Raman Spectroscopy Uncovers Microplastics in Pristine Alpine Lake Water

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A recent study published in the Journal of Raman Spectroscopy uncovered the presence of microplastics (MPs) in one of Greece’s most remote freshwater ecosystems: Dragon Lake (1). Located on Mt. Tymfi, Dragon Lake is an alpine lake located Led by Christos Salmas and Maria Perraki from the Agricultural University of Athens and the National Technical University of Athens, the research provides compelling evidence that even pristine high-altitude environments are not immune to microplastic pollution.

Dragon Lake, situated in a protected mountainous region with minimal permanent human activity, has long been considered a near-pristine system (1,2). In the study, the research team collected and analyzed surface water samples after the peak tourism season to assess potential anthropogenic impacts. In total, approximately 4,770 ± 637 liters of surface water were examined using a combination of optical microscopy and Raman microspectroscopy (1).

To capture microplastics from such large water volumes, the team employed volume-reduced sampling by filtering lake water through a plankton net. Next, the samples underwent oxidative digestion using Fenton reagent to remove organic matter before stereoscopic examination and spectroscopic analysis. This approach enabled the researchers to identify 100 microplastic particles larger than 150 μm, corresponding to a concentration of 0.021 MPs per liter (1).

What were the findings of the study?

The researchers discovered that fibers dominated the microplastic population, accounting for 66% of detected particles, while fragments made up the remaining 34% (1). The fibers were overwhelmingly blue in color (95%) and typically longer than 1,000 μm, whereas fragments were mostly transparent (73%) and smaller than 500 μm (1). These physical characteristics provided initial clues about possible sources and environmental behavior.

Raman microspectroscopy was applied in a nondestructive manner to a random subset of 70 particles directly on the filters. Of these, 83% were Raman active, allowing for polymer identification (1). The analysis revealed polyethylene (PE) fragments, polyethylene terephthalate (PET) fibers, and polyamide (nylon) fibers, which are materials commonly associated with packaging, textiles, and outdoor gear (1,3).

The study also highlights significant analytical challenges inherent in environmental microplastic research. Strong fluorescence, pigment interference, and UV-induced weathering often obscured polymer-specific Raman peaks, making identification complex and time-consuming (1). These difficulties underscored the importance of careful sample pretreatment prior to spectroscopic analysis.

By demonstrating an effective methodology for microplastic extraction and identification in remote alpine settings, this research expands the growing body of evidence that microplastic pollution is pervasive and that Raman microspectroscopy can be used for environmental monitoring applications (1).

References

1. Salmas, C.; Alexopoulos, K.; Papanikolaou, I.; et al. Microplastics Identification in Remote Aquatic Environments Using Raman Spectroscopy: A Case Study for Mt. Tymfi's Alpine Lake. J. Raman Spectrosc. 2025, 56 (11), 1315–1328. DOI: 10.1002/jrs.70007
2. The Sandy Feet, A Complete Hiking Guide to the Incredible Drakolimni. The Sandy Feet. Available at: https://thesandyfeet.com/drakolimni-dragon-lake-hike-zagori-greece/ (accessed 2025-12-16).
3. Wetzel, W. FT-IR Spectroscopy Links Tourism Intensity to Microplastic Pollution in Island Waters. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/ft-ir-spectroscopy-links-tourism-intensity-to-microplastic-pollution-in-island-waters (accessed 2025-12-16).