Determination of microplastic level in areas affected by urban deep sea discharge in the Southeastern Black Sea (Trabzon)

The rapid development of the plastic industry has enabled the production of a wide range of plastic products with advantages such as low cost, lightness, strength and durability. Annual plastic production, which was at the level of 1.5 million tons in the 1950s, has reached 390 million tons today with increasing demands. In addition to the constantly increasing production and consumption amounts, there has also been a rapid increase in the amount of plastic waste in environments due to insufficient environmental awareness and deficiencies in waste management. Thus, plastic pollution has become one of the most important environmental problems of our time on a global scale. Plastics break down photolytically, mechanically and biologically under the influence of environmental factors and form microplastics. The most important sources of plastic pollution in the seas and oceans include coastal cities, ports, shipping activities, leaks from garbage dumps and wastewater treatment plants. In this study, microplastic levels on the sea surface were determined using a manta trawl net at 21 stations determined on the Trabzon coast of the Black Sea. The stations were selected to represent the effects of deep sea discharges (11 stations) and rivers (6 stations). As a result of the research, the number of microplastics was determined to be in the range of 0.12-3.71 units/m3 (average 0.68±0.80 units/m3). High amounts of microplastics were detected in stations located close to deep sea discharge points with high population density and high discharge capacity. The highest relative abundance rate of microplastic type was determined as fiber (73.9%), followed by fragments (17.4%) and sponge/foam (5.7%) types, respectively. The color distributions of the microplastics found were determined as 26% black, 25% blue, 21% transparent, 10% white, 10% red and the remaining 8% other colors. Although the presence of a wide variety of polymers was determined in the chemical composition of microplastic particles, the dominant types were revealed to be poly(1-butene) and polycaprolactone triol.