Microplastics in agricultural soils: The role of soil texture in modulating oxygen diffusivity and soil respiration
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Date
2025-10
Publication Type
Journal Article
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yes
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Abstract
The presence of microplastics (MPs) in soils impacts nutrient cycling and soil respiration. However, the mechanisms underpinning the direction and magnitude of these effects on soil are uncertain. We hypothesized that the presence of MPs affects pore connectivity, leading to changes in oxygen (O2) diffusivity and soil respiration. Furthermore, we anticipated that the magnitude of the effects would be dependent on both soil texture and MPs morphology. 1 % (w/w) PET MPs fibers (500 μm length) and fragments (125–250 μm) were spiked into rhizotrons filled with either clay or sandy loam soils. O2 diffusivity differences were determined in microcosm using an oxygen-free chamber. The O2 concentration in the soil was also measured in optimal conditions for respiration. O2 diffusivity and concentration were measured using optode imaging. Respiration was estimated from cumulative CO2 and changes in the size of the water-extractable carbon pool. Adding MPs decreased O2 concentration in the sandy loam soil (167.4 ± 6.1 mg L−1 air), with a greater reduction observed for fragments (15 %) compared to fibers (12 %). Soil respiration decreased by 40 % in both fragment and fiber treatments in alignment with the reduction in oxygen concentration. Conversely, in the clay soil, the addition of fibers and fragments resulted in a 13 and 7 % increase in O2 concentration compared to the control (177.9 ± 3.8 mg L−1 air). Both changes in oxygen concentration and diffusivity, show a similar response to MPs for the two soils. These findings indicate that the effects of MPs on soil respiration are likely driven by changes in O2 dynamics. However, the MPs' impact on O2 dynamics depends on soil particle size distribution. Future research should consider MP size, morphology, and soil particle distribution interactions to assess MPs' impacts on soil functions.
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published
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Journal / series
Volume
209
Pages / Article No.
109906
Publisher
Elsevier
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Subject
Plastics pollution; Pore connectivity; Oxygen diffusivity; Soil respiration
Organisational unit
09717 - Mitrano, Denise M. (ehemalig) / Mitrano, Denise M. (former)
09732 - Carminati, Andrea / Carminati, Andrea
Notes
Funding
186856 - Synthesis and utility of metal-doped plastic particles and fibers: from analytical standardization to systematic understanding of fate in the environment (SUrPASS) (SNF)