Microplastics in the Danube River Basin: A First Comprehensive Screening with a Harmonized Analytical Approach

Abstract

In this study, carried out within the Joint Danube Survey 4, a comprehensive microplastic screening in the water column within a large European river basin from its source to estuary, including major tributaries, was realized. The objective was to develop principles of a systematic and practicable microplastic monitoring strategy using sedimentation boxes for collection of suspended particulate matter followed by its subsequent analysis using thermal extraction desorption-gas chromatography/mass spectrometry. In total, 18 sampling sites in the Danube River Basin were investigated. The obtained suspended particulate matter samples were subdivided into the fractions of >100 μm and <100 μm and subsequently analyzed for microplastic mass contents. The results showed that microplastics were detected in all samples, with polyethylene being the predominant polymer with maximum contents of 22.24 μg/mg, 3.23 μg/mg for polystyrene, 1.03 μg/mg for styrene-butadiene-rubber, and 0.45 μg/mg for polypropylene. Further, polymers such as different sorts of polyester, polyacrylates, polylactide, and natural rubber were not detected or below the detection limit. Additional investigations on possible interference of polyethylene signals by algae-derived fatty acids were assessed. In the context of targeted monitoring, repeated measurements provide more certainty in the interpretation of the results for the individual sites. Nevertheless, it can be stated that the chosen approach using an integrative sampling and determination of total plastic content proved to be successful.

Quantification of Poly(vinyl chloride) Microplastics via Pressurized Liquid Extraction and Combustion Ion Chromatography

“… 13 , 16 , 23 − 25 For instance, natural compounds from coniferous trees could lead to PE overquantifications. 26 Furthermore, in the case of PS, Fischer et al showed possible overdeterminations by phenylalanine from proteins during pyrolysis-GC-MS. 27 Regarding PVC, in the current literature, using pyrolysis or TGA, PVC, benzene, or naphthalene has often been used as a quantifier. 6 , 19 , 25 , 27 However, both pyrolysis products are very unspecific as they can also be generated during the pyrolysis of other synthetic polymers, such as PET or organic substances.…”

“…In recent years, different optical analytical methods, such as microscopy, Raman spectroscopy, or Fourier transform infrared spectroscopy, have been used for the identification of various types of plastic particles. − Also, analytical methods using mass spectrometry in environmental samples have been developed for different polymer types, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), poly­(vinyl chloride) (PVC), poly­(ethylene terephthalate) (PET), polycarbonate (PC), or poly­(methylmethacrylate) (PMMA) as well as their additives. − Primarily, pyrolysis or thermogravimetric analysis (TGA) has been coupled with gas chromatograpy/mass spectrometry (GC-MS). − However, these thermoanalytical methods are still under development and suffer from matrix interferences and false-positive results. ,,− For instance, natural compounds from coniferous trees could lead to PE overquantifications . Furthermore, in the case of PS, Fischer et al showed possible overdeterminations by phenylalanine from proteins during pyrolysis-GC-MS .…”

“…Furthermore, in the case of PS, Fischer et al showed possible overdeterminations by phenylalanine from proteins during pyrolysis-GC-MS . Regarding PVC, in the current literature, using pyrolysis or TGA, PVC, benzene, or naphthalene has often been used as a quantifier. ,,, However, both pyrolysis products are very unspecific as they can also be generated during the pyrolysis of other synthetic polymers, such as PET or organic substances. − Therefore, severe matrix effects leading to an overdetermination of PVC cannot be excluded. Another challenge for the quantification of microplastics is the matrix effects of different matrix ingredients. , Hence, there is still a lack of an alternative analytical method, enabling the specific and reliable quantification of PVC in environmental samples.…”

Application of electrostatic separation and differential scanning calorimetry for microplastic analysis in river sediments

“…GC-MS techniques are sensitive to organic residues in an environmental sample. Hence, sample purification with acids, bases, hydrogen peroxide, or enzymes is necessary (Kittner et al, 2022). DSC might be a promising approach for microplastic determination in environmental samples because organic residues would not influence the analysis.…”

“…Additionally, the exploitation of physical properties of polymers, such as melting and crystallization, can increase analytical robustness. In comparison to pyro/ted-GC-MS methods, extensive sample purification is obsolete for DSC (Kittner et al, 2022). Moreover, an approach to establishing an internal standard was investigated.…”