iMulch: Investigating the Influence of Polymers on a Terrestrial Ecosystem with TED-GC–MS and Raman Spectroscopy

Research on plastics in aquatic environments is well-established, but little is known about their presence, pathways, and effects in soil ecosystems. The iMulch project aims to address this need as well as the growing concern of plastic pollution in soils. Focusing on developing and validating methods to detect micro- and macroplastics in soils and drainage waters, with an emphasis on how drainage water impacts municipal wastewater treatment, a key aspect of the study is analyzing plastic emissions from agricultural mulch films. By investigating terrestrial systems, iMulch complements existing aquatic research, enabling a more comprehensive understanding of plastic pollution. We spoke to Carmen Wolf of the Institute for Environment andEnergy, Technology and Analytics e.V. (IUTA) in Duisburg, Germany, corresponding author of a recent paper on the project, about the investigations involved and how separation science was used in their experimentation.

Briefly summarize the iMulch project discussed in your recent paper (1).

Mulch films with material thicknesses in the micrometer range are increasingly used in agriculture to regulate soil temperature and moisture, suppress weeds, and prevent soil erosion. Climate change and the reduction of pesticides further promote their use. However, as plastic mulch films decompose, plastic fragments can enter the soil. The iMulch project investigated if mulch films have negative effects on the soil ecosystem. The project was funded by EU funds and conducted by a consortium of six project partners and three associated partners. The project examined polyethylene(PE) and two biodegradable film blends containing polylactic acid/ polybutylene adipate terephthalate (PLA/PBAT).

At the beginning, an analytical method consisting of thermal extraction-desorption gas chromatography–mass spectrometry (TED-GC–MS) and Raman spectroscopy (RS) was established, enabling the detection of microplastics in the soil.

Numerous experiments were also conducted to study the behavior and fate of the films in the environment. These included aging of the films in soil and water, transport in lysimeter tests, and uptake by plants. Another aspect included investigating the adsorption of pollutants onto the films. Ecotoxicological tests were also performed to evaluate potential effects on organisms.

Furthermore, a life cycle assessment (LCA) was carried out to compare PE and PLA/PBAT films. The study also investigated whether organisms in the soil can break down and transform the films, potentially generating new raw materials.

What did your team find lacking in previously existing methods that inspired you to optimize the process?

With our project, we wanted to take a holistic view of the issue and address a wide range of aspects. There were also very few analytical methods available that could detect the mass concentration of microplastics in the soil. We wanted to develop an analytical method that could determine both the mass concentration of the polymers and the number and shape of the particles.

What were your main findings?

A method for sample preparation and detection of microplastics in soils was successfully established. No adsorption within 21 days for copper, atrazine, thiacloprid and only low adsorption on biodegradable films of tebuconazole could be detected. Ageing of the biodegradable films in drainage water and soil started after eight weeks and no degradation of the PE film was detected. No transport of the films in the lysimeter test was observed, and no uptake into plants was detected. Endocrine effects for aquatic organisms were proven, with no difference between the film types; however, lower effects could be shown for aged films. We detected no difference between biodegradable and PE film with regards to LCA. The bacterial strain for upcycling of biodegradable films was successfully identified and cultivated, with the formation of TAG (triacylglycol) possible. No degradation of PE film was detected. Most unexpected was the low degradation of the biodegradable films in the field experiments which suggests an urgent review of the degradability of such products

You and other co-authors of the paper are affiliated with the Institute for Environment and Energy, Technology and Analytics e.V. (IUTA) in Duisburg, Germany. Other author affiliations include Fischer GmbH, Fraunhofer Institute UMSICHT, and various institutes affiliated with RWTH Aachen University. What did each of these organizations bring to the finished product?

The IUTA provided coordination, dissemination, and establishment of a sample preparation method for RS and TED-GC–MS, as well as measurements with TED-GC–MS, aging of the foils for further tests, and adsorption experiments. Fischer Gmbh provided expertise in spectroscopy, and Fraunhofer Institute UMSICHT performed labor experiments dealing with the aging in water and the soil test stand. In addition, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) were involved with the production of 14C labeled polymers, lysimeter experiments, and uptake in plants RWTH International Academy (IUF) performed ecotoxicity experiments, while their Institute of Applied Microbiology (iAMB) performed experiments pertaining to upcyling with organisms. Finally, the Nova Institute conducted LCA and disseminated the information.

What difficulties did you encounter in this project, and how did you overcome them?

It was difficult to find farmers who would have allowed us to take samples from their fields, but luckily we were able to get samples from testfields from the Chamber of Agriculture of North Rhine-Westphalia, Germany. However, these represent a best-case scenario, because these field are much smaller

Were there any limitations to this research that are important to note?

When we started the project, there was virtually no experience of chemically analyzing microplastics in soils. Today, we have a much better understanding of the relationships between the effects of the matrix and the products analyzed. Therefore, the concentrations we measured are rather an indication of contamination and not concentrations that are set in stone for the chemically analysis.

How could the findings of this method be applied practically in analytical laboratories?

Our sample preparation method may also be of interest to other laboratories working with soils and microplastics. Additionally, our PhD student, who conducted the analyses as part of the project, has published an article summarizing the influencing factors of individual substances on the pyrolysis products. This information could be very helpful for laboratories that also use chemical method to identify microplastics. The article not only includes experiences from iMulch but also from other projects.

Moving forward, are you considering and implementing any improvements to the method?

Our understanding of the influence of the matrix on analysis products has continued to grow, so that results can now be analyzed more reliably. We have also continued to improve the sample preparation method and adapted it for other matrices.

Are there any next steps in this research?

It was truly amazing and inspiring to be able to research in a consortium with so many different experts, as this allowed us to approach questions from a variety of perspectives. There are still many open questions regarding microplastics in the environment and in soils that need to be explored. This is also true in relation to iMulch. There are still open questions that we were unable to answer, such as the degradability of biodegradable polymers under realistic field conditions. We as a consortium would like to answer this question and others in a follow-up project.

More information on this project can be found at https://imulch.eu/?lang=en.

Reference

1. Wolf, C.; Wenzel, M.; Fischer, B. et al. iMulch: An Investigation of the Influence of Polymers on a Terrestrial Ecosystem Using the Example of Mulch Films Used in Agriculture. Environ. Sci. Eur. 2025, 37, 13 DOI: 10.1186/s12302-024-01050-0

Carmen Wolf is a Scientist at the Institute for Environment and Energy, Technology and Analytics e.V. (IUTA), in Duisburg, Germany. Her work focuses on characterizing particles in various environmental media and studying their behavior. She has contributed to various national and international projects (such as several UBA projects on nanomaterials; BMBF projects nanoGRAVUR, nanoGEM, InnoMatLife, subµTrack; EU projects MARINA, NanoImpactNet, Future Nano Needs, NanoFASE) and coordinated several projects, including the current EFRE project iMulch (investigating the influence of polymers on a terrestrial ecosystem using agricultural mulch films as an example) and the UBA project KoPilot (study of the health effects caused by urban UFP concentration). Carmen earned her doctorate at the Institute on the topic of the behavior and fate of nanoscale particles in the environment. Before her work at IUTA, she was a research associate at the Senckenberg Institute in Gelnhausen, Germany, where she mapped various animals (birds, snails, butterflies) for conservation projects.