Plastics can be found in nearly every conceivable environment. Research on the abundances and effects of plastics in a terrestrial environment is still limited compared to its marine counterpart, particularly for smaller particles, the so-called microplastics (MPs; < 5 mm). The limited amount of research on MPs in soils has particularly to do with the lack of an appropriate method to measure MPs in the soil matrix. Whereas the extraction of MP filaments from water is comparatively easy, the extraction from soil is challenging because the high amount of organic material, which can be wrongly mistaken for a MP particle. This limit prevents high scale monitoring, and thus crucial information on the number of MP particules, needed to test how MP pollution today affects plant development, plant resistance towards pathogens, soil structure and soil health. It has been suggested that due to their small size scale, they can potentially affect the soil structure; be ingested by earthworms and nematodes, and be taken up by the plant, harming the environment and affecting the food cycle.
The project MiCoS strives to understand the risks of MPs on soil ecosystem functioning. Therefore, we work on three different scales: assessing (1), testing (2) and reducing (3) the risks of MPs. We focus on agricultural soils as they possess the biggest threat in terms of food safety, plant and human health. We have screened 240 soils in the Benelux and quantify the average concentration of MPs in relation to the soil characteristics, plant growth and the soil microbial community. This will give us information on the current distribution of MPs in soils and identify the main routes and sources of contamination. To count the microplastic particles, we develop a reliable, simple and fast microscopic method to detect MPs in the soil environment. In a second stage, we will set up experiments in the greenhouse to test the effects of MP pollution on plant growth, plant defense towards pathogenic bacteria and soil structure. Finally, we aim to reduce the input of plastics in the environment by screening and isolating plastic degrading bacteria and/or fungi in the environment. Overall, MiCoS will provide new insights regarding the current MP pollution in soil ecosystem and how this affects soil and plant health. This information will be the foundation for policymakers and governments to set up legislation regarding MP input in the soil, which is urgently being called for.
