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MARINFORSK-Marine ressurser og miljø

Analysis techniques for quantifying nano-and microplastic particles and their degradation in the marine environment

Alternative title: Analysemetoder for kvantifisering av nano- og mikroplastpartikler og deres nedbrytning i marint miljø

Awarded: NOK 1.6 mill.

ANDROMEDA aims to develop an instrument platform for advanced characterization of nanoplastic (NP; <1 µm) and small MP (sMP; 1-10 µm). The project will focus on the development and optimisation of advanced techniques to measure and quantify sMP and other challenging types of MP particles (e.g. microfibres, tyre wear particles and paint flakes). This will include characterisation of the partially degraded sMP/NP generated in studies investigating the degradation and fragmentation mechanisms of plastic into MP and NP. We will also study the release of plastic-associated chemicals during fragmentation and degradation processes. ANDROMEDA is attempting to produce and study partially degraded and irregular-shaped sMP and NP representing those typically found in the environment. The main work conducted so far in the project has focused on methods for producing these sMP and NP reference materials. A range of 'pristine' bulk polymer materials (including polyethylene, polypropylene, polystyrene and polyethylene terephthalate) with varying degrees of additive chemicals have been sourced and cryomilled by CARAT GmbH, who have supplied a fraction comprising particles <100 µm. Characterisation work has indicated the cryomilling process is unable to produce significant quantities of particles in the sizes of interest to ANDROMEDA (<10 µm). We are currently investigating alternative methods to produce the reference materials we need. To isolate the particle size fractions of interest for the different studies planned in REVEAL (MP, 10-100 µm; sMP, 1-10 µm; NP <1 µm), we have used commercially available reference plastic particles to develop a fractionation procedure based on a combination of stirred cell filtration using a series of different pore-sized filters and centrifugal filtration (NPs; <1 µm). The methodology is currently being validated and is almost ready for use when required in the project. Advanced methods for MP identification and quantification need further development to push their limits of detection for smaller sizes of MP (sMP) and nanoplastics (NP) and to improve their ability to analyse MP types that are currently difficult to analyse by microspectroscopy. Within ANDROMEDA, we have begun establishing a hyphenated identification and mass-based quantification methods for individual polymer types using filed flow fractionation (FFF) and pyrolysis GC-MS. This work is completed for polyethylene and polystyrene and will be extended in the next period to include the other polymer types (PET, PP, PVC). The project has undertaken a collaborative study with the instrument producer Agilent to investigate improved analysis and quantification of microplastic fibres, which are a challenging form of MP as conventional techniques such as µFTIR can identify a single fibre as multiple particles. We have purchased and modified CaF2 slides and tested whether these can be used in µFTIR analysis to ensure all parts of the fibres remain in a single focal plane. The slides offered limited improvement, but testing with an LDIR instrument indicate significant improvement over the conventional µFTIR approach and appears a good alternative. To study plastic degradation mechanisms over a reasonable time frame, laboratory-based accelerated degradation methods are required that mimic natural fragmentation and additive chemical leaching. ANDROMEDA has developed and published a method for controlled accelerated hydrolytic degradation of selected polymers. The degree of degradation can be controlled easily with full degradation achieved within 3 hours using the conditions employed. In the next period of the project we will investigate the use of accelerated simulated sunlight to facilitate rapid UV degradation and fragmentation of the bulk materials. Preliminary studies indicate this is a highly promising approach and we will now focus on optimising the process. Comprehensive degradation studies will be conducted to study the mechanism of UV degradation in detail, as well as to investigate the influence of parameters such as temperature and pH, where attention will be given to additive chemical and degradation product leaching. Partners specialised in dissemination, communication and data management are ensuring strong stakeholder involvement and efficient outreach of the project results. A project webpage has been created (https://www.andromedaproject.net/) and regular posts are being made on social media. ANDROMEDA is currently engaged with the EU MSFD technical group on marine litter (TGML) and contributing directly to the development of a 'White Paper' on microplastic.

Current methods for microplastic (MP) analysis can be divided into low-cost versus more advanced methods. ANDROMEDA recognizes that further development and validation is needed for both approaches. Low-cost methods are needed that can identify a broad range of MP polymers with acceptable accuracy. Advanced methods need further development in order to push the limit of detectability for smaller sizes of MP and nanoplastics (NP) and improve their ability to analyze MP types that are currently difficult to analyze by microspectroscopy. Moreover, to study plastic degradation mechanisms over a reasonable time frame, lab-based accelerated degradation approaches are required that mimic natural fragmentation and additive chemical leaching. Within ANDROMEDA, in situ MP detection, efficient sampling and cost-effective laboratory methods will be developed and optimized to analyze MP. Approaches will be based on hyperspectral imaging, chemical markers and fluorometric detection techniques. Advanced analysis techniques making use of µFTIR, Raman imaging and SEM-EDX (amongst others) will be applied to quantify and characterize MP and NP down to 1 µm, 0.2 µm or lower. Specific tasks will focus on challenging types of MP such as microfibers, tire wear particles (TWPs) and paint flakes. UV, hydrolytic and thermo-oxidative methods to study accelerated plastic degradation at the lab-scale will be developed and used to prepare partially degraded reference materials. Comprehensive degradation studies will be conducted to study in detail the mechanisms of UV and microbial degradation, as well as to investigate the influence of parameters such as temperature, pH and hyperbaric pressure, where attention will be paid to additive chemical leaching. Quality assurance will be a central theme in all aspects of the project. Partners specialized in dissemination, communication and data management will ensure strong stakeholder involvement and efficient outreach of the project results.

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MARINFORSK-Marine ressurser og miljø