Prepared polypropylene microplastics: formation of eco-corona in aquatic systems and their combined toxicity with cadmium in Artemia franciscana

Our study investigated the interactions between colloids present in various aquatic environments and the surface of microplastics (MPs), with a specific focus on their behavior in tap water, lake water and marine water systems. This phenomenon is commonly referred to as "eco-corona". Polypropylene microplastics, although extensively utilized in various applications, have been less studied than polystyrene and polyethylene microplastics. The prepared polypropylene microplastics were characterized by ATR-FTIR and Raman spectroscopy, and the formation of eco-corona was monitored at specific time intervals (24, 48, 72, 96 and 120 h). Fluorescence spectroscopy was used to measure the corresponding fluorescence intensity. Further investigations through FTIR spectroscopy revealed a reduction or complete disappearance of the characteristic polymer peaks upon suspension in natural water systems. Eco-coronated MPs exhibit more cadmium adsorption than raw MPs. The combined exposure of eco-coronated MPs and cadmium to the brine shrimp Artemia leads to the bioaccumulation of microplastics. At its peak concentration (0.5 mg mL-1), both weathered and true-to-life microplastics significantly increased reactive oxygen species production (p < 0.001) in a concentration-dependent manner. Similarly, superoxide dismutase activity increased in a dose-dependent manner, with weathered microplastics showing significant elevation (p < 0.001). Conversely, total protein content was reduced at higher concentrations of both weathered and true-to-life microplastics. The interaction between microplastics and biomolecules/colloids diminishes their presence in the environment, acts as a vector for pollutants, and mimics food for aquatic organisms. Additionally, it facilitates bioaccumulation in lower-to-higher aquatic organisms and contributes to the collapse of the food web.