Microplastics can act as vectors of copper (Cu) ions, potentially altering their dynamics and availability in the marine environment through adsorption processes, which are influenced by several factors, including water pH. Given that ocean acidification is a current process that causes a reduction in pH and can be further aggravated through an increase in anthropogenic CO2 emissions, the aim of this study was to evaluate the behaviour of Cu in an acidified environment that was contaminated with photodegraded microplastics (polyethylene terephthalate (PET)) and to verify chemical changes in the carbonate system and Cu speciation under a reduced pH scenario. At the current pH (7.88), the concentration of dissolved Cu decreased after 48 h, primarily due to inorganic complexation and adsorption onto natural particles rather than adsorption onto microplastics, which exhibited a limited capacity to adsorb Cu2+ under the experimental conditions. Conversely, in the acidified pH scenario (7.59), the concentration of dissolved Cu increased, likely due to the release of previously complexed Cu and the reduced adsorption capacity of the microplastics, as Cu2+ competes with the increased H+ concentrations for the sorption sites on the surfaces of microplastics. These results indicate that under future acidification scenarios, the capacity of microplastics to act as vectors of Cu could be insufficient, potentially increasing the concentration of free ionic-Cu and increasing its availability and consequent toxicity to marine biota.
Poersch L. S., Soroldoni S., Lopes F. C., Martins C. D. M. G., Grassi M. T., Silva B. J., Camargo M. G., Kerr R. & Pinho G., 2025. Copper dynamics in the aquatic environment under ocean acidification and contamination by microplastics. SSRN. Article.
