Unique and highly diverse properties of plastics, their easily processing and the low production costs have lead steadily increasing plastic production reaching 322 million tons worldwide in 2015. Plastics have delivered many benefits to society in various sectors; however global plastics pollution is a consequence of unsustainable use, uncontrolled and inadequate plastic disposal and waste management. Enhanced performance and persistency of plastic products is achieved by additives, such as plasticizers, heat and UV stabilizers, flame retardants, and antioxidants, which are usually incorporated during the plastic manufacturing. The most abundant plastics found in the environment are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyvinylchloride (PVC), correlating well with the high worldwide consumptions of these polymers.
Plastic litter forms a continuum, from primary macroplastics to (mainly secondary) micro- and nanoplastics, the latter hardly being investigated. After the emission into the environment, plastics are subjected to weathering effects, e.g. UV radiation, mechanical abrasion and oxidants, causing a physico-chemical alteration and a slow fragmentation into small plastic pieces, often termed as microplastics (usually < 5 mm). Environmental concentrations of microplastics are likely to rise in the future with increasing input and as a result from fragmentation of macroplastics. Despite the rapidly growing body of published research into the occurrence and impact of microplastics on a variety of ecosystems, the understanding of the mechanism of plastic weathering within the environment remains limited. Although the abiotic degradability of polymers has been investigated under different artificial environmental (temperature, and in air or in water) and atmospheric conditions (O2, N2, and air), there is barely no information on how macro sized particles plastics weather in natural environments. Weathering processes in the environment include physical fragmentation, photodegradation, biodegradation and hydrolysis, all of which result in changes in the physico-chemical properties of plastics. The leaching of (potentially toxic) additives from plastics is expected to be strongly linked to those changes in plastic properties.
The investigation of fragmentation processes of macroplastics and rates of secondary microplastic formation in combination with the evaluation of the release of additives is crucial to assess their environmental fate and has been recently been identified as one of the most pressing research priorities in microplastic exposure assessment. PVC, the third largest consumed polymer worldwide, is considered to be the most critical polymer as it contains more than 60% of all additives used in plastic production. This project aims to investigate the weathering of plastics under natural-like conditions and thereby establish the link between the weathering of plastics and the leaching of additives. Dr. Thorsten Hüffer and Teja Urankar from the Department of Environmental Geosciences, University of Vienna, Austria have started the project in June 2018, introducing a variety of different test bodies into two different shore lines the Artificial Stream and Pond System (FSA) of the Federal Environment Agency (Umweltbundesamt, UBA) in Berlin.
UBA provided two stream mesocosms with different sediments and reference systems for this purpose. Fig. 1 shows the filling of the streams by UBA staff. During the course of the project, various test specimens (drinking cups, foils) were exposed (Fig. 2).
Members of the research team: Dr. Thorsten Hüffer, Teja Urankar from the University of Vienna, Austria, with support from Fabian König, Stefan Meinecke, Svenja Schulze from UBA, Germany
Project duration: June to December 2018