MIGRATION BEHAVIOR OF LEACHATE IONS IN XUZHOU YANQUN LANDFILL

Cased by Xuzhou Yanqun landfill of China, the author researches migration law of such ions as Ca²⁺,Mg²⁺ , CO₃^2-,Zn²⁺ and Cu²⁺with high concentration in landfill leachate since seeping for 20 years by numerical simulation.

The generalized model of Xuzhou Yanqun landfill is established according to the actual sectional view. Such migration characteristics in each year as depth, breadth and concentration when Ca²⁺,Mg²⁺ , CO₃^2-, Zn²⁺,Cu²⁺ seeping in the landfill site are obtained based on the concentration as well as the permeability coefficient of the five ions in clay.Mg²⁺ concentration variance decreases gradually. Particularly in terms of Mg²⁺ average concentration variance, it is 70% in the 0-10 years of migration in landfill site, but it reduces to 8% in the 10-20 years of migration. During the 20 years of migration, for 4.5 m depth, the concentration of Ca²⁺, Mg²⁺ and CO₃^2-decreases from 186ppm to 0.007ppm, from 414ppm to 3.8ppm, and from 1.241×10⁴ ppm to 9.89×10^-9 ppm, respectively. The concentration decreases faster in the 2 m clay layer area than which in other landfill sites, especially the concentration of Zn²⁺ and Cu²⁺ can reduce to zero after migration by degrees. Comparative study of the measured data and numerical simulation results are carried out. Furthermore, the migration law of Ca²⁺ in clay layer with different compaction degree is researched. When the compaction degree increases from 79% to 90%, the concentration of Ca²⁺ at the depth of 4.5m lowers from 7×10^-3 ppm to 6×10^-9 ppm after 20 years of migration. Therefore, it’s very important to design the compaction degree and thickness for controlling the ions migration.