Seite - 52 - in Freshwater Microplastics - Emerging Environmental Contaminants?

Keywords Analysis, Degradation, Freshwater, Methods, Microplastics, Occurrence 1 Analysis ofMicroplastics: Sampling, Sample Preparation, and Identification The investigation of small synthetic polymer particles (size<5 mm), so-called microplastics, stronglydependsonappropriateanalyticalmethods.Theseparticlesare present in the aquatic environment due tomechanical degradation ofmacroplastics (size>5 mm) or the introduction of man-made microparticles. The analysis of microplasticsisanewchallengeforanalyticalscientists.Thesmallsizeofmicroplastics complicates their determination inenvironmental samples compared tomacroplastics and demands formore sophisticated analytical approaches.Microplastics are hetero- geneouslydistributedintheenvironment,andthisimpedestherepresentativesampling ofsedimentsandwater.Thesamplematrix, independentofthesampledenvironmental compartment,containsahighburdenofparticlesofnaturaloriginthatstronglyinterfere with thevisual detectionofmicroplastics.Therefore, suitablemethods for the sample preparation are needed to extract microplastics and reduce the number of natural particles.Moreover, an analytical method for the identification and confirmation of the plastic particles ismandatory to obtain reliable results.Awide rangeof different samplingmethods, sample treatments, anddetectionmethodsweredescribed(Fig.1). 1.1 SamplingofMicroplastics The samplingofmicroplastics in the aquatic environment stronglydependson the compartment that is the subject of interest. In general, this can be differentiated between sampling of the aqueous phase (surface water, water column) and the sediment phase (shoreline sediments, riverbed, or lakebed sediments). 1.1.1 Samplingof theAqueousPhase Theconcentrationsofmicroplastics inaqueoussamplesarerelativelylowcompared to those in the sediments. Therefore, a large volume of the water samples (up to hundredsof liter) isusuallyfilteredduring thesamplingprocess toobtaina represen- tativesample.Samplingofthewatersurfaceiscarriedout inmostcaseswithneuston orplanktonnetssupportedbyaflowmeter todetermine theaccuratesamplevolume. Thesenetsareusedindifferentmeshsizesrangingfrom50to3,000μm,while300μm is themost commonly usedmesh size along all studies [1]. This approach leads to nonquantitativesamplingofmicroplasticswithparticlesizes<300μm.Thenetswith smallermeshsizesarepronetoclogging.Toovercomethisproblem,newmethodsare 52 S.Klein et al.