The Environmental Protection Authority of Ghana (EPA) has proposed deploying copper-based nano liquid technology on the Birim River in the Eastern Region. Similar copper-based nano liquid solutions have been proposed more broadly across the Ankobra, Pra, and Offin rivers.

These waterways collectively drain a significant portion of Ghana's southwestern and south-central highlands. They serve as sources of drinking water, irrigation, and artisanal fishing for millions of people. Their degradation, driven principally by illegal small-scale gold mining (locally termed galamsey), represents one of Ghana's most urgent environmental crises. The stated aim is to remediate heavy metal contamination, principally mercury (Hg), arsenic (As), and cyanide (CN-).

While nanotechnology offers innovative solutions for environmental cleanup, the unique properties of copper engineered nanomaterials (ENMs) present complex risks to aquatic ecosystems, ranging from acute toxicity to half-century-long environmental persistence.

The Paradox of "Toxic" Remediation

The fundamental tension at the core of this proposal concerns the dual nature of copper nanoparticles. The same physicochemical properties that make Cu NPs potentially effective at immobilising pollutants also make them acutely toxic to a broad spectrum of aquatic organisms.

Copper-based ENMs are commercially deployed as active biocidal agents in marine antifouling paints and as broad-spectrum fungicides and bactericides in agricultural pesticide formulations. Their effectiveness in these applications derives from their capacity to release cytotoxic copper ions (Cu2+). They also generate reactive oxygen species (ROS) that disrupt cellular membranes and enzymatic function. These are the same mechanisms that make them hazardous in freshwater ecosystems.

This creates a scientific paradox: deploying a substance intentionally engineered for its lethal biological activity into a river system ostensibly to restore ecological health. Cu-based NP release routes and toxicity across fish life stages emphasise that aquatic environments are the final recipient of these particles following their use in antimicrobial and industrial applications. Their high reactivity with both biotic and abiotic environmental components creates compounding ecological risks not encountered with inert remediation sorbents. Unlike approaches that rely on biochar or zeolites, Cu NPs do not discriminate between the contaminant species they are meant to address and the non-target aquatic biota that constitute the very ecosystem being protected.

Long-Term Persistence and Water Chemistry

Environmental modelling using the WASP8 framework suggests that nanocopper is not a "quick fix." Once released into a freshwater environment, both the nanoparticles and their toxic dissolution products can persist in water and sediments for over 50 years, even if the initial source of pollution is removed.

The behaviour of these particles in Ghana's dynamic river systems is highly unpredictable. Their fate, whether they remain suspended, dissolve into toxic ions, or settle into the sediment, is dictated by fluctuating factors like pH, ionic strength, and dissolved organic carbon. While high organic matter can sometimes mitigate toxicity, it can also lead to the formation of flocs that settle into the riverbed, creating a long-term reservoir of heavy metals.

Disrupting the Biological Foundation

Remediation efforts must account for the microscopic life that drives river health. Copper oxide nanoparticles have been shown to suppress essential microbial activities in the carbon and nitrogen cycles, such as nitrification and denitrification. These detrimental effects often increase over time, meaning that short-term pilot tests may significantly underestimate the long-term ecological damage to the river's self-purifying capacity.

Additionally, there is a documented risk of biomagnification. Studies confirm that particulate copper can move through the aquatic food chain, from primary producers such as algae to omnivorous consumers. This dietary exposure can alter the feeding rates of predators, potentially destabilising the entire local food web.

The Operational Risk: Mopping a Flooded Room

Perhaps the most critical critique of the EPA’s plan is its focus on treating symptoms rather than the cause. Attempting chemical remediation while illegal mining (galamsey) continues to discharge mercury, cyanide, and silt daily is likened to "mopping a floor while the tap is still running". Without strict source control and law enforcement, any technological intervention will be a temporary and resource-wasting measure that introduces new chemical hazards.

Conclusion

The restoration of Ghana's lifeblood rivers requires integrity in science and systemic environmental action. Before tonnes of liquefied copper nano solutions are deployed, a comprehensive environmental impact assessment and an alternatives analysis are essential to ensure that the "cure" does not prove more deadly than the disease.

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Dr Michael Kumi (CSIR-Water Research Institute), and Dr Wilson William Anku (University of Environment and Sustainable Development, Somanya)