Synthetic fibers released from sewage sludge and tire particles released by traffic, are among the most common types of microplastics in soil. In soil, microplastics may interact with chemicals, such as plant protection products used in agriculture.
Most studies on the interactions of microplastics and chemicals have focused on aquatic environments and only a few addressed soil arthropods. To increase the understanding of the combined effects of microplastics and chemicals on soil arthropods, the researchers studied the effects of polyester fibers and tire particles on the toxicity of the insecticide chlorpyrifos.
The article “Modulation of chlorpyrifos toxicity to soil arthropods by simultaneous exposure to polyester microfibers or tire particle microplastics” was published in Applied Soil Ecology on the 15 September 2022. The lead author of the study, Salla Selonen, Ph.D. in Environmental Ecology, works as a Senior Research Scientist at the Finnish Environment Institute (SYKE).
“The two terrestrial arthropods used in our tests are the woodlouse Porcellio scaber and the springtail Folsomia candida. They are both important soil decomposers”, says Salla Selonen.
The chemical used in the tests was chlorpyrifos, an insecticide with several agricultural applications. It has been widely used around the world since its introduction in 1965. Nowadays, the use of chlorpyrifos is restricted in several countries, but it is still widely used in developing countries. Chlorpyrifos is also commonly detected in water and food. Chlorpyrifos is characterized by poor water solubility, low volatilization, and slow degradation under aerobic conditions.
Two types of microplastics were tested: polyester fibers and tire particles. Both types of microplastic have high environmental relevance, but varying polymer compositions, chemical additives, and shapes.
The researchers aimed at finding out how the co-exposure with microplastics alters the effects of chlorpyrifos on soil arthropods, and whether the effects are dependent on the type of microplastic and the exposed arthropod species.
It turned out that different types of microplastics had different effects. Tire particles significantly decreased the chlorpyrifos-induced mortality of woodlice and springtails, while polyester fibers did not.
“Our data show that both types of microplastics, but in particular tire particles, decrease the bioavailability of chlorpyrifos”, Salla Selonen says. “The study shows that it is important to study the mixture toxicity of microplastics and other pollutants, if we are to understand realistic threats of microplastics to the soil environment.”
The study was part of the international project IMPASSE - Impacts of MicroPlastics in AgroSystems and Stream Environment led by the Norwegian Institute for Water Research.
Link to the article:
Inquiries:
Salla Selonen, Senior Research Scientist, Finnish Environment Institute, e-mail: firstname.lastname@syke.fi