Diversity of contaminants of emerging concern in a semi-arid groundwater system.

Urban coastal lagoons are heavily impacted by untreated sewage, industrial effluents and diffuse pollution, heightening ecotoxicological risks. Herein, Nile tilapia (Oreochromis niloticus) was employed as a sentinel species concerning metal exposure at the Jacarepaguá Lagoon Complex (JLC), a critical case of ecological degradation under intense anthropogenic pressure in Rio de Janeiro, Southeastern Brazil. Samplings were conducted between 2022 and 2023 during the dry (autumn-winter) and rainy (spring-summer) seasons. Organosomatic indices and total (muscle) and subcellular (liver and muscle) metal levels were determined. Antioxidant system alterations were evaluated through superoxide dismutase (SOD), glutathione-S-transferase (GST), reduced glutathione (GSH), total antioxidant capacity (TAC) and metallothionein (MT) assessments. Lipid peroxidation (LPO) and protein carbonylation (PTC) levels were also determined as oxidative effect markers, while vitellogenin (VTG) was used as an estrogenic effect indicator. Arsenic (0.018-0.033mg L⁻¹), Mn (0.041-0.050mg L⁻¹), Rb (0.019-0.023mg L⁻¹), and V (0.008-0.010mg L⁻¹) were detected in water samples in both sampling seasons; while Fe was detected only in the dry season (0.023 ± 0.03mg L⁻¹). Subcellular As, Co, Cu, Fe, Mn, Ni, Pb, Rb, Ti, V, and Zn were quantified in both liver and muscle, albeit with no significant differences between seasons or sexes. Seasonal variations were noted for male VTG, although not statistically significant, with attenuation of sexual VTG differences from the dry (M/F = 0.67) to the rainy season (M/F = 1.20). The multibiomarker approach applied to wild tilapia under diffuse urban pollution indicates mild sublethal effects while highlighting the need for expanded, integrated monitoring of additional endocrine and oxidative biomarkers. Although centered on a specific lagoon complex system, these mechanisms recur in urban lagoons worldwide, indicating the need for consumption-risk evaluations and actionable remediation/management frameworks.

Anthropogenic expansion extensively covers Earth's cultivable surface, increasing pressure on ecosystems and leading to significant biodiversity loss and widespread pollution, particularly impacting freshwater systems. Diffuse agricultural pollution, stemming from agrochemical runoff into river channels, represents a critical threat to aquatic biota. Mayflies (Ephemeroptera), with their sensitive obligately subaquatic immature stages, are excellent bioindicators of water quality. This study investigated how mayfly communities in Northwestern Argentina, a region dominated by sugarcane and citrus cultivation, respond to such diffuse pollution. Our primary objective was to determine if mayfly community characteristics (total abundance, species richness, and assemblage composition) exhibit changes downstream of cultivated areas compared to upstream sections. We collected 277 D-net samples across five rivers, at both upstream and downstream sites relative to cultivation, each two months (over nine visits) during 2009-2010. The impact of agriculture at downstream sites on mayfly abundance and richness is not uniform across all rivers, with significant reductions observed in some rivers, but not others. Non-metric multidimensional scaling and permutational multivariate analysis of variance confirmed significant effects of site, river, and their interaction on community composition. Notably, the difference in composition between upstream and downstream sites was significant. SIMPER analysis identified Baetodes as the primary contributor to upstream-downstream dissimilarities, being more abundant upstream. Indicator species analysis highlighted Haplohyphes baritu, Lachlania sp., and Nanomis galera as indicators of specific upstream conditions, while no species were exclusive indicators of downstream sites, suggesting downstream communities may be a depauperate subset. These findings underscore the context-dependent impact of diffuse agricultural pollution on mayfly communities and their utility as bioindicators.

Evaluation of extreme hydrological events and diffuse pollution losses from agriculture-dominated catchments under Nordic conditions.

Constrained sediment carbon sequestration driven by agricultural diffuse pollution: Evidence from core-derived DOM.

Agriculture consumes over 70% of global freshwater while generating substantial diffuse pollution that threatens water security and sustainable development objectives. The grey water footprint (GWF) concept quantifies the freshwater volume required to assimilate agricultural pollutants to acceptable environmental standards, providing a crucial metric for sustainable water resource management. This comprehensive review synthesizes current knowledge on agricultural GWF assessment, examining conceptual foundations, calculation methodologies, and practical applications across diverse farming systems. We analyze the evolution from simplified Tier-1 approaches to sophisticated process-based models incorporating hydrological dynamics, pollutant fate and transport, and ecosystem interactions. The review encompasses nitrogen and phosphorus from fertilizers, pesticide contamination, and livestock-derived pollutants, revealing substantial methodological challenges including data scarcity, temporal-spatial variability, and pollutant interaction effects. Comparative analysis of global case studies demonstrates order-of-magnitude differences in GWF estimates depending on calculation methods, regional conditions, and management practices. Advanced modeling frameworks integrating SWAT, HYDRUS, CROPWAT and machine learning algorithms show promise for improving accuracy and policy relevance, though standardization remains limited. Future developments should prioritize: (1) multi-pollutant interaction modeling under varying environmental conditions, (2) climate-adaptive GWF frameworks incorporating extreme weather scenarios, and (3) standardized global methodologies enabling cross-regional comparisons and policy integration. This review establishes GWF as an essential tool for achieving water-food-environment nexus sustainability, supporting evidence-based agricultural policy and contributing to SDG implementation at multiple scales.

Agricultural activities are the leading cause of the eutrophication of waterbodies downstream of farmed lands. Nature-based water protection measures, such as treatment wetlands (TW), are highly effective in reducing diffuse agricultural pollution; however, most studies evaluate their performance over short monitoring periods, potentially overlooking long-term ecological development and interannual variability. This study presents a long-term (7-year period) overview of a well-established in-stream free-water surface (FWS) TW to reduce diffuse agricultural pollution in a temperate climate zone in southern Estonia. The TW consists of two sequential in-stream FWS TWs with a catchment area of 2.2 km2. The TWs are mainly vegetated with cattail (Typha latifolia) and common reed (Phragmites australis). Biweekly monitoring of water parameters was conducted from 2017 to 2023. The results for the entire study period show positively trending removal efficiency with high seasonal variability in both wetlands for total nitrogen, total phosphorus, and total organic carbon, with retention rates reaching up to 11.33, 0.64, and 17.05 kg ha-1 d-1, respectively. The observed increase in treatment efficiency coincided with vegetation maturation and ecosystem development, showing clearly that wetland performance evolves substantially over time. Near full vegetation cover was achieved after 7 years in both wetlands. This long-term dataset provides rare observation into the temporal dynamics, maturation processes, and resilience of in-stream FWS TWs under temperate climatic conditions and demonstrates the need for multi-year continuous monitoring for assessing their treatment capacity and guiding design and management strategies.

Summary The Tietê River is an anthropogenically disturbed urban water body polluted by a combination of untreated domestic sewage releasing (carbon, nitrogen and phosphorus pollution) and diffuse pollution that cross São Paulo State in Southeast of Brazil. Along its course, it presents contrasting sites showing elevated levels of nutrients and contaminants (eutrophic sites) and oligotrophic environments, in both water and sediments. In this study, we investigated how pollution influences the taxonomic and functional diversity of microbial communities in the Tietê River watershed, with the aim of understanding their role in pollutant transformation during downstream transport. Four sampling sites along a pollution gradient—from São Paulo city to a relatively pristine area near the river mouth—were evaluated. Results indicated that diversity differences were primarily linked to water quality, with higher diversity observed in less contaminated sites. Heterotrophic metabolism was more prominent in polluted regions, whereas photoautotrophic and lithotrophic microorganisms were more abundant in clean areas. Additionally, genes associated with the metabolism of aromatic compounds and virulence factors were more prevalent in environments with higher anthropogenic influence, suggesting a functional shift geared toward environmental adaptation and bioremediation. We propose that, in areas with high organic matter concentrations, microbial communities tend to adopt an r-strategy lifestyle, characterized by rapid growth and reproduction, while in oligotrophic, less polluted sites, more competitive k-strategists predominate. Although the following hypothesis was not extensively studied, the lower abundance of genes involved in secondary metabolic synthesis in eutrophic sites suggests that pollution may reduce the availability of novel species or traits relevant for biotechnological applications. Additionally, community shifts appear to be influenced by "conditionally rare taxa," which temporarily alter their activity and abundance in response to environmental constraints, playing a critical role in water self-purification processes. Overall, these findings offer new insights into the environmental factors driving self-purification in the Tietê River and shed light on the ecological mechanisms underpinning river resilience.

The growing occurrence of emerging contaminants, particularly pharmaceutical residues, in aquatic environments represents a major environmental concern worldwide. While pharmaceutical contamination has been increasingly studied in marine systems, port environments remain largely understudied despite their complex anthropogenic pressures. This study investigates the occurrence, spatial distribution, and potential environmental risk of pharmaceutical residues in surface waters of the port of Cartagena, a multifunctional port on the Spanish Mediterranean coast. Fifteen pharmaceuticals were analysed across nine sampling sites, of which six were not detected. Diclofenac and several antibiotics (erythromycin, azithromycin, clindamycin, and trimethoprim) were the most frequently detected compounds, reaching maximum concentrations of up to 12,294.1 ng/L. Elevated concentrations were observed at sites associated with intense human activity, while the detection of multiple pharmaceuticals at a designated Special Area of Conservation suggests additional diffuse pollution sources, likely linked to insufficient wastewater management in nearby informal settlements. Most detected concentrations exceeded established environmental-quality or risk-threshold values, indicating a potential threat to marine ecosystems. These findings highlight the vulnerability of port environments to pharmaceutical pollution and underscore the need for continuous monitoring programs to support effective environmental management and biodiversity protection in coastal port areas.

This study assessed the water quality of the Tahuando River as it flows through Ibarra and analyzed its relationship with human activities over time. Seven monitoring points—representing upstream, midstream, and downstream conditions—were sampled over three consecutive years (2021–2023). Water quality was determined using the Water Quality Index (WQI) based on Brown’s parameters: pH, turbidity, temperature difference, dissolved oxygen, biochemical oxygen demand (BOD), nitrates, phosphates, total dissolved solids, and fecal coliforms. The WQI classified water quality from excellent to poor, allowing an evaluation of contamination levels and potential uses. Results showed that upstream sites consistently maintained good or acceptable quality, while urban and downstream sections exhibited progressive deterioration. From 2021 to 2023, WQI values declined significantly, with the final downstream site (“Tahuando Final Point”) reaching a poor classification despite the presence of a wastewater treatment plant. The continued discharge of untreated effluents and diffuse pollution impeded the river’s self-purification, rendering water unsuitable for consumption, recreation, or irrigation—except in the upper reaches. These outcomes were consistent with findings from other tropical Andean basins linking urbanization and untreated wastewater to declining WQI values. Overall, the study highlights that anthropogenic pressures, particularly from urban wastewater and land-use change, are the main drivers of degradation in the Tahuando watershed, threatening aquatic biodiversity and the long-term sustainability of this vital water resource.

Organophosphate flame retardants (OPFRs) and phthalate esters (PAEs) are widely used flame retardants and plasticisers; however, baseline data on their occurrence in India remain limited. This study investigated 15 OPFRs and 6 PAEs in playground soils along an urban-rural gradient in Nagpur, central India, to assess occurrence, spatial distribution, and potential sources. Total concentrations of twelve OPFRs (Σ12OPFRs) ranged from 40.9 to 2,740 ng/g (mean: 339 ± 435 ng/g), while six PAEs (Σ6PAEs) varied from 35.0 to 2,550 ng/g (mean: 320 ± 394 ng/g). Σ12OPFR concentrations were significantly higher in rural transects than in urban areas(p < 0.05). OPFR profiles were dominated by alkyl OPFRs (57%), followed by aryl (32%) and chlorinated OPFRs (11%), with tris-n-butyl phosphate (TnBP) as the most abundant compound (31%) and significantly enriched in rural soils (p < 0.05). PAEs were dominated by di-(2-ethylhexyl) phthalate (DEHP; 76%), followed by di-n-butyl phthalate (DnBP; 15%). Principal component analysis resolved five components, identifying polymeric and consumer product sources (TDCIPP, TICIPP, TPhP, TIPrP), industrial and petrochemical inputs (TpCP), plasticizer- and agriculture-related sources (DEHP, TnBP), and diffuse atmospheric, polymeric, and traffic-related contributions (DEP, TEP, DMP, TMP). Human health risk assessment indicated a negligible risk, with maximum hazard index values of 3.49 × 10-3 for children and 8.91 × 10-4 for adults, and incremental lifetime cancer risk values ranging from 3.33 × 10-9 to 4.79 × 10-8, all of which fall within the United States Environmental Protection Agency's acceptable limits. Elevated OPFRs levels in rural areas highlight concerns related to long-range atmospheric transport and diffuse pollution hotspots locally.

Water quality in South Africa’s river systems is declining, driven in part by changes in land use and management. Diffuse pollution significantly contributes to river degradation, requiring identification of critical source areas of diffuse pollutants, including nutrients and suspended solids. This study assesses diffuse pollution risks in two contrasting catchments: the Thukela and the Breede. A risk-based assessment was undertaken using the Sensitive Catchment Integrated Modelling Analysis Platform (SCIMAP). SCIMAP integrates a digital elevation model (to determine hydrological connectivity), land use based diffuse pollution potential, here assessed from national land cover classes using the Automated Land-based Activity Risk Assessment Method (ALARM), and rainfall information (representing runoff dilution potential). Results are presented as (i) risk generation of diffuse nutrients based on land use attributes, (ii) the connectivity risk of the movement of pollutants to the river channel, (iii) nutrient risk from the landscape component’s critical source areas, (iv) nutrient concentration risk in the channel component of the catchment, and (v) suspended solid risks from the landscape component. In the Thukela Catchment, landscape-scale nutrient risk patterns were relatively uniform at catchment scale, with distinctions only emerging at finer spatial scales, where elevated risks were associated with some commercial and subsistence agricultural areas. The Breede Catchment exhibited distinct nutrient risk patterns even at catchment scale, with high-risk areas closely linked to some commercial agriculture areas. Channel segments of high nutrient risk for both catchments became evident only at detailed spatial scales. Landscape-based diffuse suspended solids risk areas within the Thukela Catchment range from lows under undisturbed natural vegetation or areas of low connectivity, to highs dominated by degradation and subsistence farming, combined with a high connectivity risk. The Breede Catchment was more muted. This approach is useful to backtrack from polluted river sections to areas with high risk of generating and mobilising pollutants.

Japan has largely achieved the “first half” of SDG 6—universal access to safe drinking water and sanitation—through decades of intensive investment in water supply and sewerage systems, implementation of the Total Pollutant Load Control System, and stringent regulation of industrial effluents. National indicators show that coverage of safely managed drinking water and sanitation services is nearly 99%, and domestic statistics report high compliance rates for BOD/COD-based environmental standards in rivers, lakes, and coastal waters. Conversely, the “second half” of SDG 6 reveals persistent gaps: ambient water quality (6.3.2) remains at 57% (2023 data), while water stress (6.4.2) is at approximately 21.6%. Furthermore, SDG 6.6.1 shows that 3% of water basins are experiencing rapid changes in surface water area (2020 data), with ecosystems increasingly threatened by hypoxia in enclosed bays and climate-induced vulnerabilities. Drawing on global comparisons, this review synthesizes Japan’s progress toward SDG 6, elucidates the structural drivers for remaining gaps, and proposes policy pathways for a nature-positive water future. Using national statistics (1970–2023) and the DPSIR framework, our analysis confirms that improvements in BOD/COD compliance plateaued around 2002, reinforcing concerns that point-source measures alone are insufficient to address diffuse pollution, groundwater nitrate contamination, and emerging contaminants like PFAS. We propose six strategic directions: (1) climate-resilient water systems leveraging groundwater; (2) smart infrastructure renewal; (3) advanced treatment for emerging contaminants; (4) basin-scale IWRM enhancing transboundary cooperation; (5) data transparency and citizen engagement; and (6) scaled nature-based solutions (NbS) integrated with green–gray infrastructure. The paper concludes by outlining priorities to close the gaps in SDG 6.3 and 6.6, advancing Japan toward a sustainable, nature-positive water cycle.

Abstract Accurate exposure assessment is essential for understanding environmental health risks and for informing effective policy measures, particularly in areas where urban and industrial sources coexist. This study assessed long-term (2006–2019) air pollution exposure in the orographically complex Venafro Valley (southern Italy), an area characterized by multiple emission sources, to support an epidemiological investigation. To capture the spatial and source-specific heterogeneity of emissions, two complementary approaches, generally used independently, were combined. Diffuse pollution was characterized using fine particulate matter (PM 2.5 ) estimates derived from a satellite-based random forest model, while industrial contributions were evaluated through nitrogen oxides (NO x ) concentrations simulated by the Wrf/Calmet/Calpuff dispersion modelling system. Four exposure classes were defined for each pollutant using the “natural breaks” method to highlight relative spatial gradients rather than absolute concentration levels. The two methods revealed distinct exposure patterns. PM 2.5 peaked at the center of the valley, in the urban area of Venafro, largely influenced by traffic and biomass heating, whereas NOₓ hotspots were located near the industrial plants situated at the valley edges, close to the surrounding mountains. Overall, the findings highlight the need for integrated, multi-source approaches and additional monitoring stations to prevent biased exposure assessments. Although this study focuses on a specific area, the methodologies applied here may be transferable to other environmental or epidemiological contexts.

ABSTRACT The Maceió Stream watershed, in Fortaleza, Ceará, Brazil, plays a vital role in the city’s urban drainage system but suffers from urbanization, pollution, and environmental degradation. This study applies the Storm Water Management Model (SWMM) to develop hydrological-hydraulic and water quality models, assessing the impacts of impervious areas and diffuse pollution. The integrated model simulates flow rates, flood peaks, and pollutant concentrations, focusing on Biochemical Oxygen Demand (BOD), Total Nitrogen (TN), Total Phosphorus (TP), and Escherichia coli (E. coli). The watershed’s relevance stems from its location across densely populated and socially vulnerable areas, making its management environmentally and socially critical. Model performance showed good reproduction of Maceió Stream hydrographs (NSE = 0.78, PBIAS = -9%), with excellent accuracy for BOD (NSE = 0.97, PBIAS = 2%), TN (NSE = 0.91, PBIAS = -3%), and TP (NSE = 0.98, PBIAS = -4%). Scenario analyses considering climate change and continued urbanization revealed the necessity of drainage interventions to mitigate extreme hydrological events and strategies to improve water quality. The study concludes that integrated modeling with SWMM is an effective tool for diagnosing water-related challenges and guiding sustainable management solutions for urban watersheds.

Improving European surface water quality requires urgent action to address diffuse pollution sources particularly from agriculture, with increased frequency and intensity of hydroclimatic events also a key driver of pollutant export to waters and water quality decline worldwide. However, the need for comprehensive, practical protocols for sensor deployment, sensor maintenance and data management for the adoption of high frequency water quality monitoring has been highlighted, along with the challenges for citizen scientists in analyzing millions of water quality data points and sharing metadata. The practical method presented, with reproducibility built into the workflow, is designed for multiple users and a step-by-step application of the workflow is demonstrated including:•Deployment arrangement for water quality sondes in two temporary monitoring stations with different site characteristics.•Data collection and data validation methods.•Concise, reproducible, open-source workflow detailing the use of R, R markdown and US EPA CANARY software for data import, data cleaning, data visualization, data integrity, along with site-specific CANARY event system configuration for the detection of potential water quality events.Results for two monitoring stations on different rivers show CANARY successfully identified 100 % (n 47) and 97 % (n 39) of the manually identified turbidity events.

Assessment of surface runoff, accelerated erosion, and diffuse pollution potential in the Potengi River Watershed, Rio Grande do Norte, Brazil

Urban surface water flows contribute more PFAS to marine environments than treated wastewater.

A paired-catchment evaluation of voluntary agri-environmental scheme measures targeting diffuse phosphorus and sediment pollution.

Abstract Diffuse pollution from agriculture continues to pose a significant threat to waterbodies. This study investigates the role of diverse farming objectives on a farmers’ openness to adopt a suite of mitigative measures that could have a positive effect on water quality. Based on a farmer survey, factor analysis was used to reduce a long list of potential farming objectives to three: long-term economic objectives (LTE), short-term economic objectives (STE) and environmental objectives (ENV). The results of a multivariate ordered probit model indicate that farming objectives are a highly significant predictor of openness to adopt. Our findings suggest that farmers with LTE and ENV objectives are more open to adopting many of the same mitigation measures while farmers with STE objectives are less open.