered mills (Original Research)	36.94	10	628	1.59	[31]	Science
Comparative advantages and limitations of the fallout radionuclides 137Cs, 210Pbex and 7 Be for assessing soil erosion and sedimentation (Review)	19.29	208	328	63.41	[9]	Journal of Environmental Radioactivity
Biogeochemical processes and geotechnical applications: progress, opportunities and challenges (Review)	49.17	0	590	0	[38]	Géotechnique
Post-wildfire soil erosion in the Mediterranean: Review and future research directions (Review)	37.86	4	530	0.75	[34]	Earth-Science Reviews
(Dis)Connectivity in catchment sediment cascades: a fresh look at the sediment delivery problem (Review)	39.17	19	470	4.04	[32]	Earth Surface Processes and Landfroms
Karst hydrology: recent developments and open questions (Review)	20.35	1	468	0.21	[33]	Engineering Geology
Landscape form and millennial erosion rates in the San Gabriel Mountains, CA (Original Research)	25.8	6	387	1.55	[35]	Earth and Planetary Science Letters
The late-Holocene Gargano subaqueous delta, Adriatic shelf: Sediment pathways and supply fluctuations (Original Research)	13.77	6	194	3.09	[37]	Marine Geology
Marsh vertical accretion via vegetative growth (Original Research)	15.89	3	302	0.99	[36]	Estuarine, Coastal and Shelf Science

Note: TC Per Year = citations per year (2000–2023), LCS = local citation score (2000–2023), GCS = global citation score (2000–2023), LCS/GCS = proportion of domain-specific impact.

3.4. Institutional and National/Regional Distribution

3.4.1. Major Institutions

The cumulative number of publications by each institution continues to rise, as shown in Figure 4a, where the cumulative curve remains upward. In detail, the Chinese Academy of Sciences (CAS, 422 papers) ranks first, significantly ahead of the United States Department of Agriculture (USDA, 125 papers), the University of Exeter (UoE, 107 papers), and the French National Center for Scientific Research (CNRS, 106 papers). Trend tests based on annual publication volume (non-cumulative) indicate that CAS (r = 0.83, p < 0.001) and CNRS (r = 0.88, p < 0.001) show a significant upward trend, and the United States Department of the Interior (DOI) also shows a clear upward trend (r = 0.68, p < 0.001), although the annual trend statistics for the USDA are not significant (r = −0.19, p = 0.365). UoE was marginal and not significant (r = −0.40, p = 0.050), and the long-term cumulative output of both continued to expand moderately: the cumulative annual growth rate (CAGR) of the USDA was approximately 8.8% per year from 2004 to 2023 (approximately 4.9% per year from 2010 to 2023); the UoE was approximately 7.7% per year and 4.8% per year, respectively. This combination of “continuously rising cumulative volume but annual increments tending toward a steady state” aligns with the characteristics of a mature publication rhythm.

Figure 4b reveals that CAS’s leadership in volume is paired with an H-index of 11, G-index of 14, M-index of 0.53, and total citation number of 813—an indication of room for improvement. Both CNRS and the University of California System achieved an H-index of 14; CNRS’s G-index of 25 highlights its high proportion of top-cited papers, and the University of California System’s 1874 citations reflect a demonstration of broad impact. The Swiss Federal Institutes of Technology Domain, while not among the top by count, displayed high quality with an H-index of 10, G-index of 12, and 820 citations.

Furthermore, collaboration-network analysis (Figure 4c) identified five major clusters. CAS occupied a central position with the highest PageRank algorithm value (0.09), and USDA, Exeter, and CNRS exhibited high BC, underscoring their roles as bridges between research groups. A distinct regional collaboration pattern was observed, with CAS and its affiliated institutes forming a tightly connected core collaboration cluster.

3.4.2. Countries/Regions

International publication and collaboration patterns for radionuclide tracer research in soil erosion are illustrated in Figure 5. China produced 422 publications, surpassing the United States (286) and the United Kingdom (114), underscoring its leading output in the field. Although China’s average citations per publication (30.8) trail those of the UK (51.6) and the US (42.7), it leads both in single-country publications (SCP, 302) and multiple-country publications (MCP, 120), indicating both strong independent research capacity and active global collaboration.

In contrast, the US emphasizes independent research (SCP 227 vs. MCP 59), while the UK exhibits the highest international collaboration rate (MCP 68). The MCP comparison further demonstrates China’s increasingly active role within the global research network, with cooperative ties to major research nations strengthening over time.

This survey of research results provides key insights to guide soil erosion research using cutting-edge radionuclide tracers in three countries. China and the US have both made significant contributions using their own research methods, while the UK has focused on expanding its international research strategies, in which interactions are also important. Therefore, to increase the impact of research and promote technological innovation to drive the future development of this field, it is essential to pursue more high-quality international collaborations. However, in regions such as North Africa, where soil erosion is a particularly serious problem and international cooperation networks are weaker, it is recommended that a regional tracer database be developed with the help of the United Nations Convention to Combat Desertification (UNCCD) COP16 and the African Forest Landscape Restoration Initiative (AFR100). This would promote synergistic management in the fight against soil erosion and support sustainable development worldwide by enhancing technology transfer.

3.4.3. Author Productivity and Influence

Lotka’s law analysis revealed that 4445 authors published only a single article on radionuclide tracer soil erosion research, confirming the typical inverse relationship between author count and publication volume [39]. Only 42 authors exceeded ten publications, with the most prolific contributing 38 papers—an indication of a small cohort’s disproportionate productivity.

As illustrated in Figure 6a, author impact was assessed using the H-index, G-index, and the M-index. Evrard Olivier from Université Paris-Saclay and Walling D. E. of the University of Exeter both achieved an H-index of 22; Evrard Olivier’s G-index of 33 surpasses Walling’s 26, reflecting a greater number of top-cited works. Walling’s total citation number of 1503 further underscores his enduring influence.

Figure 6b shows that Evrard Olivier is ranked first among all authors, with a high betweenness centrality of 143.3 and a PageRank value of 0.5. This demonstrates his bridging role. Figure 6c illustrates how Evrard Olivier promotes the development of the field by cooperating closely with multiple institutions and countries. These data further confirm his pivotal position within the field.

3.5. Co-Word Evolution and Clustering

3.5.1. Keyword Co-Occurrence Network Analysis

As depicted in Figure 7a, occurrences of the radionuclide tracer “¹³⁷Cs” (372 mentions) surpass those of “soil erosion” (364) and “erosion” (103), demonstrating the central role of ¹³⁷Cs in soil erosion studies. Other prominent keywords include lead-210 (80 mentions), “sediment transport” (77), and “radionuclide” (69). Centrality metrics—betweenness centrality and PageRank algorithm scores—underscore keyword importance: ¹³⁷Cs holds the highest BC (539.5) and PageRank (0.2), followed by “soil erosion” with BC = 220.9 and PageRank = 0.1, confirming their pivotal positions.

Moreover, the keyword distribution follows a long-tail pattern, indicating focused research priorities alongside thematic breadth. The network comprises 184 keyword nodes, revealing tight interconnections. Core terms—“¹³⁷Cs”, “soil erosion”, “Pb-210”, “sediment transport”, and “radionuclide”—form the backbone structure, linking diverse research topics and methodologies.

Figure 7b presents linear-growth models for steadily rising keywords. The fit for “¹³⁷Cs” is y = 16.4 x − 13.39 (R² = 0.99), and “soil erosion”, “erosion”, and “sediment transport” each show R² > 0.95, with annual mention increases of 16.

3.5.2. Research Hotspot Evolution

As illustrated in Figure 7c, the terms “¹³⁷Cs”, “Pb-210”, “soil erosion”, and “sediment transport” have been consistently prominent throughout 2000–2023, while “climate change” and “human impact” have emerged as significant research themes. Emerging hotspots such as “paleolimnology”, “geochronology”, and regional studies (e.g., “himalaya”) have also gained traction.

The observed hotspot evolution indicates a transition from single-process erosion studies to integrated assessments of environmental change, driven by technological innovation and pressing environmental challenges. This shift has been facilitated by high-resolution remote sensing and unmanned aerial vehicle LiDAR (UAV-LiDAR) in surface erosion monitoring [40] and by the adoption of machine learning algorithms such as the random forest algorithm in sediment provenance analysis [41]. Simulations of extreme climate events further underscore the urgency of soil loss under future climate scenarios [41,42]. Moreover, interdisciplinary collaborations—merging geomorphology, ecology, and regional land-use policy research—have provided new frameworks for comprehensive soil erosion evaluation and management [41].

3.5.3. Topic Clustering Analysis

Ten principal research clusters were delineated (Figure 8). Cluster 1 (25 members, silhouette score = 1), labeled “soil erosion”, encompasses multidimensional investigations into erosion processes. Representative studies include quantitative mapping of erosion heterogeneity with ¹³⁷Cs on the southeastern Tibetan Plateau [43], analyses of Mediterranean climate change and human impacts [44], experimental evaluations of slope and flow effects on erosion mechanisms [45], and a global erosion assessment using the revised universal soil loss equation (RUSLE) model [46], These contributions have refined theoretical frameworks and broadened perspectives within the field.

Cluster 2 (22 members, silhouette = 0.958), themed “sediment yield”, addresses sediment dynamics and soil–water conservation. Notable works include an assessment of ecological service outcomes from China’s Grain-for-Green program on the Chinese Loess Plateau [47] and the identification of sediment sources in northern Iranian catchments to evaluate ecological engineering impacts [48].

Cluster 3 (20 members, silhouette = 1), labeled “Sediment Transport”, focuses on transport processes. Key studies include analyses of runoff and sediment loads in the Pearl River basin [49], erosion risk modeling in the United States [50], global erosion change assessments [51], and investigations into shallow grassland erosion in the Alps [52].

Cluster 4 (16 members, silhouette = 0.992), under “wind erosion”, examines aeolian erosion processes in arid and semi-arid environments. Landmark applications include the innovative use of ¹³⁷Cs in East Anglia, UK [53], and evaluations of climate-driven wind erosion on the US Great Plains [54].

Cluster 5 (15 members, silhouette = 0.946), labeled “soil redistribution”, examines the effects of soil redistribution on organic carbon dynamics. Key studies include assessments of redistribution rates in China’s northeastern black soil region using ¹³⁷Cs and fly ash [55] and evaluations in small agricultural catchments [56].

Cluster 6 (11 members, silhouette = 0.909), “depositional nuclide tracing”, explores applications of excess lead-210 and beryllium-7 for recent and short-term erosion monitoring [9] and compares fallout radionuclides under long-term erosion scenarios [57].

Cluster 7 (6 members, silhouette = 0.982), “sediment fingerprinting”, focuses on quantitative source apportionment using fingerprinting techniques. Multi-tracer integration approaches [58] and validations in urbanized catchments in eastern UK [59] demonstrate enhanced resolution and applicability.

Cluster 8 (5 members, silhouette = 0.933), “tillage erosion”, investigates tillage-driven soil redistribution. Research reveals that agricultural tillage erosion often exceeds natural water erosion [60], conservation tillage reduces erosion by 50–80% [61], and the mass balance model approach combines ¹³⁷Cs to quantify contributions of water versus tillage erosion [62].

Cluster 9 (four members, silhouette = 0.962), “erosion modeling”, advances global-scale models integrating high-resolution land cover and climate simulations, markedly improving future climate erosion risk predictions [51].

Cluster 10 (four members, silhouette = 0.981), “Chernobyl-derived ¹³⁷Cs”, utilizes Chernobyl-released ¹³⁷Cs to trace sediment processes. Studies of floodplain ¹³⁷Cs distribution and geomorphic relationships in central Russia [63] and floodplain chronology using high-resolution topography and ¹³⁷Cs activity [64] provide novel tools for reconstructing fluvial dynamics.

4. Discussion

Building upon the keyword clustering analysis in Section 3, the thematic framework for the forthcoming section is established. Drawing on the observed thematic trends of the clusters covered in the last section, specifically those related to spatial scales, methodological integration, sampling and testing optimization, and interdisciplinary actions, our discussion is structured into four major sub-aspects.

Section 4.1 covers groups such as #6 “depositional radionuclide tracing”, and general themes and multi-scale processes, for example, provide an example of applying radionuclide tracer methods across macro-, meso-, and micro-scales, describing their strengths and weaknesses.

Section 4.2 is relative to clusters involving #9 “erosion modelling”, #5 “soil redistribution”, and #3 “sediment transport”, consolidating the radionuclide tracing system as a feasible method with conventional and emerging methods (that is, physical monitoring, empirical models, and machine learning) that results in stronger methodical complementarity and robustness of conclusions.

Section 4.3 will be connected with #7 “sediment fingerprinting”, #8 “tillage erosion”, and the like in order to learn practice strategies for sample selection and analytical techniques, including intelligent sensor systems, high-throughput detection, and AI-directed workflows.

Section 4.4 highlights key themes, addressing current technical challenges, emerging opportunities, and the necessity of interdisciplinary collaboration across fields such as geochemistry, hydrology, ecology, remote sensing, and data analysis. Together, these elements form a clear and well-structured discussion plan. This comprehensive perspective allows us to examine and advance the application of radionuclide tracer technology in soil erosion research from multiple angles.

4.1. Multi-Scale Applications and Implications for Soil Management and SDGs

Radionuclide tracer techniques have been applied at multiple spatial scales in soil erosion research, demonstrating distinct strengths and limitations. At the watershed scale, ¹³⁷Cs and ²¹⁰Pb tracers were integrated with the Soil and Water Assessment Tool (SWAT) in southeastern Brazil to unravel erosion dynamics under complex terrain and land-use patterns [65]. In central Nepal, soil redistribution in small catchments was quantified, revealing fundamental links between hydrological processes and erosion [66]. However, large-scale spatial variability, challenging sampling logistics, and model complexity introduce significant uncertainty—particularly regarding suspended sediment adsorption and the redistribution of ¹³⁷Cs—necessitating refined sampling protocols and model calibration for validation [67,68]. This trace-based spatial information is directly actionable: it can be used to implement nature-based solutions such as riparian buffer strips and terraced fields to block sediment pathways and provides quantitative evidence of “before and after” interventions to assess project effectiveness and calibrate planning models. The IAEA’s operational guidelines also emphasize the value of this method in project design and evaluation [10].

At the hillslope scale, applications of ¹³⁷Cs and ²¹⁰Pb in cultivated Sicilian catchments quantified gully erosion contributions to total soil loss (41% vs. 44%), underpinning targeted soil and water conservation strategies [69], In Swiss alpine grasslands, quantification using ^{239 + 240}Pu demonstrated high precision but incurred substantial costs and logistical challenges, impacting long-term feasibility [70]. Dual-tracer validation represents a methodological breakthrough for mountain agricultural ecosystems [71]. For management, tracer-based source apportionment helps target tillage practices and ground cover where they matter most (e.g., in gully-dominated sub-catchments). Recent validation of ^{239 + 240}Pu strengthens confidence in using isotopic evidence to prioritize interventions and to upscale findings to planning units [72]. Long-term loss estimates via ¹³⁷Cs were shown to be sensitive to assumptions of uniform distribution and constant particle binding in rugged terrain, highlighting the need for optimized sampling designs [73].

Experimental plot scale studies offer high-precision erosion rate measurements and reproducibility [74], yet their limited spatial scope constrains representativeness. Plot scale experiments provide the gold standard for method testing; when combined with catchment-scale radionuclide datasets and independent inventories (including new global references for ¹³⁷Cs and ^{239 + 240}Pu), they offer robust baselines for evaluating conservation outcomes and for reporting against soil health and SDG frameworks [75].

Radionuclide tracing generates auditable, spatially explicit indicators that can supplement national-level soil health reports and SDG 15.3.1 (“proportion of degraded land”). Under the SDG framework, countries report on degradation through three sub-indicators, namely land cover, land productivity, and soil organic carbon. The erosion/sedimentation balance from fallout radionuclides (FRNs) provides ground-truth evidence that can be used for the targeted implementation of management measures and to validate modeled trends in these sub-indicators. This aligns with the UNCCD’s Good Practice Guidelines and the EU’s proposed Soil Monitoring Regulation (aiming for healthy soils by 2050) [76,77].

Effective replication requires integration with multi-scale datasets. Macroscale studies reveal global patterns, mesoscale analyses disentangle specific processes, and microscale experiments provide precise mechanistic verification. Similarly, our bibliometric analyses suggest that the integration of multi-scale and multi-method approaches is becoming increasingly important, as evidenced by the emergence of themes such as “erosion modelling” and “soil redistribution”. The emergence of these topics is further evidence of this trend. In the future, research into the integration of multi-scale data will contribute to a more comprehensive framework for assessing erosion from plot, watershed, and regional scales.

4.2. Integration of Radionuclide Tracer Techniques with Complementary Methods

The integration of radionuclide tracer techniques with conventional approaches has demonstrated considerable benefits. The unique advantages of ¹³⁷Cs tracing for delineating erosion and deposition hotspots were highlighted in [78], which showed that environmental radionuclide measurements can characterize soil movement more precisely than traditional methods. The combination with soil physical property assessments has facilitated the elucidation of intricate soil–vegetation–topography interactions.

In the dry, hot river valley of southwestern China, it was found that the spatial variability of soil physical properties significantly influenced the distribution of vegetation biomass. This provides a scientific foundation for the restoration and management of ecosystems [79]. Similarly, integration of ¹³⁷Cs tracing with soil physical analyses in Mediterranean mountain regions substantiated the impact of land-use changes on erosion processes [80]. Moreover, by demonstrating the complementary strengths of radionuclide tracers and conventional approaches, this combined methodology provided a robust empirical foundation for soil erosion studies (

Table 2. Comparative advantages and integrative enhancements of radionuclide tracing techniques and traditional soil erosion methods across multiple dimensions.

Dimension	Advantages of Radionuclide Tracers	Advantages of Methods	Integrated Enhancement
Spatial coverage	Cumulative, long-term spatial information	Large-scale monitoring	Enhanced spatiotemporal extrapolation across large regions
Temporal scale	Decadal records of sediment deposition	Short-term field observations	Capturing short-term pulses and long-term trends
Data accuracy	High-resolution, particle-level tracing	Detailed soil physicochemical and profile data	Reduced measurement uncertainty
Modeling capability	Empirical calibration and physically based models	Process-based simulation and forecasting	Improved model accuracy and generalizability

). Nonetheless, when interpreting radionuclide distribution patterns, it remains essential to account for variations in sediment sources and the surrounding environmental context.

Advancements in remote sensing and machine learning have further expanded the range of applications for tracers. Using ¹³⁷Cs datasets, hierarchical recurrent highway networks (HRHNs) and random forest (RF) models successfully predicted particulate ¹³⁷Cs concentrations in river systems. This offers more accurate tools for assessing erosion in complex terrain [81]. Nonetheless, the dependence of these machine learning approaches on training data and their limited interpretability necessitate careful evaluation of their outputs. Additionally, tracer-derived data have been used to improve the calibration of physical erosion models. For example, the calibration of the RUSLE with ¹³⁷Cs significantly improved assessment accuracy and depth [82]. However, radionuclide tracers predominantly capture cumulative erosion over decades; therefore, these calibration approaches are the most appropriate for estimating long-term average erosion rates and require cross-validation with field observations to resolve short-term dynamics. This complementary integrative research paradigm not only extends theoretical frontiers but also informs holistic erosion control and sustainable land management strategies.

The core themes of “soil erosion” and “¹³⁷Cs” have maintained their dominant position in traditional radionuclide tracer techniques due to their fundamental scientific value and indispensable integrative role in methodological innovation: soil erosion remains a hallmark of global challenges, directly linked to ecosystem resilience, carbon dynamics, and the United Nations Sustainable Development Goal 15.3.1 on achieving net-zero land degradation. ¹³⁷Cs tracers, with their approximately 30-year half-life and globally standardized protocols, provide a standardized, policy-relevant long-term indicator of net soil redistribution. Their ability to generate spatially explicit, decade-scale budgets serves as a backbone for calibrating and validating emerging methods such as composite sediment fingerprinting, drone-based LiDAR mapping, hyperspectral imaging, and AI-driven process modeling. Crucially, new methods typically rely on radionuclide tracing-derived datasets to establish predictive accuracy, address scale mismatch issues, and reduce biases in model assumptions rather than completely replacing them.

The continued relevance of these core themes is further strengthened by their ability to interact with emerging research frontiers, including the impact of climate change on erosion dynamics, assessments of human impacts on terrestrial systems, and thematic extensions into paleolimnology, geochronology, and geographically focused studies (e.g., the Himalayan region). These emerging themes expand the spatio-temporal and disciplinary scope of radionuclide tracer applications but often require the historical baselines and methodological rigor provided by ¹³⁷Cs and soil erosion studies to contextualize their research findings. The parallel development of complementary isotopes (e.g., ⁷Be for event-scale erosion; ²¹⁰Pb for century-scale dynamics) demonstrates a trajectory of gradually filling gaps and broadening the applicability of FRN while maintaining its comparative benchmarks. Within this continuity innovation dynamic, established tracers and concepts form a structural framework upon which next-generation monitoring and modeling capabilities—addressing persistent global challenges—can be safely built.

Overall, research trajectories are increasingly influenced by the integration of multi-source datasets and complementary methodologies—combining mature tracer benchmarks with emerging geospatial, isotopic, and computational tools—to build more resilient, policy-relevant erosion models and actionable land management strategies aligned with global sustainability frameworks such as SDG 15.3.1.

4.3. Sampling and Test Optimization

The thematic clusters of “depositional nuclide tracing”, “sediment fingerprinting,”, and “tillage erosion” all underscore the importance of high-quality sampling for tracer accuracy. An adaptive, multi-scale sampling framework leveraging Bayesian optimization was implemented to enhance sampling efficiency and accuracy. Coarse-scale samples were initially collected, followed by refinement of local sampling density informed by preliminary results and terrain complexity [83]. This combination of global batch optimization and local search was shown to optimize sampling point selection by maximizing the acquisition function [84]. In challenging or hazardous terrains, multi-sensor robotic teams conducted spatiotemporal sampling, establishing a closed-loop feedback validation between the macro- (watershed) and micro- (field and plot) scales to further improve data quality [85]. Together, these approaches strengthen the characterization capabilities of radionuclide tracer environmental assessments [86,87].

Additionally, measurement technologies have advanced markedly. Portable gamma spectrometers integrated with artificial intelligence enable rapid scanning and real-time analysis, significantly boosting field productivity and reducing data collection times [88,89]. Nanomaterial-based isotope separation techniques enable efficient extraction of target nuclides from minute soil samples, substantially improving detection sensitivity. Synchrotron X-ray fluorescence (XRF) allows for simultaneous multi-radionuclide quantification and intra-particle distribution mapping, supporting the quantitative analysis of tillage erosion processes [89,90]. Accelerator mass spectrometry (AMS) provides superior sensitivity over alpha spectrometry for low-concentration, long-lived radionuclides such as ^239+240Pu [91]. Deep learning models incorporating channel attention modules have enabled automated feature extraction and classification from spectral data, improving the quality of input datasets for sediment transport simulation [92].

Finally, Figure 9 illustrates an integrated, multi-module analytical system encompassing sampling optimization, advanced measurement technologies, data interpretation, and model development. Feedback loops within the system continuously refine sampling and testing protocols, delivering a unified technical platform that elevates efficiency and accuracy in soil erosion research.

4.4. Challenges, Opportunities, and Interdisciplinary Prospects

The advancement of radionuclide tracer techniques regarding soil erosion studies significantly entails interdisciplinary fusion in addressing far-reaching challenges holistically. The key integration pathways include building water–soil radionuclide transport models through the combination of geochemistry and hydrology, evolving the eco-soil–erosion relationship, wrapping up ecosystem science with pedology, cosmogenic radionuclide dating for geomorphology, and various geographies for long-term landscape evolution models. Also, there are many other contemporary methods to assess soil erosion or usage-related aspects by developing a fusion model based on remote sensing data or geological information systems, big data, and artificial intelligence techniques. Along with this, sediment transport dynamics and eco-engineering sustainability, assessing the impact of new tillage operations in agro-ecosystem services, and diversifying isotope tracers across scales to capture temporal dynamics are also important themes for data integration in soil erosion research.

Tracer applications currently face several obstacles, such as an incomplete understanding of nuclide migration and redistribution mechanisms [93], the scarcity of ideal reference sites complicating model validation [73], limited temporal resolution and difficulty measuring low-activity radionuclides [94], and the exacerbating effects of complex terrain and dynamic vegetation [73]. Extreme weather events introduce high spatiotemporal variability that disrupts long-term erosion signals—variability that traditional models struggle to capture [95]. Additionally, uncertainty in model parameters hinders accurate regional erosion assessments, as different datasets and computational methods yield divergent outcomes [96].

Emerging innovation opportunities could drive breakthroughs. For example, adapting high-resolution imaging from medical imaging to mapping isotopes in soils; combining optically stimulated luminescence dating techniques to date glacier ice with other tracers for multi-radionuclide applications and improved resolution dating; habitat suitability modeling with linkage explicitly made for topographic factors that can use technologies such as unmanned aerial vehicles (UAVs) from precision agriculture to overcome reference site limitations; ensemble forecasting from climate science and adaptive management principles from ecology to refine model parameters and sampling strategies; and applying extreme event analysis methods from meteorology and hydrology to build correction algorithms and event response models. Advances in GIS and ecosystem modeling can offer potential to improve the representations of terrain and vegetation process models. While these concepts remain largely theoretical and face methodological and technical hurdles, their validation through clustering analysis underscores the need for a unified platform.

Although some of these directions are still at the theoretical exploration stage, their validation studies highlight the need to build a unified, multi-source information integration platform in order to cope with more complex environmental scenarios in the future.

4.5. Contributions and Limitations of This Study

This study addresses a significant knowledge gap in the field of soil erosion research by employing a systematic bibliometric analysis of radioactive nuclide tracer technology. Its innovation and unique positioning are primarily reflected in three dimensions, namely methodological innovation, the revelation of knowledge structures, and practical guidance value.

In terms of methodological contributions, this study introduces the three-dimensional integrated analysis framework of Bibliometrix–VOSviewer–CiteSpace into the field of radionuclide tracing, achieving multi-level quantification of static network structures, dynamic evolutionary paths, and thematic clustering. This breaks through the limitations of previous reviews, which relied solely on descriptive statistics or a single software platform. This multi-tool complementary approach not only enhances the objectivity and reproducibility of results but also integrates structural indicators (such as PageRank and betweenness centrality), academic impact indicators (H-index, G-index, M-index), and thematic evolution information within the same framework, providing a unified analytical platform for cross-scale comparisons.

In terms of contributions to the knowledge system, we not only identified core journals, leading institutions, key scholars, international cooperation networks, and keywords in the field, but we also revealed the synergistic innovation relationship between traditional tracer nuclides such as 137Cs and emerging multi-nuclide technologies, filling the gap in the systematic understanding of the dynamic evolution of knowledge structures and thematic synergy mechanisms in this field. Additionally, this study spans the time period from 2000 to 2023, dynamically depicting the transformation of research hotspots from single processes to comprehensive themes such as climate change, human activities, and interdisciplinary integration, highlighting the novelty of the temporal dimension.

In terms of practical guidance value, we conducted a multi-objective association analysis between research themes and the United Nations Sustainable Development Goals (SDGs), revealing potential application pathways for radionuclide tracer technology in land degradation neutrality (LDN). This analysis not only facilitates interdisciplinary research integration but also provides an operational reference framework for policy formulation, watershed management, and technology transfer.

Based on the comparative analysis in

Table 3. Review articles on soil erosion tracer applications: a comparative overview.

References	Review	Data Sources	Temporal Coverage	Analytical Tools	Bibliometric Metrics	Research Gaps	Key Contributions
[97]	✓					Low time resolution, signal degradation needs correction	Established the first quantitative erosion/sedimentation model for 137Cs and verified its high correlation with USLE
[9]	✓					Cross-scale upscaling and uncertainty propagation	Clear; side-by-side appraisal of 137Cs/210Pb_ex/7Be advantages and limitations
[12]	✓					Insufficient treatment of post-depositional migration and grain size selectivity	Demonstrated the first integration of 7Be–137Cs for quantitative comparison of short-term and long-term soil erosion rates.
[98]	✓					Lack of alternative radionuclide tracers and models	The system refutes the four major assumptions of 137Cs tracing and questions the reliability of its erosion rate estimates for the first time
[99]	✓	CRP Project Multi-Country Measured Data	covering the CRP period 2002–2008			FRN settlement space varies greatly, and quality control needs improvement.	Summarize the results of the IAEA/FAO CRP project, standardize multi-radionuclide methods and models, and promote FRN tracer standardization
[100]	✓	59 relevant documents				Insufficient data coverage and model validation (Be2D, LODO, etc.)	Comparing the application differences between 10Be, 137Cs, and 239 + 240Pu, proposing a multi-radionuclide joint tracing and Pu substitution strategy
This Research	✓	WoS database (1692 relevant studies worldwide)	2000–2023	Bibliometrix + VOSviewer + CiteSpace	PageRank, betweenness centrality, H-index, G-index, M-index, MCP, SCP	(1) Citation metrics (H-index, G-index) are affected by update lags, potentially underestimating recent high-impact studies; (2) analysis is limited to English-language WoS Core Collection records, excluding non-English and gray literature	(1) Applied a Bibliometrix–VOSviewer–CiteSpace triad to achieve multi-level bibliometric analysis beyond single-tool reviews; (2) mapped global research patterns and linked traditional tracers with emerging methods to capture dynamic field evolution

, this study demonstrates a distinct competitive advantage among all the review-type literature in the field of radionuclide tracer technology and soil erosion: it builds on previous research while achieving substantial breakthroughs in method integration, temporal coverage, thematic synergy analysis, and policy linkage, providing a directly applicable paradigm for future bibliometric and comprehensive assessment studies in this field.

Limitations: Measurement indicators such as the H-index and G-index are affected by the lag of literature inclusion and citation update, which may underestimate the rapid accumulation of highly cited studies in the past two years. A rolling time window or real-time updating mechanism can be introduced in the future, and the values of the indicators can be corrected periodically to ensure the timeliness and accuracy of the analysis results. In addition to the time lag issue, citation-based metrics themselves often favor disciplines and journals with higher citation densities, which may lead to an underestimation of early-career researchers. It should be noted that this study is limited to English-language publications in the Web of Science Core Collection; future studies incorporating non-English databases and gray literature are expected to provide a more comprehensive perspective on the global use of radionuclide tracing in soil erosion research.

5. Conclusions

5.1. Key Findings

Over the past 24 years, with the continuous advancement of the sustainable development agenda and international policies for combating land degradation, as well as heightened concern over extreme climate and soil resource degradation issues, the application of radionuclide tracer technology in soil erosion assessment has become increasingly widespread, leading to the formation of a systematic theoretical framework in this field. This systematic review focuses on the following key findings:

(1)

Development and academic landscape: This occurred in three phases as follows: initial application (2000–2007), stabilization (2008–2015), and rapid development (2016–2023). All phases show positive growth, reflecting the potential for sustained development. Eight core journals dominate the research direction, among which Catena stands out in terms of comprehensive evaluation, and the highly cited literature highlights the methodological advantages and interdisciplinary value of radionuclide tracing in multi-scale erosion assessment and sustainable land management.

(2)

Institution and country distribution: CAS leads in terms of publication volume and network centrality, while CNRS stands out in terms of overall research influence. National level: China focuses on technological innovation, the US focuses on theoretical breakthroughs, and the UK contributes significantly to methodological research. Evrard Olivier was identified as a field leader.

(3)

Evolution of research hotspots: Core themes of “soil erosion” and “¹³⁷Cs” persisted. Emerging topics included “paleolimnology” and “geochronology”, with “climate change” and “human impact” on erosion and their radionuclide tracer signatures becoming central concerns.

(4)

Thematic cluster dynamics: Keyword co-occurrence analysis delineated ten clusters, from “soil erosion” to “Chernobyl-derived ¹³⁷Cs”, reflecting a shift from fundamental erosion mechanisms to diverse, multi-scale studies of wind erosion, sediment fingerprinting, erosion modeling, and Chernobyl tracer applications.

(5)

Radionuclide tracing will remain a transformative tool in soil erosion science and soil resource management when embedded within an integrated, multi-scale framework that leverages technological synergy. Its future impact depends on coupling FRN-based datasets with complementary approaches—such as geochemistry, hydrology, and ecology—while harnessing advanced capabilities from artificial intelligence (AI), high-resolution remote sensing (RS), and UAV-LiDAR terrain monitoring. This convergence enables the calibration and validation of emerging models, bridges spatial–temporal scale gaps, and overcomes barriers posed by complex topography and extreme climate events. Such interdisciplinary integration is essential to delivering evidence-based strategies for sustainable soil management and achieving land degradation neutrality under SDG 15.3.1.

5.2. Outlook

This study not only mapped current radionuclide tracer hotspots in soil erosion research but also identified forward-looking priorities. First, the creation of a global soil erosion database is envisioned to enable large-scale comparative analyses, facilitating the detection of global spatial patterns and temporal trends in erosion [101]. Alignment with the United Nations Sustainable Development Goals (SDGs), particularly LDN and the UNFCCC framework [2], mechanisms must be established to translate tracer findings into land management policy (e.g., technology transfer models akin to South–South cooperation frameworks).

For assessing climate and anthropogenic influences on erosion, multi-radionuclide tracing offers unparalleled resolution—especially in rapidly changing land-use contexts such as abandoned farmland—thereby enhancing the attribution of erosion responses to environmental drivers [102].

On the technological frontier, the EU Quantum Technologies Flagship has highlighted revolutionary possibilities for radionuclide detection. Superconducting quantum interference devices (SQUIDs) and nitrogen-vacancy (NV) centers deliver exceptional sensitivity and spatial resolution, potentially enabling single-atom-level radionuclide detection [103]. Tailored nano-probes or nano-sensors may facilitate real-time, in situ monitoring of radionuclide migration [104]. Furthermore, virtual reality (VR) and augmented reality (AR) platforms can provide immersive visualizations of tracer distributions and transport pathways, enhancing both researcher comprehension and public engagement [105].