Visualization of fluorescent microplastics in soil column experiments in different depths

Microplastics are ubiquitous in the terrestrial environment and have also been detected in soils. However, how microplastics are transported vertically in the soil is still a matter of research. Especially, the influence of precipitation, preferential pathways and bioturbation on the vertical translocation of microplastics is still unclear. One cause is the time-consuming microplastic analysis in soils that requires substantial sample pretreatment. Additionally, we are still lacking a standard protocol to quantify and qualify microplastic particles in environmental samples.

Therefore, in this study, we present a method for irrigation experiments with soil column to study the vertical transport of microplastics. In the upper 2 cm of the column, fluorescent microplastics are added. We spike the irrigation water with deuterium oxide to trace the breakthrough of the water during the irrigation experiment. After the irrigation experiment, the soil column is frozen and subsequently cut in 2 cm slices and photographed under UV illumination. Then, we process the images by the software MP-VAT to analyse the distribution of the MP particles within the slices and within the soil column.