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

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.