Introduction The involvement of citizens in science is increasingly recognized as a valuable resource, especially for research data collection. However, volunteers’ engagement in study procedures and their retention over time can be challenging. The availability of detailed information on recruitment strategies applied for health-related citizen science (CS) projects is still limited. Here, the recruitment process of the “One Health Travel” study and the resulting enrolment and retention of volunteers is described to provide insights into potential barriers and facilitators of recruitment and to inform future CS research studies.MethodsThe “One Health Travel” study was a prospective observational study aiming to assess the risk of mosquito-, tick-bites and arbovirus exposures among travellers within Europe or to the Dutch Caribbean. Recruitment channels used were i) mass and social media campaigns, ii) targeted campaigns for nature-focused groups, iii) snowball sampling, vi) research consortium network, v) personal invitations.ResultsThe enrolment target was met with 1,348 registrations over a 30-month period. However, this achievement required a modification of the recruitment strategy including, a lighter registration process and broader range of activities. Mass and social media, personal invitations and research consortium network recruited 506 (58.2%), 129 (14.8%), 94 (10.8%) participants, respectively. Their compliance to study procedures was between 84.4% and 89.4%. Most participants were female (605/870, 69.5%), and median age was 53.DiscussionMass and social media appeared to be an effective channel in terms of recruitment yield, given a tailored message and low-effort registration process. Most recruitment activities triggered only a short-term response. Therefore, timing of activities is an important factor to be considered.
The composition of particulate matter in lakes is considered a key indicator of underwater light-field dynamics and the proportion of organic matter. In this study, reflectance from Sentinel-3 OLCI (Ocean and Land Colour Instrument) imagery at 510, 560, and 620 nm was utilized to estimate the organic suspended matter to total suspended matter ratio (OSM/TSM) in lakes, serving as an indicator of particulate composition. The multi-year spatiotemporal characteristics of OSM/TSM in 76 lakes (>10 km2) from 2016 to 2023 were investigated. Generalized linear models were used to explore the relative ranking of meteorological and anthropogenic correlates, while a pooled linear mixed-effects model was used for association analysis. The results revealed that OSM/TSM mainly ranged from 0.2 to 0.6, and 79.96% of the lakes showed an increasing trend in OSM/TSM according to the Mann-Kendall test. Additionally, peak OSM/TSM values were often observed in summer and autumn, while the lowest values occurred in spring and winter. Temperature had the highest normalized relative weight (44.93%) for intra-annual OSM/TSM variation. For inter-annual variation, land-use variables had a combined normalized relative weight of 58.00%. The OSM/TSM estimates provided by this study for large inland lakes can serve as a valuable reference for future lake monitoring and assessment in the Eastern Plain Lakes of China.
Policy interventions redirect land use/land cover (LULC) trajectories and consequently alter both individual ecosystem services (ESs) and the relationships among them. Resolving these effects is particularly important in major grain-producing regions, where agricultural production, urban development, and ecological conservation compete for limited land. Taking the Jianghan Plain in China as a case study, we developed a policy-LULC-ES analytical framework to quantify relative and cumulative effects during 2000–2010 and 2010–2020. The socio-economic interventions comprised dry-land -to-paddy-land (DTP), the food security plan (FSP), and rapid urbanization (RU); the environmental interventions comprised the grain for green program for forest restoration (GFGP-F), the grain for green program for grassland restoration (GFGP-G), and the river-lake connectivity project (RLCP). Changes in ESs and pairwise synergies were evaluated at regional and county scales. The FSP was associated with the largest relative increase in food production (40.29%) but also the greatest reduction in habitat quality (−5.84%). The RLCP produced the strongest improvement in water conservation (34.11%) and the largest decrease in carbon storage (−9.28%). Across the full 2000–2020 period, the cumulative RU-related increases in food production and water conservation were 34.45% and 31.29%, respectively, both lower than the corresponding maximum cumulative responses associated with FSP and RLCP. Except for carbon storage, policy responses were generally stronger during 2010–2020. Socio-economic development policies reinforced synergies linking food production with other ESs but weakened the relationship between water conservation and habitat quality. Eco-environmental protection policies exhibited the reverse pattern by improving the water conservation-habitat quality synergy while weakening the synergies between food production and other services and shifting these relationships toward the trade-off end. County-level analysis further identified the FSP and RLCP as the principal policy levers for agricultural and ecological outcomes, respectively. Coordinating these interventions is therefore necessary to limit cross-service trade-offs and improve land-use governance. The findings clarify how policy-driven land-use dynamics generate spatially differentiated socio-ecological consequences and provide evidence for sustainable land management in major grain-producing regions.
Sampling aquatic habitats for environmental DNA (eDNA) has emerged as a valuable population monitoring tool, particularly for species that are difficult to survey with conventional methods. However, eDNA approaches are limited in their ability to provide demographic information, resulting in most applications focusing on documenting species presence and distributions. Advancing molecular detection methods to assess reproductive phenology could significantly improve conservation outcomes by informing management efforts. In this study, we leveraged the unique double uniparental mitochondrial inheritance system of one of the most imperiled taxonomic groups, freshwater mussels, to enable detection of reproductive activity. We developed separate qPCR assays for eDNA detection of male mitotypes, found almost exclusively in male gametic tissue, and female mitotypes, found in female gametes and somatic cells of both sexes, of the endangered spectaclecase, Cumberlandia monodonta (Say, 1829). Following assay development and laboratory validation, we verified their utility in situ by detecting male and female mitotypes from captive populations in a controlled mesocosm and from natural populations in streams at sites with known and previously unconfirmed occupancy. Male mitotype eDNA was detected almost exclusively during the March–May spawning window, with concentrations often an order of magnitude higher than female mitotype concentrations. Our findings suggest targeting male mitotype DNA and strategically timing eDNA sampling during spawning periods can improve detection probabilities and aid efforts to conserve at-risk freshwater mussels.
IntroductionUsing panel data for 282 Chinese cities from 2011 to 2023, this study examines whether AIoriented place-based policy promotes urban green development.MethodsWe exploit the staggered rollout of China’s National New Generation Artificial Intelligence Innovation and Development Pilot Zones (AIIDPZ) as a quasi-natural experiment and estimate its causal effect on urban green total factor productivity (GTFP) using a staggered difference-in-differences approach.ResultsThe results show that AIIDPZ significantly improves urban GTFP. Mechanism analyses suggest that this effect mainly operates through industrial structure upgrading and green technological innovation. Heterogeneity tests further show that the effect is stronger in eastern cities, non-resource-based cities, and cities with better digital infrastructure.DiscussionOverall, this study provides new evidence that AI-oriented public policy can contribute to green development and offers implications for the design of regional innovation policy.
IntroductionAgriculture remains a vital sector for economic development and food security in MENA countries, yet it faces increasing challenges from climate change. At the same time, economic diversification and renewable energy development may offer opportunities to enhance agricultural performance. This study examines the relationships among agricultural value added, economic diversification, climate change, and renewable energy in MENA countries over the period 1993–2022.MethodsThe study employs the Cross-Sectionally Augmented Autoregressive Distributed Lag (CS–ARDL) model, which accounts for cross-sectional dependence among countries and allows for heterogeneous short- and long-run dynamics across panel members.ResultsThe findings indicate that economic diversification exerts a positive immediate effect on agricultural value added. In contrast, climate change negatively affects agricultural value added in the long run. Renewable energy is found to promote agricultural value added in both the short and long run, highlighting its role in supporting agricultural productivity and resilience.DiscussionThe results suggest that strengthening renewable energy adoption and implementing effective economic diversification strategies can contribute to sustainable agricultural development in the MENA region. Furthermore, policies aimed at mitigating climate change impacts and enhancing climate adaptation are essential to safeguard long-term agricultural performance and food security.
The growing accumulation of microplastics (MPs) in the environment highlights the urgent need for greener, more scalable treatment options compared to traditional physicochemical methods. In this review, we summarize progress in the microbial breakdown and enzymatic depolymerization of major plastic types, mapping out the distinct biochemical degradation routes for polyolefins, polystyrene, polyvinyl chloride, and polyesters. To clarify how these processes are validated experimentally, we detail the key analytical tools used to confirm MP biodegradation. We also evaluate the practical engineering limitations that currently prevent these technologies from being deployed at an industrial scale. Key hurdles discussed include short hydraulic retention times in standard wastewater treatment plants, interference from complex pollutants in real-world matrices, and the poor kinetic rates of enzymes when applied at economically realistic concentrations. To tackle these scalability issues, we explore several promising solutions, including advanced chemo-physical pretreatments and the genetic engineering of microbes for upcycling plastics into valuable biochemicals. Ultimately, these advances in biotechnology lay the groundwork for integrating biological plastic degradation into broader, closed-loop waste management systems, offering a practical route to achieving a true circular economy.
Interactions between hydrology and microtopography are a key factor shaping habitat heterogeneity in lakeshore zones, yet their synergistic effects on the Chaohu lakeshore plant communities remain unclear. Here, we addressed this issue by delineating four flooding zones along an elevation gradient and selecting four microtopographic types: Estuarine Zone, Sheltered Cove, Windward Upland, and Terraced Wave-Breaker to explore how their combined effects shape community structure and diversity. We conducted systematic field vegetation surveys and soil physicochemical measurements, and employed non-metric multidimensional scaling, two-way permutational multivariate analysis of variance, and redundancy analysis to quantify the individual and interactive effects of hydrology and microtopography on plant community composition and species diversity. Results showed that: (1) Hydrology predominantly shaped plant community differentiation along the elevation gradient, with composition transitioning from hygrophytes and hydrophytes to meso-xerophytes as flooding decreased; (2) The ecological effect of microtopography varied with hydrological conditions—masked by strong hydrological filtering in long-term flooded areas, it drove further differentiation by regulating local conditions as flooding stress weakened; (3) Species diversity was jointly regulated by both factors, with richness peaking in the short-term flooding zone and the Estuarine Zone hosting the highest species diversity. This study clarifies plant community assembly under anthropogenic disturbance, highlighting the synergy between hydrology and microtopography as key to understanding regional biodiversity patterns, and offering a basis for lakeshore restoration through integrated hydrological and microtopographic management.
Mercury (Hg) pollution remains a global environmental challenge, and human biomonitoring is essential for linking environmental contamination to exposure pathways. However, total Hg and species concentrations in hair, urine and blood often cannot separate overlapping sources or distinguish environmental inputs from biological processing. Hg stable isotopes provide an additional line of evidence because mass-dependent fractionation (δ202Hg) and mass-independent fractionation (Δ199Hg, Δ201Hg and Δ200Hg) retain information on source, environmental transformation and biomarker chemistry. This Review synthesizes peer-reviewed evidence for Hg isotope applications in human biomarkers and related exposure media, with emphasis on source attribution, matrix selection and monitoring readiness. Hair isotope measurements currently provide the strongest evidence for screening dietary methylmercury exposure from fish, marine mammals and rice, especially when paired with local source samples and Hg speciation. Urine is more relevant for inorganic Hg and elemental Hg vapor exposure, but the evidence base is smaller and more affected by analytical and biological uncertainty. The exploratory quantitative synthesis comprised 360 extracted observations aggregated into 26 study/location/biomarker/source records. Between-study heterogeneity was substantial (I2 generally >95%). Leave-one-out linear discriminant analysis achieved 25.0% accuracy and 15.0% balanced accuracy, both below the 41.7% majority-class baseline; leave-one-reference-out accuracy was 16.7%. Isotope contrasts should therefore not be treated as universal diagnostic cutoffs. We propose an explicit, ordinal decision framework for deploying Hg isotope biomarkers in environmental monitoring programs and identify reporting standards needed for reproducible source attribution. These priorities can help move Hg isotope applications from geochemical case studies toward carefully validated tools for environmental pollution monitoring.
IntroductionManure nutrient recycling is an important pathway for reducing mineral fertilizer dependence and improving agricultural nutrient circularity, but its mitigation effect should be distinguished from actual realized emission reduction. This study estimates the upper-bound theoretical carbon-mitigation potential of substituting mineral fertilizer nutrients with livestock and poultry manure-derived nutrients in China.MethodsUsing provincial panel data for 31 provinces from 2005 to 2024, manure resources and manure-derived N, P2O5, and K2O supplies were quantified, and upper-bound ER was calculated using nutrient-specific fertilizer emission factors. Dagum Gini decomposition, global Moran’s I, and the Spatial Durbin Model were applied to examine regional inequality, spatial clustering, and conditional spatial associations. ResultsResults show that national upper-bound ER declined from 2.183 × 107 t CO2-eq in 2005 to 1.677 × 107 t CO2-eq in 2019, rebounded to 2.021 × 107 t CO2-eq in 2023, and slightly decreased to 1.962 × 107 t CO2-eq in 2024. The western region contributed 42.43% of the national total in 2024. Spatial dependence was significantly positive. Manure resource intensity had positive direct and total effects, whereas fertilizer intensity had negative direct and total effects. Agricultural GDP was positively associated with mitigation potential, while mechanization, urbanization, and cropping structure showed heterogeneous local and spillover effects. Robustness and regional analyses confirmed a stable local resource-endowment effect but region-specific spillover patterns. These estimates represent theoretical upper bounds rather than realized mitigation.DiscussionChina possesses substantial but spatially uneven theoretical carbon-mitigation potential from manure-based mineral fertilizer substitution. Converting this technical upper bound into realized mitigation requires region-specific improvements in manure collection, treatment, transport, nutrient matching, and field application. Policies should therefore shift from maximizing manure return alone toward spatially coordinated, agronomically appropriate, and environmentally controlled nutrient recycling.
Forest fires are a major threat to the ecosystem stability in the face of a growing global climate change; however, long-term post-fire recovery quantitative assessment is methodologically limited in mountainous terrain. In this study, OTSU-optimized differenced Normalized Burn Ratio (dNBR) thresholds were integrated with multi-temporal Remote Sensing Ecological Index (RSEI) model to systematically investigate the extent of burned area, classification of burn severity and spatiotemporal patterns of post-fire ecological recovery for the representative wildfire event, the 3.30 Lushan fire (March 2020) in Xichang City, China. Results indicated that there were 28.26 km2 of burned area, and the OTSU-derived dNBR classification thresholds of 0.18/0.30/0.42 effectively discriminated low, moderate and high-severity burn areas in the Lushan fire. The RSEI dropped from 0.69 (pre-fire) to 0.33 (post-fire) for an overall decrease in ecological quality of 52.2%. The recovery trajectory unfolded in three phases: rapid recovery in the initial phase with the mean RSEI reaching 0.47 in 2021; decelerated recovery in the second phase, where the RSEI slightly decreased to 0.45 in 2022; and the third phase of accelerated recovery to 0.56 in 2023, and then stabilized at 0.55 in 2024. The Good and Excellent grades recovered to just 37.2% (11.26 km2) by 2024, suggesting that ecological restoration is not yet complete. There were significant differences in the post-fire ecological recovery rates in different burn severity areas. Specifically, increasing burn severity promotes the rate of ecological recovery. These findings show that ecological restoration in highly complex mountainous environments requires longer than the four-year observation period to achieve full restoration, especially in the high severity burn areas. This study confirms the applicability of the integrated dNBR–RSEI assessment framework, and offers a scientific basis and theoretical support for post-fire ecological restoration planning in mountainous Southwestern China.
The efficient management of groundwater requires judicious use of resources, considering the limited surface water availability and unprecedented rainfall occurrence. The Tikamgarh district area is a need more effective policy for sustainable groundwater development and management due to severe groundwater stress, over-extraction, limited recharge capacity, and recurrent drought conditions. Artificial recharge is another method for enhancing groundwater and surface water resources. The various thematics layers such as soil, geomorphology, lineament density, slope, land use and land cover (LULC), drainage density (DD), geology, and aspect have been used in this study. These layers were normalized using the analytic hierarchy process (AHP) eigenvector method and weighted based on Saaty’s five-point scale in order to identify groundwater potential zones (GWPZs) and recommend suitable sites for artificial recharge structures by using geographic information system (GIS) framework throughout the district area. Spatial maps have been created from satellite datasets using ArcGIS10.5 software. These maps provide valuable information related to the study area. The developed GWPZs were divided into five classes according to the statistical data, which ranges from very high to very low potential zones. The accuracy and the feasibility of the recharge sites recommended by the GWPZ maps are validated using ROC curve analysis. During validation of recharge sites map accuracy is showing the area under the curve (AUC) of 0.79%, while the GWPZ map showing training and testing accuracy is 0.724 and 0.704, respectively. After the investigate of the study area, we have suggested artificial recharge structures, such as cement nala bunds (CNBs), check dams, dams, farm ponds, and wells. This results of study area can helpful and valuable information for planning groundwater resources and sustainable farming practices and enhance local water security.
IntroductionClimate change remains one of the most pressing global challenges, particularly in highly industrialized and technologically advanced economies. This study examines how sustainable digital technologies, clean energy transition, industrial structural upgrading, and socio-economic dynamics influence climate change in the world’s five largest robot-adopting economies: China, Japan, Germany, the United States, and South Korea.MethodThe study uses panel data from 2000 to 2024, and a multilayer neural network (MNN) framework combined with surface slope analysis and Deep SHAP interpretation to capture nonlinear relationships between key variables and climate indicators.ResultThe findings reveal strong nonlinear effects across the four dimensions. Robotics adoption, environmental technologies, and ICT development contribute to emission reduction as technological maturity increases. Modern renewable energy and access to clean energy technologies significantly reduce emissions, while nuclear power shows weaker and heterogeneous effects. Industrial structural upgrading, represented by industrialization and research and development, improves environmental outcomes when technological innovation supports cleaner production systems. However, economic growth and urban population growth continue to exert upward pressure on emissions. The Deep SHAP results highlight renewable energy, robotics, and industrial innovation as the most influential predictors of climate outcomes.DiscussionTheoretically, the findings align with Ecological Modernization Theory and Innovation and Technology Diffusion Theory, demonstrating that climate mitigation emerges from cumulative technological diffusion and structural transformation rather than isolated interventions. Policy implications highlight the need for coordinated industrial–energy–digital strategies, threshold-targeted green technology investment, and adaptive urban development frameworks.
The Surface Water and Ocean Topography (SWOT) mission provides new opportunities for inland water monitoring by observing surface water extent and water surface elevation (WSE). However, the direct use of SWOT Level-2 HR Raster products for surface water mapping remains limited by fragmented water patterns, random noise, mixed pixels, and systematic stripe artifacts. To improve product usability, this study develops an analysis-ready data (ARD) processing framework for SWOT-derived inland surface water products, with emphasis on surface water extent and water-mask structure rather than independent WSE accuracy validation. The framework integrates wse_qual, wse_uncert, water_frac, water_area, sig0, dark_frac, and layover_impact for multi-parameter filtering and spatial structure optimization, where WSE-related variables are used as product-native quality indicators. Dongting Lake was selected as the study area, and Sentinel-1 SAR-derived water masks were used only as reference data for water-extent consistency and spatial-structure assessment. Results show that ARD processing moderately improves the water-extent agreement between SWOT-derived water masks and the Sentinel-1 reference. IoU increases from 0.2926 to 0.4081, Precision from 0.3203 to 0.5154, and F1-score from 0.4527 to 0.5796, while Recall decreases from 0.7718 to 0.6621, indicating a trade-off between reducing false positives and preserving reference water pixels. Spatial fragmentation is also substantially reduced: connected components decrease from 18,187 to 557, the small-patch area ratio drops from 5.63% to 0, and boundary density declines from 0.0048 to 0.0034. The persistence of along-track stripe artifacts represents a central constraint of the current ARD framework, indicating that geometry-related systematic errors require additional correction beyond pixel-level filtering and spatial optimization. Overall, the proposed framework improves the analysis readiness of SWOT-derived inland surface water products for water mapping and flood monitoring.
Lyme disease, caused by B. burgdorferi sensu lato, is the most prevalent tick-borne disease in the temperate Northern Hemisphere. Existing studies on the spatial distribution prediction of Borrelia burgdorferi s.l. have commonly relied on single modeling algorithms, lacking systematic comparisons among multiple ensemble learning methods. Based on pathogen occurrence records and tick distribution data, a predictive framework combining ecologically constrained sampling with multi-algorithm systematic comparison was constructed. Pseudo-absence points were restricted to suitable tick habitats, and training datasets were generated through 50 iterations of 5-fold spatial cross-validation. The predictive performances of four ensemble learning algorithms—Random Forest, XGBoost, LightGBM, and CatBoost—were compared, with hyperparameter tuning conducted via Bayesian optimization. The predicted AUC values for the four target taxa—B. burgdorferi s.l., Borrelia afzelii, Borrelia garinii, and B. burgdorferi sensu stricto—reached 0.862, 0.794, 0.763, and 0.753, respectively. SHAP (SHapley Additive exPlanations) analysis suggested that annual precipitation was the most crucial factor; threshold effects and interactions were also identified through dependence plots. The resulting maps represent conditional environmental suitability for B. burgdorferi within suitable tick habitats, providing a scientific basis for identifying its key environmental drivers and supporting targeted surveillance design.
Northern peatlands store large quantities of organic carbon that are vulnerable to decomposition under climate warming, producing the greenhouse gases methane (CH4) and carbon dioxide (CO2). Because CH4 has greater radiative forcing than CO2, processes regulating CH4 emissions strongly influence climate feedbacks. In peatlands, CH4 oxidation is often assumed to be limited because of the low availability of terminal electron acceptors. Here, we combined peat incubations with field-constrained modeling of CH4 and CO2 concentrations and stable isotope profiles to quantify CH4 cycling in an inundated fen. Potential CH4 oxidation rates approached 50% of CH4 production rates, despite persistently waterlogged conditions in the fen. Multi-omic analyses (16S rRNA gene, metagenomic, and metatranscriptomic) showed that the methanotroph community was dominated by aerobic Methylobacter_C taxa with genomic potential for alternative electron acceptor use. In particular Methylobacter_C were actively expressing nirB and narG consistent with respiration of nitrogen compounds. In contrast, anaerobic methane-oxidizing Methanoperedenaceae ANME were detected only at the deepest depth and at very low abundance (0.026%). CH4 oxidation potential also remained high with depth, contrary to predictions from current ecosystem models, suggesting that deep peat and microaerophilic CH4 oxidation may be underrepresented in peatland CH4 budgets.
Global phosphorus (P) reserves are finite, making the development of sustainable fertilizer alternatives critical for agricultural production. While algae biomass can supply plant-available P, its performance relative to conventional synthetic and organic fertilizers across varying soil textures and soil conditions associated with recurring crop P deficiency remains poorly understood. We conducted two incubation studies to assess the effects of dry microalgae powder on P dynamics. The first study compared Tribonema minus algae with synthetic fertilizers and a bone meal pellet across four soils differing in texture (coarse and fine) and whether they originated from fields with or without a history of recurring crop P deficiency. The second compared three algal types (T. minus, Uronema high P, and Uronema low P) with poultry manure, hydrolyzed fish liquid, and corn steep powder in coarse and fine soils from fields with recurring crop P deficiency. Pore water P was measured over 3 months, followed by analysis of Olsen P, resin-extractable P, and microbial P at the end of each incubation. Across both studies, P availability depended strongly on soil texture, field P deficiency history, and amendment composition; soils from fields without recurring crop P deficiency and coarse-textured soils consistently showed greater pore water and resin-extractable P. In Study 1, synthetic fertilizers yielded the highest P recovery, while organic amendments released P more slowly. In Study 2 which focused on soils from fields with a history of crop P deficiency all algal types showed greater pore water P recovery than most other organic fertilizers in the coarse soil. Conversely, in fine textured soil, algae had the lowest pore water P recovery. However, by the end of Study 2, resin-extractable P recovery was greater in Tribonema than in one hydrolyzed fish product, regardless of texture. Our findings indicate that dead algal biomass is a promising P source relative to other organic fertilizers, though its performance is highly context-dependent.
The Democratic Republic of the Congo recently adopted a necessary national legal system on the protection of human rights defenders, which now complements the Protection and Responsibility of Human Rights Defenders law and its ministerial implementing decree of 2024. Provincial protection frameworks were adopted earlier in provincial edicts in South Kivu in 2016 and North Kivu in 2019. The combination of these instruments creates a good prospect for a legal architecture. Nevertheless, a critical gap exists, as none of these laws directly acknowledge or safeguard environmental human rights activists, despite compounding threats related to escalating environmental disputes in the extractive sector, conservation areas, and land control. This study argues that the lack of express consideration of environmental human rights defenders in national and provincial tools cripples the system of protection and renders it incompatible with international norms that enhance the right to defend the environment. To determine the gaps in the Congolese legal texts and environmental governance realities, this study takes into account ecological governance realities on legal norms and recommendations for reforms, such as explicit recognition, customized protective measures, legal framework harmonization, strengthening institutional mandates, and integrating native perspectives.
Karst soils represent significant carbon sinks, yet their stability is increasingly threatened by intensified wet-dry cycles under climate change. Although Ca2+ derived from carbonate weathering can stabilize soil organic carbon through cation bridging, the efficacy of this mechanism under conditions of multi-cation competition and varying intensities of Ca2+ inputs remains poorly understood. To clarify the role of carbonate weathering-derived cations on dissolved organic carbon (DOC) leaching, three sequential leaching experiments (S1–S3) were conducted using a lysimeter device packed with karst soil to model wet-dry cycles. Natural multi-cation karst water was applied via a simulated rainfall apparatus. Leachate was collected at 5-min intervals over 60 min (12 samples per experiment). Results showed that DOC concentrations declined over time by 53.8%–61.9% within 60 min, a pattern potentially linked to the “Birch effect” induced by drying–rewetting. Successive concentration peaks showed a declining trend, potentially reflecting a progressively reduced availability of labile organic matter under repeated leaching. Based on Pearson correlation analysis, calcite saturation index, and ion ratio analysis, three distinct regulatory stages were suggested: during the S1 stage, the relatively high intensity of carbonate dissolution appeared to release substantial Ca2+, potentially saturating the soil cation bridging capacity, while adsorbed Na+, K+, and Mg2+ seemed to displace weakly bound DOC via ion exchange. In S2, as carbonate dissolution appeared to weaken, Ca2+ release decreased, and the reduced availability of soil Ca2+ may have led to unsaturated bridging sites, possibly reflecting a transition from Ca2+ release to retention, while correlations among Na+ and K+ were decreased. In S3, carbonate dissolution further weakened, Ca2+ limited, and Na+, K+, and Mg2+ again drove DOC leaching through ion exchange. Overall, this preliminary study suggests that carbonate dissolution may influence soil Ca2+ levels and exchange site saturation, possibly affecting the interplay between Ca2+ cationic bridging and ion exchange competition by Na+, K+, and Mg2+ in regulating DOC leaching. Site-specific Ca amendment and CO2 degassing may be worth considering in karst soil carbon management. However, these exploratory findings from a single lysimeter with non-independent sequential leaching and an inferred “Birch effect” require validation through future in situ and long-term studies.
