Extraction and determination of microplastics and associated PAHs in seawater and beach sediments from the northwestern part of the Caspian Sea

The adsorption of persistent organic pollutants (POPs) on microplastics (MPs) in the marine environment is a pressing issue. This study, which focused on the northwestern part of the Caspian Sea, aimed to assess the extent of MP pollution and investigate the origin of polycyclic aromatic hydrocarbons (PAHs) adsorbed on MPs isolated from seawater and coastal sediments. In this study, gas chromatography-mass spectrometry (GC–MS) measured the amount of PAHs. Detection limits were 0.1–1.3 ng g-1. Recovery experiments were conducted in 5 replicates at two concentration levels, 5 and 25 ng g-1. The recovery of standards was from 80.2 ± 5.2% to 99.1 ± 4.9%. The study also considered the relationship between PAH content and the size of the MPs. The concentration of Σ16PAHs at all investigated sampling sites ranged from 97.6 to 210.5 ng g-1 and from 93.9 to 332.3 ng g-1 in MPs from seawater and beach sediments, respectively. Notably, the study found that for MPs of 0.1 to 1 mm in size, the PAH concentrations determined by GC-MS were, on average, 20–40% higher than for 3–5 mm MPs. The concentration of PAHs in the northwestern part of the Caspian Sea was found to be lower than in the southern part, as indicated by our results, underscoring the significance of this study’s findings.