ABSTRACT Legacy mercury from historic atmospheric deposition poses a continued threat to aquatic ecosystems. A change in water level management plans for the Moses–Saunders hydropower dam on the Upper St. Lawrence River (USLR) resulted in water level fluctuations that more closely resemble natural fluctuations. Prior stable water levels (1958–2016) created conditions for overgrowth of cattail (Typha spp.) in riparian wetlands. This study of 81 wetlands during a flood year (2017) built upon a previous assessment (2016, non-flood year; 16 wetlands), quantified methylmercury content, and hgcA, a microbial gene responsible for mercury methylation. Here, total mercury, methylmercury, and hgcA copy number per gram of hydric soil did not differ significantly among geomorphological types of riparian cattail wetlands (p > 0.05). Total mercury, total carbon, and longitude (distance downstream) were the top three predictors of methylmercury content in hydric soils. After adjusting for organic matter, total and methylmercury concentrations increased with distance downstream (proximity to the dam), where younger wetlands were created by the impoundment. Historic flooding may have created sites of legacy mercury accumulation in wetlands close to the hydropower dam, while ongoing flooding generates a continued risk of mobilizing wetland mercury into adjacent food chains.

ABSTRACT This systematic review examines the pathways and risks associated with pesticides, microplastics, and emerging contaminants in drinking water sources in Ghana. The current review employed the PRISMA approach to synthesize peer-reviewed literature published between 2020 and 2025. It identifies the routes, levels, and sources of contaminants, as well as their related public health and environmental impacts. A total of 1,160 articles were initially identified, and 450 were shortlisted after a careful screening process. Of these, 39 articles were selected for final inclusion. The key findings showed contaminants enter water sources through runoff from agricultural activities, industrial effluent, and poor waste disposal, presenting a significant health risk. The quantitative data showed widespread contamination by pesticides (0.5–18 μg/L), microplastics (12–547 particles/L), pharmaceuticals, and per- and polyfluoroalkyl substances (PFAS), with significant health implications, such as hormonal disruptions, antibiotic resistance, endocrine disorders, neurological problems, carcinogenic effects, and developmental impairment in children. The presence of endocrine-disrupting chemicals and PFAS in 30% of tap water samples further indicates contamination after treatment. These findings highlight for an urgent comprehensive risk assessment, enforced policy action, and area-specific interventions to provide clean drinking water and protect public health in Ghana.

ABSTRACT The water quality of drinking water reservoirs is critical for human and ecosystem health. In this study, we examined the drivers of three metals, aluminum (Al), barium (Ba), and copper (Cu), across two drinking water reservoirs in southwestern Virginia, USA, over 4 years. One reservoir has a hypolimnetic oxygenation system; the other does not. We used time series modeling and multivariate analysis of water column chemistry, suspended sediment, inflow, and precipitation data to assess the relative roles of hydrologic and geochemical drivers of metal behaviors in the two reservoirs. Results suggest that Al concentrations were primarily influenced by high-flow events, consistent with the mobilization of clays from physical weathering. In contrast, Ba showed stronger sensitivity to geochemical drivers, specifically redox conditions. Drivers of Cu behavior were obscured by low Cu concentrations. For all metals, patterns varied among years. Our findings highlight the importance of long-term monitoring and integrated approaches to evaluate the drivers of metal dynamics in reservoir ecosystems and inform strategies for maintaining safe drinking water supplies.

ABSTRACT Microbial water quality monitoring is essential for safe drinking water, but can be difficult to carry out in contexts without access to well-resourced laboratories. Numerous testing kits have been developed to operate in these contexts, but many have drawbacks in terms of precision of results, cost, and contextual fitness. To this end, Faircap has developed a new low-cost (USD 38) microbial water quality testing kit, which includes a lightweight and low-power incubator and a membrane filtration-based water quality testing device. This kit was evaluated for reliable and accurate microbial water quality testing. The incubator maintained adequate temperature conditions in all selected ambient temperatures. Escherichia coli counts were not significantly different from a reference method, and a priori risk categorization agreed 80% of the time. The membrane filtration method had high sensitivity and specificity, but E. coli counts were less than those of the reference method. The decontamination protocol applied in between tests successfully decreased E. coli concentrations to non-detectable levels, without leaving significant decontamination residual. Overall, the Faircap Portable Lab, specifically the incubator, is a promising option for microbial water quality monitoring and could result in considerable cost savings and reduction of plastic waste compared with other accepted testing methods.

ABSTRACT Nitrification is limited in horizontal flow (HF) wetlands due to prevailing anaerobic conditions in these systems. This study examined how high interstitial velocity affects nitrification performance in HF systems used for tertiary wastewater treatment. Experiments were conducted using planted and unplanted HF wetlands operated in batch recycle mode, functioning as continuous stirred tank reactors across interstitial velocities of 15, 36, 56, and 72 m/d. From the Reynolds (Re) number, these velocities fall within a transition hydraulic flow range. In planted and unplanted cells, the levels of DO (2.7-3.3 mgO2/L and 1.9-2.4 mgO2/L, respectively) and COD (15-27 mg/L and 21-35 mg/L, respectively) differed significantly at different velocities. However, the rate constants for NH4-N in planted (0.24-0.33 d−1) and unplanted cells (0.18-0.31 d−1) differed insignificantly at varying velocities due to enhanced aeration caused by high velocities. Similarly, NO3-N concentrations did not differ significantly between systems, although each system showed notable changes with velocity. Up to interstitial velocities of 36 m/d and 1<Re<4, mass transfer effects on NO3-N formation were significant, beyond which they were insignificant. This suggests that high interstitial velocities 36 m/d enhance nitrification in HF wetlands for tertiary wastewater treatment. Further research is recommended to improve denitrification in these systems. .

ABSTRACT The practical remedy to emitter clogging in micro-irrigation systems is essential owing to water pollution issues worldwide. This research presents a modified irrigation water quality index (IWQI) that integrates normalized tolerance values and weighted factors to simplify the interpretation of irrigation water quality data. Validated through emitter clogging experiments, the index offers a robust and accessible tool for assessing water suitability in drip irrigation systems. Emitter clogging was assessed by discharge ratio, clogging degree (C), and emitter's dried residue. C values were between 4.7 for unclogged and 6.3 for general clogging in categories I and V, respectively, which were attributed to electrical conductivity (EC), sodium percentage (Na%), and total suspended solids (TSS). A gradual decline in emitter discharge was observed at escalated pollution (1.77 to 1.26, 1.79 to 1.20, 1.78 to 1.50, 1.76 to 1.48, 1.77 to 1.19, 1.79 to 1.44, 1.78 to 1.58, and 1.78 to 1.54 L/H for EC, Na%, sodium adsorption ratio, total dissolved solids, TSS, pH, chloride, and calcium, respectively). By translating complex water quality metrics into an intuitive grading scale, this research facilitates informed decision-making among farmers, engineers, and policymakers for proactive water management by enhancing the micro-irrigation efficiency.

ABSTRACT Lake Saint-Pierre (LSP), the largest fluvial lake in the St-Lawrence River system, is a vital freshwater floodplain with rich biodiversity. However, expanding agricultural activities have disrupted the landscape, increasing turbidity and threatening the ecosystem. In response, the Quebec government launched the LSP strategic research cluster in 2018 to encourage sustainable land and water management. This study examines how different land-use types affected turbidity during the spring floods of 2019, 2020, and 2022, using Sentinel-2 satellite imagery. Land types included conventional and improved agriculture, cultivated and natural grasslands, and flooded forests. A new empirical model for flooded forests showed strong accuracy (adjusted R2 of 0.88, RMSE (root mean square error) of 10.91 FNU (Formazin Nephelometric Unit)). Combined with an existing model for open water, turbidity maps were created across all land types. Using a linear mixed model, we found that conventional and improved practices increased turbidity in the LSP floodplain by up to 600% compared with natural forests. Grasslands also contributed to higher turbidity, though to a lesser extent. The findings underscore that even improved practices cannot fully mitigate turbidity. Effective control requires integrated watershed management, including upstream inputs and targeted best practices to protect the LSP floodplain.

ABSTRACT This study employed the environmental fluid dynamics code model framework to construct a hydrodynamic-water quality model for Futou Lake, a typical shallow lake located in Hubei Province, China. Critical findings of this work were as follows: (1) tracer simulations indicate that pollutants discharged from the Gan He River, the main inflow river of Futou Lake, took approximately 45 days to reach the monitoring section at the center of the lake; (2) the spatial distribution of flow fields and water quality parameters in Futou Lake exhibited significant variability under different hydrological and meteorological conditions and were closely linked to hydrodynamic characteristics, flow velocity, water level and discharge; and (3) under the Class II water quality standard, the simulated environmental capacities for total phosphorus, ammonia nitrogen and chemical oxygen demand at the center of the lake were 0.18, 1.08 and 159.64 kt/a, respectively, in 2023. Among the major inflow rivers, Gan River contributed the highest pollutant load, and the required reduction in total phosphorus and chemical oxygen demand loads were quantified. These results provide a scientific basis for understanding the spatiotemporal hydrodynamic-water quality dynamics and supporting aquatic environment management strategies in Futou Lake and similar shallow lake systems.