Retention of microplastics by interspersed lagoons in both natural and constructed wetlands

Natural wetlands, the transitional zones found between the land and the sea, are considered hot spots for plastic accumulation. Constructed wetlands (CW) attempt to mimic these natural wetlands in order to provide potential Nature-Based Solutions (NBS) for reducing microplastic (MP) contamination in wastewater treatment plants, and mitigating MP pollution in rivers. In this work, the role played by an interspersed lagoon surrounded by aquatic vegetation (Juncus Maritimus) in retaining MP was investigated using experimental laboratory simulations. Four MP types (125–500 μm and 500–1000 μm PA fragments, 2 mm PET fibers and 5 mm PET fibers) along with suspended sediments were injected into the model wetland to study their transport throughout the system. Five different vegetated patch lengths surrounding the lagoon were considered (LP). Results showed that aquatic vegetation protected wetlands from PA fragments and PET fibers by increasing the dispersion of the particle-laden flow and consequently MP sedimentation. When the use of vegetated patches was coupled with an interspersed lagoon, MP retention rates were maximized (with total percentages of 88 ± 3 % and 99 ± 1.5 % for PA fragments and PET fibers, respectively), suggesting that CW are a potential NBS for trapping MP pollution from specific sources.