Subterranean transport of microplastics as evidenced in karst springs and their characterization using Raman spectroscopy

Ion Nesterovschi; Ioana Marica; Erika Andrea Levei; Simion Bogdan Angyus; Marius Kenesz; Oana Teodora Moldovan; Simona Cîntă Pînzaru

doi:10.1016/j.saa.2023.122811

Subterranean transport of microplastics as evidenced in karst springs and their characterization using Raman spectroscopy

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Oct 5:298:122811. doi: 10.1016/j.saa.2023.122811. Epub 2023 May 2.

Authors

Ion Nesterovschi¹, Ioana Marica¹, Erika Andrea Levei², Simion Bogdan Angyus³, Marius Kenesz⁴, Oana Teodora Moldovan⁴, Simona Cîntă Pînzaru⁵

Affiliations

¹ Babeș-Bolyai University, Physics Faculty, 1 Kogălniceanu, 400084 Cluj-Napoca, Romania.
² INCDO INOE 2000, Research Institute for Analytical instrumentation, 67 Donath, 400293 Cluj-Napoca, Romania.
³ INCDO INOE 2000, Research Institute for Analytical instrumentation, 67 Donath, 400293 Cluj-Napoca, Romania; Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos, 400028 Cluj-Napoca, Romania.
⁴ Emil Racovita Institute of Speleology, Cluj-Napoca Department, 5 Clinicilor, 400006 Cluj-Napoca, Romania; Romanian Institute of Science and Technology, Saturn 24-26, 400504 Cluj-Napoca, Romania.
⁵ Babeș-Bolyai University, Physics Faculty, 1 Kogălniceanu, 400084 Cluj-Napoca, Romania. Electronic address: simona.pinzaru@ubbcluj.ro.

PMID: 37156178
DOI: 10.1016/j.saa.2023.122811

Abstract

The increasing use of plastic materials has led to accumulation of large amounts of plastic waste in environment and a global challenge to be tackled with. The natural process of macro-plastics aging generates a multitude of secondary microplastic fragments accumulating in all areas of the planet. The pollution with microplastics of large water bodies, such as rivers, seas and oceans was already proven, but the presence of microplastics even in karst spring water was not reported yet. In this study, Raman micro-spectroscopy was used to confirm the presence of microplastics in the spring water samples collected from two rural karst springs in the Apuseni Mountains (Țarina and Josani), North-Western Romania. Two sets of water samples of 1000 L collected in spring time 2021 and one in autumn 2021 were filtered and analyzed. Using the Python programming language and combining two separate Raman databases, one for plastics and the other for pigments, we established a customized database to unambiguously identify the type of plastic and pigment present in the discovered micro-fragments. The generated reference pigment-plastic spectra were compared to those of potential microplastics found on filters and Pearson's coefficient was used to measure the level of similarity. The presence of microplastics in karst spring waters was confirmed and a quantitative estimation expressed as number of fragments or fibers per liter was 0.034 in Josani and 0.06 in Țarina karst spring. Five months later sampling (autumn 2021) revealed 0.05 microplastics per liter. The spectral results revealed that most microplastics found were dominated by polyethylene terephthalate (PET), followed by polypropylene and interestingly, abundant blue micro-fragments were identified according to their copper phthalocyanine pigments (pigment Blue 15) or indigo carmine (pigment Blue 63) characteristic spectral fingerprints, which surpassed the inherent spectral background level characteristic for the Raman spectra of naturally contaminated waste micro-samples. Their origin in mountain karst spring waters and potential decrease in time is discussed.

Keywords: Karst spring water; Microplastics; Raman Spectroscopy; Rural areas.