Black and green – The impact of tire wear particles on soil and plant nutrient cycles
Dr. Collin Weber, Dr. Kai Nils Nitzsche, Prof. Moritz Bigalke
Technical University Darmstadt, Department of Materials- and Geosciences, Chair of Soil Mineralogy and Soil Chemistry
Tire wear particles (TWP) represent the most dominant source of microplastics released into the environment. Originating from the friction between tires and road surfaces, TWP are typically encrusted with minerals from the road and form particle with sizes < 40 nm up to 400 µm. Once formed, TWP can be transported through runoff from roads and airborne transport over short distances by air and spray water in roadside agricultural soils and into the soil-plant system (see figure). Owing to the chemical composition and resulting toxicity of TWP, they represent a potential threat to the soil ecosystems. While toxic compounds (e.g., S and Zn) can leach from TWP, they could also sorb macronutrients. Thus, TWP can have serious effects on the soil solution chemistry and potentially negatively affect plant performance over time.
Up to now, research on the potential hazardous effects of TWP was performed only by using laboratory-generated TWP which differ substantially from “real-world” TWP in soils as the latter are a mixture of different ages, surfaces and shapes originating from different tires with different compositions. Therefore, the overall objective of the project is to reveal the underlying effects of “real-world” TWP and of the released S and Zn for the element cycling in soils and plant performance. The project is built up of three working packages (WP). In WP1, topsoil sampling of roadside- and agricultural soils adjacent to high traffic streets in the region Rhine-Main will provide the basis for extracting large amounts of “real-world” TWP using a modified two-phase density separation method including an additional purification step. In WP2, the extracted TWP will be used in batch experiments to investigate the leaching of trace elements (e.g., Zn), of organic carbon and of S using pH values relevant in soil solutions, as well as the sorption of the important nutrients phosphate and ammonium. Within final pot experiments with extracted TWP additions (WP3), the effects of different “real-world” TWP concentrations (0.01%, 0.1%, 1%) on nutrient cycling and impacts on the performance of lettuce and summer wheat will be investigated.