Characteristics and Seasonal Distribution of Microplastics in the Surface Waters of Southwest Coast of the Caspian Sea (Guilan Province, Iran)

The aim of this study was to investigate the occurrence, abundance and distribution of microplastics (MPs) in the southwest coast of the Caspian Sea in four seasons. Three stations were chosen and their surface waters were sampled between April 2019 and February 2020. The average number of MPs was 1.37 ± 0.47 items/m 3 and the predominant frequency in different seasons were as follows: summer > autumn > spring > winter. MPs were dominated by fiber in shape. Black and blue were the most common colors respectively. The size was in the range of 0.3–5 mm with a mean of 1.44 ± 1.08 mm. Due to Fourier-transform infrared spectroscopy equipped with attenuated total reflection (ATR-FTIR), four different polymers were identified dominating by polypropylene. The low MP concentrations detected in the present study can be related to lower sewage inlet and more MPs sedimentation in the investigated stations.