A Global Comparative Study on Microplastics Sampling, Identification and Quantification Techniques in Freshwater Environment: A Review

Microplastics are emerging pollutants that have a very adverse effect on the environment. While there have been extensive studies on marine microplastics, the research on freshwater microplastics is still lagging behind. This paper reviews advancements in microplastic analysis within freshwater environments, encompassing water bodies across continents. It highlights the challenges and uncertainties in microplastic sampling, processing, and identification methods. Among the reviewed studies, the highest microplastics concentration was recorded in Lake Ziway (30000 items/m3). Fibres are the most prevalent shape of microplastics found among all studies. Plastic types include polyethylene (PE) as the most common type of polymer recorded in different studies. The pollution trend in rivers shows lower microplastic concentrations at their origins, with a gradual increase downstream and confluence sites. In lakes, pollution trends are influenced by factors such as inlet and outlet connections, proximity to rivers, and anthropogenic activities. From this extensive review, it can be inferred that the sampling, as well as processing techniques of microplastics, need to be developed and standardized. While some studies have adopted modified methods to retain a feasible amount of microplastic, others rely on simpler methodology for collection and identification. Furthermore, the standardization of units for measuring microplastic abundance is crucial, as inconsistent notations across studies hinder comparative analyses and comprehensive evaluations of microplastic pollution.