On April 24, Sara Martínez Pérez defended her doctoral thesis, “Environmental fate and risks of microplastics in soil and freshwater ecosystems”, a study that takes an in-depth look at microplastic pollution and how these particles behave and affect ecosystems when analyzed under realistic conditions, considering different sizes, shapes, and polymer types.

The main objective of the thesis was to study the environmental fate of microplastics and their effects on organisms in freshwater and terrestrial ecosystems. To this end, experiments were carried out in both water and soil. The mobility of microplastics through runoff and soil infiltration was analyzed, as well as their ingestion and toxicity in different species of aquatic and terrestrial invertebrates.

The results indicate that in lentic freshwater ecosystems (such as lakes, lagoons, ponds, wetlands, and reservoirs), microplastics tend to sink and accumulate in sediments, whereas in soils they mainly accumulate on the surface. Their mobility in soils is limited, reducing the risk of groundwater contamination. Toxicity tests show that environmentally realistic mixtures of microplastics can cause long-term negative effects, especially on the reproduction of aquatic invertebrates, while the risk to terrestrial invertebrates is lower at the concentrations commonly detected in soils.

This work highlights the importance of using environmentally representative mixtures to improve environmental risk assessment and to advance strategies aimed at reducing soil contamination and the transport of microplastics to surface waters.

The thesis was carried out within the µNanoCare project (RTC2019-007261-5, funded by MICIU/AEI /10.13039/501100011033) and as part of the PhD Programme in Hydrology and Water Resources Management at the University of Alcalá. It was supervised by Andreu Rico Artero, researcher at the University of Valencia affiliated to Aquatic ecology and biotechnology group at IMDEA Agua , and María de las Virtudes Martínez Hernández, researcher in the Soil and Water Quality in the Environment group at IMDEA Agua.