Identifying microplastics found on beaches in marine environments is crucial for detecting the source of the pollution. A recent study in Sensors discusses applying laser-induced breakdown spectroscopy technology to identify marine plastics. The plastic pellets can be accurately classified with more than 80% accuracy owing to the application of chemometric analytical instruments.
The laser-induced breakdown spectroscopy spectra and statistical tests swiftly identify polymers, particularly for differentiating PE from PP and C-O from C-C backbone pellets. The PCA analysis confirmed a relationship between color and appearance.
Microplastics as a Global Concern
More than 150 million tons of plastic are entering the oceans globally, of which roughly 250,000 tons are broken down into 5 trillion floating fragments. The United Nations Environment Programme (UNEP) estimates that the economic harm to the fish market and tourism is around 13 million USD annually.
The Mediterranean has more than 62 million floating objects covering its entire surface area, which means it has one of the highest densities of plastic pollution. This enormous volume of plastic has many different sources; 80% originates from land, and the remaining 20% comes from ships.
Marine microplastics are introduced directly or result from the photooxidation and fragmentation of macroplastics. Resin pellets compose a significant portion of the microplastics. Granules of various polymeric types called pellets are utilized to create macroplastic items through melting, extrusion, and molding.
Harmful Effects of Plastic Pollution
Plastic infiltrates the food chain by deliberate or involuntary consumption, potentially harming organisms both mechanically and physically as a result of their accumulation and chemically by transferring dangerous compounds into the stomachs of animals.
Resin pellets are easily disseminated in the environment. They are currently found in many regions, including polar zones, as there are still no solid restrictions for adopting steps to avoid the potential loss of these plastics during their storage, transport, and processing. Such pellets have a strong capacity to absorb metals and persistent organic pollutants (POP).
Importance of Individuating the Origin of Plastic Pollution
Plastic pellets have been employed as non-living passive samplers for coastal environmental media over the years due to their capacity to absorb and concentrate pollutants from marine environments and prevent the time-consuming and expensive production of samples of coastal environmental media.
It is crucial to produce techniques for quick in-situ identification of the elements that make up plastic pellets to pinpoint the source of plastic pollution. Recent research has demonstrated how plastic pellets function as an accumulator matrix and a transport for metals in marine systems.
Current Techniques for Microplastic Analysis and their Limitations
FTIR and Raman spectroscopy are typical methods for the characterization of microplastics. These complimentary vibrational techniques are frequently used to analyze plastic waste removed from sediments, water, and living things. A stereoscopic microscope is used for manual visual sorting before most FTIR and Raman studies.
These methods, however, are relatively slow and sensitive to the surface composition of the pellets, despite being generally accurate in determining the content of the pellets. The pellets must be well dried because the FTIR spectra interact with water and the Raman spectra technique reveals high fluorescence caused by micro-biological, organic, and inorganic substances on the plastic surface. The cost of the expensive experimental equipment needed for analysis is a disadvantage of these systems.
Investigation of Laser-Induced Breakdown Spectroscopy (LIBS) Technique for Monitoring Marine Plastic Pollution
The laser-induced breakdown spectroscopy technique was investigated as a potential new quick strategy to monitor marine habitats by Giugliano et al. The benefits of laser-induced breakdown spectroscopy over the aforementioned approaches include speed, usability, and cheap experimental instrument.
The laser-induced breakdown spectroscopy method can also analyze the composition on the sample surface, guaranteeing a complete characterization of the pellets.
The viability of an in-situ laser-induced breakdown spectroscopy analysis of preproduction microplastic pellets obtained from a marine environment has been successfully evaluated in this research.
The main benefit of the technique is the ability to perform a very quick analysis on untreated samples providing the same measurement of the pellet material and the concentration of the metals accumulated on the pellet's surface.
The cost of a portable laser-induced breakdown spectroscopy instrument is comparable to that of a portable FTIR or a portable Raman instrument.
Rapid identification of polymers can be done using laser-induced breakdown spectroscopy spectra and statistical testing, particularly in separating C-O from C-C backbone pellets and PE from PP ones.
Preliminary research on the prospect of locating and measuring the metals deposited on the surfaces of beached pellets has produced positive results.
Giugliano, R., Cocciaro, B., Poggialini, F., Legnaioli, S., Palleschi, V., Locritani, M., & Merlino, S. (2022) Rapid Identification of Beached Marine Plastics Pellets Using Laser-Induced Breakdown Spectroscopy: A Promising Tool for the Quantification of Coastal Pollution. Sensors, 22(18), 6910. https://www.mdpi.com/1424-8220/22/18/6910/htm