Effect Of Near-Surface Ecological Conditions On Soil Erosion And Transference Of Cd

Near-surface soil-hydrological conditions including precipitation, infiltration and soil water saturation, interflow freely, with the impact of factors such as antecedent soil water, rainfall intensity and slope. Heavy metal Cd ions in soil isolate and transport from the soil, with the effect of rainfall on soil aggregate crushing. The research was based on red soil and calcareous soil in karst area in Guangxi, the erosion mechanism and relationship between the process of Cd migrating and near-surface erosion was studied, from its special physical and chemical properties on immobilization of heavy metals, the effects of different factors on soil erosion on slope, and discussed the effect on soil erosion and Cd migration of near-surface hydrologic conditions. The main results are as follows:1) Rainfall intensity has a significant impact on surface runoff and sediment of both red and lime soil, soil antecedent moisture and slope has different impact under different rainfall intensities. The maximum surface runoff volume and sediment yield of the soil was saturated, the slope was 15 degrees, and the rainfall intensity was 100mm/h, red soil were 133.18 L,1874.41 g, lime soil were 150.47 L, 1400.14 g. The minimum surface runoff volume and sediment yield of the soil was dry, the slope was 5°, and the rainfall intensity was 30mm/h, red soil were 0.161 L,0.62 g, lime soil were 0.165 L,0.44 g. Red soil ruoff volume is less than lime soil and sediment is greater in the same treatment.2) The ablity to hold the Cd of lime soil is stronger than red soil. Soil Cd loss of rainfall total fluxes of red soil were higher than alkaline lime soil. Both soil had the highest Cd loss in slope of 15°, antecedent soil water saturation and 100 mm/h rainfall. Red soil was 2569.08 mg/m and lime soil was 2158.02 mg/m2. The particulate Cd levels in surface runoff in the early rainfall were far above the dissolved Cd content, the ratio decreased with the rainfall time increasing, the ratio of red soil showed significant differences in the early soil saturation in the condition of antecedent soil water saturation, lime soil showed no significant difference. Both red soil and lime soil had a significant positive correlation between particulate Cd content and sediment concentration> dissolved Cd content and runoff volume, and the particulate Cd content was more closely related to the sediment concentration. The Pearson correlation coefficient was:dry>saturation,15°>5°.