Sorption of alkylphenols and estrogens on microplastics in marine conditions

In marine ecosystems, living organisms are continuously exposed to a cocktail of anthropogenic contaminants, such as microplastics (MPs) and endocrine disrupting compounds (EDCs). Being able to adsorb organic compounds, MPs would act as an additional contamination vector for aquatic organisms. To support this hypothesis, the sorption of six EDCs on MPs, including 4-t-butylphenol, 4-t-octylphenol, 4-n-octylphenol, 4-n-nonylphenol, 17β-estradiol and its synthetic analog 17α-ethinylestradiol, has been investigated. These compounds belong to two contaminant families, alkylphenols and estrogens, included in the EU priority and watch lists of the Water Framework Directive. Sorption kinetics were studied onto polyethylene and polypropylene MPs under seawater conditions. MPs at a concentration of 0.400 mg mL−1 were added to a mix of the six EDCs, each at the individual concentration of 100 ng mL−1. The concentrations of contaminants were chosen to be close to environmental ones and comparable with those found in literature. The results demonstrated that the hydrophobicity of the compounds and the MP type are the two factors influencing the sorption capacity. The distribution coefficient (K d) of each compound was determined and compared to others found in the literature. A high affinity was demonstrated between 4-n-NP and PE, with a sorption reaching up to 2,200 ng mg−1.