Shape matters: microplastic fibers disrupt soil carbon cycling via shape-driven physical disturbance

Summary

This laboratory study examined how microplastic shape influences soil carbon cycling, finding that fiber-shaped microplastics (both acrylic and polyethylene) reduced total CO2 emissions by 25% compared to bead-shaped particles through primarily physical disturbance rather than chemical effects. Using isotopic tracing, the authors demonstrated that soil priming effect increased with microplastic addition and that higher concentrations of microplastics decomposed up to 10 times more slowly, likely due to particle clumping that restricts microbial access. The findings suggest fiber-shaped microplastic pollution poses a distinct threat to soil carbon cycling globally.

Regional applicability

The study is a controlled laboratory experiment using standard polymers and does not focus on a specific geography. Findings are potentially applicable to United Kingdom agricultural and soil systems where microplastic contamination is an emerging concern, though field validation under UK soil and climatic conditions would be needed to confirm transferability.

Key measures

Total CO2 emissions, polymer-derived CO2 emissions, decomposition rates, soil priming effect, microplastic concentration (0.1% and 1% w/w), fiber vs bead morphology

Outcomes reported

The study measured CO2 emissions (total and polymer-derived) and soil priming effect over 63 days using δ13C isotopic analysis, comparing microplastic beads and fibers at two concentrations against glass particle and soil-only controls.

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