“A Sail for the Blue: Research for Oceans and Microplastics”: results of Unipd study on microplastics sampling and analysis methodologies published
The results of the research project “A sail for the Blue”, which saw the Environmental Health Engineering group of the University of Padua engaged for two months in a sailboat crossing of the Atlantic Ocean from Cape Canaveral (Florida) to Gibraltar carrying out plastic sampling activities to monitor its dispersion in ocean waters, were recently published in STOTEN – Science of Total Environment, a leading journal in the field.
The project, included among the initiatives for the celebration of the University of Padua’s Ottocentenary and carried out with the financial support of the National Center for Biodiversity and AcegasApsAmga S.p.A., delved into the issue of dispersion of micro- and nanoplastics: due to the absence of a specific analytical standard to refer to, the quantities detected by different sampling methods can be significantly influenced by distorting the results of plastics analysis.
The study therefore compared two different sampling methods: the Manta net, a drag-and-drop method in which water passes through a net with a mesh size of 300 µm, and instantaneous sampling, by sampling a given volume of water collected inside a glass container.
The first method allows large volumes of water to be sampled, but is size-selective, in that only microplastics larger than the mesh size of the net can be sampled and analyzed, and carries the risk of underestimating the actual presence of plastic particles in water. The second method, on the contrary, is volume-selective, whereby a volume of water equal to the maximum capacity of the container can be sampled and analyzed. In the latter case, it is therefore possible to analyze microplastics of all sizes, but with the significant risk of poor sample representativeness. The collected samples were then processed in the laboratory using the innovative tape-lifting technique, borrowed from forensic science, which makes it possible to limit contamination by environmental microplastics found in the air or on work surfaces.
The results obtained from the study show a microplastic concentration more than four orders of magnitude higher by adopting the instantaneous sampling technique than the Manta net approach (average values of 0.24 and 4050 fragments/m3, respectively). With instantaneous sampling, samples characterized by a great variability of polymers (PVC, polyacrylonitrile, styrene, butadiene, nylon, etc.) were collected, while in the samples taken with the Manta net, mainly three categories of plastics (cellulose acetate, polycarbonate, and polyester) were highlighted, due to their greater disintegration in the marine environment.
Thus, the analysis of the data obtained allows us to conclude that the optimal sampling method depends on the objectives from time to time, and may sometimes require a combination of two methods. The “A Sail for the Blue” study thus paves the way for standardizing new methods of monitoring plastics for their reliable quantification and realistic estimation of their impacts on aquatic ecosystems.