Impacts of Microplastics on the Soil Biophysical Environment

TLDR

Soils, vital to terrestrial ecosystems, are increasingly polluted by microplastics, yet their impact on fundamental soil properties that support biodiversity remains poorly understood. This study investigates how microplastics disturb soil–water relationships and affect soil structure and microbial function. A five‑week garden experiment exposed loamy sand soil to up to 2 % nominal concentrations of four common microplastic types, after which bulk density, water‑holding capacity, hydraulic conductivity, soil aggregation, and microbial activity were measured. Microplastics altered bulk density, water‑holding capacity, and the link between microbial activity and water‑stable aggregates, and these effects are underestimated when particle type and concentration are ignored, indicating that microplastics are long‑term anthropogenic stressors driving global change in terrestrial ecosystems.

Abstract

Soils are essential components of terrestrial ecosystems that experience strong pollution pressure. Microplastic contamination of soils is being increasingly documented, with potential consequences for soil biodiversity and function. Notwithstanding, data on effects of such contaminants on fundamental properties potentially impacting soil biota are lacking. The present study explores the potential of microplastics to disturb vital relationships between soil and water, as well as its consequences for soil structure and microbial function. During a 5-weeks garden experiment we exposed a loamy sand soil to environmentally relevant nominal concentrations (up to 2%) of four common microplastic types (polyacrylic fibers, polyamide beads, polyester fibers, and polyethylene fragments). Then, we measured bulk density, water holding capacity, hydraulic conductivity, soil aggregation, and microbial activity. Microplastics affected the bulk density, water holding capacity, and the functional relationship between the microbial activity and water stable aggregates. The effects are underestimated if idiosyncrasies of particle type and concentrations are neglected, suggesting that purely qualitative environmental microplastic data might be of limited value for the assessment of effects in soil. If extended to other soils and plastic types, the processes unravelled here suggest that microplastics are relevant long-term anthropogenic stressors and drivers of global change in terrestrial ecosystems.