Does plastic and microplastic change the soil physical properties? A review

Abstract

Microplastics (5mm) enter the soil in several ways, including directly through the purposeful use of plastic (e.g., in plastic mulch, greenhouses, or coated items) or inadvertently through the addition of sewage sludge, compost, or irrigation water that has been polluted with plastic. The effect of microplastic on plant growth, soil biota, and soil physicochemical properties has been reviewed (Shafea et al., 2022), while soil physical properties have yet to be synthesized. Soil structure is an important soil feature affecting key variables in earth system models like, e.g., soil aggregation and soil hydraulic properties (Fatichi et al., 2020). These soil physical properties are influenced by widespread microplastic dispersion and pervasiveness, which might affect the soil's capacity to provide different ecosystem services and is a potential obstacle to sustainable agriculture (Rillig & Lehmann, 2020). Thereby, we present the preliminary results of a review on the plastic and microplastic impact on soil physical properties, including soil compaction, soil aggregation, water retention and transmission, and porosity, from peer-reviewed publications. Our review indicates that increasing plastic and microplastic concentration reduces soil compaction due to changes in bulk density. Soil structure and aggregate stability are also subject to alteration due to plastic contamination. Microplastic in the soil might affect water repellency, mainly measured by water drop penetration time. However, data on hydraulic properties, thermal properties, and pore-size distribution are scant. Moreover, potential factors, i.e., plastic-type, size, concentration, and soil type, by which microplastic can influence soil physical properties, are also discussed. This communication tries to identify trends in the influence of plastic and microplastic among different treatments using different indexes. From this analysis, we identify knowledge gaps for future studies.

Keywords: agroecosystem, microplastic, soil aggregates, infiltration.

References

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Rillig, M. C., & Lehmann, A. (2020). Microplastic in terrestrial ecosystems. Science, 368(6498), 1430–1431. https://doi.org/10.1126/science.abb5979

Shafea, L., Yap, J., Beriot, N., Felde, V. J. M. N. L., Okoffo, E. D., Enyoh, C. E., & Peth, S. (2022). Microplastics in agroecosystems: A review of effects on soil biota and key soil functions. Journal of Plant Nutrition and Soil Science. https://doi.org/10.1002/jpln.202200136