Migration Behavior of NH4+ and Na+ in a Bentonite-Clay Mixed Soil Column and Numerical Simulation

The landfill barriers effectively prevented the migration of high-concentration pollutants, such as NH4+ and Na+, from landfills to surrounding environment. However, due high hydraulic head inside compared environment, Na+ can migrate towards outside barrier with infiltrating solution, potentially causing harm To address this, saturated mixed soil column samples made bentonite Shanghai clay, contents 3% 10%, were used in this study. Permeability coefficients solutions are obtained by using permeation tests, NaCl NH4Cl concentrations 37.4 mmol/L 74.8 mmol/L, respectively. concentration-depth result after tests was determined Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) Ion Chromatography (ICS-1100). Numerical simulations investigate effect downstream solute concentration on upstream concentration, dry density, content barriers. results indicate that permeability coefficient exposed solution is greater than solution. This be attributed stronger cation exchange montmorillonite for NH4+, resulting less swelling more micro-pores, leading an increase coefficient. higher at same depth samples, indicating has a rate sample. could relatively fast diffusion surface larger hydration radius Na+. According simulation results, recommended values clay mixed-soil wall follows study: thickness 43 cm, density 1.5 g/cm3, 5%.