Occurrence and characteristics of microplastics in surface water and sediment of Zayandeh-rud river, Iran

Background: Zayandeh-rud river is the most important river in the central regions of Iran and the present study aimed to provide new insights into microplastics (MPs) pollution in surface water and sediments of this river. Methods: Water and sediment samples were collected in July ۲۰۲۱ from ۱۹ sampling sites along the river. Organics matters were removed from the samples by wet peroxide oxidation (WPO), and MPs were extracted by floatation in ZnCl۲-saturated salt and filtration on a polytetrafluoroethylene (PTFE) membrane filter. Trapped MPs on the filter were counted and qualified by a stereomicroscope. Results: MPs were found in ۱۳ sites from ۱۹ sampling sites along the river. The minimum and maximum levels of MPs in water samples were ۰ and ۵۱ ± ۱۶.۵ particles/m۳, respectively. MPs also were detected in the sediments of all sampling sites except the first two sampling sites (the maximum level was ۵۸ ± ۲۵.۹ particles/kg as dry sediment). Fragments were the most common shape of MPs in both water and sediment samples. ۷۲.۳% of MPs detected in water samples were ۱-۵ mm in size, while this percentage for sediment was ۴۹.۲%. The five main polymer types found in water and sediment samples were polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Conclusion: These levels of MPs in the water and sediments of Zayandeh-rud river and longtime persistence of plastics in the environment is a significant threat to environmental and human health and need serious attention to restrict MPs release into the river.

کلیدواژه ها:

Rivers ، Polyvinyl chloride ، Iran ، Spectroscopy ، Fourier transform infrared