Assessing the sorption of pharmaceuticals to microplastics through in-situ experiments in New York City waterways

Adsorption of organic pollutants onto microplastics has been reported in prior studies, indicating the potential of these particles to serve as vectors of pollutants. Most prior investigations, however, have been conducted in laboratories under conditions with relatively little environmental relevance. Here we report the results of in-situ experiments to investigate the adsorption of pharmaceuticals (atenolol, sulfamethoxazole, and ibuprofen) on to eight types of test materials (pellets from five types of widely-used polymers, small pieces of straws, fragments of bags, and glass beads for control). Three sample sets survived 28 days of deployment in New York City waterways. Concentrations of each analyte in water samples taken at these sites were also measured. Adsorption coefficients were calculated based on mass and surface area for each type. Mass-based coefficients showed much higher values for straw and bag samples than other types, consistent with their greater surface area to mass ratios. The surface area-based coefficients were similar among the plastic materials tested as well as the glass beads, indicating that surface area is a major determinant of the pharmaceutical adsorption, regardless of material type. Rapid biofouling, which was observed on all samples, appeared to be the predominant factor controlling the sorption capacity of the plastics. Our observations suggest that extensive biofouling and the formation of biofilms in nutrient-enriched waters can significantly impact the adsorption of pharmaceuticals onto plastics.