Diving into the Depths: Uncovering Microplastics in Norwegian Coastal Sediment Cores.

High concentrations of microplastics (MPs) have been documented in the deep-sea surface sediments of the Arctic Ocean. However, studies investigating their high-resolution vertical distribution in sediments from the European waters to the Arctic remain limited. This study examines MPs in five sediment cores from the Norwegian Coastal Current (NCC), encompassing the water-sediment interface and sediment layers up to 19 cm depth. Advanced analytical methods for MP identification down to 11 µm in size were combined with radiometric dating and lithology observations. MPs were present across all sediment cores, including layers predating the introduction of plastics, with concentrations exhibiting significant variation (54-12,491 MP kg-1). The smallest size class (11 µm) predominated in most sediment layers (34-100%). A total of 18 different polymer types were identified across all sediment layers, with polymer diversity and depth correlations varying widely between stations. Our findings suggest that differences in seafloor topography and the impact of anthropogenic activities (e.g., fishing) lead to varying environmental conditions at the sampling sites, influencing the vertical distribution of MPs. This challenges the reliability of using environmental parameters to predict MP accumulation zones and questions the use of MPs in sediment cores as indicators of the Anthropocene.

Spatial distribution of small microplastics in the Norwegian Coastal Current.

High concentrations of microplastic (MP) particles have been reported in the Arctic Ocean. However, studies on the high-resolution lateral and vertical transport of MPs from the European waters to the Arctic are still scarce. Here, we provide information about the concentrations and compositions of MPs in surface, subsurface, and deeper waters (< 1 m, ∼ 4 m, and 17-1679 m) collected at 18 stations on six transects along the Norwegian Coastal Current (NCC) using an improved Neuston Catamaran, the COntinuos MicroPlastic Automatic Sampling System (COMPASS), and in situ pumps, respectively. FTIR microscopy and spectroscopy were applied to measure MP concentration, polymer composition, and size distribution. Results indicate that the concentrations of small microplastics (SMPs, <300 µm) varied considerably (0-1240 MP m-3) within the water column, with significantly higher concentrations in the surface (189 MP m-3) and subsurface (38 MP m-3) waters compared to deeper waters (16 MP m-3). Furthermore, the average concentration of SMPs in surface water samples was four orders of magnitude higher than the abundance of large microplastics (LMPs, >300 µm), and overall, SMPs <50 µm account for >80 % of all detected MPs. However, no statistically significant geographical patterns were observed in SMP concentrations in surface/subsurface seawaters between the six sampling transects, suggesting a relatively homogeneous horizontal distribution of SMPs in the upper ocean within the NCC/Norwegian Atlantic Current (NwAC) interface. The Lagrangian particle dispersal simulation model further enabled us to assess the large-scale transport of MPs from the Northern European waters to the Arctic.

Unveiling high concentrations of small microplastics (11-500 µm) in surface water samples from the southern Weddell Sea off Antarctica.

Recent studies have highlighted the prevalence of microplastic (MP) pollution in the global marine environment and these pollutants have been found to contaminate even remote regions, including the Southern Ocean south of the polar front. Previous studies in this region have mostly focused on MPs larger than 300 µm, potentially underestimating the extent of MP pollution. This study is the first to investigate MPs in marine surface waters south of the polar front, with a focus on small MPs 500-11 µm in size. Seventeen surface water samples were collected in the southern Weddell Sea using an in-house-designed sampling system. The analysis of the entire sample using micro-Fourier transform infrared spectroscopy (µFTIR) with focal plane array (FPA) detection revealed the presence of MPs in all samples, with the vast majority of the MPs detected being smaller than 300 µm (98.3 %). The mean concentration reached 43.5 (± 83.8) MPs m-3, with a wide range from 0.5 to 267.2 MPs m-3. The samples with the highest concentrations differed from the other samples in that they were collected north of the continental slope and the Antarctic Slope Current. Sea ice conditions possibly also influenced these varying concentrations. This study reports high concentrations of MPs compared to other studies in the region. It emphasizes the need to analyze small MPs, down to a size of 11 µm or even smaller, in the Antarctic Treaty Area to gain a more comprehensive understanding of MP pollution and its potential ecological impacts.

At second glance: The importance of strict quality control - A case study on microplastic in the Southern Ocean key species Antarctic krill, Euphausia superba.

The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of microplastic (MP), by testing different sample volumes, extraction approaches, and applying hyperspectral imaging Fourier-transform infrared spectroscopy (µFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide.

Generation of macro- and microplastic databases by high-throughput FTIR analysis with microplate readers.

FTIR spectral identification is today's gold standard analytical procedure for plastic pollution material characterization. High-throughput FTIR techniques have been advanced for small microplastics (10-500 µm) but less so for large microplastics (500-5 mm) and macroplastics (> 5 mm). These larger plastics are typically analyzed using ATR, which is highly manual and can sometimes destroy particles of interest. Furthermore, spectral libraries are often inadequate due to the limited variety of reference materials and spectral collection modes, resulting from expensive spectral data collection. We advance a new high-throughput technique to remedy these problems using FTIR microplate readers for measuring large particles (> 500 µm). We created a new reference database of over 6000 spectra for transmission, ATR, and reflection spectral collection modes with over 600 plastic, organic, and mineral reference materials relevant to plastic pollution research. We also streamline future analysis in microplate readers by creating a new particle holder for transmission measurements using off-the-shelf parts and fabricating a nonplastic 96-well microplate for storing particles. We determined that particles should be presented to microplate readers as thin as possible due to thick particles causing poor-quality spectra and identifications. We validated the new database using Open Specy and demonstrated that additional transmission and reflection spectra reference data were needed in spectral libraries.

Common types of microdebris affect the physiology of reef-building corals.

Marine debris, particularly microdebris (< 1 mm) poses a potential threat to marine life, including reef-building corals. While previous research has mainly focused on the impact of single polymer microplastics, the effects of natural microdebris, composed of a mixture of materials, have not been explored. Therefore, this study aimed to assess the effects of different microdebris, originating from major sources of pollution, on reef-building corals. For this, we exposed two scleractinian coral species, Pocillopora verrucosa and Stylophora pistillata, known to frequently ingest microplastics, to four types of microdebris in an 8-week laboratory experiment: fragmented environmental plastic debris, artificial fibers from clothing, residues from the automobile sector consisting of tire wear, brake abrasion, and varnish flakes, a single polymer microplastic treatment consisting of polyethylene particles, and a microdebris-free control treatment. Specifically, we (I) compared the effects of the different microdebris on coral growth, necrosis, and photosynthesis, (II) investigated the difference between the microdebris mixtures and the exposure to the single polymer treatment, and (III) identified potential mechanisms causing species-specific effects by contrasting the feeding responses of the two coral species on microdebris and natural food. We show that the fibers and tire wear had the strongest effects on coral physiology, with P. verrucosa being more affected than S. pistillata. Both species showed increased volume growth in response to the microdebris treatments, accompanied by decreased calcification in P. verrucosa. Photosynthetic efficiency of the symbionts was enhanced in both species. The species-specific physiological responses might be attributed to feeding reactions, with P. verrucosa responding significantly more often to microdebris than S. pistillata. These findings highlight the effect of different microdebris on coral physiology and the need for future studies to use particle mixtures to better mimic naturally occurring microdebris and assess its effect on corals in more detail.

Journey to the deep: plastic pollution in the hadal of deep-sea trenches.

The global increase of plastic production, linked with an overall plastic misuse and waste mismanagement, leads to an inevitable increase of plastic debris that ends up in our oceans. One of the major sinks of this pollution is the deep-sea floor, which is hypothesized to accumulate in its deepest points, the hadal trenches. Little is known about the magnitude of pollution in these trenches, given the remoteness of these environments, numerous factors influencing the input and sinking behavior of plastic debris from shallower environments. This study represents to the best of our knowledge the largest survey of (macro)plastic debris sampled at hadal depths, down to 9600 m. Industrial packaging and material assignable to fishing activities were the most common debris items in the Kuril Kamchatka trench, most likely deriving from long-distance transport by the Kuroshio extension current (KE) or from regional marine traffic and fishing activities. The chemical analysis by (Attenuated Total Reflection Fourier transform infrared (ATR-FTIR) spectroscopy revealed that the main polymers detected were polyethylene (PE), polypropylene (PP) and nylon. Plastic waste is reaching the depths of the trench, although some of the items were only partially broken down. This finding suggests that complete breakdown into secondary microplastics (MP) may not always occur at the sea surface or though the water column. Due to increased brittleness, plastic debris may break apart upon reaching the hadal trench floor where plastic degrading factors were thought to be, coming off. The KKT's remote location and high sedimentation rates make it a potential site for high levels of plastic pollution, potentially making it one of the world's most heavily contaminated marine areas and an oceanic plastic deposition zone.

The influence of complex matrices on method performance in extracting and monitoring for microplastics.

Previous studies have evaluated method performance for quantifying and characterizing microplastics in clean water, but little is known about the efficacy of procedures used to extract microplastics from complex matrices. Here we provided 15 laboratories with samples representing four matrices (i.e., drinking water, fish tissue, sediment, and surface water) each spiked with a known number of microplastic particles spanning a variety of polymers, morphologies, colors, and sizes. Percent recovery (i.e., accuracy) in complex matrices was particle size dependent, with ∼60-70% recovery for particles >212 µm, but as little as 2% recovery for particles <20 µm. Extraction from sediment was most problematic, with recoveries reduced by at least one-third relative to drinking water. Though accuracy was low, the extraction procedures had no observed effect on precision or chemical identification using spectroscopy. Extraction procedures greatly increased sample processing times for all matrices with the extraction of sediment, tissue, and surface water taking approximately 16, 9, and 4 times longer than drinking water, respectively. Overall, our findings indicate that increasing accuracy and reducing sample processing times present the greatest opportunities for method improvement rather than particle identification and characterization.

Patterns of microparticles in blank samples: A study to inform best practices for microplastic analysis.

Quality assurance and quality control (QA/QC) techniques are critical to analytical chemistry, and thus the analysis of microplastics. Procedural blanks are a key component of QA/QC for quantifying and characterizing background contamination. Although procedural blanks are becoming increasingly common in microplastics research, how researchers acquire a blank and report and/or use blank contamination data varies. Here, we use the results of laboratory procedural blanks from a method evaluation study to inform QA/QC procedures for microplastics quantification and characterization. Suspected microplastic contamination in the procedural blanks, collected by 12 participating laboratories, had between 7 and 511 particles, with a mean of 80 particles per sample (±SD 134). The most common color and morphology reported were black fibers, and the most common size fraction reported was 20-212 µm. The lack of even smaller particles is likely due to limits of detection versus lack of contamination, as very few labs reported particles <20 µm. Participating labs used a range of QA/QC techniques, including air filtration, filtered water, and working in contained/'enclosed' environments. Our analyses showed that these procedures did not significantly affect blank contamination. To inform blank subtraction, several subtraction methods were tested. No clear pattern based on total recovery was observed. Despite our results, we recommend commonly accepted procedures such as thorough training and cleaning procedures, air filtration, filtered water (e.g., MilliQ, deionized or reverse osmosis), non-synthetic clothing policies and 'enclosed' air flow systems (e.g., clean cabinet). We also recommend blank subtracting by a combination of particle characteristics (color, morphology and size fraction), as it likely provides final microplastic particle characteristics that are most representative of the sample. Further work should be done to assess other QA/QC parameters, such as the use of other types of blanks (e.g., field blanks, matrix blanks) and limits of detection and quantification.

Finding the Balance between Research and Monitoring: When Are Methods Good Enough to Understand Plastic Pollution?

Plastic pollution is an international environmental problem. Desire to act is shared from the public to policymakers, yet motivation and approaches are diverging. Public attention is directed to reducing plastic consumption, cleaning local environments, and engaging in citizen science initiatives. Policymakers and regulators are working on prevention and mitigation measures, while international, regional, and national bodies are defining monitoring recommendations. Research activities are focused on validating approaches to address goals and comparing methods. Policy and regulation are eager to act on plastic pollution, often asking questions researchers cannot answer with available methods. The purpose of monitoring will define which method is implemented. A clear and open dialogue between all actors is essential to facilitate communication on what is feasible with current methods, further research, and development needs. For example, some methods can already be used for international monitoring, yet limitations including target plastic types and sizes, sampling strategy, available infrastructure and analytical capacity, and harmonization of generated data remain. Time and resources to advance scientific understanding must be balanced against the need to answer pressing policy issues.

Comparison of two rapid automated analysis tools for large FTIR microplastic datasets.

One of the biggest issues in microplastic (MP, plastic items <5 mm) research is the lack of standardisation and harmonisation in all fields, reaching from sampling methodology to sample purification, analytical methods and data analysis. This hampers comparability as well as reproducibility among studies. Concerning chemical analysis of MPs, Fourier-transform infrared (FTIR) spectroscocopy is one of the most powerful tools. Here, focal plane array (FPA) based micro-FTIR (µFTIR) imaging allows for rapid measurement and identification without manual preselection of putative MP and therefore enables large sample throughputs with high spatial resolution. The resulting huge datasets necessitate automated algorithms for data analysis in a reasonable time frame. Although solutions are available, little is known about the comparability or the level of reliability of their output. For the first time, within our study, we compare two well-established and frequently applied data analysis algorithms in regard to results in abundance, polymer composition and size distributions of MP (11-500 µm) derived from selected environmental water samples: (a) the siMPle analysis tool (systematic identification of MicroPlastics in the environment) in combination with MPAPP (MicroPlastic Automated Particle/fibre analysis Pipeline) and (b) the BPF (Bayreuth Particle Finder). The results of our comparison show an overall good accordance but also indicate discrepancies concerning certain polymer types/clusters as well as the smallest MP size classes. Our study further demonstrates that a detailed comparison of MP algorithms is an essential prerequisite for a better comparability of MP data.

What determines accuracy of chemical identification when using microspectroscopy for the analysis of microplastics?

Fourier transform infrared (FTIR) and Raman microspectroscopy are methods applied in microplastics research to determine the chemical identity of microplastics. These techniques enable quantification of microplastic particles across various matrices. Previous work has highlighted the benefits and limitations of each method and found these to be complimentary. Within this work, metadata collected within an interlaboratory method validation study was used to determine which variables most influenced successful chemical identification of un-weathered microplastics in simulated drinking water samples using FTIR and Raman microspectroscopy. No variables tested had a strong correlation with the accuracy of chemical identification (r = ≤0.63). The variables most correlated with accuracy differed between the two methods, and include both physical characteristics of particles (color, morphology, size, polymer type), and instrumental parameters (spectral collection mode, spectral range). Based on these results, we provide technical recommendations to improve capabilities of both methods for measuring microplastics in drinking water and highlight priorities for further research. For FTIR microspectroscopy, recommendations include considering the type of particle in question to inform sample presentation and spectral collection mode for sample analysis. Instrumental parameters should be adjusted for certain particle types when using Raman microspectroscopy. For both instruments, the study highlighted the need for harmonization of spectral reference libraries among research groups, including the use of libraries containing reference materials of both weathered plastic and natural materials that are commonly found in environmental samples.

Quantitative assessment of visual microscopy as a tool for microplastic research: Recommendations for improving methods and reporting.

Microscopy is often the first step in microplastic analysis and is generally followed by spectroscopy to confirm material type. The value of microscopy lies in its ability to provide count, size, color, and morphological information to inform toxicity and source apportionment. To assess the accuracy and precision of microscopy, we conducted a method evaluation study. Twenty-two laboratories from six countries were provided three blind spiked clean water samples and asked to follow a standard operating procedure. The samples contained a known number of microplastics with different morphologies (fiber, fragment, sphere), colors (clear, white, green, blue, red, and orange), polymer types (PE, PS, PVC, and PET), and sizes (ranging from roughly 3-2000 µm), and natural materials (natural hair, fibers, and shells; 100-7000 µm) that could be mistaken for microplastics (i.e., false positives). Particle recovery was poor for the smallest size fraction (3-20 µm). Average recovery (±StDev) for all reported particles >50 µm was 94.5 ± 56.3%. After quality checks, recovery for >50 µm spiked particles was 51.3 ± 21.7%. Recovery varied based on morphology and color, with poorest recovery for fibers and the largest deviations for clear and white particles. Experience mattered; less experienced laboratories tended to report higher concentration and had a higher variance among replicates. Participants identified opportunity for increased accuracy and precision through training, improved color and morphology keys, and method alterations relevant to size fractionation. The resulting data informs future work, constraining and highlighting the value of microscopy for microplastics.

No evidence of microplastic ingestion in emperor penguin chicks (Aptenodytes forsteri) from the Atka Bay colony (Dronning Maud Land, Antarctica).

Microplastic (<5 mm; MP) pollution has been an emerging threat for marine ecosystems around the globe with increasing evidence that even the world's most remote areas, including Antarctica, are no longer unaffected. Few studies however, have examined MP in Antarctic biota, and especially those from Antarctic regions with low human activity, meaning little is known about the extent to which biota are affected. The aim of this study was to investigate, for the first time, the occurrence of MP in the emperor penguin (Aptenodytes forsteri), the only penguin species breeding around Antarctica during the austral winter, and an endemic apex predator in the Southern Ocean. To assess MP ingestion, the gizzards of 41 emperor penguin chicks from Atka Bay colony (Dronning Maud Land, Antarctica), were dissected and analyzed for MP >500 µm using Attenuated Total Reflection Fourier-transform Infrared (ATR-FTIR) spectroscopy. A total of 85 putative particles, mostly in the shape of fibers (65.9 %), were sorted. However, none of the particles were identified as MP applying state-of-the-art methodology. Sorted fibers were further evidenced to originate from contamination during sample processing and analyses. We find that MP concentrations in the local food web of the Weddell Sea and Dronning Maud Land coastal and marginal sea-ice regions; the feeding grounds to chick-rearing emperor penguin adults, are currently at such low levels that no detectable biomagnification is occurring via trophic transfer. Being in contrast to MP studies on other Antarctic and sub-Antarctic penguin species, our comparative discussion including these studies, highlights the importance for standardized procedures for sampling, sample processing and analyses to obtain comparable results. We further discuss other stomach contents and their potential role for MP detection, as well as providing a baseline for the long-term monitoring of MP in apex predator species from this region.

Human footprints at hadal depths: interlayer and intralayer comparison of sediment cores from the Kuril Kamchatka trench.

Microplastic (MP) pollution affects almost all ecosystems on Earth. Given the increasing plastic production worldwide and the durability of these polymers, concerns arise about the fate of this material in the environment. A candidate to consider as a depositional final sink of MP is the sea floor and its deepest representatives, hadal trenches, as ultimate sinks. In this study, 13 sediment samples were collected with a multiple-corer at depths between 5740 and 9450 m from the Kuril Kamchatka trench (KKT), in the Northwest (NW) Pacific Ocean. These samples were analysed for MP presence in the upper sediment layer, by slicing the first 5 cm of sediment cores into 1 cm horizontal layers. These were compared against each other and between the sampling areas, in order to achieve a detailed picture of the depositional system of the trench and small-scale perturbations such as bioturbation. The analyses revealed the presence of 215 to 1596 MP particles per kg -1 sediment (dry weight), with a polymer composition represented by 14 polymer types and the prevalence of particles smaller than 25 µm. A heterogeneous microplastic distribution through the sediment column and different microplastic concentration and polymer types among sampling stations located in different areas of the trench reflects the dynamics of this environment and the numerous forces that drive the deposition processes and the in situ recast of this pollutant at the trench floor.

Microplastics in two German wastewater treatment plants: Year-long effluent analysis with FTIR and Py-GC/MS.

Microplastics (MP) have been recorded in various environments around the globe. For a better understanding of distribution patterns and for providing a basis for risk assessments, detailed data on MP concentrations and polymer compositions are required. This study investigated the effluents of two German wastewater treatment plants (WWTP) monthly over one year, in order to better understand their temporal input of MP into the receiving river systems. MP item data down to 11 µm were obtained by means of Fourier Transform Infrared (FTIR) spectroscopy under the application of an improved polymer database. Complementary mass data were obtained by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) (for one WWTP). Both FTIR and Py-GC/MS analysis revealed a homogeneous polymer composition over the year, with a general dominance of polyolefins. Elevated MP item and mass concentrations (maximum: 3 × 104 items m-3 and 3.8 × 103 µg m-3) were observed during winter months and were accompanied by either heavy rainfall (increased discharge and total organic carbon) or elevated turbidity values. These observations emphasize the need for the assessment of background parameters in future MP monitoring studies. By providing monthly data over one year on MP items and masses in WWTP effluents, this study helps enhancing the understanding of temporal MP dynamics and can act as a valuable reference point for future assessments.

Microplastics in the Weddell Sea (Antarctica): A Forensic Approach for Discrimination between Environmental and Vessel-Induced Microplastics.

Microplastic (MP) pollution has been found in the Southern Ocean surrounding Antarctica, but many local regions within this vast area remain uninvestigated. The remote Weddell Sea contributes to the global thermohaline circulation, and one of the two Antarctic gyres is located in that region. In the present study, we evaluate MP (>300 µm) concentration and composition in surface (n = 34) and subsurface water samples (n = 79, ∼11.2 m depth) of the Weddell Sea. All putative MP were analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. MP was found in 65% of surface and 11.4% of subsurface samples, with mean (±standard deviation (SD)) concentrations of 0.01 (±0.01 SD) MP m-3 and 0.04 (±0.1 SD) MP m-3, respectively, being within the range of previously reported values for regions south of the Polar Front. Additionally, we aimed to determine whether identified paint fragments (n = 394) derive from the research vessel. Environmentally sampled fragments (n = 101) with similar ATR-FTIR spectra to reference paints from the research vessel and fresh paint references generated in the laboratory were further subjected to micro-X-ray fluorescence spectroscopy (µXRF) to compare their elemental composition. This revealed that 45.5% of all recovered MP derived from vessel-induced contamination. However, 11% of the measured fragments could be distinguished from the reference paints via their elemental composition. This study demonstrates that differentiation based purely on visual characteristics and FTIR spectroscopy might not be sufficient for accurately determining sample contamination sources.

Characterizing the multidimensionality of microplastics across environmental compartments.

Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of >60,000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR-imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks.

Microplastic pollution in the Weser estuary and the German North Sea.

Microplastics (MP) are defined as synthetic organic pollutants sized <5 mm and have been recorded in various environments worldwide. Due to their small size, they pose a potential risk for many organisms throughout the food web. However, little is known about MP distribution patterns and associated transport mechanisms. Rivers may act as pathways for MP into marine environments. In this study, we investigate the occurrence of MP in the estuary and lower stretch of the second-largest German River, the Weser, representative of a significant interface between fresh water and marine environments. The aim of the study was to enhance the general understanding by providing novel, comprehensive data and suggestions for future studies on estuarine systems. Surface water samples of two different size classes were collected by ship using an on-board filtration system (11-500 µm fraction) and net sampling (500-5000 µm fraction). After a thorough sample preparation, all samples were analysed with Focal Plane Array (FPA) Fourier Transform Infrared (FTIR) spectroscopy and Attenuated Total Reflection (ATR) FTIR spectroscopy in order to obtain information on MP concentrations, polymer composition and size distribution. Our findings show highest concentrations in the 11-500 µm fraction (2.3 × 101 - 9.7 × 103 MP m-3), with the polymer cluster acrylates/polyurethanes(PUR)/varnish being dominant. The >500 µm fraction was dominated by polyethylene. Estimated MP concentrations generally increased in the Turbidity Maximum Zone (TMZ) and decreased towards the open sea. This study contributes to the current research by providing novel insights into the MP pollution of the estuary and lower stretch of an important European river and provides implications for future MP monitoring measures.