This work package aims to investigate the persistence of today’s and future plastic litter and to identify the environmental conditions most likely to inhibit and promote its degradation to secondary microplastics. It will also identify the processes most significant for dispersal and deposition of plastic litter and fragments.
SCOPE OF WORK PACKAGE 4
WP4 aims to answer the questions; how many years do secondary microplastics take to form from plastic litter, which internal and external factors have greatest influence in the process and do all plastic types, both petroleum-based and new generation have the potential to form microplastics? It will also establish and compare the distribution patterns of plastic pollution between water columns and sediment layers based on fragment dimensions and chemical compositions in order to determine whether internal or external factors have greatest influence over dispersion and deposition.
SYNERGIES WITH OTHER WPS
The causes and rates of fragmentation of plastic litter from macro- to micro dimensions and its subsequent mobility are fundamental to WP 3 and WP 5 in which its abundance, dispersion and impact are studied. Knowledge of the lifetimes of today’s petroleum-based and tomorrow’s bioplastic and biodegradable plastic litter and the plastics most likely to fragment in the various environmental compartments are essential to design effective strategies to minimize its impact on the marine environment. The analytical techniques developed in WP2 will be applied in WP4 and the plastic study collection will be shared with all WPs as reference samples.
How do plastics degrade in the marine environment?
The first step to investigating this research question will be to develop a novel Plastic Degradation Index by which the extent of degradation can be qualified and quantified. The Index will be formulated from the most significant indicators of physical breakdown (fragment dimensions, tensile strength, surface damage and color), chemical breakdown (bond structure of polymer, adsorption of organic pollutants) and biological activity (biofouling) detected on plastics exposed to the marine environment by the National Museum of Denmark’s researchers and partners in MarinePlastic.
The Index will combine the spectroscopic and chromatographic techniques developed in WP1 with quantitative FTIR to follow the rate of chemical breakdown, evolved gas analysis to examine the presence of organic pollutants and X-ray fluorescence to detect the presence of inorganic polymer additives and metals adsorbed by exposure to the marine environment.
The Index will then be applied to samples collected in WP3 in collaboration with J. Strand (AU)
Which processes are the most significant for dispersal and deposition of plastic fragments in the marine environment?
This research question will build on WP 4.1 by examining the factors that control movement of plastic litter at macro- and micro dimensions once formed by degradation. Microplastics can be considered as inert particles and their movement attributed to their size and shape alone. However, they may also be considered as reactive chemical composites that interact with their surrounding environment by forming weak forces and stronger chemical bonds. These two approaches suggest that relocation of plastics may be either controlled primarily by internal factors such as their chemical and physical compositions or external factors including wind, ocean currents, salinity and biological factors/biofilms.
In turn, new and degraded samples of petroleum-based, recycled, bio- and biodegradable plastics collected or produced by accelerated weathering in WP 4.1 will be exposed to weathering chambers or mecocosms designed and developed for the project in which water and air movement, temperature, salinity and biological factors can be varied