Microplastic particles as a vector for toxic-heavy metals: A study on selective aquatic and terrestrial ecosystems

This study examines the prevalence, characteristics, and potential sources of microplastics (MPs) in terrestrial and aquatic ecosystems. Microplastics were extracted from soil and sediment samples and characterized by shape, color, and polymer type using visual analysis and ATR-FTIR spectroscopy. The most abundant MP shapes identified were fragments (45.5 % in soil, 57.7 % in aquatic sediments), with polypropylene and polyurethane being the predominant polymer types. Blue and red were the most common colours observed. Potential MP sources include plastic waste, agricultural films, and sewage sludge. The study also examined the concentration of heavy metals (Cd, Cr, Zn) in MPs and compared them to the surrounding soil and sediment. Results indicated that MPs can act as vectors for heavy metals, potentially increasing their toxicity and environmental impact, with higher concentrations of Zn observed in MPs compared to sediments. When compared to terrestrial sediments, the aquatic sediments are found to have a higher concentration of MP contamination. Microplastics and sediment samples both occasionally showed detectable levels of Cd, Cr, and Zn, but Pb and Cu were below the detection limit in all cases. Cd concentrations reached up to 0.146 mg/g and Zn up to 15.31 mg/g in microplastic samples from the study area. These MPs can enter food chains through flora and fauna, affecting soil biophysics and potentially contaminating groundwater. Direct field observations suggest that human daily plastic usage is a significant source of microplastics in aquatic environments, while agricultural practices and waste management contribute to terrestrial microplastic pollution. This research highlights the widespread contamination of MPs and the associated risks of heavy metal pollution, emphasizing the need for effective waste management and mitigation strategies to protect ecosystem health. This research is the first to provide baseline data on trace metal concentrations in aquatic microplastics from the Coimbatore area.