This study employed an integrated field monitoring approach, combining chemical analysis and ecotoxicity testing of multiple environmental matrices—water, sediment, and sediment elutriates—to comprehensively assess the environmental health of the Andong watershed, located near a Zn smelter and mining area. The primary objectives were to evaluate the extent of metal contamination, identify key toxicants contributing to ecological degradation, and trace the sources of these pollutants. Our findings revealed severe metal contamination and significant ecotoxicological effects both in proximity to and downstream from industrial sites. Specifically, Cd, Zn, and Pb were strongly linked to the smelter, while Hg, Ni, Cu, and As were predominantly associated with mining activities in the tributaries. To further assess toxicity of field-collected sediment and their elutriates, a logistic regression analysis was employed to estimate benchmark values for distinguishing between toxic and non-toxic samples, using the sum of toxic units for sediment elutriates and the mean probable effect level (PEL) quotient for sediment toxicity. These models demonstrated greater predictive accuracy than conventional benchmarks for determining toxicity thresholds. Our results highlight that integrating chemical and ecotoxicological monitoring with site-specific concentration–response relationships enhances the precision of ecological risk assessments, facilitating more accurate identification of key toxicants driving mixture toxicity in complex, pollution-impacted aquatic ecosystems.

Plastic pollution has emerged as a pervasive and systemic driver of ecological and biogeochemical disruption in freshwater and marine environments. Unlike natural materials that circulate within closed biogeochemical loops, synthetic polymers predominantly follow unidirectional and irreversible trajectories, a phenomenon we describe as “irreversible plastic transport.” These flows culminate in sedimentary entrapment, where plastics persist as long-term ecological stressors and potential vectors of contaminant transfer. Recent global syntheses indicate that sedimentary microplastic loads can exceed 27,000 particles/kg dry weight in certain river systems, highlighting the urgency of sediment-inclusive risk assessments. This review synthesizes interdisciplinary findings to conceptualize plastics as both pollutants and governance challenges. We highlighted the dominant transport pathways of micro- and nanoplastics and emphasize that sedimentary sinks are critical long-term retention zones. Current monitoring frameworks often underestimate sedimentary burdens by focusing on surface water and overlooking subsurface ecological legacies. We propose an integrated governance approach combining cross-media monitoring, Earth system modeling, and adaptive policies to address these persistent synthetic agents. Embedding plastic dynamics within comprehensive risk assessment frameworks is essential for sustainable water management during the Anthropocene. Our synthesis supports risk-based decision-making and encourages proactive, transdisciplinary global governance strategies that integrate sediment-focused monitoring and long-term ecological risk management.

The SPEcies At Risk index for metals (${\mathrm{SPEAR}}_{metal}$ index) was refined using updated physiological sensitivity data and validated to assess the ecological impact of metal contamination on benthic macroinvertebrate communities in the upper Nakdong River, near a Zn smelter in Korea. Biosurvey and chemical monitoring data were collected at 18 sites surrounding the smelter and nearby mines. Acute ecotoxicity tests on 20 indigenous species from the Korean peninsula were conducted and used to update taxon-specific metal sensitivity data. The refined ${\mathrm{SPEAR}}_{metal}$ index, based on this updated sensitivity, was significantly lower than previous versions, with most values below the severe impact threshold (0.5) in the main stream. The correlation between hazard quotients in water and the SPEAR index improved, with the correlation coefficient increasing from 0.63 to 0.70. Despite consistently high benthic macroinvertebrate indices (BMIs) across the study area, generic ecological indices, such as total richness, EPT (Ephemeroptera, Plecoptera, and Trichoptera taxa richness), and Shannon’s diversity index, showed correlations with metal contamination levels. Principal component analysis identified the ${\mathrm{SPEAR}}_{metal}$ index as the primary indicator associated with metal contamination in both water and sediment. These findings highlight the improved performance of the refined ${\mathrm{SPEAR}}_{metal}$ index as a more sensitive and specific tool for assessing the ecological status of metal-impacted aquatic ecosystems compared to traditional indices.

Microcystins (MCs) are cyanobacterial hepatotoxins that contaminate bloom-affected freshwater, drinking-water sources, aquatic food webs, and recreational environments. Human evidence for chronic or repeated exposure remains fragmented across study designs and organ systems. We systematically reviewed epidemiological evidence for hepatic, renal, and metabolic outcomes and integrated supporting mechanistic toxicology. PubMed, Scopus, and Web of Science searches identified 9021 records published from 1990 to 2025; an update search was conducted in April 2026. Risk of bias was assessed using a domain-based framework adapted from the Newcastle–Ottawa Scale and OHAT. The review was not prospectively registered. The qualitative evidence architecture retained 192 studies: 34 human epidemiological studies and 158 supporting mechanistic or contextual studies. Only seven independent adjusted estimates met the one-study–one-main-estimate rule for the primary quantitative synthesis. The hepatic meta-analysis included two estimates (OR 2.13; 95% CI, 1.29–3.53), the renal finding was a descriptive single-study estimate (OR 4.81; 95% CI, 1.96–11.81), and the metabolic meta-analysis included four estimates (OR 1.73; 95% CI, 1.00–2.98) with substantial heterogeneity (I² = 91%; prediction interval, 0.56–5.36). Mechanistic evidence supported biological plausibility but was not treated as causal human evidence. Human evidence was relatively more consistent for hepatic outcomes, although it remained limited to two independent studies with different endpoints; renal and metabolic findings remain sparse or heterogeneous.

The SPEcies-At-Risk index for metals (SPEARmetal) was refined using updated physiological sensitivity data and validated to assess the ecological impact of metal contamination on benthic macroinvertebrate communities in the upper Nakdong River, near a Zn smelter in Korea. Biosurvey and chemical monitoring were collected at 18 sites surrounding the smelter and nearby mines. Acute ecotoxicity tests on 20 indigenous species from the Korean peninsula were conducted and used to update taxon-specific metal sensitivity data. The refined SPEARmetal index, based on this updated sensitivity, was significantly lower than previous versions, with most values below the severe impact threshold (0.5) in the mainstream. The correlation between hazard quotients in water and the SPEAR index improved, with the correlation coefficient increasing from 0.63 to 0.70. Despite consistently high benthic macroinvertebrate indices (BMI) across the study area, generic ecological indices such as total richness, EPT (Ephemeroptera, Plecoptera, Trichoptera), and Shannon diversity showed correlations with metal contamination levels. Principal component analysis identified SPEARmetal as the primary indicator associated with metal contamination in both water and sediment. These findings highlight the improved performance of the refined SPEARmetal index as a more sensitive and specific tool for assessing the ecological status of metal-impacted aquatic ecosystems compared to traditional indices.

Recurrent freshwater cyanobacterial harmful algal blooms (CyanoHABs) are often managed as isolated episodes. Rapid clearing can leave nutrient stores, sediment recycling, benthic recruitment, and food web instability largely unchanged. This critical narrative review summarizes intervention roles, failure modes, and monitoring needs using a structured inventory of 53 selected core sources, with contextual reviews and guidance. Searches covered PubMed, selected publisher interfaces, and citation tracing through 27 September 2026; the inventory is not an exhaustive or systematic evidence map. Of 30 empirical sources, only seven extend beyond six weeks, including one 56-day mesocosm, so evidence for sustained recurrence reduction is limited. We distinguish Tier 1 (prevention and ecological stabilization), Tier 2 (targeted response and localized exposure reduction), and Tier 3 (restricted emergency containment). The proposed Intervention Decision Audit adapts established adaptive management and impact assessment principles into a practical checklist linking the recurrence mechanism, study scale and follow-up, intervention choice, safeguards, responsible authority, exit conditions, and outcome evaluation. Its contribution is this explicit linkage for recurrent CyanoHAB decisions, rather than new principles of adaptive management. Success should be assessed through bloom recurrence and duration, toxin and exposure risk, ecological condition, and dependence on repeated emergency treatment. The checklist has not yet been prospectively validated in management practice.