Key Facts

A field experiment has been set up in Spring 2024 at the Unifarm of Wageningen University to study the transport of microplastics within the soil. In the SOILPROM project, the soil depth to which applied microplastics reach, through leaching and colloidal transport, will be tracked twice per year. Two kinds of plastics being studied are certified biodegradable in soils; the effects of degradation on their sizes, shapes and transport will be taken into account. With common crops grown in the field and the farm management and the plants themselves affecting the transport, the results will be closer to a real-world situation. The field experiment data, correlated with data from the local meteorological station, will be used to set a reference point of field conditions to calibrate the HYDRUS model.

Agricultural field: Corn

Microplastics

Soil & water

Process

Colloidal transport of microplastics in the soil.

Actions and expected results

• Microplastics (0.1% w/w applied in the first 20 cm of the soil) originating from three different variants of commercial plastic mulches will be tested: Polyethylene -based, polybutylene adipate terephthalate –based, and starch –based. The last two are certified biodegradable in soils.
• Soil samples have been collected from 0-10 cm in 2024 in Spring and in autumn.  In 2025, soil samples will be collected at 0-10 cm, 20-30cm and 40-50cm–in spring and in autumn. Depending on the 2024 and 2025 results the sample depths will be justified in 2026.
• Microplastic quantity, size and shape will be measured through microscopic analysis.
• Field study outcomes will serve to validate the model.

Challenges

The main challenges stem from the recovery of the plastic particles in the soil samples. First, we will only be able to recover particles >10µm, which won’t give us information about smaller particles which might behave differently in soil. Additionally, we chose microplastics from black plastic mulch for representativity and availability. However, this plastic is dyed with carbon black and therefore has a low infrared (IR) transmission resulting in low recoveries from IR imaging techniques. We will calibrate an identification method based on the color of the particles under the microscope.

Partners involved