Microplastic mitigation in urban stormwater using green infrastructure: a review

Microplastic pollution in aquatic environments has emerged as a significant environmental concern, posing risks to ecosystems and human health. Urban stormwater runoff has been identified as a major source of microplastics, with microplastic concentrations reaching up to six times higher than those in wastewater treatment plant effluents. Given the increasing urbanization and inadequate waste management, effective mitigation strategies are urgently needed to prevent the discharge of microplastics into natural water systems. Green infrastructure, designed for sustainable stormwater management, has gained attention as a promising approach to reducing microplastic pollution while providing additional environmental benefits. Here, we review various green infrastructure technologies, including bioretention systems, permeable pavements, stormwater ponds, and constructed wetlands, focusing on their effectiveness in microplastic mitigation. Bioretention systems exhibit removal efficiencies ranging from 80% to over 99%, and are particularly effective for particles sized 20 μm or above. Constructed wetlands achieve removal rates between 28 and 75%, effectively treating microplastics in the 100–500 μm range. Permeable pavements demonstrate removal efficiencies of 89–96.6%, especially for particles less than 100 μm. Retention ponds retain 55–98% of microplastics, with sediment retention reaching up to 85%. We found that the performance of these systems is influenced by soil amendments, vegetation, and adsorption-based mechanisms such as biochar applications, which can enhance removal to over 99% under optimized conditions. Phytoremediation with aquatic plants such as Lemna minor achieves a 76% removal rate, while biofilm-based strategies offer slower but potentially sustainable solutions. This review highlights the necessity of integrating multiple green infrastructure approaches to optimize microplastic removal.