Spatial distribution of microplastics in surface sediments of the Zayandehroud Dam reservoir
Document Type : Research Paper
Authors
1 Department of Natural Resources, Isfahan University of Technology, Iran.
2 Environmental Department
Abstract
The present study was conducted with the aim of investigating the spatial distribution of microplastics in the surface sediments of Zayandehroud Dam reservoir, as one of the most important sources of water in the central plateau of Iran. For this purpose, surface sediment sampling was carried out at 20 stations along the Zayandehroud Dam reservoir using Ekman grab on December 20 and 21, 2022. Microplastic particles were separated based on their physical properties, including shape, color, and size, and the type of polymers was determined by Fourier transform infrared spectroscopy (FT-IR).The average concentration of microplastics in the surface sediments of the Zayandehroud Dam reservoir (223.3 ± 133.8 particles per kg of dry sediment) is medium compared to other regions of the world. The spatial distribution analysis of the microplastics density showed generally the pattern of increasing gradually from the dam wall towards the entrance of the lake. The detected particles had a great variety in terms of color, shape and size. The highest frequency was assigned to filamentous particles (65.3±32.1%) and amorphous particles (28.1±30.3%). The dominant colors included red (40.4% ± 29.4), yellow (38.4% ± 26.8) and blue (13.7% ± 14.9), and the particle size was mainly in the range of 125 to 500 microns. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed the polymer composition of the particles and showed the chemical diversity of microplastics in the region. So that polypropylene (PP) has the largest share among the identified polymers, followed by polyvinyl chloride (PVC) and polyethylene (PE). In addition, aromatic polyesters such as polybutylene terephthalate (PBT) and polyethylene naphthalate (PEN) were also detected in some samples. In general, the dam has acted as an effective factor in the deposition of microplastics in the upstream parts of Zayandehroud River. However, it seems necessary to adopt and implement management strategies in order to reduce the release of plastics in the upstream areas of the basin.
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