Methodenentwicklung zur Analyse und Quantifizierung von Mikroplastikpartikeln in Mischwasserproben

This master thesis deals with the development of a method for separation, identification and quantification of microplastic particles (1 μm to 5 mm) in combined wastewater samples. In an experimental series already existing treatments were tested for their applicability on combined wastewater matrices by using an iterative process. Due to a long dry weather period in summer 2015 pure effluent samples were mostly used for the tests. As a result of the experiments a method for sample preparation was developed consisting of six sub-steps: (1.) sampling of 1 L combined wastewater, (2.) wet sieving of the sample through a 63 μm stainless steel mesh sieve and drying of the solids at 60°C, (3.) „wet peroxide oxidation“ (WPO) with Fe(II) solution as a catalyst, (4.) intermediate washing step, (5.) density separation by using a ZnCl2 solution (density = 1;6-1;7 g / cm³) and (6.) filtration of the microplastic particles on a polycarbonate filter. Due to the used mesh size the lower detection limit of the method is 63 μm. Furthermore, three identification methods described in literature were tested on their applicability. The optical assessment via microscope allowed for a first identification of potential microplastic particles and synthetic fibers in combined wastewater samples, however, a precise characterization was not possible. ... mehrThe trial with micro-Raman spectroscopy as an identification method displayed high fluorescence during the measurements caused by small amounts of natural organic material on the filter or particle surface. For this reason, micro-Raman was unsuitable for analyzing combined wastewater samples. In contrast, the Fourier-transform infrared (FTIR) spectroscopy showed great potential for the identification and quantification of microplastic particles. Especially the FPA-based micro-FTIR imaging could characterize individual particles on a filter or a filter surface of 170x170 μm in a single run. In summary it can be concluded that there is urgent need for a standardized method to identify and quantify microplastic particles in various types of samples and to allow for better comparability between studies. This is also confirmed by scientific literature.