Combined effects of salt and microplastics on evaporation and crystallization dynamics in porous media

This study investigates the combined effects of salinity and microplastic contamination on the evaporation process and salt crystallization in porous media through complementary column- and pore-scale experiments. Laboratory soil columns were packed with either pure sand or sand mixed with 5% (w/w) poly(vinyl chloride) (PVC) microplastics and subsequently saturated with freshwater or saline (NaCl) solution. Evaporation and crystallization dynamics were monitored by using mass loss measurements, surface optical and thermal imaging, and synchrotron X-ray tomography. Results show that salinity consistently suppressed evaporation by roughly 25–30%, whereas PVC microplastics enhanced it, generating substantial differences in cumulative water loss across treatments. Moreover, thermal imaging revealed distinct surface responses: NaCl samples developed salt crusts that progressively reduced local temperature contrasts and led to more spatially uniform surface conditions, whereas PVC-NaCl samples exhibited lower mean surface temperatures but substantially higher spatial variability, reflected in larger and more persistent temperature anomalies during drying. Pore-scale μCT imaging further confirmed that microplastics altered crystallization patterns by redistributing salt deposition over the upper part of the sand profile and modifying the nucleation behavior. Together, these findings underscore the complex interplay between microplastics and salinity, with implications for soil moisture regulation, surface energy flux, and environmental monitoring strategies.

DDC Class

660: Chemistry; Chemical Engineering

Funding(s)

Wie beinflusst trocknungsbedingtes Kristallsalz die Dynamik der Wasserverdunstung aus porösen Medien?

SFB 1313 - Teilprojekt C01: Multiskalige Untersuchung von Zwei-Phasen-Elektrolytflüssen in porösen Strukturen mit Veränderungen der Morphologie und steuerbarem Benetzungsverhalten

EXC 3120 - BlueMat - Wassergesteuerte Materialien

Open-Access-Publikationskosten / 2026-2027 / Technische Universität Hamburg (TUHH)

More Funding Information

We gratefully acknowledge the financial support provided by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under grant no. 497539130, and the partial funding from DFG SFB 1313 (project no. 327154368). Support by DFG as part of the Excellence Strategy of the Federal Government and the federal states-EXC 3120/1 BlueMat: Water-Driven Materials (project no. 533771286), is also acknowledged. Funding and resources provided by the Institute of Geo-Hydroinformatics at Hamburg University of Technology and the invaluable technical assistance of Theodor Wassiliou are greatly appreciated. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III. Data was collected using the P05 Imaging Beamline operated by Helmholtz-Zentrum Hereon. We would like to thank Jörg Hammel for assistance during the experiments. Beamtime was allocated for proposal I-20230847. Publishing fees supported by the Funding Programme Open Access Publishing of Hamburg University of Technology (TUHH) are acknowledged.

Lizenz

https://creativecommons.org/licenses/by/4.0/

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publishedVersion

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combined-effects-of-salt-and-microplastics-on-evaporation-and-crystallization-dynamics-in-porous-media.pdf

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Main Article

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9.07 MB

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Combined effects of salt and microplastics on evaporation and crystallization dynamics in porous media