Spatial Modeling of Microplastic Concentration in Lake Volta
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Date
2025-09
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UENR
Abstract
Microplastics (MPs), defined as plastic particles smaller than 5 mm, have emerged over the past decade as one of the most pressing global environmental challenges, particularly in aquatic systems. While initial research has predominantly focused on marine environments, examining MPs in sediments, surface waters, and biota, it is now increasingly evident that freshwater ecosystems are equally vulnerable. MPs enter aquatic systems through land-based sources transported via rivers and streams, as well as contributions from fisheries and shipping activities. Although global attention to MPs in freshwater is expanding, significant research gaps persist in Africa, with Ghana's inland waters—especially Lake Volta—receiving minimal investigation despite their ecological and socioeconomic importance. Specifically, there is a lack of spatially explicit data on MP distribution, limited understanding of source-to-sink pathways in large tropical reservoirs, and inadequate integration of social practices with environmental contamination patterns in the region.
This study addresses these gaps through an innovative, multi-matrix spatial assessment that integrates household surveys, environmental sampling, and biological analysis within a unified analytical framework. Guided by the Pressure-State-Response (PSR) theoretical model, the research systematically examines human-induced pressures (solid waste management practices), environmental state (MP distribution in water and sediment), and biological impacts (bioaccumulation in fish), culminating in evidence-based response strategies. The study is further structured by a novel conceptual framework that maps the complete pollution pathway from land-based activities through aquatic transport to biological uptake, enabling holistic source attribution and risk assessment. Key innovations include: (1) the first comprehensive spatial mapping of MPs across Lake Volta using GISbased interpolation to identify pollution hotspots; (2) integrated sourceto-impact analysis linking household waste practices directly to environmental contamination and biological exposure; and (3) application of advanced spectroscopic techniques (ATR-FTIR) combined with ecological risk indices to quantify both immediate and long-term contamination threats. Empirical findings revealed that solid waste mismanagement—a critical pressure—was widespread, with 40.0% of lakeshore households generating predominantly plastic waste, yet only 40.0% aware of waste segregation and 51.9% disposing of waste near their homes. Environmental analyses confirmed significant MP contamination, with average concentrations of 15.88 ± 10.69 MPs/L in surface water and 148.33 ± 119.35 MPs/kg in sediment, significantly higher in sediments (p < 0.001). Fibers and polyethylene dominated, with spatial hotspots identified in fishing-intensive zones (SII, SVI, SVII). Biological uptake was confirmed with 229 MPs detected in 96 fish specimens, averaging 2.47 ± 1.30 MPs per tilapia and 2.29 ± 1.73 MPs per catfish. MPs were negatively correlated with pH and dissolved oxygen, revealing physicochemical controls on distribution. While Ecological Risk Index (ERI) values (30.52 water, 27.44 sediment) indicated low immediate risk, Polymer Hazard Index (PHI) values (14.76 water, 13.02 sediment) signaled significant long-term contamination potential.
Collectively, these findings demonstrate that Lake Volta faces escalating MP pollution with clear ecological and socioeconomic implications. The study provides the first spatially explicit evidence base for MP contamination in Ghana's largest freshwater reservoir, offering novel insights into pollution drivers, distribution patterns, and biological transfer. Informed by the PSR framework, urgent interventions—including strengthened waste management, targeted plastic recovery, community education, and spatially explicit monitoring—are required to safeguard fisheries, livelihoods, and water security in the Lake Volta basin. This research establishes a transferable methodological framework for assessing MP pollution in similar freshwater systems across West Africa.
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Keywords
Aquatic Systems, Waste Management, Environments