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Veröffentlichung The challenge in preparing particle suspensions for aquatic microplastic research(2019) Eitzen, Lars; Paul, Sophia; Braun, Ulrike; Ruhl, Aki SebastianThe occurrence of small particles consisting of organic polymers, so-called microplastic (MP), in aquatic environments attracts increasing interest in both public and science. Recent sampling campaigns in surface waters revealed substantial numbers of particles in the size range from a few micrometers to a few millimeters. In order to validate sample preparation, identification and quantification and to investigate the behavior of MP particles and potential toxic effects on organisms, defined MP model particles are needed. Many studies use spherical compounds that probably behave differently compared to irregularly shaped MP found in environmental samples. However, preparation and handling of MP particles are challenging tasks and have been systematically investigated in the present study. Polystyrene (PS) as a commonly found polymer with a density slightly above that of water was selected as polymer type for milling and fractionation studies. A cryogenic ball mill proved to be practical and effective to produce particles in the size range from 1 to 200 Ìm. The yield of small particles increased with increasing pre-cooling and milling durations. Depending on the concentration and the size, PS particles do not completely disperse in water and particles partly creep vertically up along glass walls. Stabilized MP suspensions without use of surfactants that might harm organisms are needed for toxicological studies. The stabilization of PS particle suspensions with ozone treatment reduced the wall effect and increased the number of dispersed PS particles but increased the dissolved organic carbon concentration and changed the size distribution of the particles. © 2018 Elsevier Inc. All rights reserved.Veröffentlichung A new concept for the ecotoxicological assessment of plastics under consideration of aging processes(2023) Kittner, Maria; Isernhinke, Lisa; Altmann, Korinna; Braun, Ulrike; Lukas, MarcusMicroplastics are widely distributed in aquatic and terrestrial environments, but up tonow less is known about (eco)toxicological impacts under realistic conditions. Researchso far has focused mainly on impacts on organisms by fresh, single-origin plasticfragments or beads. However, plastics found in the environment are complex incomposition, this means different polymer types and sources, with and withoutadditives and in all stages of age, and therefore, in a more or less advanced stage ofdegradation. For oxidized degradation products that might be released from plasticmaterials during aging, there is a lack of information on potentially adverse effects onaquatic biota. The latter is of particular interest as oxidized degradation products mightbecome more water soluble due to higher polarity and are more bioavailable, therefore.The present study focused on plastic leachates of polystyrene (PS) and polylactic acid(PLA), which were derived from alternating stress by hydrolysis and ultraviolet (UV)radiation-representing a realistic scenario in the environment. Test specimens of PS,PLA, or a PLA/PS layer (each 50%) were alternately exposed to UV radiation for 5 daysfollowed by hydrolysis for 2 days, for several weeks alternating. Ecotoxicological effectsof the storage water (artificial freshwater) of the test specimens and additionally, in asecond experimental setup, the effects of five potential polymer degradation productswere detected by 72 h algae growth inhibition tests withDesmodesmus subspicatus.Results clearly indicate inhibitory effects on algae growth by contaminants in thestorage water of stressed plastics with increasing growth inhibition of proceedinghydrolysis and UV stress times. Different polymers caused variable inhibitions of algaegrowth with stronger inhibitions by PS and less effects by PLA and the mixed layer ofboth. Moreover, not microplastic particles but the resulting dissolved degradationproducts after aging caused theecotoxicological effectsââą Ìwith strong effects by theoxidized degradation products. The existing data highlight the relevance of plastic agingas a framework for microplastic ecotoxicity evaluation and allow a proof of concept. © 2023 The Authors.