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Effects of Microplastics in Soil Ecosystems: Above and Below Ground
Summary
Researchers tested how three types of microplastics, including biodegradable polylactic acid, conventional polyethylene, and synthetic clothing fibers, affect soil ecosystems containing earthworms and ryegrass. They found that different plastic types caused distinct effects: fibers and biodegradable plastics reduced seed germination, polyethylene reduced earthworm body mass, and all types altered the structure of soil aggregates. The study provides evidence that microplastic contamination can disrupt both above-ground plant growth and below-ground soil health.
Environmental contamination by microplastics is now considered an emerging threat to biodiversity and ecosystem functioning. Soil ecosystems, particularly agricultural land, have been recognized as a major sink of microplastics, but the impacts of microplastics on soil ecosystems (e.g., above and below ground) remain largely unknown. In this study, different types of microplastics [biodegradable polylactic acid (PLA)], conventional high-density polyethylene (HDPE), and microplastic clothing fibers were added to soil containing the endogeic Aporrectodea rosea (rosy-tipped earthworm) and planted with Lolium perenne (perennial ryegrass) to assess the biophysical soil response in a mesocosm experiment. When exposed to fibers or PLA microplastics, fewer seeds germinated. There was also a reduction in shoot height with PLA. The biomass of A. rosea exposed to HDPE was significantly reduced compared to control samples. Furthermore, with HDPE present there was a decrease in soil pH. The size distribution of water-stable soil aggregates was altered when microplastics were present, suggesting potential alterations of soil stability. This study provides evidence that microplastics manufactured of HDPE and PLA, and synthetic fibers can affect the development of L. perenne, health of A. rosea and basic, but crucial soil properties, with potential further impacts on soil ecosystem functioning.
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