Agricultural soils are a major reservoir of microplastics, and concerns have arisen about the impacts of microplastics on soil properties and functioning. Here, we measured the physical properties of a silt loam in response to the incorporation of polyester fibers and polypropylene granules over a wide range of concentrations. We further elucidated the underlying mechanisms by determining the role of microplastic shape and the baseline effects from the amendment of soil particles. The incorporation of microplastics into soil tended to increase contact angle and saturated hydraulic conductivity and decrease bulk density and water holding capacity, but not affect aggregate stability. Polyester fibers affected soil physical properties more profoundly than polypropylene granules, due to the vastly different shape of fibers from that of soil particles. However, changes in soil properties were gradual, and significant changes did not occur until a high concentration of microplastics was reached (i.e., 0.5% w/w for polyester fibers and 2% w/w for polypropylene granules). Currently, microplastic concentrations in soils not heavily polluted with plastics are far below these concentrations, and results from this study suggest that microplastics at environmentally relevant concentrations have no significant effects on soil physical properties.

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在环境相关浓度下，微塑料对土壤物理特性的影响最小

农业土壤是微塑料的主要储存库，人们开始担心微塑料对土壤特性和功能的影响。在这里，我们测量了淤泥壤土的物理特性，以响应在各种浓度范围内掺入聚酯纤维和聚丙烯颗粒。我们通过确定微塑料形状的作用和土壤颗粒改良的基线效应，进一步阐明了潜在机制。将微塑料掺入土壤往往会增加接触角和饱和导水率，降低容重和持水能力，但不会影响团聚体稳定性。聚酯纤维比聚丙烯颗粒对土壤物理特性的影响更深远，因为纤维的形状与土壤颗粒的形状大不相同。然而，土壤特性的变化是渐进的，直到达到高浓度的微塑料（即，聚酯纤维为 0.5% w/w，聚丙烯颗粒为 2% w/w），才发生显着变化。目前，未被塑料严重污染的土壤中的微塑料浓度远低于这些浓度，这项研究的结果表明，环境相关浓度的微塑料对土壤物理性质没有显着影响。