Agricultural soils always contain microplastics (MPs) residues and farmlands often undergo continuous drying‐wetting alternations. However, little is known about how the existing MPs and MPs particle size affect soil physical properties under drying‐wetting cycles; also their combined influences are not well understood. Hence, we completed measurements of hydraulic parameters and calculations of water characteristics and pore distributions in soil‐MPs mixtures subjecting to five drying‐wetting cycles and four MPs particle sizes. Quantitative findings indicated that both MPs and drying‐wetting cycles reduced saturated conductivity, which firstly decreased and then increased with the increase of MPs particle size and the progress of drying‐wetting cycles. The drying‐wetting cycles increased field capacity (FC) and permanent wilting coefficient (PWC), but reduced gravity water (GW) and available water content (AWC). Oppositely, the MPs reduced FC and PWC but increased GW and AWC; furthermore, the average FC and PWC overall firstly decreased and then increased with the increase in MPs particle size; however, the average GW and AWC firstly increased and then stabilized. The MPs reduced total porosity and the drying‐wetting cycle also reduced it in soil‐MPs mixtures, which whereas increased as the drying‐wetting cycles proceeded. Factors contribution analyses indicated that the drying‐wetting cycle made greater contributions than MPs particle size to the variation of soil physical properties, and their combined effects mainly made great contributions to the variation of soil hydraulic parameters. Our findings provide evidence for MPs influence on soil physical properties, which deserves attention with regard to the developments of sustainable agricultural practical managements in plastic‐polluted soil‐crop systems.

中文翻译：

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干湿交替和微塑料粒径对土壤水和土壤孔隙性质的影响和贡献


农业土壤总是含有微塑料（MP）残留物，农田经常经历连续的干湿交替。然而，人们对干湿循环下现有的MPs和MPs粒径如何影响土壤物理性质知之甚少。它们的综合影响也没有得到很好的理解。因此，我们完成了水力参数的测量以及经过五个干湿循环和四种MPs粒径的土壤-MPs混合物中水特性和孔隙分布的计算。定量研究结果表明，MPs和干湿循环都会降低饱和电导率，并且随着MPs粒径的增大和干湿循环的进行，饱和电导率先降低后增加。干湿循环增加了田间持水量（FC）和永久萎蔫系数（PWC），但降低了重力水（GW）和有效含水量（AWC）。相反，国会议员减少了FC和PWC，但增加了GW和AWC；此外，平均FC和PWC总体上随着MPs粒径的增大先减小后增大；但平均毛重和平均载重先上升后趋于稳定。 MPs 降低了土壤-MPs 混合物中的总孔隙度，干湿循环也降低了总孔隙度，而随着干湿循环的进行而增加。因素贡献分析表明，干湿循环对土壤物理性质变化的贡献大于MPs粒径，其综合作用主要对土壤水力参数的变化贡献较大。 我们的研究结果为MP对土壤物理性质的影响提供了证据，这在塑料污染土壤作物系统可持续农业实践管理的发展方面值得关注。