Microplastics as vector for persistent organic pollutants in urban effluents: The role of Polychlorinated Biphenyls

The presence of microplastics in the environment is considered a global threat, not only for the physical damage induced to the organisms that ingest them and leachability of their constituent, but also as a potential carrier of organic and inorganic contaminants, with an interaction poorly described. Microbeads collected from four facial cleansers, with a well-known polymeric and additive composition, were used as an indicator for the sorption of polychlorinated biphenyls (PCBs) in treated urban effluents, in order to study the behavior of microplastics versus these persistent organic pollutants in water. A stock standard solution (EPA 525, 525.1 PCB mix) was used for this purpose, being a certified material produced in accordance with ISO Guide 34:2009 and ISO/IEC 17025:2005. It consists of a mixture of eight congeners: PCB1, PCB5, PCB31, PCB47, PCB91, PCB154, PCB171 and PCB200 in n-hexane (500 g/ml of each component). Sorption experiments were carried out in batch mode, previously in bi-distilled water, and finally in treated urban effluents. PCB congeners retained by microplastics and remaining in water were further analyzed by means of gas chromatography, using a protocol previously described with an initial column temperature of 70C and a ramp of 10C/min up to 150C, 3C/min up to 200C, and 8C/min to a final temperature of 280C. The sorption process proved to be reliable and repeatable both for samples in bi-distilled water and treated urban effluents, showing different interactions between the organic pollutants and the microplastics. PCB congeners with a low-molecular weight proved to be preferentially sorbed by an oxidized polyethylene included in one of the microbeads, although the maximum amount for total PCB sorption was for the facial cleanser with TiO 2 in its composition.