Simulation of the impacts of native vegetation and polyacrylamide on hydraulic properties and heavy metal concentrations at mine dumps

Abstract

The ecological restoration of mine dumps is challenging because of the loose soil structure, toxic heavy metal, and severe soil erosion at such sites. The impacts of native grass and polyacrylamide (PAM) on the soil sediment concentration, hydraulic properties, and heavy metals at mine dumps were investigated via scouring tests with a flow discharge of 90 L min −1 . In the initial stages of the tests, fluctuating decreasing trends in the soil sediment concentration, flow velocity, and flow Ni concentration were observed, while a fluctuating increasing trend was observed in the flow resistance f. After a period of adjustment, the steady-state soil sediment concentrations, hydraulic properties, and Ni concentrations in the flow were attained. An increasingdecreasing trend for the V concentration and a decreasing-increasing trend for the Cu concentration in the flow were observed over time. In addition, Zn was not dissolved or transported by the overland flow. A significant correlation between the heavy metal concentration in the flow and soil sediment concentration was observed (p ≤ 0.01). Both native grass and PAM could effectively control soil loss and change hydraulic properties by increasing the surface roughness. The steady-state flow velocity of B5 was 1.11-1.36 times higher than in the other treatments, while the steady-state resistance f of B5 was 12.54-45.02% lower than in the other treatments. However, the native grass and PAM had different effects on the transport of heavy metals. The native grass could effectively reduce the mobility of V, while the PAM could reduce the mobility of Cu and V.