Assessment of potentially toxic metals adsorbed on small macroplastics in urban roadside soils in southeastern Nigeria

Plastic pollution is a worldwide problem. In an urban setting, road dust is a major source of plastics, and their presence may be harmful to the health of the inhabitants. The distribution of small macroplastics (SMaPs; > 5mm to 10 cm) and adsorbed heavy metals in road side soils in Owerri, Imo state, were evaluated in this study. Top soils (< 5 cm) were collected along the Okigwe road at designated points (Orji flyover, Amawire Junction, Hardel junction, Orji Town primary school and Orji mission). The soil was characterized for physicochemical properties using standard methods. SMaPs were quantified and identified by visual counting and Fourier transform infrared (FTIR) spectroscopy. Adsorbed heavy metals (Pb, As, Cd, Cr, Ni and Cu) following weak acid digestion (20 % aqua regia) of SMaPs were quantified by Atomic absorption spectrophotometer. Results showed that the quantity of SMaPs particle /30 g of soil ranged from Orji mission (20.2 ± 2.59 to Orji town primary school (10.4 ± 2.6). FTIR confirmed the presence of polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polycarbonate (PC), polyethylene (PE) and macro rubber (Ma-R), which were mainly fragments (70 %). The mean distribution of the studied metals on the SMaPs showed Pb, As, Cd, Ni, Cr and Cu was highest on PET, PP, PE (Cd and Ni) and PVC (Cr and Cu) respectively. The plastic type showed variable adsorption behavior as revealed by Principal Component Analysis and multiple linear regression analysis reveals the influence of soil properties on adsorption. The ecological risks of plastics and metals were generally high. The SMaPs may serve as vector for these metals in soil. The source of the SMaPs can be attributed to local activities that appropriate regulatory bodies should monitor.