# Microplastic Pollution on the Beaches of the Black Sea in Romania and Bulgaria
## 4 Discussion  
Microplastics have become a significant environmental concern, with numerous studies highlighting their widespread presence in aquatic ecosystems, particularly in marine and freshwater environments. According to [PERSON] [29], microplastics, defined as plastic particles smaller than 5 mm, originate from both primary sources (e.g., microbeads in personal care products) and secondary sources (e.g., the breakdown of larger plastic debris). The persistence of microplastics in the environment is largely due to the durability of plastic materials, which are resistant to natural degradation processes [30]. Recent studies have shown that microplastics are ubiquitously distributed in coastal regions, rivers, and even remote areas, demonstrating their ability to travel long distances via water currents [31]. For instance, in a study conducted by [PERSON] et al. [32], microplastics were found in significant quantities on beaches along the Mediterranean coast, similarly to findings from the Black Sea region [33]. In comparison, research by [PERSON] et al. [34] reported that microplastic concentrations in river systems, such as the Danube, were notably high, suggesting that rivers serve as a major transport route for microplastics from inland regions to marine environments. The accumulation of microplastics on beaches is not only due to natural transportation but is also influenced by human activities such as tourism, which contribute to the deposition of plastic waste [35]. Overall, despite variations in concentrations and compositions, the presence of microplastics across different geographical regions emphasizes the global nature of this pollution and the urgent need for effective management strategies. The abundance of microplastics in beach samples worldwide varies considerably, reflecting both regional differences and the methods of collection and analysis. In the coastal marine environment of Singapore, the maximum concentration of microplastics in beach sediments was 470.8 microplastic particles/kg dry weight of sand [36]. In contrast, beaches in Slovenia showed average values of 155.6 microplastic particles/kg [37]. In sand from Baja California, Mexico, the average abundance of particles larger than 1 mm was 135 \(\pm\) 92 microplastic particles/kg, indicating significant pollution with large variations from one area to another [38]. In China, in the Bohai Sea area, values of between 102.9 and 163.3 microplastic particles/kg have been recorded for the abundance of 1 \(\upmu\)m particles [39], while in Wanning, on the Chinese coast, the concentrations are alarmingly high, with an abundance ranging from 5000 to 8714 microplastic particles/kg for particles smaller than 5 mm [40]. In Germany, on the beaches of Rugen Island, located in the Baltic Sea, the concentrations ranged between 77.9 and 107.3 microplastic particles/kg for the 63 \(\upmu\)m-5 mm fraction of microplastics [41]. A similar situation was observed in the northwestern Mediterranean Sea, where two distinct locations recorded abundance values ranging from 56 to 150 and 60 to 182 microplastic particles/kg for the same size range [42]. In the Mediterranean region (France, Italy, Spain), typical values range from 100 to 500 microplastic particles/kg in the surface layer of the sand. On the western European coast (Mediterranean Sea, Atlantic Ocean), beaches commonly show values of between 50 and 300 microplastic particles/kg,with peaks of up to 1000 particles/kg in heavily industrialized or estuarine areas, such as the Thames Estuary (United Kingdom) [43]. In a regional and international context, studies conducted in other areas of the Black Sea coast, such as Turkey and Georgia, have reported microplastic concentrations in sand ranging from 20 to over 300 particles/kg, with higher values associated with urban or industrial zones. For example, in the vicinity of cities like Istanbul and Samsun, concentrations of up to 350-500 microplastic particles/kg have been recorded, especially after the tourist season.