Abstract
Plastic pollution in the marine environment has turned into an important research topic in recent decades. Until recently, studies were often based on visual assessment only, which is not enough to draw any conclusion about the chemical nature of found plastic items and could lead to incorrect results. Standardized, fast, and efficient low-cost methods for marine plastic litter identification are urgently needed to monitor the occurrence and distribution worldwide. In this paper, we demonstrate that a miniaturized handheld near-infrared spectrometer—MicroNIR—can be used for on-site identification of different plastic polymers. A database containing polymer spectra of the most produced and reported polymer types in the marine environment was created including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), polycarbonate (PC), polyurethane (PUR), and Silicone. Using spectral match value (SMV, included in the instrument software) for spectra analysis resulted in an accurate classification of all nine polymer types. The method was used for the identification of marine macro-, meso-, and microplastic litter collected on beaches in sediments and seawater and enabled the correct identification of marine plastic litter for macro-, meso- (96%), and microplastics (73%) with exception of totally black items and items less than 1 mm in size. The method and instrumentation presented here are very well suited to support “Citizen Science” marine litter monitoring projects during beach cleaning and similar activities.
Highlights
Contamination of the World Oceans by synthetic non-biodegradable litter has become a high-profile environmental concern
We describe our experience in the application of a simple method to detect polymer type down to the micro range (1 mm) using a portable NIR spectrometer MicroNIR that is expected to be a major step towards large-scale monitoring of marine plastic litter
One spectral library based on industrial reference materials and the other on household plastic with known polymer composition according to Resin identification codes (RIC)
Summary
Contamination of the World Oceans by synthetic non-biodegradable litter has become a high-profile environmental concern. All commercial plastic products have triangular symbols indicating the type of material (plastic polymer) from which the product is made (Table 1) This is helpful for the identification of large marine litter items without any special equipment. Results of beach cleaning programs showed that more than 20% of found items are of unknown origin of polymer type, especially smaller fragments (meso- and microplastics), because they do not have RICs and only visual identification was performed. A number of hand-held near-infrared spectrometers were developed [14,15,16] that could be a good alternative to very expensive, large, and complicated techniques, i.e., FTIR Some of these instruments have already been applied to polymer identification in line with the complex methods of classes classification. Nylon fabric (PA); eyeglasses lenses, roofing sheets (PC); medical implants, surgical devices, membranes, protective coatings, etc
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