Investigation of Microplastics in Ready-to-Use Compost in the Urban and Agricultural Green Spaces of Isfahan City, Iran

Abstract

Background: The environmental and health hazards posed by microplastics (particles < 5 mm) have raised significant concerns in contemporary society. This study investigates the quantity, types, and forms of microplastics present in ready-to-use compost from urban and agricultural green spaces in Isfahan City, Iran, in 2023. Methods: In this study, we analyzed the frequency, types, and morphological characteristics of microplastics in readyto-use compost sourced from urban and agricultural green spaces in Isfahan City. We employed various methods, including sieving, Fenton digestion, flotation based on density with saturated salt, and filtration, to separate microplastic particles. A stereo microscope was utilized to count and characterize their shapes, while Fourier transform infrared (FTIR) spectroscopy was used to identify the types of polymers present. Findings: The study revealed an average of 36145.8 ± 7395.1 microplastic particles per kilogram of compost. Microplastics measuring between 1000 and 5000 µm constituted the highest frequency, accounting for 78 of the total. Five types of polymers were identified in the ready-to-use compost: polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC), with PET being the most prevalent at 28.7. Microplastics were observed in various forms, including fibers, foam, fragments, and films, with fibers being the most common form, comprising 60 of the total. Conclusion: The concentration of microplastics in ready-to-use compost from urban and agricultural green spaces in Isfahan City is comparable to levels found in other studies conducted within the country; however, it is notably higher than those observed in countries where organic materials are properly segregated. Due to the lack of standardized limits for microplastics in compost, making international comparisons is challenging. The choice of methodologies for sampling, separation, identification protocols, measurement, and the establishment of permissible limits significantly influences study outcomes. Hence, it is crucial to establish standardized methods to ensure consistency and accuracy in assessing microplastics in compost. © 2025, Isfahan University of Medical Sciences(IUMS). All rights reserved.