Abstract:

A high osmotic pressure flow device was used to simulate the flow and contaminant transport processes through the aquitard. The concentration of the organic pollutant (phenanthrene) through saturation clay layer was studied with different degrees of mineralization and pH conditions. The results show that the increase of degree of mineralization can encourage the adsorption of phenanthrene leachate in the aquitard; sodium ions (Na⁺) in high degree of mineralization water alternate calcium and magnesium ions (Ca²⁺ and Mg²⁺) in the soil layer , so that Ca²⁺ and Mg²⁺ in the water increase, HCO^-₃ participate the formation of complexes with phenanthrene. Under different pH conditions, the ions Ca²⁺, Mg²⁺, and HCO^-₃ retard the migration of phenanthrene. In the reductive reaction SO^2-₄ participates the formation of complexes with the phenanthrene. SO^2-₄ promotes the migration of phenanthrene. The migration ability of phenanthrene is very weak in the aquitard, the decay rate is 82%-96%; under hyper osmotic pressure, the migration speed of the phenanthrene front is about 0.714 m/d. When pH=8, the migration concentration of phenanthrene through the aquitard is the smallest. Control of leachate’s pH and ion composition can effectively prevent the migration of phenanthrene through the aquitard.

Key words: aquitard, phenanthrene, degree of mineralization, pH, cross-flow migration