“Beached and Commercial Plastics’ Leachates: assessment of chemical composition and ecotoxicity to marine biota”

Five plastic categories representative of beach litter from the Central Adriatic Sea were selected to assess the hazard of leachates to marine biota: Heterogeneous Fragments (HF), Mussel Nets (MN), Polystyrene Box fragments (PB), Drink Bottles (DB), and “Rapido” Trawl Rubber (RTR). Leachates (L1) were prepared by agitating beached and commercial plastics in seawater for 72 hours; a sequential extraction (L2) with nitric acid or methanol quantified residual chemicals (metals or organics, respectively). Trace metals, polycyclic aromatic hydrocarbons (PAHs), and aliphatic hydrocarbons (AHs) effectively desorbed in L1, with beached plastics generally releasing higher amounts, reflecting pollutants enrichment and weathering-enhanced leaching. Specifically, Al and Fe were the most abundant metals in MN (35.78 ± 12.86 and 79.16 ± 6.59 μg/g), while PAHs and AHs reached 1070.60 ± 362.74 ng/g and 381.88 ± 57.87 μg/g in PB. L2 further mobilized some chemicals, notably Al and Fe in beached PB and Zn and PAHs in commercial RTR (up to 10-fold increase). L1 ecotoxicity showed only commercial RTR inhibited Aliivibrio fischeri bioluminescence and Phaeodactylum tricornutum growth, whereas Paracentrotus lividus embryos were sensitive to most leachates. A Weight of Evidence model identified commercial RTR as most hazardous, emphasizing environmental concerns over its widespread use in trawling. • Beached plastics generally leached more chemical compounds than commercial ones. • Al and Fe were the most abundant metals in leachate from beached mussel nets. • Beached and commercial PS-boxes leachate showed the highest PAHs and AHs levels. • Trawl-derived commercial rubber leachate affected all tested biological endpoints. • WOE identified commercial PS-boxes and rubber leachates as the most hazardous.