The immense production of plastic polymers over the past century has led to vast plastic contamination across the geosphere, particularly in aqueous environments. These pollutants include the larger macroplastics, as well as microplastics, typically defined as plastic pieces less than 5 mm in size, and nanoplastics, whose particles are smaller than a micrometer. Of particular concern are the nanoplastics, whose quantification and analyses in real-word conditions are much more challenging than for microplastics. While health effects from nanoplastic exposure have been studied and documented, especially recently, little has been reported about their redox behavior in real-world waters, nor how their redox chemistry impacts their role in organic pollutant transport. In this work we report on our measured oxidation (hydroxyl radical, OH) and reduction (hydrated electron, eaq-) reaction rate constants for real world and waste (aged) polyethylene, polystyrene, polycarbonate and polyethylene terephthalate plastic nanoplastic particles in different quality waters. Although the formation of micro- and nanoplastics in aqueous media to date has been largely attributed to mechanical fragmentation of plastics by natural (i.e., abrasion, photolysis, biotic) we have been able to generate reproducible particle-size distributions of nanoplastics in water using small volumes of co-solvent solubilizers such as n-dodecane, in combination with vigorous mixing and sonication. Utilizing electron pulse radiolysis and transient absorption spectroscopy techniques the kinetic reactivity of these two important radicals has been quantified, and the subsequent impacts of overall oxidation and reduction on the NP’s organic pollutant transport investigated using steady-state gamma radiolysis.

Nanoplastic redox behavior in aqueous solution: Impacts on organic pollutant transport

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