Probing the nanoplastics adsorbed by microalgae in water using polarized light scattering

Nanoplastics have been found in marine biological habitats. There is now an urgent need to effectively detect these nanoplastics. Due to the small size of these plastics, it is challenging to directly measure the total abundance while in a suspension. In this study, a backward 120° polarized light scattering device was used to measure the polarization parameters of Phaeodactylum tricornutum, before and after the adsorption of nanoplastics. The polarization parameters were observed to be affected by the adsorption of nanoplastics, with different concentrations and sizes. Moreover, the polarization parameter X changed with time after mixing the nanoplastics with the microalgae, which showed the details of the adsorption of nanoplastics by the microalgae, and was further confirmed by a scanning electron microscope image. The simulation results demonstrated how the polarization parameter X of the scatterers (e.g. microalgae) were affected by the adsorption of the nanoplastics. The results of this work indicate that the polarization scattering method can be used to probe the concentration and size of nanoplastics adsorbed by microalgae in water.