Microplastic in the environment – Analyses of the Warnow catchment
Analysing Microplastics Sinks and Sources from a typical Catchment area to the open Baltic
Microplastic pollution in the oceans is increasing worldwide. High concentrations found at the mouth of rivers suggest a substantial contribution of contamination from inland. To what extent is agriculture responsible for these inputs?
Background and Objective
To date, microplastic research is mainly restricted to oceans. Studies are missing that elucidate the connections between contaminations across multiple ecosystems. Plastic tarps used in agriculture, or microplastic entering the field with application of sewage sludge and fermentation residues, can accumulate in the soil and erode into surface waters.
In the exemplary Warnow river catchment (Mecklenburg-Vorpommern), this collaborative project funded by the Federal Mistry of Education and Research will identify microplastic sources and sinks on land and in surface waters. The use of models will help quantify relevant pathways into the open Baltic. In a sub-project, the Thünen Institute approaches the aim to estimate spatial distributions of microplastics on fields and field margins and to identify pollution hot spots. Eventually these results will be used to infer potential mitigation measures.
In a first step, a land use analysis identified areas or regions that are contaminated with microplastic due to their historic land use. Regulative reporting data, statistic data and expert information was used, amongst others. Microplastic concentrations in sewage sludge and compost were derived from literature data. The modelling approach provides the expected microplastic concentrations in soils originating from agricultural use only. Other sources, such as improper disposal (littering) and tyre wear, are not considered in this model.
The spatially explicit results were fed into a hydrogeological model that quantified the pathways into surface waters.
The work in MicroCatch_Balt was conducted in direct cooperation with the partner project PLAWES.
Our Research Questions
What are the relevant sources and sinks of microplastic associated with agriculture?
Do non-agricultural sources, such as plastic litter in road side ditches, play a role?
How can input pathways be characterized, e.g., do lakes act as a sink?
According to our initial estimates, a total of 213 t of microplastics were introduced into agricultural soils in the Warnow catchment area from 1960 to 2016 through sewage sludge, 52 t through compost, and 7 t through mulch and cover films. Especially in the case of sewage sludge, the spatial variability of the inputs is very high. In comparison, the results of the catchment areas of the Warnow and the Weser show clear differences. In the rural Warnow catchment, the stronger influence of sewage sludge stands out, while compost and films are more important in the Weser catchment. Sewage sludge is more widely applied in the Warnow catchment due to the light, sandy soils and is partly imported from other federal states. Plastic-intensive special crops play only a minor role.
Involved external Thünen-Partners
- Leibniz-Institut für Ostseeforschung Warnemünde (IOW)
- Leibniz-Institut für Polymerforschung Dresden (IPF)
- Fraunhoher-Institut für Graphische Datenverarbeitung (IGD)
8.2017 - 4.2021
Publications to the project
Tagg A, Brandes E, Fischer F, Fischer D, Brandt J, Labrenz M (2022) Agricultural application of microplastic-rich sewage sludge leads to further uncontrolled contamination. Sci Total Environ 806(Part 4):150611, DOI:10.1016/j.scitotenv.2021.150611
Brandes E, Henseler M, Herrmann F, Kreins P, Wendland F (2022) Microplastics in the environment: Investigations in the Warnow catchment. Braunschweig: Thünen Institute of Rural Studies, 2 p, Project Brief Thünen Inst 2022/08a, DOI:10.3220/PB1658302607000
Brandes E, Henseler M, Herrmann F, Kreins P, Wendland F (2022) Mikroplastik in der Umwelt: Untersuchungen im Einzugsgebiet der Warnow. Braunschweig: Thünen-Institut für Lebensverhältnisse in ländlichen Räumen, 2 p, Project Brief Thünen Inst 2022/08, DOI:10.3220/PB1646647736000
Brandes E, Henseler M, Kreins P (2021) Identifying hot-spots for microplastic contamination in agricultural soils - a spatial modelling approach for Germany. Environ Res Lett 16(10):104041, DOI:10.1088/1748-9326/ac21e6
Brandes E (2020) Die Rolle der Landwirtschaft bei der (Mikro-)Plastik-Belastung in Böden und Oberflächengewässern. Mitt Fachgruppe Umweltchemie Ökotoxikol Gesellsch Dt Chemiker 26(4):111-114