Micro-Nano Plastic in the Aquatic Environment: Methodological Problems and Challenges

SIMPLE SUMMARY: The topic of plastic wastes, microplastic (MP) and nanoplastic (NP) particles in the aquatic environment has been the focus of much scientific effort over the last decade and has gained immense public attention through the media. While numerous scientific reports underscore the ubiquitous presence of MPs and NPs in aquatic environments, particularly the oceans, there are many unresolved issues involved in their sampling, identification and characterization. This paper addresses some of the main problems and suggests what needs to be undertaken to overcome these issues. An overriding problem is the lack of harmonization of the protocols used for sampling MPs at sea and identifying them in the laboratory. There are technological challenges in polymeric characterization of NPs in environmental samples. Researchers use a wide variety of net types and net mesh sizes to capture and separate MP floating in the sea which makes comparing MP concentrations from different teams and areas extremely difficult and calls for establishing inter-comparison exercises among the various research teams. Furthermore, the issue of whether chemicals in MPs and NPs leach following ingestion by biota or whether they transport and release contaminants adsorbed on MP/NP surfaces is still unresolved. In essence, these and other issues have to be addressed and resolved before society has an accurate picture of their importance as an aquatic pollutant. There are no datasets on the environmental concentration of NPs, hence their effect on biota is solely relied on laboratory experiments using extremely high concentrations. The legitimacy of these effects and interactions in the biotic system is something that warrants discussion. ABSTRACT: Microplastic research has become a buzz word. It is seen as one of the most pressing issues of Anthropocene contamination. There is certainly no doubt about the ubiquitous presence of microplastic (MP) in almost all environmental matrices. However, the validity of considering them as a vector for contaminants needs some reconsideration, there are other more potent pathways. Their effect on marine biota also calls for some realistic experiments with environmental concentrations of MP and nanoplastic (NP). It has been observed that in most published literature, polymer characterization is performed. Is it necessary to do, or will merely finding and confirming the particle as plastic suffice for environmental research? Harmonization of protocols is necessary, and there is likely a need for some inter-laboratory comparison exercises in order to produce comparable data and reliable assessments across regions. Samples collected from the same area using different techniques show an order of magnitude difference in MP concentration. The issue of nanoplastic is more contentious; are we technologically ready to identify NP in environmental samples?