Environment: Microplastics in lakes, the role of forests

In fact, in this basin of the National Park of Casentino Forests, Mount Falterona and Campigna, the concentration of microplastics in samples taken at the surface and in the water column was 0.02-0.04 MP/m3, compared with an average value of 13 MP/m3 found in Lakes Bracciano and Trasimeno. The results of the study were presented at the Life Blue Lakes Project event: a monitoring campaign for microplastics in the Ridracoli Dam, among thousand-year-old forests in Capaccio di Santa Sofia (Forlì-Cesena).

“The choice fell on this reservoir, a crucial resource for the entire region, because of its strategic location within an area rich in biodiversity and drinking water” pointed out Patrizia Menegoni at the ENEA Biodiversity and Ecosystems Laboratory. “At the same time,” she added, "we were also prompted by the hypothesis that, given its high quality water index, the lake could be used as a fundamental reference point for scientific research, which has confirmed the role of the surrounding forest ecosystems in reducing the dispersion of microplastics, acting as a filter and protecting the quality of fresh water.

In all the samples taken, the densitỳ of MP/m3 is very low compared to the other lake mirrors studied, both at the surface and in the water column: the minimum value is 0, the maximum 2.08 (found at the surface). A total of 15 different types of polymers were found; among the most̀ frequent were polyethylene and polypropylene, materials widely used in various industries and for making everyday consumer products.

“The form of the microplastics need focused attention since, unlike the other lakes studied, no filaments or fibers usually carried by air were ever observed in the dam,” Menegoni explained. “Also in this case,” he said, "the most plausible hypothesis is a forest filter effect and, in particular, of certain trees, which can capture airborne microplastic fibers through their leaves. When leaves fall or are washed by rain, these trapped microplastics can be deposited in the soil, limiting their spread to other environmental compartments

A recent study, conducted in the Apennines by ENEA in collaboration with SIRF (Italian Society of Forest Restoration), found a significant presence of microplastics in the form of microfibers in the water of rain gauges collected from tree crowns. A further study just published by ENEA confirms the widespread nature of the phenomenon, showing the presence of large quantities of microplastics and microfibers deposited to the ground by the snow that fell on the summit of Mount Terminillo.

“These data suggest that forests may help to intercept microfibers in the air and then transfer and incorporate them into the soil, and strenghtens the need to further study the role of mountain and forest ecosystems in capturing pollutant particles in the atmosphere,” pointed out Bartolomeo Schirone at SIRF.

The activity was carried out as part of the European Life Blue Lakes project, led by ENEA and Legambiente, in which the first European protocol for the sampling and characterization of microplastics in freshwaters was developed, tested in several campaigns and subsequently shared through training courses with Arpae technicians and relevant local authorities. In parallel, a state-of-the-art laboratory has been set up at the ENEA Casaccia Research Center (Rome) that has the spectroscopic instruments and knowledge necessary for the isolation and analysis of microplastics, with the aim of assessing and quantifying the presence of microplastics in various environmental compartments. The Blue Lakes protocol aims to make a key contribution to the development and sharing of integrated methodologies for a functional Marine Protected Area (MPA) monitoring program for the management of freshwater quality protection.

 “In light of these results, we hope to initiate as soon as possible a specific project to study the role forests have in reducing the impact of weather-borne microplastics, with the goal of quantifying and describing in depth the important ecosystem service of capture and storage performed on lake habitats that are vital to human life, serving as sources of drinking water, recreation, fishing, irrigation and energy production,” Menegoni concluded.