Adsorption of <i>N</i> -Nitrosodimethylamine onto Polyvinyl Chloride and Polyethylene Terephthalate Microplastics in Drinking Water

N-Nitrosodimethylamine (NDMA) poses significant public health risks as a potent carcinogen found in drinking water, while microplastics have raised concerns due to their ubiquity and potential to act as contaminant carriers. This study investigates the adsorption behavior of NDMA onto virgin and weathered polyvinyl chloride (PVC) and polyethylene terephthalate (PET) microplastics and evaluates the influence of water quality parameters on their adsorptive capacities. Adsorption isotherm experiments were conducted across diverse water matrices (ultrapure water, artificial freshwater, lake, river, and groundwater). The results demonstrated low NDMA adsorption on virgin or weathered PVC (generally <1 ng/g), and while virgin PET also experienced minimal adsorption, weathered PET displayed up to an order of magnitude higher adsorption than other materials, ranging from 0.5 to 7.5 ng/g. The adsorption capacity was influenced by ionic strength, natural organic matter, and polymer surface properties. Higher adsorption occurred in matrices with lower natural organic matter (NOM), and the NOM fractions of humic substances, biopolymers, and low-molecular-weight neutrals competitively reduced NDMA adsorption. These findings highlight the need for further research on microplastics as vectors for toxic contaminants and the regulation of microplastic pollution to mitigate associated risks in water systems.