Effect of soil internal forces on fragment size distributions after aggregate breakdown and their relations to splash erosion

Abstract

Soil aggregate breakdown is the key step of splash erosion. Recent studies have shown that it is the soil internal forces that induce aggregate breakdown and subsequent splash erosion. However, little is known about the size characteristics of soil aggregate breakdown and corresponding effects on splash erosion. In this study, Cinnamon soil and Heilu soil were adopted to investigate the effects of soil internal forces on the characteristics of aggregate fragments and splash erosion through wet sieving and rainfall simulation. The results showed the following. (1) With a decrease in electrolyte concentration in soil solution, soil net repulsive force increased; meanwhile, aggregate stability decreased and splash erosion rate increased. Additionally, when the electrolyte concentration was less than 10−2 mol L−1, soil net repulsive force hardly changed, and aggregate stability and splash erosion rate accordingly varied very little. (2) With the increase in the soil net repulsive force, the content of fragments <0.053 mm released from aggregates increased, whereas the content of fragments >0.25 mm decreased, thus suggesting that the aggregates tended to break into fine fractions as soil net repulsive forces increased. (3) Regression analyses showed that soil splash erosion rate decreased linearly with increases in the aggregate stability; moreover, correlation analyses showed that splash erosion rate was significantly and positively correlated with the fragments with a diameter of <0.053 mm, and negatively correlated with the fragments with a diameter of >0.25 mm. This study suggests that soil internal forces induce the aggregate crush and determine the size distribution of fragments available for mobilization by the raindrop impact force. Also, the raindrop impact force is the driving mechanism leading to the movement of fragments. This study provides new insights into the mechanism responsible for splash erosion and could be valuable for controlling soil erosion. Highlights Soil aggregates breakdown dynamics and splash erosion were quantitatively investigated. Soil internal forces determined the size distribution of fragments after aggregates breakdown. The movement of soil fragments largely depended on raindrop impact force. Splash erosion was driven by the soil internal forces and raindrop impact force.

Effects of soil internal forces on splash detachment and transport of aggregate fragments in Mollisols of Northeast China

“…Besides, the net attractive pressure was higher and the net repulsive pressure was lower in Binxian soil than Keshan soil under the same electrolyte concentration (Figure 4); this may be due to the higher soil organic matter (SOM) content in Keshan soil than Binxian soil (Table 1). Increasing SOM can improve the effective Hamaker constant of soils (F. N. Hu et al, 2021; J. F. Liu et al, 2021; Yu et al, 2017). According to Equation , higher effective Hamaker constant will result in higher van der Waals attractive force between soil particles (Table S1).…”

“…Among these forces, the hydration and electrostatic forces are repulsive and cause soil aggregates to break down, however, van der Waals force is attractive which prevents the soil aggregates from dispersing (Huang et al, 2016). The net pressure of soil internal forces (generally up to 100-1000 atm) determines the degree of aggregate breakdown in an aqueous system (F. N. Hu et al, 2015;J. F. Liu et al, 2021;Yu et al, 2017).…”

“…Among these forces, the hydration and electrostatic forces are repulsive and cause soil aggregates to break down, however, van der Waals force is attractive which prevents the soil aggregates from dispersing (Huang et al, 2016). The net pressure of soil internal forces (generally up to 100–1000 atm) determines the degree of aggregate breakdown in an aqueous system (F. N. Hu et al, 2015; J. F. Liu et al, 2021; Yu et al, 2017). During rainfall, as rainwater enters the soils, the electrolyte concentration in soil bulk solution is diluted, and strong electrostatic and hydration repulsive forces between soil particles rapidly build up, causing aggregates to break up into aggregate fragments of various sizes (F. N. Hu et al, 2015; S. Li et al, 2013).…”

“…on the splash erosion. There are few studies on the effect of soil internal forces on the splash erosion process (S. Li et al, 2013; J. F. Liu et al, 2021).…”

Influence of slope incline on the ejection of two-phase soil splashed material

“…There are many factors that influence the soil splash phenomenon. Generally, three groups of factors can be distinguished: a) soil properties, e.g., moisture content [24], particle size distribution [25], organic matter content [26], and characteristics of soil aggregates [27]; b) parameters of raindrops or rainfall-erosivity [28,29]; c) external factors: e.g., surface characteristics [30,31], vegetation cover [32], or soil additives [33]. Another important factor is the incline of the surface (slope) [34][35][36].…”