Abstract: As a new type of soil remediation agent, reactive magnesium oxide has a broad application prospect in the treatment of heavy metal contaminated soils due to its efficient heavy metal immobilization capacity, superior durability buffering capacity and other characteristics. Previous studies have focused on the chemical reaction mechanism between reactive MgO and heavy metals, neglecting its effect on the hydromechanical properties of soil. In this paper, the effect of reactive magnesium oxide on the resistance of Xiashu soil to rainwater erosion was investigated by indoor simulated rainfall test. The soil was artificially contaminated by lead at the concentration of 5000 mg/kg. It was found that 5% reactive MgO treatment led to a 24.2% increase in the runoff volume of the specimen, while the lead concentration in the runoff decreased by 69.8%. The lead concentration in the infiltration of the specimens did not show much difference at the beginning of the test, but as the test progressed, the lead
concentration in the infiltration collected from the soil specimens increased, while the lead concentration in the infiltration of the specimens with the addition of magnesium oxide did not change significantly. Reactive magnesium oxide significantly reduced the mass of erosion in the samples (by 82.7%). The proportion of clay (17%) and sand (6%) in the sediment carried by the runoff decreased with MgO treatment, and the sediment size composition changed considerably compared to that of the soil samples (9% clay and 12% sand). The total amount of lead carried in the sediments of the specimens containing MgO decreased by 21% compared to the plain soil specimens. The results of the present study indicate that reactive MgO can significantly enhance the erosion resistance of Xiashu soil with lead contamination, and also immobilize heavy metals, which has a good potential for application in the remediation of lead-contaminated soil.

Key words: reactive magnesium oxide, rainfall erosion, surface runoff, lead contamination, soil remediation