To be or not to be – Challenges of identifying microplastics in complex environmental matrices

With global plastic production rising the occurrence of microplastic particles (<5 mm) in the marine environment has been acknowledged as an emerging topic of international concern. However, the extent of this microplastic pollution as well as the resulting impacts on the marine environment remain largely unknown. Especially when it comes to specific quantities, polymer composition and spatial distribution of tiny microplastics. For baseline studies as well as future monitoring, standardized and reliable methods to detect microplastics are urgently needed. The conclusive identification requires a successful extraction from different environmental matrices. The smaller the microplastic particles the more challenging it is to extract and identify them in complex environmental matrices. Thus, we developed a highly promising procedure to successfully extract microplastics from sediments and surface water samples. This procedure consists of an enzymatic purification in newly developed microplastic reactors and a subsequent state-of-the-art analysis via micro-Fourier-transform infrared (µFTIR) spectroscopy. First results show that microplastics are present in the southern North Sea in form of different polymer types dominated by very small particles, less than 100 µm in length. This stresses the importance of focusing even more on the smaller microplastics regarding risk assessment.