Experimental studies on the transfer of dissolved solutes from soil into surface runoff on loess slopes in China

Abstract

Overland flow and concomitant solute transport were a major source of pollutants in receiving surface water. The objective of this study was to better understand the mechanisms of soil erosion, solute transport from soil to runoff and lost via runoff, especially the effects of cumulative infiltration before the runoff generation. Laboratory experiments were conducted with three initial soil moisture contents, three rainfall intensities and three slope gradients to evaluate the effects of these variables and their interactions on soil erosion and solute losses to the runoff. The results indicated that if infiltration could be facilitated, the loss of solutes could be increased. Rainfall intensity increases the mass of sediment carried away by the runoff, decreases the time required for runoff formation and increases the solute content in the surface layer. Both the masses of solute and sediment in the runoff increase as the slope gets steeper. The rainfall splash and infiltration before runoff generation were found to play important roles in soil erosion and solute lost to the runoff, if ponding time could be prolonged, the loss of solutes could be reduced. The relationship between cumulative infiltration during ponding time and the average solute concentration in the runoff can be well described by the linear equations. The average solute concentration in the runoff was positive linear correlation with solute concentration in the soil surface layer at the time when runoff took place.

The Effects of Rainfall Patterns on Runoff, Sediment, and Nutrients Under Various Artificial Rainfall Experiments

“…; raindrop size and amount, storm duration and velocity of raindrops, rainfall intensity were the main rainfall factor as an intense storm produces high kinetic energy because high-intensity storm contains a greater percentage of energy to impact on the soil. An experimental study conducted by Dong et al (2018) tested the rainfall intensities of 60, 96, and 129 mm/hr under similar conditions and found that the high intensity produces the highest soil content in the runoff. The nding is similarly found in Almeida et al (2021) where the highest rainfall intensity varied from 75.0 to 44.6 mm h-1 produced a maximum sediment yield (0.138 g m-2 min-1) and runoff rates (0.87 mm min-1).…”

“…Rainfall especially with higher intensity increases the risk of soil erosion and eventually nutrient loss. Dong et al (2018) investigated the solute transport by using Potassium Bromide as a tracer and concluded that solute content in runoff is related to the sediment mass by showing that; a) under initial moisture content of 15% and 25%, the solute content was 1.51 and 2.63 times greater than when the initial moisture content was 5%, respectively, b) the higher the rainfall intensity applied, the higher the amount of runoff solute content and c) under slope gradient of 15° and 25°, the solute content was 1.43 and 3.51 times greater than when slope gradient was 5°, respectively. Dai et al (2018) have studied the amount of nitrogen (TN) and phosphorus (TP) losses under natural rainfall events and found that sediment yield is the major controller of the TN and TP loss.…”