Our research points that microplastics can affect the soil biophysical environment. That means that soil microorganisms will live and function differently. So what are the consequences of this environmental change?
You come home after work. It was an ordinary and busy day, so you decided to relax for a moment on your favorite couch. But shortly after resting your body on it you notice that something is different. It is not as comfortable as usual. Someone changed the magnificent leathery seat by a polyethylene chair that does the job of accommodating your body in a much less inviting manner. Later at the dinner table, you feel that certain vegetables of your salad have an unusual consistency. Your source of natural fibers somehow has a synthetic texture. Would that be polyester? Confused, you wash your face trying to make sense of the whole situation. But then another surprise. Your cotton towels were replaced by nylon fabrics. Finally, you realize: some of your favorite or essential items were plasticized.
Soil microbes play essential roles on biogeochemical cycles, for instance determining the fate of carbon and organic matter. Thus, the activity of soil tinny inhabitants is certainly relevant for humans
It is easy to imagine how having inconveniently plasticized surfaces of our mundane life activities would require some adaptation of our habits. But, would plastic pollution also affect the everyday business of soil microscopic inhabitants? This was exactly the question addressed in our latest publication on the impacts of microplastic on the soil as a biophysical habitat. We wanted to know whether #microplastic pollution changes the properties of soils as a home to many organisms. Similar to us, most terrestrial organisms evolved to interact with certain surface properties of natural solid matter. As new synthetic matter, plastic surfaces might thus have unknown effects on soil biota. This is particularly concerning because soil microbes play essential roles on biogeochemical cycles, for instance determining the fate of carbon and organic matter. Thus, the activity of soil tinny inhabitants is certainly relevant for humans.
The impacts of microplastics on the soil environment
In a previous study, we reviewed the issue of microplastic pollution on land and hypothesized that microplastics could affect soil biophysical environments. Now, in the latest publication in the scientific journal Environmental Science and Technology, we were also the first to provide experimental evidence confirming this hypothesis. We exposed soil to increasing concentrations of 4 different microplastic types, let it sit in the experimental garden of Freie Universität Berlin (FUB) for 5 weeks and analyzed the soil and the activity of its microbes afterward. Microplastics, particularly polyester fibers, changed fundamental properties of the structure of the soil and how it interacts with water. The soil bulk density (how tidily the soil particles were packed) and the interaction of those particles in forming aggregates were different when microplastics were present in the soil. This has multiple influences in the soil functioning as a habitat for living beings. For instance, soil contaminated with plastics had altered pore space for holding water. It is like someone changed the architecture of your house, making up space in a room, decreasing in other room, and changing the surfaces of the furniture inside. Some shifts on your way of performing certain daily tasks would be observed.
Microplastics, particularly polyester fibers, changed fundamental properties of the structure of the soil and how it interacts with water.
And this is exactly what seems to be the case. The activity of microbes displayed symptoms of functional change. This research article was the first study of its kind, and it is not possible yet to infer whether there would be negative impacts of those changes in the natural roles of soils in supporting terrestrial ecosystems. It might be too early to fully elaborate on the mechanism driving the microbial responses and to predict its consequences, but the fact is that soil #microbiomes are perceiving the environmental change initiated by microplastics pollution and responded to it.
Acknowledgements: Thanks to Prof. Matthias Rillig for checking the earlier versions of this text.