How to detect small microplastics (20-100 μm) in freshwater, municipal wastewaters and landfill leachates? A trial from sampling to identification.

The quantification of microplastics (MPs), especially small MPs (20-100 μm), in freshwater environment and wastewaters is a great challenge due to the complexity of environmental compartment. In the present study, a novel method based on the optimization of sampling, pretreatment, and detection was developed for small MPs (20-100 μm) in freshwater and wastewaters. A customized plankton sampler was installed to efficiently collect MPs and avoid sampler clogging; a novel dual filter system simplified the pretreatment, achieving full examination for small MPs in the samples. The recoveries of small MPs at environmental abundance, which were specified for the first time, verified the feasibility of the developed method. The method was successfully applied for small MPs detection in river, municipal wastewaters and landfill leachates, demonstrating a large bias in the determination of MPs if small MPs were not involved in quantification. To the authors' knowledge, it is the first study that realized the determination of such small MPs in the high-strength wastewater, i.e. landfill leachates.