Laboratory simulation experiment on chemical transport from soil to surface runoff

Although there is a conceptual understanding on chemical transport from soil to surface runoff, there are little literature and research results actually quantifying those individual processes. A laboratory flow cell and experimental procedures to quantify chemical transport from soil to runoff by each of the individual processes: i.e., 1 soil erosion; 2 Bernoulli effect; 3 diffusion; and 4 convention were developed. Different vertical hydraulic gradients were imposed by setting the flow cell to saturation condition and artesian seepage conditions. Additional quantitative data describing the contribution from each individual chemical loading process under different surface runoff and soil hydrologic conditions were obtained. The experimental data clearly demonstrated that Bernoulli effect caused increased chemical transport from soil into surface runoff. Under saturation condition, with increasing of runoff flow rate from 55 mL/s to 250 mL/s, bromide loss flux caused by Bernoulli effect was augmented from 14% to 53% from soil into surface runoff. According to the data, the mixing zone depth was gotten by mixing theories under saturation condition and artesian seepage conditions. The mixing zone depth was less than 5 mm under saturation condition, and it changed as hydraulic head and runoff flow rate under artesian seepage conditions. Chemical transport has a significant relationship to surface runoff flow rate and groundwater table.