Characteristics of Runoff Nutrient Loss and Particle Size Distribution of Eroded Sediment under Varied Rainfall Intensities

摘要

Soil erosion is a serious problem of worldwide concern. Rainfall intensity is an important factor affecting soil erosion and the resulting nutrients loss. Field experiments were conducted to investigate the effect of rainfall intensity (60, 100 and 140 mm/h) on runoff nutrients loss and sediment particles size distribution under simulated rainfall conditions. The results showed that rainfall intensity had a significant effect on runoff, sediment and the associated nutrients loss. In general, higher rainfall intensity led to higher runoff nutrients loss. Furthermore, the nutrients mostly lost through sediment instead of runoff water. Inorganic nitrogen loss was mainly due to runoff, primarily in the form of NO_3-N. Positive linear relationships existed between soil loss and nutrients loss. Rainfall intensity had more significant effects on enrichment ratio of nitrogen (ER_N) than that of organic matter (ER_(OM)) and phosphorus (ER_P). Compared with the original surface soil, the sediment contained more fine particles (<20μm). The clay content significantly decreased with increasing rainfall intensity (p<0.05). ER of sediment-bound nutrients was positively correlated with ER of particles smaller than 2μm. This suggested that the clay fraction (<2μm) was preferentially eroded and soil nutrients were mainly adsorbed on or contained within this part of particles.