Microplastic contamination in agricultural soil ecosystems and the effect on soil and plant health

Project Information

MiCoS

Grant agreement ID: 101075944

DOI

10.3030/101075944

EC signature date 2 February 2023

Start date 1 May 2023

End date 30 April 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 498 813,00

EU contribution

€ 1 498 813,00

Coordinated by

UNIVERSITEIT GENT
Belgium

Periodic Reporting for period 1 - MiCoS (Microplastic contamination in agricultural soil ecosystems and the effect on soil and plant health)

Reporting period: 2023-05-01 to 2025-10-31

Summary of the context and overall objectives of the project

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.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

For assessing the MP pollution in terrestrial ecosystems, and in particular agricultural soils, we have developed a fast and cost-effective method to extract MPs from the soil matrix. Currently, we are able to distinguish 7 different plastic polymers (particularly conventional plastics like polyethylene and PET), but are extending our database to include up to 12 commonly found plastic polymers in agriculture. Our method can detect MPs up to 10 µm, but we are taking efforts to go to a minimal value of 1 µm size.

This method is currently used to monitor MP pollution in 240 agricultural fields in the Benelux. After a risk analysis 240 arable fields out of over 400 were selected and sampled from January - April 2024. We have gathered information on the total number of macroplastics, the soil microbiome profile (to look to the effects on soil health), the soil penetration resistance, soil texture and nutrient profile. In addition, we analysed at least one replicate per field on microplastic content. Overall, we found high pollution, with values for microplastics exceeding 3000 particles per kg and over 2000 macroplastic particles (> 5 mm diameter) per hectare in arable fields. Currently, we are examining the sources of this plastic pollution, taking into account geographical location and agricultural practices.

To test the effect of plastic pollution, we have started toxicity tests on cress seeds. A pot trial is conducted in which plastic (PE, PVC and PLA) is weathered for one year in two different types of soils. Each month, plastic is assembled (for microbial profiling) and the remaining soil is used within a pot trial to verify if the plastic weathering (and potential leaking of chemicals) affect plant health. After 4 months, no severe results are noted, but we are still in the beginning on testing the effects of microplastics on soil and plant health.

For risk reduction, we have done a first small isolation campaign from PVC plastic. We isolated several bacteria and through taxonomic analysis isolated some new, unknown species with potential PVC degradation capacity. These organisms will be followed up and used further in degradation experiments.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The methodology developed to measure microplastics is under investigation to see if this can be commercialized by industrial partners for monitoring within Belgium and/or The Netherlands. At the time of writing, monitoring of microplastics is not obligated in the European Union, although it has been suggested by the scientific community. Within Belgium and The Netherlands, there is however a growing interest from policy makers to monitor soil pollution, including microplastics. To make commercialization possible, we need however to increase the number of samples we can analyse per batch to speed up the process and perform a market study that goes beyond the Belgian and Dutch market (e.g. on European scale).

Regarding the scientific breakthroughs, we are the first to monitor macroplastic pollution on a large scale on arable fields. Therefore, we needed to adjust the current standardized classification systems for litter. This classification system, partly derived from the Joint List, is already used in other projects that aim to set up large monitoring campaign following our study. In addition, our results majorly contribute to the identification of plastic sources in agricultural soils.

Regarding microplastics, the current results already show a high pollution rate in arable fields. However, we aim to identify the sources of these plastics and see potential effects on the soil nutrient content and soil microbiome. Therefore, correlation and association studies still need to be conducted further in the course of the project.