Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic envi-ronments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organ-isms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with ad- ditive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabiliza- tion of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). How- ever, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Automated summary

This study aims to review the toxicity of microplastics and plastic additives to aquatic organisms, as well as available remediation methods. It was found that microplastics showed oxidative stress, neurotoxicity, altered enzyme activity, growth and feeding performance in fish. Microalgae species exhibited growth inhibition and ROS formation. Zooplankton experienced premature molting, growth retardation, increased mortality, altered feeding behavior, lipid accumulation and decreased reproduction activity. Polychaete faced neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Various methods, such as coagulation and filtration, electrocoagulation, advanced oxidation process, and magnetic filtration, showed high removal rates of microplastics. However, effective extraction methods are still needed for large-scale research on microplastic removal from aquatic environments.