Optimizing spectral classification and oxidation estimation of environmental Microplastics

Microplastics (MPs) research has been challenging due to the wide range of methodologies that have been applied for sampling, extraction, counting and polymer type identification. Identifying MPs with microscopy only can yield to false positive and false negative results. Thus, polymer type identification is required to confirm that particles classified as MPs are indeed plastic polymers. The accurate identification of the small and weathered microplastics found at sea is critical. Therefore building spectral libraries based on weathered MPs is important. Here, we performed an intercalibration exercise using 200 spectra of sea surface floating microplastics (¿300μm) applying two different FTIR spectrometers. Differences and similarities of the results were investigated using various spectral preprocessing methods and tools and checked against various libraries. In addition, for a total of 2000 spectra from marine floating microplastics the carbonyl index (CI) of polyethylene (PE) polypropylene (PP) and Polystyrene (PS), including a diversity of sizes, and shape types, was calculated, using two different CI measurement techniques as described in the literature. The CIs of marine floating MPs were compared with those from literature data from accelerated ageing experiments and from MPs of known 'age'. CI calculation of the specified area under band (SAUB), revealed high variability ranging from 0.04 to 5.98 for the PE and 0.06 to 3.96 for the PP. The percentage of PE particles with SAUB ratio between 0.04 - 0.44 was 28 Also see: https://micro2024.sciencesconf.org/559692/document