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Microplastic‐Bound Heavy Metals in the Sediments of a Peninsular River in South India
Summary
Microplastics in Noyyal River sediments accumulate heavy metals such as aluminum, barium, and iron through electrostatic and π-π interactions, with risk assessment identifying molybdenum, barium, and silver at high ecological risk. The study demonstrates that microplastics act as secondary metal sources that can re-release contaminants into the environment, compounding pollution in industrial river systems.
ABSTRACT The spatial and temporal interaction and accumulation of heavy metals (HMs) in microplastics (MPs) were studied in sediment samples from the Noyyal River of the southern Indian Peninsula. The sedimentary MP concentrations ranged from 0.20 to 12.70 g kg −1 . Polystyrene, nylon, polypropylene, and polycarbonate were dominant MPs containing high concentrations of Al and Fe. Heavy metal speciation was carried out in sedimentary MPs using Tessier's method: exchangeable (F1), carbonate (F2), and Mn‐oxide (F3). Al and Ba showed high concentrations in the F1 and F2 fractions, while F3 had high for Fe, Mn, and Zn. HMs are primarily adsorbed by π–π interactions, electrostatic interactions, and ion exchange processes, and their adsorption varies with particle size, surface area, polymer type, and aging as inferred from the literature. Risk Assessment Code indicates high risk for metals Mo, Ba, and Ag with RAC >50. Cluster analysis indicates that metals tend to accrue in MPs mostly from the release of industrial effluent and weathering. Consumer plastics, organic/inorganic pigments, packaging materials, natural and synthetic rubbers, and antimicrobial compounds promote metal–MP interactions in the environment, leading to environmental deterioration. The study finds that the metal fractionation method can be used to understand the adsorption and scavenging capacity of HMs by MPs. The fractionation results imply that microplastics can act as secondary sources of metals, facilitating their release into the water column and influencing metal cycling and toxicity in freshwater ecosystems.