Iris pseudacorus and Lythrum anceps as Plants Supporting the Process of Removing Microplastics from Aquatic Environments—Preliminary Research

(1) Background: Since microplastics in aquatic environments are difficult to prevent and can cause adverse physiological and biochemical reactions to various organisms, we aimed to analyze the effectiveness of using aquatic plants with well-developed roots and excellent water purification capabilities to remove microplastics in an eco-friendly manner. Additionally, we examined the differences in removal efficiency based on the sizes of the microplastic particles and the types of aquatic plants used. (2) Methods: Two types of polyethylene (PE) microplastic particles (46 µm and 140 µm) and two types of aquatic plants (Iris pseudacorus and Lythrum anceps) were used in this study. These plants were cultivated in tap water containing microplastics for a duration of four months in an aquatic setup without soil. Water samples from the cultivation area were analyzed using Fourier-transform infrared spectroscopy (FT-IR) to determine the reduction in microplastics. Scanning electron microscopy (SEM) was employed to examine the adsorption of microplastics on the plants’ roots. Plant growth was assessed by measuring plant height, plant width, and the number of branches (number of leaves). (3) Results: The results revealed significant reductions in the numbers of microplastics in the water of the cultivation boxes containing Iris pseudacorus and Lythrum anceps, irrespective of the microplastic particle size or plant type. These reductions were further confirmed by the adsorption of microplastics on the roots of both plant species. Moreover, the presence of microplastics had no significant negative effects on the plants’ growth. These findings suggest that Iris pseudacorus and Lythrum anceps are suitable plants for removing microplastics in aquatic environments. (4) Conclusions: To effectively reduce aquatic microplastics using plants, it is essential to establish a sustainable vegetation cover using perennial plants with well-developed roots and rapid reproductive capabilities. Follow-up research should consider not only the type of plant but also various aspects related to their tolerance to different environmental conditions.