Plastic pollution poses a grave threat to our planet's ecosystems, with abandoned fishing gear contributing significantly to this environmental crisis.
Approximately 85% of plastic pollution in marine environments originates from fishing gear disposal. Among these pollutants, nylon fishing nets and lines stand out for their longevity, with lifetimes stretching over hundreds of years.
To combat this issue, organizations strive to collect and recycle damaged or discarded fishing gear. However, an essential step in this process involves accurately identifying the type of polymer used in the gear, such as nylon, polypropylene, or polyethylene. This is particularly challenging for nylon, which can exist in various forms. Here, we will explore how Raman spectroscopy plays a pivotal role in identifying these polymers and tracking chemical changes during polymerization reactions, using epoxy as an example.
Microplastics are a growing concern in the field of environmental science due to their pervasiveness, and potential adverse effects on ecosystems and human health. We provide an overview of the nature, size, characteristics, and environmental dangers posed by microplastics. We discuss the various sources of microplastics, their persistence in the environment, and their potential ecological and human health impacts. Additionally, we explore the methods used for microplastic detection and characterization and emphasize the importance of continued research and global initiatives to mitigate the risks associated with these microscopic pollutants.
Microplastics are small plastic pieces less than 5 millimeters in length. These tiny plastic fragments, resulting from the breakdown of larger plastic items or from the direct release of micro-sized plastic products, have infiltrated terrestrial, freshwater, and marine environments, raising alarms among scientists, policymakers, and the public alike.
Nature of Microplastics
Microplastics encompass two primary categories: primary microplastics and secondary microplastics. Primary microplastics are intentionally manufactured small plastic particles found in personal care products (e.g., microbeads) and industrial abrasives. Secondary microplastics, on the other hand, result from the breakdown of larger plastic items due to weathering, UV radiation, and mechanical forces.
Size and Characteristics of Microplastics
Microplastics are typically categorized based on their size: nanoplastics (less than 1 μm), microplastics (1 μm to 5 mm), and mesoplastics (5 mm to 2.5 cm). They can take various shapes, including fragments, fibers, pellets, and microbeads. The composition of microplastics varies, with polyethylene (PE) and polypropylene (PP) being the most common polymers. Their small size and diverse shapes make microplastics challenging to detect and remove from the environment.
Sources of Microplastics
Microplastics originate from a multitude of sources, including:
- Plastic debris breakdown: Larger plastic items, such as bottles and packaging materials, undergo fragmentation over time, generating microplastics.
- Synthetic textiles: Washing synthetic clothing releases microfibers into wastewater, eventually entering aquatic systems.
- Microbeads: Personal care products, like exfoliating scrubs and toothpaste, contain microbeads that are washed down drains into water bodies.
- Tire wear: Vehicle tires shed microplastics in the form of rubber particles during usage.
Environmental Dangers
Microplastics pose several environmental dangers, including:
- Ingestion by marine life: Microplastics are often mistaken for prey by marine organisms, leading to bioaccumulation in the food chain.
- Habitat alteration: The presence of microplastics can alter the physical and chemical properties of sediments, affecting benthic ecosystems.
- Toxicity and pollutant transport: Microplastics can absorb and transport pollutants, potentially transferring harmful chemicals to organisms upon ingestion.
- Disruption of nutrient cycling: Microplastics can hinder nutrient cycling processes in aquatic systems.
The Challenge of Polymer Identification
Determining the precise type of polymers or nylon as in abandoned fishing gear, identified as a major issue, is a crucial part of the recycling process. Raman spectroscopy has proven to be an excellent technique for distinguishing between different polymer types, even within the same class, such as various nylon varieties. Raman spectra of nylon are unique enough that a high-resolution Raman microscope is not required for definitive identification. a benchtop Raman spectrometer coupled with a remote touch probe simplifies this identification process.
Current Technical Landscape
Traditional methods of polymer identification often involve time-consuming and complex laboratory procedures, making them less suitable for real-time, on-site analysis. Handheld Raman devices offer some portability but may lack the resolution and advanced data analysis software needed for intricate polymer discrimination.
Pros of existing technologies:
- High-resolution Raman spectroscopy can distinguish between various polymer types with unique spectral fingerprints.
- Handheld Raman devices offer portability for on-site measurements.
Cons of existing technologies:
- Traditional laboratory methods for polymer identification are time-consuming and complex.
- Handheld Raman devices may lack the required spectral resolution and advanced data analysis software for precise polymer discrimination.
New benchtop Raman spectroscopy instruments address these challenges by combining high-performance Raman spectroscopy with ease of use, making it a valuable tool for field measurements.
Solving the Identification Challenge
In a recent study, various monofilament gillnets and a polytwine gillnet were subjected to Raman spectroscopy analysis (MacroRAM benchtop Raman spectrometer, equipped with a BallProbe, Horiba Scientific). The technique offers rapid, alignment-free Raman characterization. Its use of near-infrared 785 nm laser excitation effectively suppresses fluorescence from pigmented fibers, making it an ideal choice for identifying polymer types in fishing gear. The results revealed that all monofilament samples were nylon 6, thanks to the distinctive spectral features of nylon 6 in their Raman spectra.
However, the green polytwine gillnet presented a more complex scenario. Analysis of its different strands revealed two types with varying Raman band intensities. Subtraction of the two spectra allowed for the identification of polyethylene and pigmosol green, demonstrating the capability to differentiate polymers even in complex mixtures.
Furthermore, the technique's versatility opens possibilities for real-time, on-site measurements during fishing gear collection. Its advanced data processing capabilities in LabSpec 6 spectroscopy suite software provide in-depth analysis, particularly valuable for samples with significant pigment contributions, ensuring the unambiguous determination of polymer types.
These results also hold promise for identifying microplastics in real-time, enabling rapid chemical identification during sorting and classification. The next step is deploying the system in the field, such as coastlines or boats, to identify microplastics at their source.
Conclusion
The benchtop Raman spectrometer, in combination with a remote touch probe, provides easy, accurate identification of polymer type from a variety of colored fishing nets. There is not only a clear distinction among different polymer classes but also within a single polymer class. Its ease of use, high-resolution capabilities, and advanced data processing software make it suitable for both laboratory and field applications. This technology not only assists in mitigating plastic pollution by accurately identifying polymer types in fishing gear but also holds the potential for the real-time identification of microplastics and monitoring chemical reactions in various industries.