Effect of reactive magnesia on erosion control of a lead contaminated lean clay: insights from runoff, infiltration and disintegration characteristics

The erosion-induced environmental risks of contaminated soil and the corresponding remediation strategies remain inadequately understood. This study investigates the effect of reactive magnesia (MgO), a low-carbon-dioxide and highly effective remediation material, on the erosion control of lead (Pb)-contaminated silty clay, focusing on runoff, infiltration and disintegration characteristics. This study found that the co-migration of lead with soil particles by way of runoff is the primary pathway for its transport. Magnesia treatment decreases the chemically dissolved lead concentration in runoff by 71% due to enhanced lead precipitation, and the mass of lead-contaminated soil loss to runoff erosion by 92·4%. Furthermore, magnesia treatment lowers the clay content in eroded soil particles from 17% in the parent soil to 7%, reduces their lead concentration from 4960 to 3600 mg/kg, and increases their proportion of stable lead from 79 to 96%, thereby substantially mitigating the environmental risk posed by eroded soil particles. Further hydro-mechanical analysis reveals that magnesia significantly delays the onset of disintegration in lead-contaminated soil and reduces the final disintegration ratio from 100 to 35%. Magnesia is anticipated to demonstrate superior long-term effectiveness. This study presents a new perspective on balancing chemical stabilisation with physical solidification for the remediation of heavy metal-contaminated soils.