The sink is leaking! – Enabling citizen science for global mapping of microplastic leakage from coastal soils

The growing amount of marine plastic pollution calls for the need to better understand the mechanisms of its dispersal, geophysical processes involved, and quantitative distribution throughout different environmental compartments. Transported by winds, waves and currents, plastic washes up on coastal, lake- and fluvial shores. Here, it can sediment within the local soil horizon, where further macroplastic decomposition driven by both abiotic and biotic factors contributes to an ever-increasing amount of secondary microplastic (MP). While soil has been theorized to act as a sink, its permanence remains yet to be questioned. Much data on a global scale is needed. To achieve this, whilst also ensuring adequate geographical coverage, it is vital to enable contributions from research in developing countries as well as from citizen scientists (CS). Unfortunately, many of the commonly used analytical methods for MP-quantification in environmental samples are both complex and costly. Here we used CS-friendly methods to document and quantify the so far little researched phenomenon of MP-leakage from coastal soil through a case study on Smøla island in Mid-Norway. Precipitation was simulated over 9 locally collected soil core samples in a laboratory experiment, and leachate analyzed for MPs in the size range 100µm-1mm. The methodological approach involved filtration for size-separation and H2O2[30 Also see: https://micro2024.sciencesconf.org/559346/document