Microplastics in freshwater sediment in the Indo-Sri Lankan region: a review of methodologies

Abstract There is an increased concern about microplastic pollution globally due to its significance for environmental and human health. Even though there is a vast variety of studies based on marine environments, studies relevant to microplastics in freshwater sediments are rarely understood and discussed, especially in the Indo-Sri Lankan region. By focusing on freshwater sediments in the region, historical records of microplastics pollution can be provided and help identifying sources and trends. This report comprehensively summarizes and compares the methodologies used for sampling, extraction, identification and quantification of microplastics from freshwater sediment based on 34 studies, all from India while no studies were found that specifically address microplastic contamination in Sri Lankan freshwater bodies. Many different methods, from sampling to analyses were identified. Nevertheless, common and frequent methodologies used in the region were identified. The current state of freshwater methods for monitoring has a Technological Readiness Level (TRL) of 5.5 when averaging the six method steps of the relevant studies. This means that the methods currently used are relevant for freshwater sediment and there are records of success in their application. However, some approaches need to be improved and harmonized. For example, sampling equipment and survey design should follow international guidelines. Quality control and quality assurance practices should be performed more thoroughly to ensure the reliability of the data. Based on the findings, there is a significant need for localised studies for Sri Lankan freshwater ecosystems and future research in the region is needed to identify specific approaches to improve the method from sampling to data reporting, to further implement mitigation and management measures to reduce microplastic pollution.