engleski

DSC analysis of submillimeter microplastics from Adriatic sea

Microplastics (MP) is a widespread pollutant that originates from plastic debris accumulating in the environment. It mostly ends up in the ocean and other bodies of water. There it may become a vehicle for transport of various substances including toxic trace metals. By definition MP consists of particles that are less than 5 mm in length, [1] but a great part is of submillimeter dimensions. While larger MP particles can be easily analyzed by various common techniques, submillimeter ones are difficult to handle and separate, making even qualitative analysis challenging. MP constituents are mostly semicrystalline polymers[1] like polyethylene, (LDPE and HDPE), polypropylene, (PP), poly(ethylene terephthalate), (PET), polystyrene (PS), poly(vinyl chloride), (PVC) and polyamide (PA). Differential scanning calorimetry (DSC) is a fast and relatively simple method of thermal analysis routinely used for polymer identification. If melting and/or crystallization (transformation) temperatures and heats are known quantitative analysis is relatively simple. MP polymer transformation temperatures differ sufficiently so qualitative analysis is relatively straightforward even for mixed polymers. However, even for virgin polymers the heats are not a single value but a range[2] that can be further extended by a number of factors. In case of MP environmental degradation changes transformation heats to an unknown extent. The studied marine MP samples were collected in Stupica Mala bay at Žirje island. The goal of the presented study was to assess how much reliable information can be acquired on submillimeter fraction of MP (250 μm - 1 mm) by DSC. Larger MP particles collected in the same area and treated in the same manner were used as references along with virgin polymers. The peak temperatures in DSC thermograms revealed that the studied MP consists exclusively of polyolefines, (LDPE, HDPE and PP) and their blends. Since the measured samples contained MP particles of various composition some peak overlapping could not be avoided what made full quantification unreliable. Still, semiquantitative results were acceptable.

marine pollution ; microplastics ; differential scannig calorimetry

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