Microplastiglomerates as emerging pollutant sinks: Characterization and heavy metal retention studies

This study reports the occurrence and characterization of plastiglomerates and their micro-scale derivatives, termed microplastiglomerates, from the northeastern Bay of Bengal coast. These composite materials, formed through thermal fusion of diverse polymers with mineral and organic matter, were examined to elucidate their morphology, composition, and contaminant retention behaviour. Stereomicroscopy, confocal fluorescence microscopy, and FESEM revealed heterogeneous textures, molten polymer interfaces, and mineral inclusions, confirming their hybrid lithoplastic nature. Raman spectroscopy identified seven polymer types-polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polylactic acid (PLA), polyester (PES), polysulfone (PESU), and polyvinyl ether (PVE)-while XRD confirmed crystalline mineral phases such as quartz and calcite embedded within amorphous polymer matrices. TGA indicated mixed organic-inorganic composition with high thermal stability. Metal adsorption experiments demonstrated significant retention of toxic metals (Hg, Cd, Ni, Cr, and Co) on microplastiglomerate surfaces, verified through XPS, EDX, and ICP-OES analyses. Metal binding was facilitated by oxidized polymer surfaces and mineral interfaces, highlighting their capacity to act as persistent pollutant sinks. Collectively, the results reveal that microplastiglomerates represent stable, reactive, and environmentally significant composites that influence metal mobility and pollutant dynamics in coastal systems. The findings underscore the need to include plastiglomerates in coastal pollution monitoring and environmental policy frameworks, with future studies directed toward their degradation kinetics, trophic interactions, and implications for marine sediment geochemistry.