Microplastics Locked in Water-Stable Aggregates of the Haplic Luvisol and Role of Land Use on Their Potential Mobility

Microplastics (MPs) have long been the subject of scientific articles dealing with environmental pollution. The purpose of this study was to determine the occurrence and amount of MPs in soil aggregates depending on land use. The soil in the research area was formed on loess parent material and classified as Haplic Luvisol. From the soil samples were determined particle size distribution curves, and subsequently 40 mixed samples were dry sieved and then wet sieved to determine the percentage of individual soil fractions of water-stable soil aggregates (WSA). The representation and number of MPs were determined for the most common fractions. It was found that MPs occur in both cases of land use, slightly more (62 pt/5 g) in forest soil compared to arable (40 pt/5 g). It is generally known that soil is not homogeneous, but the amount of MPs in top layer for arable soil (8000 pt/kg) and forest (12,400 pt/kg) was estimated. The effect of land use is that forest WSA have a larger mean weight diameter (MWD) than arable land. By being larger, they are also more stable to movement during water erosion. MPs are bound in soil aggregates and they move together with them. This can be deduced from our measurements, because MPs extracted from WSA do not disintegrate in water after 2 hours and even after subsequent wet sieving. The effect of land use on microplastic occurrence and movement should be continually of concern in the future.