Polarization transmission characteristics of polystyrene microplastics in aqueous environments

Polystyrene microplastics are now widely distributed in aquatic environments, encompassing natural waters, bottled water, and even biological fluids such as blood and urine. We investigate the polarization transmission characteristics of polystyrene suspensions. Monodisperse polystyrene microspheres with diameters of 0.2, 0.5, and 1 μm were used to create uniform scattering environments in water. Incident wavelengths of 470, 532, and 670 nm were selected, respectively. The study examines which type of polarized light maintains its polarization most effectively. For polystyrene suspensions containing 0.2 μm particles, parallel polarized light demonstrated superior polarization retention at the 532 and 670 nm wavelengths. In all other instances, right-handed circular polarized light exhibited better polarization retention. This phenomenon can be tentatively explained by the vector Fokker–Planck approximation. According to the vector Fokker–Planck approximation, the retention of circular polarization is correlated with the asymmetry parameter g. Circular polarization preserves its helicity and handedness during propagation through anisotropic random media. By contrast, linear polarization states become randomized more rapidly. This reversal occurs as the anisotropy of the environment decreases. The investigation also addresses which wavelength demonstrates enhanced polarization retention. Longer wavelengths exhibit improved polarization retention. Both parallel and right-handed circular polarized light achieve optimal polarization retention at the 670 nm wavelength. The outcomes of this research are anticipated to aid in endeavors such as underwater communication, underwater detection, and blood flow imaging techniques.