Interactions of natural colloids with microplastics in aquatic environment and its impact on FTIR characterization of polyethylene and polystyrene microplastics

The demand for plastics is expected to rise due to the exponential growth of the manufacturing sector. The plastic industries get subsidies from Governments to boost foreign exchange. The mismanagement of plastic waste has contaminated water bodies with macro, micro, and nano plastics ultimately causing varied toxicological impairment to the aquatic and terrestrial environments. We have investigated the interaction of polystyrene (PS) and polyethylene (PE) microplastics with the natural colloids in waters. Eco-corona formation due to adsorption of colloids and dissolved contaminants on the microplastic’s surface was observed upon suspending PS and PE microplastics in natural marine and freshwater tagged with 2 µg ml−1 acridine orange. Fourier transform infrared spectroscopy (FTIR) studies revealed a diminishing intensity in the characteristic peaks of the and the disappearance of minor vibrations in IR spectra of the polymers upon suspension in natural waters for over 40 days. The alterations in the peaks were restored, and PE was recovered upon treatment with 30 % hydrogen peroxide (H2O2). In contrast, the recovery of PS was only partial, denoting the strong interactions of PS with natural colloids. The active groups on the polymer structure interacting with the colloids creates an eco-corona layer absorbing the light. The ecocorona formation hinders light transmission and detection by analytical methods such as FTIR, thereby substantiating the lower quantities of PS isolated and detected from aquatic animals and environmental samples. Eco-coronated microplastics could mimic the natural feed for small fishes and lower marine animals, facilitating their uptake and further transfer across the aquatic food web.