Abstract. Soil colloidal particles are the most active components of all, and they also vary in elemental composition and environmental behaviors with the particle size. The purposes of the present study are to clarify how particle size affects the physiochemical properties and aggregation kinetics of soil colloids, and to further reveal the underlying mechanisms. Soil colloidal particles from two alkaline soils—Lou soil and cinnamon soil were subdivided into three ranges: d < 2 μm, d < 1 μm and d < 100 nm. The organic and inorganic carbon contents, clay mineralogy, surface electrochemical properties, including surface functional groups and zeta potentials, were characterized. Through time-resolved light scattering technique, the aggregation kinetics of soil colloidal fractions were investigated, and their critical coagulation concentrations (CCCs) were determined. With decreasing colloidal particle diameter, the total carbon content, organic carbon, organic functional groups content and illite content all increased. The absolute zeta potential values and the charge variability decreased with decreasing particle diameter. The CCC values of Lou soil and cinnamon soil colloids followed the descending order of d < 100 nm, d < 1 μm, d < 2 μm. Compared with the course factions (d < 1 μm and d < 2 μm), soil nanoparticles were more abundant in organic carbon and more stable clay minerals (d < 100 nm), thus they exhibited strongest colloidal suspension stability. The differences in organic matter contents and clay mineralogy are the fundamental reasons for the differences in colloidal suspension stability behind the size effects of Lou soil and cinnamon soil colloids. The present study revealed the size effects of two alkaline soil colloids on carbon content, clay minerals, surface properties and suspension stability, emphasizing that soil nanoparticles are prone to be more stably dispersed instead of being aggregated. These findings can provide references for in-depth understanding of the environmental behaviors of the heterogeneous soil organic-mineral complexes.

中文翻译：

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胶体粒径对两种碱性土壤理化性质及聚集行为的影响


摘要。土壤胶体颗粒是其中最活跃的组分，其元素组成和环境行为也随颗粒尺寸的变化而变化。本研究的目的是阐明粒径如何影响土壤胶体的理化性质和聚集动力学，并进一步揭示其潜在机制。两种碱性土壤——娄土和褐土的土壤胶体颗粒被细分为三个范围：d < 2 μm、d < 1 μm 和 d < 100 nm。对有机和无机碳含量、粘土矿物学、表面电化学性质（包括表面官能团和 zeta 电位）进行了表征。通过时间分辨光散射技术，研究了土壤胶体部分的聚集动力学，并确定了它们的临界混凝浓度（CCC）。随着胶体粒径的减小，总碳含量、有机碳、有机官能团含量和伊利石含量均增加。绝对 zeta 电位值和电荷变异性随着粒径的减小而减小。娄土和褐土胶体的CCC值由大到小依次为d < 100 nm、d < 1 μm、d < 2 μm。与土层派(d<1μm和d<2μm)相比，土壤纳米颗粒的有机碳含量更丰富，粘土矿物更稳定(d<100nm)，因此表现出最强的胶体悬浮稳定性。有机质含量和粘土矿物学的差异是娄土和褐土胶体尺寸效应背后胶体悬浮稳定性差异的根本原因。 本研究揭示了两种碱性土壤胶体对碳含量、粘土矿物、表面性质和悬浮稳定性的尺寸效应，强调土壤​​纳米粒子更容易更稳定地分散而不是聚集。这些发现可为深入了解异质土壤有机矿物复合体的环境行为提供参考。