Sources and Distribution of Polycyclic Aromatic Hydrocarbons and Microplastics in Sediments from the Gulf of Trieste

This paper presents the results of important problems of marine pollution with polycyclic aromatic hydrocarbons (PAH) and microplastics (MP). The Gulf of Trieste, the investigated area, is affected by the accumulation of various pollutants and microplastics due to its geomorphological and hydrological characteristics. The distribution, content and origin of PAH and MP in marine sediments are presented. The concentrations of hydrocarbons were higher close to pollution sources (harbors, marinas) and decreased towards the offshore areas. PAH were mainly of two origins, the pyrogenic and petrogenic. Petrogenic PAH originate from crude oil and oil products, while pyrogenic PAH originate from the combustion of organic matter, especially fossil fuels. MP were extracted by density separation. The size, shape, and color of the extracted MP were determined using an optical microscope, and the composition of the polymers was determined by FTIR spectroscopy. The highest concentrations of up to 125 particles per 100 g dry weight of sediment were found in coastal areas. In the open sea, the concentrations were much lower, with an average of 3 particles per 100 g of dry sediment. Filaments and fragments were the most abundant shape, mostly made of polyethylene and polypropylene, 100–300 µm in size, and colorless/blue. The presented results show a moderate pollution of the investigated area with PAH and MP, in great part limited to the coastal areas.