Impacts of soil disturbed depth on variations in soil erosion and solute loss processes

Soil erosion-induced solute loss contributes to non-point source pollution (NPS). The extent and depth of soil solute involvement in runoff exchange processes are determined by soil disturbed depth ( D s ), encompassing runoff depth ( D r ), and effective mixing depth ( D e ). This study aimed to investigate the impacts of D s on soil erosion and solute loss. The varying D r (0.04 ~ 0.59 cm) and D e (0.08 ~ 10.35 cm) were generated through rainfall (60, 90, and 120 mm h −1 ) and overland flow (0, 1, and 2 L min −1 ). D r and D e were quantified by the KMnO 4 and Br tracing methods, respectively. Additionally, runoff coefficient ( R c ), sediment concentration ( C s ), sediment yield rate ( S y ), Br concentration in runoff ( C Br ), D r , and D e were determined at 2 or 3-minute intervals. Significant differences were observed in runoff initiation time ( T r ) (15 ~ 187 s), R c (0.49 ~ 0.99), S y (4.04 ~ 242.89 g m 2 min -1 ), C s (2.88 ~ 48.66 g L -1 ), and C Br (0.70 ~15 601.26 mg L -1 ) across different D s (F>3, P 0.89). S y , C s , and C Br demonstrated increasing trends with rising D s , though the magnitude of these increases varied across different D s ( R 2 adj > 0.55). Furthermore, a notable linear correlation was identified between cumulative runoff generation, sediment yield, Br loss, and mean D r , D e ( R 2 adj > 0.75). Collectively, D s accounted for 64.9% and 46.2% of the variation in soil erosion and Br loss, respectively. These results would facilitate an improvement of NPS models.